Build Your Own Reptilian Robot（机器人参考书，英文版）：Build Your Own Reptilian Robot - McGraw Hill

Amphibionics
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Amphibionics
Build Your Own Biologically
Inspired Robot
Karl Williams
McGraw-Hill
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DOI,10.1036/0071429212
ebook_copyright 8.5 x 11.qxd 6/27/03 9:36 AM Page 1
To Laurie
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vii
Introduction xv
Acknowledgments xvii
1 Tools,Test Equipment,and Materials 1
2 Printed Circuit Board Fabrication 17
3 Microcontrollers and PIC Programming 25
4 Frogbotic,Build Your Own Robotic Frog 51
5 Serpentronic,Build Your Own
Robotic Snake 117
6 Crocobot,Build Your Own
Robotic Crocodile 191
7 Turtletron,Build Your Own
Robotic Turtle 271
Summary of
Contents
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8 Taking It Further 345
Bibliography 349
Index 351
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viii
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ix
Introduction xv
Acknowledgments xvii
1 Tools,Test Equipment,and Materials 1
Test Equipment 10
Construction Materials 12
Summary 15
2 Printed Circuit Board Fabrication 17
Summary 22
3 Microcontrollers and PIC Programming 25
Microcontrollers 25
PIC 16F84 MCU 26
PicBasic Pro Compiler 28
Contents
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Software Installation 31
Compiling a Program 35
Using the EPIC Programmer to Program the PIC 40
Testing the Controller Board 44
MicroCode Studio Visual Integrated
Development Environment 45
Using a Programmer with MicroCode Studio 47
MicroCode Studio in Circuit Debugger 48
Summary 49
4 Frogbotic,Build Your Own Robotic Frog 51
Frogs and Toads 51
Overview of the Frogbotic Project 52
R/C Servo Motors 54
Modifying Servos for Continuous Rotation 55
Controlling a Modified Servo 66
Mechanical Construction of Frogbotic 68
Assembling the Legs 77
Attaching the Legs to the Robot’s Body 82
Fabricating the Servo Mounts 84
Constructing the Front Legs 90
Leg Position Sensors 91
Wiring the Limit Switches 91
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Frogbotic’s Main Controller Board 94
Creating Frogbotic’s Printed Circuit Board 96
Fabricating the Power Connector 98
Putting It All Together 100
Programming and Experiments with Frogbotic 103
5 Serpentronic,Build Your Own
Robotic Snake 117
Snakes 117
Overview of the Serpentronic Project 119
Mechanical Construction of Serpentronic 120
Constructing the Body Sections 121
Constructing the Tail Section 130
Constructing the Head 132
Assembling the Snake’s Mechanical Structure 137
Connecting the Body Sections,Tail,and Head 138
Serpentronic’s Main Controller Board 144
Creating the Main Controller Printed
Circuit Board 146
The Infrared Sensor Board 148
Constructing the Infrared Sensor Circuit Board 152
Calibration 154
Mounting the Controller and Infrared
Sensor Board 155
Contents
xi
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Wiring the Robot 158
Programming and Experiments with Serpentronic 164
Motion Control 171
Infrared Sensor 177
Summary 188
6 Crocobot,Build Your Own
Robotic Crocodile 191
Crocodilians 191
Overview of the Crocobot Project 193
Mechanical Construction of Crocobot 194
Constructing the Chassis 199
Constructing the Body Covers and Tail Section 202
Wiring the Limit Switches 209
Constructing the Legs 211
Assembling the Legs 213
The Controller Circuit Board 216
L298 Dual Full-Bridge Driver 218
Creating the Main Controller Printed
Circuit Board 222
Putting It All Together 226
Constructing the Remote Control Transmitter 228
PIC 16C71 232
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Creating the Remote Control Printed
Circuit Board 234
Programming Crocobot 239
7 Turtletron,Build Your Own
Robotic Turtle 271
Turtles and Tortoises 271
Overview of the Turtletron Project 272
The History of Robotic Turtles 273
Mechanical Construction of Turtletron 275
Assembling the Gearboxes and
Attaching the Wheels 277
Electronics 283
Ultrasonic Range Finding 286
The Remote Control Transmitter 298
Programming Turtletron 300
Testing the SRF04 Ultrasonic Ranger 308
Obstacle Avoidance Using the
Ultrasonic Range Finder 313
Distance Measurement Using an Optical
Shaft Encoder 325
Fabricating the Shaft Encoder 327
Room Mapping Using the Shaft Encoder
and Ultrasonic Range Finder 334
Contents
xiii
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8 Taking It Further 345
Frogbotic 345
Serpentronic 346
Crocobot 346
Turtletron 347
Bibliography 349
Index 351
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xv
The robots in this book were designed to imitate biological life-
forms,Watching the snake robot moving through a room,it is
interesting to observe the surprised reactions of people when it
quickly turns towards them,People actually regard the robot as
being alive,I am struck with the thought that although these
machines are not alive in our biological sense,they actually are
alive,but as life-forms unto themselves,These artificially intelli-
gent machines are the products of human imagination and techni-
cal understanding,As the technology advances,the line between
living and non-living matter is slowly becoming blurred.
Being a collector of robotics books,old and new,I am always excit-
ed to see the robots and devices that other people have created,or
interesting ways in which they have implemented various tech-
nologies and theories,I am often inspired by some of the outdat-
ed mechanical diagrams and circuits in the old robotics books.
Even with today’s advanced computer technology,nothing is quite
as fascinating to see as the ingenious mechanical workings of a
well-designed machine.
Introduction
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Amphibionics is a continuation on the theme of building biological-
ly inspired robots introduced in Insectronics,which explored the
building and experimentation of a hexapod walking insect robot.
The practical research detailed in Amphibionics is aimed at devel-
oping a new class of biologically inspired mobile robots that
exhibits much greater robustness of performance in unstructured
environments than a lot of today’s robots,This new class of robot
is aimed at being substantially more compliant and stable than
current wheeled robots.
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xvii
Thanks to my parents Gordon and Ruth Williams for their encour-
agement,To my brothers and their wives,Doug Williams,Gylian
Williams,Geoff Williams,and Margaret Sullivan-Williams,Thanks
to Laurie Borowski for her love,patience,and suggestions,Thanks
to Judy Bass and the team at McGraw-Hill for all of their hard
work,Thanks to Patricia Wallenburg for doing a great job of put-
ting the book together,Thanks to the following people who always
have the time to discuss robotics and new ideas,James
Vanderleeuw,Stacey Dineen,Sachin Rao,Chris Meidell,John
Lammers,Tom Cloutier,Darryl Archer,Paul Steinbach,Jack
Kesselman,Charles Cummins,Maria Cummins,Tracy Strike,
Raymond Pau,Clark MacDonald,Rodi Snow,Steve Frederick
Sameer Siddiqi,Dan Dubois,and Steve Rankin,Thanks to Jason
Jackson,Roland Hofer,Kenn Booty,JoAnna Kleuskens,Patti
Ramseyer,Myke Predko,Roger Skubowius,and Tim Jones at
Cognitive Symbolics.
Acknowledgments
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1
During the mechanical construction phase of building the robots
in this book,a number of tools will be required,You will need a
workbench or sturdy table in an area with good lighting,Try to
keep your work area clean and free of clutter.
The first tool that will be used is the hacksaw,The hacksaw is
designed to cut metal and hard plastics,When using the hacksaw
to make straight cuts,it is a good idea to use a miter box,Figure
1.1 shows the hacksaw (labeled L) and the miter box (K).
If you have a little extra money and think that you will be building
a lot of robots,then you really need a band saw fitted with a metal
cutting blade,The band saw shown in Figure 1.2is 9 inches,mean-
ing that the saw can cut pieces up to a maximum length of 9 inch-
es,This is perfect for building smaller robots,like the ones detailed
in this book,With the metal cutting band saw,pieces of aluminum
can be cut fast and with greater accuracy than a hacksaw.
An important piece of equipment that will be needed in your work-
shop is a vise,like the one shown in Figure 1.3,The vise will be
needed quite often when cutting,drilling,and bending aluminum.
Always clamp metal pieces tightly in the vise when working on
Tools,Test
Equipment,and
Materials
1
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Amphibionics
2
FIGURE 1.1
Hacksaw and miter box.
FIGURE 1.2
Band saw fitted with a
metal cutting blade.
Amphibionics 01 3/24/03 8:01 AM Page 2
them with other tools,It is dangerous to try drilling metal pieces
that are not clamped in a vise.
You will need an electric drill during the mechanical construction
phase of building the robots and the fabrication of the printed cir-
cuit boards,You will be required to drill approximately 150 holes
during the process of creating each robot in the book,An electric
hand drill,like the one shown in Figure 1.4,can be used.
If you plan to build robots as a hobby,then a small drill press,like
the one shown in Figure 1.5,would be a great idea,Using a drill
press is highly recommended when drilling holes in printed circuit
boards,where accuracy and straightness are important,These
small drill presses don’t cost much more than a good electric hand
drill,I added an adjustable X-Y vise to the drill press in my work-
Chapter 1 / Tools,Test Equipment,and Materials
3
FIGURE 1.3
Work bench vise.
Amphibionics 01 3/24/03 8:01 AM Page 3
Amphibionics
4
FIGURE 1.4
Hand held electric drill.
FIGURE 1.5
A small electric drill
press with an X-Y
adjustable vise.
Amphibionics 01 3/24/03 8:01 AM Page 4
shop,This makes it possible to mill aluminum if an endmill,like
the one shown in Figure 1.6,is purchased from a machine shop
supplier,The drill press can then double as a small milling
machine.
You will need a set of drill bits like the ones pictured in Figure 1.7.
The 5/32-inch and 1/4-inch drill bits are used most often during
the projects,You will need to separately buy the small 1/32-inch
and 3/64-inch bits that will be used to drill the component holes
in the printed circuit boards.
Chapter 1 / Tools,Test Equipment,and Materials
5
FIGURE 1.6
Aluminum-cutting
endmill.
FIGURE 1.7
Drill bit set.
Amphibionics 01 3/24/03 8:01 AM Page 5
You will need an adjustable wrench (marked E in Figure 1.8),side
cutters (F),pliers (G),needle nose pliers (H),a Phillips screwdriv-
er (I),and a Robertson screwdriver (J) during construction of the
robots,A set of miniature screwdrivers may be useful as well,The
needle nose pliers can be used to hold wire and small compo-
nents in place while soldering,bending wire,and holding
machine screw nuts.
The wire strippers,shown in Figure 1.9 (A),are used to strip the
protective insulation off wire,without cutting the wire itself,The
device is designed to accommodate a number of wire sizes you
will need,A pair of wire cutters (C) can cut wire when fabricating
jumper wires and wiring power to the circuits,You will need
rosin-core solder (B) when soldering components to the circuit
boards,creating jumper wires,and wiring the battery connectors
and power switches,To make soldering components to the print-
ed circuit boards as easy as possible,buy the thinnest solder that
you can find,You will definitely need a chip-pulling tool (D) for
removing the PIC 16F84 chips from the 18-pin sockets,The PIC
16F84 will be inserted and removed from the sockets on the main
controller boards many times,as the software is changed and the
Amphibionics
6
FIGURE 1.8
Various pliers,a
wrench,and
screwdrivers.
Amphibionics 01 3/24/03 8:01 AM Page 6
PIC is reprogrammed during experiments,An adjustable work
stand,like the one shown in Figure 1.10 (M),will be useful when
soldering components to circuit boards,or holding wires when
soldering header connectors to the bare wires,A utility knife (N)
will also be helpful when cutting heat-shrink tubing or small
parts.
A soldering iron,similar to the one shown in Figure 1.11,will be
required when building the main controller circuit boards and the
sensor boards for each robot,An expensive soldering iron is not
necessary,but the advantage to buying a good one is that the tem-
perature can be set,A 15- to 25-watt pencil-style soldering iron
will work and will help to protect delicate components from burn-
ing out.
An adjustable square (O) and a good ruler (P) will be required
when measuring the cutting and drilling marks on the aluminum
pieces that make up each robots’ body and legs,You will need a
hot glue gun (Q) and glue sticks at certain points in the construc-
tion,See Figure 1.12.
Chapter 1 / Tools,Test Equipment,and Materials
7
FIGURE 1.9
Wire strippers,cutters,
solder,and a chip-
pulling device.
Amphibionics 01 3/24/03 8:01 AM Page 7
Amphibionics
8
FIGURE 1.10
Adjustable work stand
and utility knife.
FIGURE 1.11
Soldering iron with
adjustable temperature.
Amphibionics 01 3/24/03 8:01 AM Page 8
A hammer (R),shown in Figure 1.13,will be needed for bending
aluminum,along with a metal file (S) to smooth the edges of metal
pieces after they have been cut or drilled,You may use a tube of
Chapter 1 / Tools,Test Equipment,and Materials
9
FIGURE 1.12
Adjustable square,
ruler,and glue gun.
FIGURE 1.13
Hammer,file,epoxy,
and safety glasses.
Amphibionics 01 3/24/03 8:01 AM Page 9
quick-setting epoxy (T) to secure parts,Safety glasses (U) should
be worn at all times when cutting and drilling metal or soldering.
Test Equipment
To calibrate and troubleshoot the electronics,you will need a dig-
ital multimeter with frequency counting capabilities,similar to the
Fluke 87 multimeter (Figure 1.14,left),When working with elec-
tronic circuits,a good multimeter is invaluable,The second multi-
meter in Figure 1.14 (right) is manufactured by Circuit Test and
measures capacitance,resistance,and inductance,It is nice to be
able to measure the exact values of components when working on
precise circuits,but in most cases,this is not necessary,If you are
winding your own transformers or chokes,the ability to measure
inductance will be helpful,The specific use of the multimeter will
be explained during the construction of the robot’s electronics in
later chapters.
Amphibionics
10
FIGURE 1.14
Fluke and Circuit Test
multimeters.
Amphibionics 01 3/24/03 8:01 AM Page 10
If you are really serious about electronics,then an oscilloscope,
like the one pictured in Figure 1.15,is a great investment,This is
the Tektronix TDS 210 dual channel,digital real-time oscilloscope,
with a 60-MHz bandwidth,The TDS 210 on my bench also has the
RS-232,GPIB,and centronics port module added,so that a hard
copy of waveforms can be output,The great advantage to using an
oscilloscope is the ability to visualize what is happening with a
circuit,The new digital oscilloscopes also automatically calculate
the frequency,period,mean,peak to peak,and true RMS of a
waveform,You will probably need to use a regulated direct current
(DC) power supply and a function generator quite often as well.
None of the equipment shown in Figure 1.15 is required when
building the robots in this book,but it will make your life as an
Chapter 1 / Tools,Test Equipment,and Materials
11
FIGURE 1.15
Oscilloscope,regulated
DC power supply,and
function generator.
Amphibionics 01 3/24/03 8:01 AM Page 11
electronics experimenter much easier,There is nothing more
frustrating than finding out that a circuit you are working on is
malfunctioning because of a dead battery or an oscillator cali-
brated to the wrong frequency,If you use a good power supply
and oscilloscope when building and testing a circuit,the chance
of these kinds of problems surfacing is much lower,I have always
found that if I am working late at night and start to encounter a
lot of small problems and make mistakes,the best thing to do is
to shut my equipment down and get a good night’s sleep.
Sometimes the difference between frying an expensive chip or
the circuit’s working perfectly on the first try is just one mis-
placed component.
Construction Materials
The robots in this book are constructed using aluminum and fas-
teners that are readily available at most hardware stores,Five
sizes of aluminum will be used,The first stock measures 1/2-inch
wide by 1/8-inch thick,and is usually bought in lengths of 4 feet
or longer,Many of the robot parts are constructed from aluminum,
with the dimensions as shown in Figure 1.16.
Amphibionics
12
FIGURE 1.16
1/2-inch by 1/8-inch
aluminum stock.
Amphibionics 01 3/24/03 8:01 AM Page 12
The second type of aluminum stock that will be used measures
1/4-inch H11003 1/4-inch,and is shown in Figure 1.17,It is usually
bought in lengths of 4 feet or longer as well.
The third kind of aluminum stock is 1/2-inch H11003 1/2-inch angle
aluminum,and is 1/16-inch thick,as shown in Figure 1.18.
The fourth type is 1/16-inch thick flat aluminum,as shown in
Figure 1.19,and it is usually bought in larger sheets,However,
most metal suppliers will cut it down for you,This thickness of
aluminum is great for cutting out custom parts and it is easy to
Chapter 1 / Tools,Test Equipment,and Materials
13
FIGURE 1.17
Aluminum stock with
1/4-inch by 1/4-inch
dimensions.
FIGURE 1.18
1/2-inch angle
aluminum.
Amphibionics 01 3/24/03 8:01 AM Page 13
bend,making it ideal for the hobbyist experimenter,I buy all of
my metal from a company called The Metal Supermarket
(www.metalsupermarkets.com) because its prices are much lower
than buying metal at a hardware store,Their friendly staff is
always helpful,and will cut the stock to whatever size you
require,I usually ask them to cut the raw stock in half so that it
will fit into the back seat of my car.
The fifth type of stock that will be needed is 3/4-inch H11003 3/4-inch
angle aluminum.
The fasteners that will be used are 6/32-inch diameter machine
screws,nuts,lock washers,locking nuts,and nylon washers,as
shown in Figure 1.20,Three different lengths of machine screws
will be used,1-inch,3/4-inch,and 1/2-inch.
Amphibionics
14
FIGURE 1.19
1/16-inch thick flat
aluminum.
Amphibionics 01 3/24/03 8:01 AM Page 14
Summary
Now that all the tools,test equipment,and materials necessary to
build robots have been covered,you should have a good idea
about what will be necessary to build the robots in this book,In
the next chapter,the fabrication of printed circuit boards will be
discussed so that you can make your own professional-looking
boards.
Chapter 1 / Tools,Test Equipment,and Materials
15
FIGURE 1.20
6/32-inch diameter
machine screw,lock
washer,nuts,and nylon
washer.
Amphibionics 01 3/24/03 8:01 AM Page 15
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17
Four robot projects are in this book,Each robot will require a con-
troller and sensor circuit boards,The most efficient way of imple-
menting the circuit designs is to create printed circuit boards
(PCBs),The great thing about each project is that the finished PCB
artwork is included,along with a parts placement diagram,All of
the circuit boards and robots in this book have been built and test-
ed to ensure that they function as described,If you decide not to
fabricate PCBs,most of the circuits are simple enough to construct
on standard perforated circuit board (holes spaces 0.10-inch on
centers) using point-to-point wiring if you wish,I don’t recom-
mend this method because one misplaced or omitted wire can
cause hours of frustration.
The easiest way to produce quality PCBs is by using the positive
photo fabrication process,To fabricate the PCBs for each robot proj-
ect,photocopy the PCB artwork onto a transparency,Make sure that
the photocopy is the exact size of the original,For convenience,you
can download the artwork files for each robot project from the
Thinkbotics Web site,located at www.thinkbotics.com,and print
the file onto a transparency using a laser or ink-jet printer with a
minimum resolution of 600 dpi,Figure 2.1 shows the artwork for a
Printed Circuit
Board Fabrication
2
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Copyright 2003 by The McGraw-Hill Companies,Inc,Click Here for Terms of Use.
circuit board that has been printed onto transparency film using an
ink-jet printer.
After successfully transferring the artwork to a transparency,the
following instructions can be used to create a board,A 4- H110036-inch
presensitized positive copper board is ideal for all of the projects
presented in this book,When you place the transparency on the
copper board,it should be oriented exactly as shown in each
chapter,Make any sensor boards that go with the particular proj-
ect at the same time,A company that specializes in providing pre-
sensitized copper boards and all the chemistry needed to fabricate
boards is M.G,Chemicals,Information on how to obtain all of the
supplies can be found on its Web site,www.mgchemicals.com.
Figure 2.2 shows the developer,ferric chloride,and presensitized
copper board that will be used for fabricating the circuit boards.
Amphibionics
18
FIGURE 2.1
PCB artwork printed
onto transparency film.
Amphibionics 02 3/24/03 8:08 AM Page 18
Follow the next six steps to make your own PCBs:
1,Setup—Protect surrounding areas from developer and other
splashes that may cause etching damage,Plastic is ideal for
this,Work under safe light conditions,A 40-W incandescent
bulb works well,Do not work under fluorescent light,Just
prior to exposure,remove the white protective film from the
presensitized board,Peel it back carefully.
2,Exposing your board—For best results,use the M.G.
Chemicals cat,#416-X exposure kit,However,any inexpen-
sive lamp fixture that will hold two or more 18-inch fluores-
cent tubes is suitable.
Directions,Place the presensitized board,copper side toward
the exposure source,Positive film artwork should be laid onto
the presensitized copper side of the board and positioned as
desired,Artwork should have been produced by a 600-dpi or
better printer,If you don’t have a printer that can handle 600
Chapter 2 / Printed Circuit Board Fabrication
19
FIGURE 2.2
Photo fabrication kit.
Amphibionics 02 3/24/03 8:08 AM Page 19
dpi,then make two transparencies and lay them on top of
each other,Make sure that the traces line up perfectly,and
then staple them together,A glass weight should then be
used to cover the artwork,ensuring that no light will pass
under the traces (approximately 3-mm glass thickness or
greater works best),Use a 10-minute exposure time at a dis-
tance of 5 inches.
3,Developing your board—The development process removes
any photoresist that was exposed through the film positive to
ultraviolet light,Warning,The developer contains sodium
hydroxide and is highly corrosive,Wear rubber gloves and
eye protection while using it,Avoid contact with eyes and
skin,Flush thoroughly with water for 15 minutes if it is
splashed in eyes or on the skin.
Directions,Using rubber gloves and eye protection,dilute one
part M.G,cat,#418 developer with 10 parts tepid water
(weaker is better than stronger),In a plastic tray,immerse the
board,copper side up,into the developer,and you will quick-
ly see an image appear while you are lightly brushing the
resist with a foam brush,This should be completed within
one to two minutes,Immediately neutralize the development
action by rinsing the board with water,The exposed resist
must be removed from the board as soon as possible,When
you are done with the developing stage,the only resist
remaining will be covering what you want your circuit to be.
The rest should be completely removed.
4,Etching your board—For best results,use the 416-E
Professional Etching Process Kit or 416-ES Economy Etching
Kit,The most popular etching matter is ferric chloride,M.G.
cat,#415,an aqueous solution that dissolves most metals.
Warning,This solution is normally heated up during use,
generating unpleasant and caustic vapors; adequate venti-
Amphibionics
20
Amphibionics 02 3/24/03 8:08 AM Page 20
lation is very important,Use only glass or plastic contain-
ers,Keep out of reach of children,May cause burns or
stain,Avoid contact with skin,eyes,or clothing,Store in
plastic container,Wear eye protection and rubber gloves.
If you use cold ferric chloride,it will take a long time to etch
the board,To speed up the etching process,heat up the solu-
tion,A simple way of doing this is to immerse the ferric chlo-
ride bottle or jug in hot water,adding or changing the water
to keep it heating,A thermostat-controlled crock pot is also
an effective way to heat ferric chloride,as are thermostati-
cally controlled submersible heaters—(glass enclosed,such
as an aquarium heater),An ideal etching temperature is 50°C
(120°F),Be careful not to overheat the ferric chloride,The
absolute maximum working temperature is about 57°C
(135°F),The warmer your etch solution,the faster your
boards will etch,Ferric chloride solution can be used over
and over again,until it becomes saturated with copper,As
the solution becomes more saturated,the etching time will
increase,Agitation assists in removing unwanted copper
faster,This can be accomplished by using air bubbles from
two aquarium air wands with an aquarium air pump,Do not
use an aquarium air stone,The etching process can be assist-
ed by brushing the unwanted resist with a foam brush while
the board is submerged in the ferric chloride,After the etch-
ing process is completed,wash the board thoroughly under
running water,Do not remove the remaining resist protecting
your circuit or image,as it protects the copper from oxida-
tion,If you require it to be removed,use a solvent cleaner.
Figure 2.3 shows an etched board ready for drilling.
5,Drilling and parts placement—Use a 1/32-inch drill bit to
drill all the component holes on the PCB,Drill the holes for
larger components with a 3/64-inch bit where indicated,Drill
any holes that will be used to mount the circuit board at this
Chapter 2 / Printed Circuit Board Fabrication
21
Amphibionics 02 3/24/03 8:08 AM Page 21
time,It is best to use a small drill press,like the one shown
in Figure 2.4,rather than a hand drill,when working with
circuit boards,This is to ensure that the holes are drilled
straight and accurately.
6,Soldering your board—Removal of resist is not necessary
when soldering components to your board,When you leave
the resist on,your circuit is protected from oxidation,Tin-
plating your board is not necessary,In the soldering process,
the heat disintegrates the resist underneath the solder,pro-
ducing an excellent bond.
Summary
In the next chapter,the PIC microcontroller and how it is pro-
grammed will be described,Chapter 3 covers the use of compilers,
hardware programmers,and the use of a development studio
designed to speed up programming and debugging.
Amphibionics
22
FIGURE 2.3
An etched board ready
for drilling.
Amphibionics 02 3/24/03 8:08 AM Page 22
Chapter 2 / Printed Circuit Board Fabrication
23
FIGURE 2.4
A small drill press used
to drill holes in a PCB.
Amphibionics 02 3/24/03 8:08 AM Page 23
This page intentionally left blank.
25
Microcontrollers
The microcontroller is an entire computer on a single chip,The
advantage of designing around a microcontroller is that a large
amount of electronics needed for certain applications can be elim-
inated,This makes it the ideal device for use with mobile robots
and other applications where computing power is needed,The
microcontroller is popular because the chip can be reprogrammed
easily to perform different functions,and is very inexpensive,The
microcontroller contains all the basic components that make up a
computer,It contains a central processing unit (CPU),read-only
memory,random-access memory (RAM),arithmetic logic unit,
input and output lines,timers,serial and parallel ports,digital-to-
analog converters,and analog-to-digital converters,The scope of
this book is to discuss the specifics of how the microcontroller can
be used as the processor for the various robots that will be built.
Microcontrollers
and PIC
Programming
3
Amphibionics 03 3/24/03 8:11 AM Page 25
Copyright 2003 by The McGraw-Hill Companies,Inc,Click Here for Terms of Use.
PIC 16F84 MCU
Microchip technology has developed a line of reduced instruction
set computer (RISC) microprocessors called the programmable
interface controller (PIC),The PIC uses what is known as,Harvard
architecture.” Harvard uses two memories and separate busses.
The first memory is used to store the program,and the other is to
store data,The advantage of this design is that instructions can be
fetched by the CPU at the same time that RAM is being accessed.
This greatly speeds up execution time,The architecture common-
ly used for most computers today is known as Von Neumann
architecture,This design uses the same memory for control and
RAM storage,and slows down processing time.
We will be using the PIC 16F84,shown in Figure 3.1,as the
processor for the robots in the book,This device can be repro-
grammed over and over because it uses flash read-only memory
for program storage,This makes it ideal for experimenting because
the chip does not need to be erased with an ultraviolet light source
every time you need to tweak the code or try something new.
The PIC 16F84 is an 18-pin device with an 8-bit data bus and reg-
isters,We will be using a 4-MHz crystal for the clock speed,This
is very fast for our application when you consider that it is run-
Amphibionics
26
FIGURE 3.1
Pinout of the PIC 16F84
microcontroller.
Amphibionics 03 3/24/03 8:11 AM Page 26
ning machine code at 4 million cycles per second,The PIC 16F84
is equipped with two input/output (I/O) ports,port A and port B.
Each port has two registers associated with it,The first register is
the TRIS (Tri State) register,The value loaded into this register
determines if the individual pins of the port are treated as inputs
or outputs,The other register is the address of the port itself,Once
the ports have been configured using the TRIS register,data can
then be written or read to the port using the port register address.
Port B has eight I/O lines available and Port A has five I/O lines.
For example,the first robot project in the book details the con-
struction and programming of a robotic frog,This project will use
the same main controller circuit board as the hexapod robot fea-
tured in the book Insectronics so that readers who have built the
Insectronic robot will be able to jump right into this project,The
frog will be using all eight I/O lines of Port B and all five lines of
Port A,as shown in Figure 3.2.
Chapter 3 / Microcontrollers and PIC Programming
27
FIGURE 3.2
Frogbotics main
controller board
schematic.
Amphibionics 03 3/24/03 8:11 AM Page 27
Table 3.1 shows how the various pins of Port A and Port B will be
used as inputs and outputs to control the different functions of the
frog robot,It is useful to have a list of the various I/Os connected
to the ports when programming.
Port B Configuration Robot connection
RB0 Output Left light-emitting diode
RB1 Output Right light-emitting diode
RB2 Input Sensor input
RB3 Input Sensor input
RB4 Output Piezoelectric buzzer
RB5 Output Right servo
RB6 Output Left servo
RB7 Output Extra servo
Port A Configuration Robot connection
RA0 Input Radio control input 1
RA1 Input Radio control input 2
RA2 Input Mode select jumper
RA3 Input Left leg limit switch
RA4 Input Right leg limit switch
PicBasic Pro Compiler
MicroEngineering Labs developed the PicBasic Pro Compiler,shown
in Figure 3.3,It is a programming language that makes it quick and
easy to program Microchip Technology’s powerful PICmicro micro-
Amphibionics
28
TABLE 3.1
PIC 16F84 Port A and
B Connection Table
Amphibionics 03 3/24/03 8:11 AM Page 28
controllers,It can be purchased from microEngineering Labs,
whose Web site is located at www.microengineeringlabs.com.
The BASIC language is much easier to read and write than
Microchip assembly language,and will be used to program the
robots in this book,The PicBasic Pro Compiler is,BASIC Stamp II-
like,” and has most of the libraries and functions of both the BASIC
Stamp I and II,Because it is a true compiler,programs execute
much faster,and may be longer than their Stamp equivalents.
One of the advantages of the PicBasic Pro Compiler is that it uses
a real IF..THEN..ELSE..ENDIF,instead of the IF..THEN(GOTO) of
the Stamps,These and other differences are spelled out in the PBP
manual.
PicBasic Pro (PBP) defaults to create files that run on a PIC 16F84-
04/P clocked at 4 MHz,Only a minimum of other parts are neces-
sary,two 22pf capacitors for the 4-MHz crystal,a 4.7K pull-up
Chapter 3 / Microcontrollers and PIC Programming
29
FIGURE 3.3
PicBasic Pro Compiler.
Amphibionics 03 3/24/03 8:11 AM Page 29
resistor tied to the /MCLR pin,and a suitable 5-volt power supply.
Many PICmicros other than the 16F84,as well as oscillators of fre-
quencies other than 4 MHz,may be used with the PicBasic Pro
Compiler.
The PicBasic Pro Compiler produces code that may be pro-
grammed into a wide variety of PICmicro microcontrollers having
from 8 to 84 pins and various on-chip features,including A/D con-
verters,hardware timers,and serial ports,For general purpose
PICmicro development using the PicBasic Pro Compiler,the PIC
16F84,16F876,and 16F877 are the current PICmicros of choice.
These microcontrollers use flash technology to allow rapid erasing
and reprogramming to speed program debugging,With the click of
the mouse in the programming software,the flash PICmicro can be
instantly erased and then reprogrammed again and again,Other
PICmicros in the 12C67x,14C000,16C55x,16C6xx,16C7xx,
16C9xx,17Cxxx,and 18Cxxx series are either one-time program-
mable (OTP) or have a quartz window in the top (JW) to allow era-
sure by exposure to ultraviolet light for several minutes,The PIC
16F84 and 16F87x devices also contain between 64 and 256 bytes
of nonvolatile data memory that can be used to store program data
and other parameters,even when the power is turned off,This
data area can be accessed simply by using the PicBasic Pro
Compiler’s READ and WRITE commands,(Program code is always
permanently stored in the PICmicro’s code space,whether the
power is on or off.)
By using a flash PICmicro for initial program testing,the debug-
ging process may be sped along,Once the main routines of a pro-
gram are operating satisfactorily,a PICmicro with more capabili-
ties or expanded features of the compiler may be utilized.
Amphibionics
30
Amphibionics 03 3/24/03 8:11 AM Page 30
Software Installation
The PicBasic Pro files are compressed into a self-extracting file on
the diskette,They must be uncompressed to your hard drive before
use,To uncompress the files,create a subdirectory on your hard
drive called PBP or another name of your choosing by typing:
md PBP
at the DOS prompt,Change to the directory:
cd PBP
Assuming the distribution diskette is in drive a:,uncompress the
files into the PBP subdirectory:
a:\pbpxxx -d
where xxx is the version number of the compiler on the disk,Don’t
forget the -d option on the end of the command,This ensures that
the proper subdirectories within PBP are created.
Make sure that FILES and BUFFERS are set to at least 50 in your
CONFIG.SYS file,Depending on how many FILES and BUFFERS are
already in use by your system,allocating an even larger number
may be necessary.
See the README.TXT file on the diskette for more information on
uncompressing the files,Also,read the READ.ME file that is
uncompressed to the PBP subdirectory on your hard drive for the
latest PicBasic Pro Compiler information,Table 3.2lists the differ-
ent PicBasic Pro Compiler statements that are available to the
PICmicro software developer.
Chapter 3 / Microcontrollers and PIC Programming
31
Amphibionics 03 3/24/03 8:11 AM Page 31
Statement Description
@ Insert one line of assembly language code.
ADCIN Read on-chip analog to digital converter.
ASM..ENDASM Insert assembly language code section.
BRANCH Computed GOTO (equiv,to ON..GOTO).
BRANCHL BRANCH Out of page (long BRANCH).
BUTTON Debounce and auto-repeat input on specified
pin.
CALL Call assembly language subroutine.
CLEAR Zero all variables.
CLEARWDT Clear (tickle) Watchdog Timer.
COUNT Count number of pulses on a pin.
DATA Define initial contents of on-chip EEPROM.
DEBUG Asynchronous serial output to fixed pin and
baud.
DEBUGIN Asynchronous serial input from fixed pin and
baud.
DISABLE Disable ON DEBUG and ON INTERRUPT
processing.
DISABLE DEBUG Disable ON DEBUG processing.
DISABLE INTERRUPT Disable ON INTERRUPT processing.
DTMFOUT Produce touch-tones on a pin.
EEPROM Define initial contents of on-chip EEPROM.
ENABLE Enable ON DEBUG and ON INTERRUPT
processing.
ENABLE DEBUG Enable ON DEBUG processing.
(continued on next page)
Amphibionics
32
TABLE 3.2
PicBasic Pro Statement
Reference
Amphibionics 03 3/24/03 8:11 AM Page 32
Statement Description
ENABLE INTERRUPT Enable ON INTERRUPT processing.
END FOR..NEXT Stop execution and enter low power mode.
FOR..NEXT Repeatedly execute statements.
FREQOUT Produce up to 2 frequencies on a pin.
GOSUB Call BASIC subroutine at specified label.
GOTO Continue execution at specified label.
HIGH Make pin output high.
HSERIN Hardware asynchronous serial input.
HSEROUT Hardware asynchronous serial output.
I2CREAD Read bytes from I2C device.
I2CWRITEWrite bytes to I2C device.
IF..THEN..ELSE..ENDIF Conditionally execute statements.
INPUT Make pin an input.
LCDIN Read from LCD RAM.
LCDOUT Display characters on LCD.
{LET} Assign result of an expression to a variable.
LOOKDOWN Search constant table for value.
LOOKDOWN2 Search constant/variable table for value.
LOOKUP Fetch constant value from table.
LOOKUP2 Fetch constant/variable value from table.
LOW Make pin output low.
NAP Power down processor for short period of
time.
(continued on next page)
Chapter 3 / Microcontrollers and PIC Programming
33
TABLE 3.2
PicBasic Pro Statement
Reference (continued)
Amphibionics 03 3/24/03 8:11 AM Page 33
Statement Description
ON DEBUG Execute BASIC debug monitor.
ON INTERRUPT Execute BASIC subroutine on an interrupt.
OUTPUT Make pin an output.
PAUSEDelay (1mSec resolution).
PAUSEUS Delay (1uSec resolution).
PEEK Read byte from register,(Do not use.)
POKEWrite byte to register,(Do not use.)
POT Read potentiometer on specified pin.
PULSIN Measure pulse width on a pin.
PULSOUT Generate pulse to a pin.
PWM Output pulse width modulated pulse train to
pin.
RANDOM Generate pseudo-random number.
RCTIMEMeasure pulse width on a pin.
READ Read byte from on-chip EEPROM.
READCODE Read word from code memory
RESUME Continue execution after interrupt handling.
RETURN Continue at statement following last GOSUB.
REVERSE Make output pin an input or an input pin an
output.
SERIN Asynchronous serial input (BS1 style).
SERIN2 Asynchronous serial input (BS2 style).
SEROUT Asynchronous serial output (BS1 style).
SEROUT2 Asynchronous serial output (BS2 style).
(continued on next page)
Amphibionics
34
TABLE 3.2
PicBasic Pro Statement
Reference (continued)
Amphibionics 03 3/24/03 8:11 AM Page 34
Statement Description
SHIFTIN Synchronous serial input.
SHIFTOUT Synchronous serial output.
SLEEP Power down processor for a period of time.
SOUND Generate tone or white-noise on specified pin.
SWAP Exchange the values of two variables.
TOGGLEMake pin output and toggle state.
WHILE..WEND Execute statements while condition is true.
WRITE Write byte to on-chip EEPROM.
WRITECODE Write word to code memory.
XIN X-10 input.
XOUT X-10 output.
Compiling A Program
For operation of the PicBasic Pro Compiler,you will need a text
editor or word processor for creation of your program source file,
some sort of PICmicro programmer such as the EPIC Plus Pocket
PICmicro Programmer,and the PicBasic Pro Compiler itself,Of
course you also need a PC to run it.
Follow this sequence of events:
First,create the BASIC source file for the program,using your favorite
text editor or word processor,If you don’t have a favorite,DOS EDIT
(included with MS-DOS) or Windows NOTEPAD (included with
Windows and Windows 95/98) may be substituted,A great text edi-
tor called Ultraedit is available at,www.ultraedit.com,It is geared
towards the software developer and does not add any undesirable
formatting characters that will cause the compiler to error out.
Chapter 3 / Microcontrollers and PIC Programming
35
TABLE 3.2
PicBasic Pro Statement
Reference (continued)
Amphibionics 03 3/24/03 8:11 AM Page 35
The source file name should (but is not required to) end with the
extension,BAS,The text file that is created must be pure ASCII
text,It must not contain any special codes that might be inserted
by word processors for their own purposes,You are usually given
the option of saving the file as pure DOS or ASCII text by most
word processors.
Program 3.1 provides a good first test for programming a PIC and
for testing the frog robot controller board when it is built in Chapter
4,You can type it in or download it from the author’s Web site
www.thinkbotics.com,and follow the links for book software.
The file is named frog-test.bas and is listed in Program 3.1,The
BASIC source file should be created in or moved to the same direc-
tory where the PBP.EXE file is located.
'------------------------------------------------------------------------------------------------------------------------------
' Name,Frog-test.bas
' Compiler,PicBasic Pro MicroEngineering Labs
' Notes,Program to test the main controller
',board by flashing LEDs,producing
',sounds and slowly rotating the servos
'------------------------------------------------------------------------------------------------------------------------------
' set porta to inputs
trisa = %11111111
' set portb pins 2 & 3 to inputs
trisb = %00001100
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
servo_pos_l VAR BYTE
servo_pos_r VAR BYTE
timer1 VAR BYTE
timer2 VAR BYTE
timer3 VAR BYTE
temp1 VAR BYTE
servo_r VAR PORTB.5
servo_l VAR PORTB.6
Amphibionics
36
PROGRAM 3.1
frog-test.bas program
listing
Amphibionics 03 3/24/03 8:11 AM Page 36
switch_r VAR PORTA.4
switch_l VAR PORTA.3
led_l VAR PORTB.1
led_r VAR PORTB.0
piezo VAR PORTB.4
'------------------------------------------------------------------------------------------------------------------------------
low servo_l
low servo_r
start:
for temp1 = 1 to 10
SOUND piezo,[80,4,100,2]
low led_l
low led_r
pause 50
high led_l
high led_r
next temp1
SOUND piezo,[100,4,120,2,80,2,90,2]
low led_l
low led_r
rotate:
servo_pos_r = 170
gosub right_servo
servo_pos_l = 130
gosub left_servo
goto rotate
'------------------------------------------------------------------------------------------------------------------------------
' subroutines to set servos
both_servo,
for timer1 = 1 to 15
pulsout servo_l,servo_pos_l
pulsout servo_r,servo_pos_r
pause 6
next timer1
return
left_servo:
for timer2 = 1 to 10
Chapter 3 / Microcontrollers and PIC Programming
37
PROGRAM 3.1
frog-test.bas program
listing (continued)
Amphibionics 03 3/24/03 8:11 AM Page 37
pulsout servo_l,servo_pos_l
pause 6
next timer2
return
right_servo
for timer3 = 1 to 10
pulsout servo_r,servo_pos_r
pause 6
next timer3
return
end
Once you are satisfied that the program you have written will work
flawlessly,you can execute the PicBasic Pro Compiler by entering
PBP,followed by the name of your text file at a DOS prompt,For
example,if the text file you created is named frog-test.bas,at the
DOS command prompt,enter:
PBP frog-test.bas
The compiler will display an initialization (copyright) message and
process your file,If it likes your file,it will create an assembler
source code file (in this case,named frog-test.asm) and automat-
ically invoke its assembler to complete the task,If all goes well,the
final PICmicro code file will be created (in this case,frog-text.hex).
If you have made the compiler unhappy,it will issue a string of
errors that will need to be corrected in your BASIC source file
before you try compilation again.
To help ensure that your original file is flawless,it is best to start
by writing and testing a short piece of your program,rather than
writing an entire 100,000-line monolith all at once and then trying
to debug it from end to end.
If you don’t tell it otherwise,the PicBasic Pro Compiler defaults to
creating code for the PIC 16F84,To compile code for PICmicros
Amphibionics
38
PROGRAM 3.1
frog-test.bas program
listing (continued)
Amphibionics 03 3/24/03 8:11 AM Page 38
other than the F84,just use the -P command line option,described
later in the manual,to specify a different target processor,For
example,if you intend to run the above program,frog-test.bas,on
a PIC 16C74,compile it using the command:
PBP -p16c74 frog-test.bas
An assembler source code file for frog-test.bas is also generated.
It is called frog-test.asm,The assembler source code can be used
as a guide if you want to explore assembly language program-
ming because the listing shows the PicBasic Pro statement and
the corresponding assembly code on the next line,The rest of the
chapters discussing software will not be addressing assembly
code,All we really need to be concerned with is the PicBasic
source code and the generated,HEX machine code,as listed in
Program 3.2.
If you do not have the resources to buy the PicBasic Pro compiler,
simply type the listings of the,HEX files into a text editor and save
the file with the program name and,HEX extension,All the pro-
gram listings in the book can also be downloaded from
www.thinkbotics.com to make things easier,However,I recom-
mend buying a copy of the compiler if you wish to experiment,
change,or customize the programs,If you decide to continue with
robotics and electronics,you will eventually need to buy a com-
piler,such as PicBasic Pro,when working with microcontrollers.
:100000007B28A0003B200C080D04031976287020E3
:1000100084132008800664000D280E288C0A03191A
:100020008D0F0B28800676288F0022088400200977
:100030003C2084138F0803197628F03091000E08B5
:1000400080389000F03091030319910003198F0359
:10005000031976282B283F2003010C1820088E1F37
:1000600020088E0803190301900F382880061F28E6s
:10007000392800002228FF3A8417800576280D08C9
Chapter 3 / Microcontrollers and PIC Programming
39
PROGRAM 3.2
frog-test.hex program
listing
Amphibionics 03 3/24/03 8:11 AM Page 39
:100080000C0403198C0A80300C1A8D060C198D068D
:100090008C188D060D0D8C0D8D0D76288F018E0020
:1000A000FF308E07031C8F07031C762803308D005A
:1000B000DF305C2050288D01E83E8C008D09FC303B
:1000C000031C65288C07031862288C0764008D0FB9
:1000D00062280C186B288C1C6F2800006F28080001
:1000E0008C098D098C0A03198D0A080083130313E8
:1000F0008312640008008316FF3085000C308600F0
:100100008312061383160613831286128316861231
:1001100083120130A60064000B3026020318B028B9
:100120000630A2001030A00050308E0004301420A1
:1001300064308E00023014208610831686108312DD
:10014000061083160610323083124E208614831652
:10015000861083120614831606108312A60F8B28AE
:100160000630A2001030A00064308E00043014204D
:1001700078308E000230142050308E00023014206F
:100180005A308E0002301420861083168610831297
:100190000610831606108312AA30A50000218230B3
:1001A000A400ED20CC280130A70064001030270205
:1001B0000318EC2824088C008D01063084004030A0
:1001C000012025088C008D0106308400203001209C
:1001D00006304E20A70FD52808000130A800640083
:1001E0000B3028020318FF2824088C008D010630EC
:1001F00084004030012006304E20A80FEF28080070
:100200000130A90064000B302902031812292508C7
:100210008C008D01063084002030012006304E20F5
:0A022000A90F02290800630013294A
:02400E00F53F7C
:00000001FF
Using the EPIC Programmer
to Program the PIC
The two steps left are putting your compiled program into the
PICmicro microcontroller and testing it,The PicBasic Pro Compiler
generates standard 8-bit Merged Intel HEX (.HEX) files that may
be used with any PICmicro Programmer,including the EPIC Plus
Amphibionics
40
PROGRAM 3.2
frog-test.hex program
listing (continued)
Amphibionics 03 3/24/03 8:11 AM Page 40
Pocket PICmicro Programmer,shown in Figure 3.4,PICmicros
cannot be programmed with BASIC Stamp programming cables.
An example of how a PICmicro is programmed using the EPIC
Programmer with the DOS programming software follows,If
Windows 95/98/NT is available,using the Windows version of
EPIC Programmer software is recommended.
Make sure there are no PICmicros installed in the EPIC
Programmer programming socket or any attached adapters,Hook
the EPIC Programmer to the PC parallel printer port using a DB25
male-to-DB25 female printer extension cable,Plug the AC adapter
Chapter 3 / Microcontrollers and PIC Programming
41
FIGURE 3.4
EPIC Programmer by
microEngineering Labs.
Amphibionics 03 3/24/03 8:11 AM Page 41
into the wall and then into the EPIC Programmer (or attach two
fresh 9-volt batteries to the programmer and connect the,Batt
ON” jumper),The light-emitting diode (LED) on the EPIC
Programmer may be on or off at this point,Do not insert a
PICmicro into the programming socket when the LED is on or
before the programming software has been started.
Enter:
EPIC
at the DOS command prompt to start the programming software.
The EPIC software should be run from a pure DOS session or from
a full-screen DOS session under Windows or OS/2,(Running
under Windows is discouraged,Windows [all varieties] alters the
system timing and plays with the port when you are not looking,
which may cause programming errors.)
The EPIC software will look around to find where the EPIC
Programmer is attached and get it ready to program a PICmicro,If
the EPIC Programmer is not found,check all the above connections
and verify that there is not a PICmicro or any adapter connected
to the programmer.
Typing:
EPIC /?
at the DOS command prompt will display a list of available options
for the EPIC software.
Once the programming screen is displayed,use the mouse to click
on Open file or press Alt-O on your keyboard,Use the mouse (or
keyboard) to select frog-test.hexor any other file you would like to
program into the PICmicro from the dialog box,The file will load
and you should see a list of numbers in the window at the left.
Amphibionics
42
Amphibionics 03 3/24/03 8:11 AM Page 42
This is your program in PICmicro code,At the right of the screen
is a display of the configuration information that will be pro-
grammed into the PICmicro,Verify that it is correct before pro-
ceeding,In general,the oscillator should be set to XT for a 4-MHz
crystal,and the Watchdog Timer should be set to ON for PicBasic
Pro programs,Most important,Code Protect must be OFF when
programming any windowed (JW) PICmicro,You may not be able
to erase a windowed PICmicro that has been code protected.
Figure 3.5 shows the EPIC MS-DOS interface.
Insert a PIC 16F84 into the programming socket and click on
Programor press Alt-Pon the keyboard,The PICmicro will first be
checked to make sure it is blank,and then your code will be pro-
grammed into it,If the PICmicro is not blank and it is a flash
device,you can simply choose to program over it without erasing
first,Once the programming is complete and the LED is off,it is
time to test your program.
Chapter 3 / Microcontrollers and PIC Programming
43
FIGURE 3.5
EPIC graphics user
interface.
Amphibionics 03 3/24/03 8:11 AM Page 43
Testing the Controller Board
Later in Chapter 4,when the controller board is finished and the
PIC 16F84 is programmed with the frog-test.hex program,insert
the PIC into the socket on the controller board,Place the PIC into
the 18-pin I.C,socket,with the notch and pin 1 facing toward the
LEDs as shown in Figure 3.6.
Place four AA batteries in the 6-volt battery pack and secure it in
position in the holder at the back of the robot,Make sure that the
battery clip is attached,and then turn the power switch to the on
position,If all is well,then the left and right LEDs should be alter-
natively flashing on and off,while the piezo element is producing
robotic frog noises,When the flashing is finished,the servos
should start rotating in a forward direction,This ensures that the
16F84 was programmed and that the controller board is function-
ing properly.
If nothing is happening when the power is switched on,try going
through the process of programming the PIC again,and choose the
verify option from the EPIC user interface,If the chip fails verifica-
Amphibionics
44
FIGURE 3.6
PIC 16F84 inserted into
I.C,socket on controller
board.
Amphibionics 03 3/24/03 8:11 AM Page 44
tion,check the RS-232 cable and power supply to the programmer.
If that does not work,try using a different 16F84 chip.
If there was no error when programming the PIC,insert it back into
the controller board and make sure that pin 1 is facing toward the
LEDs,Check the battery wiring and verify that the 6-V DC polarity
is not reversed to the power connectors,Check the controller board
for any missed components or cold solder connections.
MicroCode Studio Visual Integrated
Development Environment
Mecanique’s MicroCode Studio is a powerful,visual Integrated
Development Environment (IDE),with an In Circuit Debugging
(ICD) capability designed specifically for microEngineering Labs’
PICBasic Pro Compiler,The MicroCode Studio user interface is
shown in Figure 3.7.
This studio makes programming PIC microcontrollers very easy
with a one-button process of compiling,assembling,and program-
ming,MicroCode Studio is completely free for noncommercial use
and can be downloaded at www.mecanique.co.uk/code-studio/,It
is not time-limited in any way,and does not have any nag screens.
However,you can only use one ICD model with MicroCode Studio.
MicroCode Studio is not copyright-free,If you wish to redistribute
MicroCode Studio,or make it available on another server,you must
contact Mecanique and obtain permission first.
The main editor provides full syntax highlighting of your code,
with context-sensitive keyword help and syntax hints,The code
explorer allows you to automatically jump to include files,
defines,constants,variables,aliases and modifiers,symbols,and
labels that are contained within your source code,Full cut,copy,
paste,and undo is provided,together with search and replace
features,It also gives you the ability to identify and correct com-
Chapter 3 / Microcontrollers and PIC Programming
45
Amphibionics 03 3/24/03 8:11 AM Page 45
pilation and assembler errors,MicroCode Studio lets you view
serial output from your microcontroller,It includes keyword-
based context-sensitive help,and also supports MPASM and
MPLAB.
It is easy to set up your compiler,assembler,and programmer
options,or you can let MicroCode Studio do it for you with its
built-in autosearch feature,as shown in Figure 3.8.
MicroCode Studio has support for MPLAB-dependent program-
mers such as PICStart Plus,Compilation and assembler errors can
be easily identified and corrected using the error results window.
Just click on a compilation error and MicroCode Studio will auto-
matically take you to the error line,MicroCode Studio even comes
with a serial communications window,allowing you to debug and
view serial output from your microcontroller.
Amphibionics
46
FIGURE 3.7
MicroCode Studio
makes PIC
programming easy.
Amphibionics 03 3/24/03 8:11 AM Page 46
With MicroCode Studio,you can start your preferred programming
software from within the IDE,This enables you to compile and
then program your microcontroller with just a few mouse clicks (or
keyboard strokes,if you prefer),MicroCode Studio also supports
MPLAB dependant programmers.
Using a Programmer with
MicroCode Studio
The first thing you need to do is tell MicroCode Studio which pro-
grammer you are using.
Select VIEW...OPTIONS from the main menu bar,then select the
PROGRAMMER tab,as shown in Figure 3.9,Next,select the Add
New Programmer button,This will open the Add New Programmer
wizard,
Select the programmer you want MicroCode Studio to use,then
choose the Next button,MicroCode Studio will now search your
Chapter 3 / Microcontrollers and PIC Programming
47
FIGURE 3.8
Automatically setting up
the compiler.
Amphibionics 03 3/24/03 8:11 AM Page 47
computer until it locates the required executable,If your device
uses MPLAB,you will be presented with two further screens,the
select options and development mode screens,If your programmer
is not in the list,you will need to create a custom programmer
entry,Your programmer is now ready for use,When you press the
Compile and Program button on the main toolbar,your PICBasic
program is compiled and the programmer software is started,The
hex filename and target device is automatically set in the pro-
gramming software (if this feature is supported),ready for you to
program the microcontroller,as shown in Figure 3.10.
MicroCode Studio in Circuit Debugger
The MicroCode Studio ICD enables you to execute a PICBasic
Program on a host PIC microcontroller and view variable values,
Special Function Registers (SFR),memory,and EEPROM as the
program is running,Each line of source code is animated in the
Amphibionics
48
FIGURE 3.9
Adding a new
programmer.
Amphibionics 03 3/24/03 8:11 AM Page 48
main editor window,showing you which program line is current-
ly being executed by the host microcontroller,You can even tog-
gle multiple breakpoints and step through your PICBasic code line
by line.
Using the MicroCode Studio ICD can really accelerate program
development,It’s also a lot of fun and a great tool for learning
more about programming PIC microcontrollers.
Summary
Now that the concept of programming and compiling code for
microcontrollers has been covered,it will be easy to program the
robots in the following chapters,Using MicroCode Studio for cre-
ating your source code,compiling the code,and programming PIC
microcontrollers makes development much faster.
Chapter 3 / Microcontrollers and PIC Programming
49
FIGURE 3.10
One button compile and
programming using
MicroCode Studio.
Amphibionics 03 3/24/03 8:11 AM Page 49
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51
Frogs and Toads
There are more than 4,100 species of frogs and toads,making
them the largest group of amphibians,The majority lives in tropi-
cal environments,mostly in or close to fresh water,In adulthood,
frogs and toads are characterized by the absence of a tail,The
frog’s hind limbs are much larger than their front limbs,enabling
them to jump very long distances.
There is much diversity among frogs and toads,There are species
that use their legs to swim,burrow into the soil,climb trees,and
glide through the air,in addition to jumping and crawling,The pri-
mary senses of frogs and toads are vision and hearing,Many frogs
and toads use loud calls to communicate with one another,Frogs
and toads typically lay their eggs in water,The eggs hatch into lar-
vae (tadpoles),which have spherical bodies and are herbivorous.
Adult frogs and toads are carnivorous,feeding mostly on insects.
They are generally only active at night.
The biologically inspired robot in this chapter is based on the frog
and its capability to achieve locomotion by jumping,This locomo-
Frogbotic,
Build Your Own
Robotic Frog
4
Amphibionics 04 3/24/03 8:23 AM Page 51
Copyright 2003 by The McGraw-Hill Companies,Inc,Click Here for Terms of Use.
tion is achieved by releasing the energy stored in the frog’s hind
legs,Figure 4.1 shows a tree frog,along with its biologically
inspired mechanical counterpart.
Overview of the Frogbotic Project
The robotic frog to be built possesses two spring-loaded hind legs
that are used to achieve locomotion by jumping,as shown in
Figures 4.2 and 4.3,The functions of the leg mechanisms,sen-
sors,and leg position limit switches are controlled by a Microchip
PIC 16F84 microcontroller.
The spring of each leg is independently loaded with a mechanism
that uses a standard servo,modified for continuous rotation,A
close-up of the spring-loading mechanism is shown in Figure 4.4.
When the servo is rotated to the position where the cam-like
device is fully set and the spring is loaded,a limit switch is trig-
gered,At this point,the microcontroller stops the servo and holds
this position until both legs are in jumping position.
Amphibionics
52
FIGURE 4.1
A tree frog and its
biologically inspired
robotic counterpart.
Amphibionics 04 3/24/03 8:23 AM Page 52
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
53
FIGURE 4.2
Robot frog leg
mechanism—outside
view.
FIGURE 4.3
Robot frog leg
mechanism—inside
view.
Amphibionics 04 3/24/03 8:23 AM Page 53
When both servos have been positioned so that the springs are
loaded and the legs are in their jumping position,the microcon-
troller gives both servos the command to move forward,This
moves the lever past the position where the spring is loaded,at
which time the spring quickly pulls the upper leg mechanism
downward,giving the legs enough energy to leap the frog forward.
R/C Servo Motors
The R/C servo is a geared,direct current motor with a built-in
positional feedback control circuit,as pictured in Figure 4.6,This
makes it ideal for use with small robots because the experimenter
does not have to worry about motor control electronics.
A potentiometer is attached to the shaft of the motor and rotates
along with it,For each position of the motor shaft and poten-
tiometer,a unique voltage is produced,The input control signal is
a variable-width pulse between 1 and 2 milliseconds (ms),deliv-
ered at a frequency between 50 and 60 Hz,which the servo inter-
nally converts to a corresponding voltage,The servo feedback cir-
Amphibionics
54
FIGURE 4.4
Spring-loading
mechanism with limit
switch sensor.
Amphibionics 04 3/24/03 8:23 AM Page 54
cuit constantly compares the potentiometer signal to the input
control signal provided by the microcontroller,The internal com-
parator moves the motor shaft and potentiometer either forward
or in reverse,until the two signals are the same,Because of the
feedback control circuit,the rotor can be accurately positioned
and will maintain the position as long as the input control signal
is applied,The shaft of the motor can be positioned through 180
degrees of rotation,depending on the width of the input signal.
The PicBasic Pro language makes servo control with a PIC micro-
controller easy,using a command called Pulsout,The syntax is
Pulsout Pin,Period,A pulse is generated on Pin of specified
Period,Toggling the pin twice generates the pulse; thus,the initial
state of the pin determines the polarity of the pulse,Pin is auto-
matically made an output,Pin may be a constant,0–15,or a vari-
able that contains a number between 0 and 15 (e.g.,B0) or a pin
name (e.g.,PORTA.0).
The resolution of Pulsout is dependent on the oscillator frequen-
cy,Since we are using a 4-MHz oscillator,the Period of the gener-
ated pulse will be in 10 microsecond increments,To send a pulse
to port B on pin 7 that is 1.4 ms long (at 4 MHz,10 μs H11003 140 H11005
1400 μs or 1.4 ms),the command would be,Pulsout PortB.7,140.
To illustrate the kind of signal being produced by the microcon-
troller,see Figure 4.5,The oscilloscope trace for channel 1 was
generated with the Pulsoutcommand configured to produce a 1.4-
ms pulse at 55.68 Hz,and the trace for channel 2 was configured
for a 6-ms pulse,also at 55.68 Hz.
Modifying Servos for Continuous Rotation
The robot frog will use two standard R/C servos,modified for con-
tinuous rotation,This is because servos are inexpensive,can be
controlled directly from a microcontroller,and will provide the
torque needed to load the spring-driven jumping leg mechanisms.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
55
Amphibionics 04 3/24/03 8:23 AM Page 55
An unmodified servo has a rotational radius limited to approxi-
mately 180 degrees,For our application,we will need a full 360
degrees of continuous rotation,This is accomplished by taking the
servo apart,removing a mechanical stop as well as removing the
potentiometer,and replacing it with a fixed resistor network,Note
that there may be differences between servos built by different
manufacturers,The concept for modifying servos is basically the
same for all servo types,Depending on the make,you may have to
improvise and stray from the procedure a little,The servo in this
example is a JR NES-527,The parts needed for this procedure are
listed in Table 4.1.
Part Quantity Description
Resistors 4 2.4-KH9024 resistors,1/4-watt
Heat-shrink tubing 3 inches Heat-shrink tubing
Amphibionics
56
FIGURE 4.5
Oscilloscope display of
a 1.4-ms and 6.0-ms
pulse train.
TABLE 4.1
Parts Need for
Modifying the Servos
Amphibionics 04 3/24/03 8:23 AM Page 56
The instructions for modifying a standard servo are as follows:
1,Place the servo on a table and remove the servo horn and
screw,as shown in Figure 4.6,if there is one attached.
2,Flip the servo over so that the bottom is facing upward,and
remove the four screws that hold the cover on,See Figure 4.7
for details.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
57
FIGURE 4.6
Remove servo horn and
screw.
FIGURE 4.7
Servo cover screws
removed from servo.
Amphibionics 04 3/24/03 8:23 AM Page 57
3,Next,turn the servo back over so that it is upright,Remove the
top cover and the gears,as shown in Figure 4.8,You may
need to use a small screwdriver to carefully break the seal and
pry the cover off,When the cover has been removed,remove
each of the gears in order,and place them somewhere safe.
Leave the gear that connects to the motor in place.
Amphibionics
58
FIGURE 4.8
Servo with cover and
gears removed.
Amphibionics 04 3/24/03 8:23 AM Page 58
4,Now that the top cover is removed,open the bottom cover.
Again,you may have to use a small screwdriver to get it open.
Locate the small potentiometer and pry back the plastic clips
that hold it in place,as shown in Figure 4.9,You may have
to actually break them off,If you do break them off,make
sure that they are removed from inside the servo and dis-
carded,If glue is holding the potentiometer in place,scrape it
off with a small screwdriver.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
59
FIGURE 4.9
Potentiometer clips.
Amphibionics 04 3/24/03 8:23 AM Page 59
5,Turn the servo over so that the top is facing upward,Use a
screwdriver to force the potentiometer shaft through the hole
that it is mounted in,as shown in Figure 4.10,Pull the poten-
tiometer all the way through and remove any glue holding the
wires in place so that it resembles Figure 4.11.
Amphibionics
60
FIGURE 4.10
Push potentiometer
through mounting hole.
FIGURE 4.11
Potentiometer removed
from servo housing.
Amphibionics 04 3/24/03 8:23 AM Page 60
6,Use a soldering iron to de-solder the three wires that are
attached to its leads,as shown in Figure 4.12,Take note of
which wire is attached to the center terminal,Either mark the
wire or write down the color,as this wire must be connected
to the middle lead of the resistor network that will be fabri-
cated in the next step.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
61
FIGURE 4.12
Potentiometer with
wires attached.
Amphibionics 04 3/24/03 8:23 AM Page 61
7,For this step,you will need two 1/4-watt,2.4 KH9024resistors to
create a resistor network that will replace the potentiometer
that was just removed,Try to select two resistors that have
very close resistance values,although it is not extremely
important,since any discrepancies can be compensated for
in the control software,Cut the resistor leads to a length of
3/8-inch,Twist two of the ends together and solder,as
shown in Figure 4.13.
Amphibionics
62
FIGURE 4.13
Resistor network.
Amphibionics 04 3/24/03 8:23 AM Page 62
8,Cut three pieces of heat-shrink tubing,and slip each one over
each of the wires that were attached to the potentiometer.
Solder the middle wire from the potentiometer to the two
resistor leads that are twisted together,Solder the left wire to
the left resistor lead,and solder the right wire to the right
resistor lead of the resistor network,Push the heat-shrink
tubing up over the solder connections and shrink into place
with a heat source,The finished resistor network with the
wires soldered and the heat-shrink tubing in place should
look like the one in Figure 4.14,Once this is complete,push
the resistor network and the wires back into the servo in the
space where the potentiometer was previously.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
63
FIGURE 4.14
Resistor network with
wires soldered into
place.
Amphibionics 04 3/24/03 8:23 AM Page 63
9,Take the large output gear and locate the nub on its bottom
side,Use a pair of side cutters to remove the nub,as shown
in Figure 4.15,Use a file or a sharp knife to remove any
excess plastic so that the bottom of the gear where the nub
used to be is flat.
Amphibionics
64
FIGURE 4.15
Removing the nub from
the output gear.
Amphibionics 04 3/24/03 8:23 AM Page 64
10,Now that the gear has been modified,make sure that the bot-
tom servo cover is in position,Replace the gears in the same
order that they were removed from the servo,Use Figure
4.16 as a guide when replacing the gears.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
65
FIGURE 4.16
Servo gear placement.
Amphibionics 04 3/24/03 8:23 AM Page 65
11,Finally replace the top servo cover and secure it in place with
the four screws that were removed during step 2,When the
cover and screws are replaced,the servo should resemble the
one shown in Figure 4.17,Be sure to mark the servo,indi-
cating that it has been modified,since it will look exactly the
same as an unmodified servo.
Controlling a Modified Servo
A modified servo is controlled in the same way as an unmodified
servo,The only difference is that when the pulse width signal is
sent to the servo,it will start turning the motor in the required
direction and will continue to rotate as long as the signal is
applied,Since the potentiometer that keeps track of the output
gear position has been removed and replaced with the resistor
network,the internal circuitry will think that the motor has not
Amphibionics
66
FIGURE 4.17
A servo modified for
continuous rotation.
Amphibionics 04 3/24/03 8:23 AM Page 66
reached the specified position and will continue to seek for it in
one direction or another,With identical resistors in the network,
if a pulse with a width of 150 ms is sent to the servo,it will
remain motionless,Since no two resistors are exactly the same,
you may have to experiment with the pulse width value needed
for the servo to remain motionless,It will probably be within the
range of 147–153 ms,Figure 4.18 illustrates how the modified
servo will behave when control signals between 100 and 200 ms
are applied,When a signal with a pulse width of 100 ms is
applied to the servo’s control line,the servo will move in a coun-
terclockwise direction at full speed,The servo speed can be con-
trolled by varying the pulse-width value,with 100 ms being the
fastest speed in the counterclockwise direction,and 149 ms
being the slowest,The same holds true for the servo rotating in
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
67
FIGURE 4.18
Pulse width values used
to control a modified
servo.
Amphibionics 04 3/24/03 8:23 AM Page 67
the clockwise direction,with 151 ms being the slowest speed and
200 ms being the fastest.
Mechanical Construction of Frogbotic
The construction of the robot frog will begin with the robot’s body.
The parts needed for the mechanical construction are listed in
Table 4.2.
Parts Quantity
1/2-inch H11003 1/8-inch aluminum stock 4 feet,2 inches
1/16-inch thick aluminum stock 12-inch H11003 12-inch piece
1/4-inch H11003 1/4-inch aluminum stock 2 inches
1/4-inch diameter nylon feet 2
6/32 H11003 1/2-inch machine screws 39
6/32 H11003 3/4-inch machine screws 8
6/32 nuts 23
6/32 lock washers 23
6/32 locking nuts 16
Standard R/C servo–modified 2
3/8-inch diameter H11003 5/8-inch spring 2
Amphibionics
68
TABLE 4.2
Parts List for Frog
Robot Mechanical
Construction
Amphibionics 04 3/24/03 8:23 AM Page 68
The body is constructed using a piece of 1/16-inch thick alu-
minum cut to a size of 4 H11003 7 inches,Use Figure 4.19 as a guide
to cutting and bending the aluminum piece,When the piece has
been cut,use a file to remove any rough edges,Use Figure 4.20to
measure and mark where all of the holes are to be drilled,Drill
each of the holes with a 5/32-inch drill bit,except for the holes
marked as being drilled with 1/4-inch and 7/64-inch bits,Figure
4.21 shows the finished frog robot body on which all of the other
mechanical and electronic components will be mounted.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
69
FIGURE 4.19
Cutting and bending
guide for the
Frogbotic’s body.
Amphibionics 04 3/24/03 8:23 AM Page 69
Amphibionics
70
FIGURE 4.20
Drilling guide for the
Frogbotic’s body.
Amphibionics 04 3/24/03 8:23 AM Page 70
The next step is to fabricate six mounting brackets that will be used
to attach the robot legs to the body and to fasten two leg sensor limit
switches,Use Figure 4.22as a cutting and drilling guide to fabricate
pieces A,B,C,D,E,and F out of 1/16-inch thick aluminum,Pieces
A and B measure 1-3/4 inches in length,pieces C and D are 1-1/2
inches in length,and pieces E and F are 2-1/4 inches in length,Drill
the holes with a 5/32-inch drill bit where indicated in Figure 4.22.
The finished pieces are shown in Figure 4.23.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
71
FIGURE 4.21
Cut,bent,and drilled
aluminum for the
Frogbotic’s body.
Amphibionics 04 3/24/03 8:23 AM Page 71
Amphibionics
72
FIGURE 4.22
Cutting and drilling
guide for mounting
brackets.
Amphibionics 04 3/24/03 8:23 AM Page 72
Fasten the leg mounting brackets and limit switch brackets to the
frog’s body piece,as shown in Figure 4.24,Fasten each bracket in
place using two 6/32-inch H11003 1/2-inch machine screws,lock
washers,and nuts,The frog’s body with the brackets mounted in
position should look like the one in Figure 4.24.
Cut two pieces of the 1/4-inch H11003 1/4-inch aluminum,marked as
G and H,to a length of 1 inch,and drill according to Figure 4.22.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
73
FIGURE 4.23
Finished mounting
brackets.
FIGURE 4.24
Mounting brackets
fastened to the body.
Amphibionics 04 3/24/03 8:23 AM Page 73
Use hot glue to fasten one of the 1/4-inch diameter plastic feet,
marked as I in Figure 4.22,to the end of piece G,Do the same for
pieces H and J,The finished leg stops are shown in Figure 4.25,
and will be used to stop the legs from overtravelling when assem-
bled later.
Using the 1/2-inch aluminum stock,cut and drill 10 pieces
labeled K,L,M,N,O,P,Q,R,S,and T,as shown in Figure 4.26.
Cut two pieces of 1/16-inch aluminum to a size of 1-1/2 inches
H11003 2 inches,Photocopy the image in Figure 4.27 onto a sheet of
paper and use the enlarge feature until the dotted outline is
exactly 1-1/2 inches H11003 2 inches,Another method is to scan the
image into your computer and use a graphics editor program to
make the enlargement and then print the image,Cut the images
out and glue them to the aluminum pieces,Use a metal cutting
band saw or a hack saw to cut the aluminum along the guide
lines,Once the cuts have been made,bend the top part of the
pieces upward,along the dotted lines,on 90-degree angles,as
shown in Figure 4.29,These two pieces are the frog’s feet and
will be attached to pieces S and T.
Amphibionics
74
FIGURE 4.25
Cut and drilled leg
stops.
Amphibionics 04 3/24/03 8:23 AM Page 74
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
75
FIGURE 4.26
Cutting and drilling
guide for robotic frog
leg pieces.
Amphibionics 04 3/24/03 8:23 AM Page 75
Attach the assembled leg stops (pieces G and H) to pieces L and K
using two 6/32-inch H11003 3/4-inch machine screws,lock washers,
and nuts,as shown in Figure 4.28,These assemblies will be part
of the robot’s leg-jumping mechanism.
Use hot glue to attach the robot’s feet pieces U and V to pieces S
and T on the sloped ends,Figure 4.29 shows the feet pieces,U
and V,attached to lower leg pieces S and T.
Amphibionics
76
FIGURE 4.27
Cutting guide for robotic
frog’s feet.
FIGURE 4.28
Assembled leg stops.
Amphibionics 04 3/24/03 8:23 AM Page 76
Assembling the Legs
Now that all of the individual leg pieces have been fabricated,it is
time to assemble the legs,Starting with the frog’s right leg,refer to
Figure 4.34 for overall parts placement,Place the part labeled L
on a table and place a nylon washer over the 5/32-inch drill hole
at the sloped end of the piece,Place the part labeled N on top and
place another nylon washer on top of part N,lining up the holes.
Next,place the part labeled P on top of the washer and insert a
6/32-inch H110033/4-inch machine screw through all three pieces and
the nylon washers,Figure 4.30 is an exploded view,illustrating
how the parts are assembled,The nylon washers separating parts
L,N,and P act as bearings,Secure in place with a 6/32-inch lock-
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
77
FIGURE 4.29
Feet attached to lower
leg pieces S and T.
Amphibionics 04 3/24/03 8:23 AM Page 77
ing nut,Tighten the nut with enough torque to hold the parts in
place,but allowing them to move freely,Figure 4.31 shows the
assembled parts,Take pieces R and T and assemble with piece R
underneath T,placing a nylon washer between the two pieces,as
shown in Figure 4.32.
Amphibionics
78
FIGURE 4.30
Exploded-view
illustration of nylon
washer bearing
assembly.
FIGURE 4.31
Right leg subassembly
made up of parts L,N,
and P.
Amphibionics 04 3/24/03 8:23 AM Page 78
To complete the right leg,take the subassembly made up of pieces
L,N,and P and place it on top of the subassembly made up of
pieces R and T,with a nylon washer between each of the holes.
Secure in place with two 6/32-inch H11003 1/2-inch machine screws
and locking nuts,Tighten the nuts with enough torque to hold the
parts in place,but allowing them to move freely,Refer to Figure
4.33 to see what the finished leg should look like.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
79
FIGURE 4.32
Lower right leg
assembly made up of
parts R and T.
Amphibionics 04 3/24/03 8:23 AM Page 79
To assemble the left leg,refer to Figure 4.34 for overall parts
placement,Place the part labeled K on a table and place a nylon
washer over the drill hole at the sloped end of the piece,Place the
part labeled M on top and place another nylon washer on top of
part M,lining up the holes,Next,place the part labeled O on top
of the washer and insert a 6/32-inch H11003 3/4-inch machine screw
through all three pieces and the nylon washers,The nylon wash-
ers separating parts K,M,and O act as bearings,Secure in place
with a 6/32-inch locking nut,Tighten the nut with enough torque
to hold the parts in place,but allowing them to move freely,Take
pieces Q and S and assemble with piece Q underneath S,placing
a nylon washer between the two pieces.
To complete the right leg,take the subassembly made up of pieces
K,M,and O and place it on top of the subassembly made up of
pieces Q and S,with a nylon washer between each of the holes.
Secure in place with two 6/32-inch H11003 1/2-inch machine screws
Amphibionics
80
FIGURE 4.33
Assembled right leg.
Amphibionics 04 3/24/03 8:23 AM Page 80
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
81
FIGURE 4.34
Parts placement
diagram for right and
left legs.
Amphibionics 04 3/24/03 8:23 AM Page 81
and locking nuts,Tighten the nuts with enough torque to hold the
parts in place,but allowing them to move freely,The left leg is
identical to the right leg,with the only difference being that the
parts placement is a mirror of the right leg.
Attaching the Legs to the Robot’s Body
Now that both the right and left legs have been constructed,it is
time to attach them to the robot’s body,Starting with the right leg,
attach leg piece R to body mounting bracket B,and leg piece L to
body mounting bracket D,with two 6/32-inch H11003 1/2-inch
machine screws and locking nuts with nylon washers separating
each piece,as shown in Figure 4.35,Tighten the nuts with enough
torque to hold the parts in place,but allowing them to move freely.
Amphibionics
82
FIGURE 4.35
Right leg attached to
the robot’s mounting
brackets.
Amphibionics 04 3/24/03 8:23 AM Page 82
Take the left leg and attach leg piece Q to body mounting bracket
A,and leg piece K to body mounting bracket C,with two 6/32-inch
H11003 1/2-inch machine screws and locking nuts with nylon washers
separating each piece,Tighten the nuts with enough torque to hold
the parts in place,but allowing them to move freely,Refer to Figure
4.24and Figure 4.34for identification of parts,Figure 4.36shows
the left and right legs attached to the mounting brackets.
The next step is to attach the leg springs,Cut two springs with a
diameter of 3/8-inch to a length of 5/8-inch,like the one shown in
Figure 4.37,Attach one end of each of the springs to leg pieces L
and K,and the other ends to the robot’s body,as shown in Figure
4.38,Make sure that the springs fit snugly so that they do not fall
loose when the legs are retracted.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
83
FIGURE 4.36
Right and left legs
attached to the robot
body.
Amphibionics 04 3/24/03 8:23 AM Page 83
Fabricating the Servo Mounts
Use 1/16-inch thick aluminum to create two servo mounts,as
detailed in Figure 4.39,Use a 5/32-inch bit to drill the holes,Once
the pieces have been cut and drilled,bend the pieces,as shown by
the arrows in Figure 4.39,Use a table vise or the edge of a table
to bend the pieces,Figure 4.40 shows a finished servo mount.
Amphibionics
84
FIGURE 4.37
Spring used for the
right and left legs.
FIGURE 4.38
Spring attached to the
robot’s leg and body.
Amphibionics 04 3/24/03 8:23 AM Page 84
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
85
FIGURE 4.39
Cutting,bending,and
drilling guide for the
servo mounts.
FIGURE 4.40
Finished servo mount.
Amphibionics 04 3/24/03 8:23 AM Page 85
To fabricate the two servo horn spring-loading mechanisms,take
a piece of the 1/2-inch aluminum stock and cut two pieces to a
length of 2 inches each,Cut and drill the pieces,as shown in
Figure 4.41,The finished pieces should resemble the one shown
in Figure 4.42,Modify two servo horns so that they resemble the
one shown in Figure 4.42,This is accomplished by cutting two of
the cross pieces off with a pair of side cutters,and then lining up
the middle hole of the servo horn with the middle hole in piece W
or X,When the middle holes are lined up,mark the area where the
5/32-inch holes line up,Use a 5/32-inch bit to drill on the mark-
ings so that the finished horn looks like the one in Figure 4.42.
Attach one of the modified servo horns to piece W with two 6/32-
inch H110031/2-inch machine screws and locking nuts,Attach the sec-
ond servo horn to piece X,also using two 6/32-inch H11003 1/2-inch
machine screws and locking nuts,Insert two 6/32-inch H11003 3/4-
inch machine screws through the two outer holes of piece W,and
secure in place with two lock washers and nuts,Do the same for
piece X,One of the finished spring-loading mechanisms is shown
in Figure 4.43,and can be used as a guide.
Amphibionics
86
FIGURE 4.41
Cutting and drilling
guide for spring-loading
mechanism.
Amphibionics 04 3/24/03 8:23 AM Page 86
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
87
FIGURE 4.42
Spring-loading
mechanism and
modified servo horn.
FIGURE 4.43
Finished spring-loading
mechanism.
Amphibionics 04 3/24/03 8:23 AM Page 87
Take the two completed spring-loading mechanisms and attach
each one to a servo that has been modified for continuous rota-
tion,Use the servo screw that came with the servo horn to secure
the mechanism in place on the servo shaft,as shown in Figure
4.44.
Take one of the servos with the spring-loading mechanism
attached and secure it to a servo mount,using four 6/32-inch H11003
1/2-inch machine screws,lock washers,and nuts,Attach the sec-
ond servo to the second servo mount,also using four 6/32-inch H11003
1/2-inch machine screws,lock washers,and nuts,but note that
the servo is attached so that it mirrors the first one,as shown in
Figure 4.45.
Attach the servo mounts to the frog’s body using four 6/32-inch H11003
1/2-inch machine screws,lock washers,and nuts,The servo
Amphibionics
88
FIGURE 4.44
Spring-loading
mechanism attached to
a modified servo.
Amphibionics 04 3/24/03 8:23 AM Page 88
mounts should be positioned with the servo shaft closest to the
frog’s head,Figure 4.46 illustrates the proper orientation of the
servo mounts on the frog’s body.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
89
FIGURE 4.45
Servos attached to
servo mounts,Note the
mirrored configuration.
FIGURE 4.46
Servo mounts attached
to the frog’s body.
Amphibionics 04 3/24/03 8:24 AM Page 89
Constructing the Front Legs
Cut two front leg pieces to a length of 4 inches,using the 1/2-inch
aluminum,Use Figure 4.47 as a guide to cut,drill,and bend the
aluminum,Attach the finished legs to the robot’s body,using two
6/32-inch H110031/2-inch machine screws,lock washers,and nuts,as
shown in Figure 4.48.
Amphibionics
90
FIGURE 4.47
Cutting,drilling,and
bending guide for the
front legs.
FIGURE 4.48
Front legs attached to
the robot’s body.
Amphibionics 04 3/24/03 8:24 AM Page 90
Leg Position Sensors
The leg position sensors are limit switches that will determine
when the legs are set to their jumping position,at which point the
spring mechanism is fully loaded,This information will be used by
the microcontroller to coordinate the legs for jumping,To attach
the limit switches,manually rotate each servo by hand so that the
spring is fully loaded toward the top of the spring-loading mecha-
nism’s travel,as shown in Figure 4.49,While maintaining this
position,use hot glue to fix the limit switch to part E so that the
switch is triggered,as shown in Figure 4.49,Do the same for the
other leg,attaching the second limit switch to part F.
Wiring the Limit Switches
Cut a piece of 2-strand connector wire to a length of 6 inches and
solder the wire to connect the two limit switches,as shown in
Figure 4.50,Cut another piece of the 2-strand connector wire to
a length of 3-1/2 inches,Solder one end of each wire to a 2-post
female header connector,and the opposite ends to the left leg limit
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
91
FIGURE 4.49
Limit switch hot glued
to part E.
Amphibionics 04 3/24/03 8:24 AM Page 91
switch,as shown in Figure 4.50,The header will be plugged into
the H110015 VDC and the GND connector on the main controller circuit
board later in the chapter.
Next,cut two single-strand connector wires to a length of 5-1/2
inches,Solder one end of each wire to a single-post female head-
er connector,and the other end of each wire to the left and right
limit switches,as shown in Figure 4.50,The limit switch connec-
tors will eventually be attached to microcontroller inputs,Figure
4.51 shows the connectors wired to the limit switches.
Fabricate a 6-volt battery pack holder using 1/16-inch thick alu-
minum by following the cutting,drilling,and bending guide shown
in Figure 4.52,When the battery pack holder is finished,attach it
to the robot’s body using a 6/32-inch H11003 1/2-inch machine screw,
lock washer,and nut,Figure 4.53 shows the completed battery
pack holder fastened to the robot’s body.
At this point,the robot’s mechanical construction is complete,The
next section of Chapter 4 will focus on the electronics.
Amphibionics
92
FIGURE 4.50
Limit switch wiring
diagram.
Amphibionics 04 3/24/03 8:24 AM Page 92
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
93
FIGURE 4.51
Limit switches wired to
connectors.
FIGURE 4.52
Cutting,drilling,and
bending guide for the
battery pack holder.
Amphibionics 04 3/24/03 8:24 AM Page 93
Frogbotic’s Main Controller Board
This section focuses on the construction of the robot’s main con-
troller circuit and the fabrication of the printed circuit board (PCB).
Table 4.3 lists all of the parts necessary to build the controller
board,All of the robot’s functions are controlled by a Microchip
PIC 16F84 microcontroller,The microcontroller is an entire com-
puter on a chip,and makes it possible to eliminate a large amount
of hardware that would otherwise be required,The microcontroller
serves as the robot’s,brain,” controlling and managing all func-
tions,sensors,and reflexes,The 16F84 microcontroller that we are
using will be clocked at 4 MHz,and operates on a 5-volt DC sup-
ply,produced from a 78L05 voltage regulator,with the source
being a 6-volt battery pack,The two leg servos are also powered
by the same 6-volt DC battery pack,As you can see from the
schematic shown in Figure 4.54,the input/output (I/O) lines are
Amphibionics
94
FIGURE 4.53
Battery pack holder
fastened to the robot’s
body.
Amphibionics 04 3/24/03 8:24 AM Page 94
used as inputs and outputs to monitor the robot’s leg position limit
switches,turn on two light-emitting diodes (LEDs),and output
sound to a piezo speaker,Each of the controller board’s functions
will be covered in detail when programming the robot.
Part Quantity Description
Semiconductors
U1 1 78L05 5V regulator
U2 1 PIC 16F84 flash microcontroller mounted
in socket
Q1 1 2N3904 NPN transistor
D1 1 Red light-emitting diode
(continued on next page)
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
95
FIGURE 4.54
Frogbotic’s main
controller board
schematic.
TABLE 4.3
Parts List for
Frogbotic’s Main
Controller Board
Amphibionics 04 3/24/03 8:24 AM Page 95
Part Quantity Description
D2 1 Green light-emitting diode
Resistors
R1 1 4.7 KH9024 1/4-watt resistor
R2,R3,R4 3 1 KH9024 1/4-watt resistor
R5 1 100 H9024 1/4-watt resistor
Capacitors
C1 1 0.1 μf capacitor
C2,C3 2 22 pf
Miscellaneous
JP1–JP5,JP8 6 3-post header connector—2.5 mm spacing
JP6,JP7 4 2-post header connector—2.5 mm spacing
Battery 2 2-post header connector—2.5 mm spacing
connectors
Y1 1 4-MHz crystal
Piezo buzzer 1 Standard piezoelectric element
Battery holder 1 4-cell AA battery holder—6V output
Battery strap 1 9V-type battery strap
IC socket 1 18-pin IC socket—soldered to PC board U2
Printed circuit 1 See details in chapter.
board
Creating Frogbotic’s Printed Circuit Board
To fabricate the PCB,photocopy the artwork in Figure 4.55onto a
transparency,Make sure that the photocopy is the exact size of the
original,For convenience,you can download the file from the
Amphibionics
96
TABLE 4.3
Parts List for
Frogbotic’s Main
Controller Board
(continued)
Amphibionics 04 3/24/03 8:24 AM Page 96
author’s Web site,located at www.thinkbotics.com,and simply
print the file onto a transparency using a laser or ink-jet printer
with a minimum resolution of 600 dpi,After the artwork has been
successfully transferred to a transparency,use the techniques out-
lined in Chapter 2 to create a board,A 4-inch H11003 6-inch presensi-
tized positive copper board is ideal,When you place the trans-
parency on the copper board,it should be oriented exactly as in
Figure 4.55.
Circuit board drilling and parts placement,Use a 1/32-inch
drill bit to drill all of the component holes on the PCB,Drill the
holes for the voltage regulator (U1) with a 3/64-inch drill bit,Use
Table 4.3 and Figure 4.56 to place the parts on the component
side of the circuit board,Note that the PIC 16F84 microcontroller
(U2) is mounted in an 18-pin I.C,socket,The 18-pin socket is sol-
dered to the PC board and the PIC is inserted after it has been pro-
grammed,Use a fine-toothed saw to cut the board along the guide
lines and drill the mounting holes using a 6/32-inch drill bit.
Figure 4.57 shows the finished main controller board.
Check the finished board for any missed or cold soldered connec-
tions,and verify that all the components have been included,The
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
97
Figure 4.55
PCB foil pattern
artwork.
Amphibionics 04 3/24/03 8:24 AM Page 97
board will be tested later when programming the PIC microcon-
troller to coordinate the legs for jumping.
Fabricating the Power Connector
The next subassembly will be used to connect the battery pack to
the controller board,Table 4.4 lists the parts that will be needed.
Amphibionics
98
Figure 4.56
PCB component side
parts placement.
Figure 4.57
Parts soldered to the
finished PCB.
Amphibionics 04 3/24/03 8:24 AM Page 98
Part Quantity Description
Battery clip 1 Connects to the battery pack
2-connector 2 2.5-mm spacing
female header
Switch 1 Single-pole single-throw 2-position
toggle
Connector wire 9 inches 18-gauge wire
Battery pack 1 6V output 4-cell AA battery holder
Nylon standoffs 2 1/4-inch diameter H11003 3/8-inch in
length
6/32 nylon 2 3/4-inch in length
machine screws
6/32 nylon nuts 2 Nylon nuts
Solder the negative wire (black) of the battery clip to one of the ter-
minals of the switch,Cut two pieces of connector wire to a length
of 1 inch,Solder one end of each of the wires to each connector of
a 2-terminal female connector,Solder the other end of each wire to
each of the second 2-terminal female connectors,Cut a connector
wire to a length of 7 inches,and solder one end to the other termi-
nal of the switch,Solder the other end of the 7-inch wire to one of
the connectors of one of the 2-terminal female connectors,Solder
the positive (red) wire from the battery clip to the other terminal of
the 2-terminal female connector,Figure 4.58 shows how the bat-
tery clip,switch,and connectors are to be wired.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
99
TABLE 4.4
List of Parts Needed to
Fabricate the Power
Connector
Amphibionics 04 3/24/03 8:24 AM Page 99
Putting It All Together
Fabricate two standoffs using 1/4-inch nylon or plastic tubing cut
to a length of 3/8-inch,These will be used to raise the PCB up off
of the robot’s body when it is mounted,Place the standoffs
between the mounting holes and the circuit board and secure in
place with two 6/32-inch H11003 3/4-inch nylon machine screws and
nuts,Figure 4.60 shows the board mounted to the robot.
Follow the connection diagram in Figure 4.59 to connect all of the
individual components,The power connector cable that was just
fabricated should be connected so that the female 2-post headers
are plugged into the BT1 connectors,so that the terminals with the
Amphibionics
100
FIGURE 4.58
Finished power
connector.
Amphibionics 04 3/24/03 8:24 AM Page 100
positive (red) battery lead are connected to the top posts,The
switch is mounted in the 1/4-inch hole to the rear,right side of the
body,and the battery clip should be positioned so that it is near
the battery holder,Figure 4.61shows the power switch and the 6-
volt battery pack hooked up to the battery clip,When the servos
are plugged into the board,make sure that the yellow wires of the
servo connectors are positioned to the inside of the board and the
black wires are closest to the edge of the board,Connect the left
and right limit switches to the controller board,as indicated in
Figure 4.59,The completed frog robot is shown in Figure 4.62.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
101
FIGURE 4.59
Frogbotic component
connection diagram.
Amphibionics 04 3/24/03 8:24 AM Page 101
Amphibionics
102
FIGURE 4.60
Controller board with
connectors attached.
FIGURE 4.61
Power switch and 6-volt
battery pack.
Amphibionics 04 3/24/03 8:24 AM Page 102
Now that Frogbotic’s hardware is complete,we will focus on pro-
gramming the robot to read input from the limit switch sensors,
control the leg servos,make sounds,and turn the LEDs on and off.
Programming and Experiments
with Frogbotic
To test the main controller board,the PIC 16F84 will be pro-
grammed to flash the LEDs,make frog-like noises,and then start
rotating the servos,This will ensure that all of the components
have been correctly soldered to the board and that power has been
connected,The first program is called frog-test.basand is listed in
Program 4.1,Type the program into your favorite text editor and
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
103
FIGURE 4.62
Rear-side view of the
finished robot frog.
Amphibionics 04 3/24/03 8:24 AM Page 103
then compile the code,Program the PIC 16F84,as detailed in
Chapter 3,with the frog-test.hex file,listed in Program 4.2,When
the chip has been successfully programmed,insert it into the 18-
pin I.C,socket on the main controller board with the notch and pin
1 facing toward the LEDs and then apply power,If everything is
working properly,the LEDs should flash on and off while making
frog noises,When the light and sound stops,the servos should
start rotating in a forward direction toward the front of the robot.
If the servos are rotating in the opposite direction,then switch the
two servo connectors on the controller board.
'------------------------------------------------------------------------------------------------------------------------------
' Name,Frog-test.bas
' Compiler,PicBasic Pro MicroEngineering Labs
' Notes,Program to test the main controller
',board by flashing LEDs,producing
',sounds and slowly rotating the servos
'------------------------------------------------------------------------------------------------------------------------------
' set porta to inputs
trisa = %11111111
' set portb pins 2 & 3 to inputs
trisb = %00001100
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
servo_pos_l VAR BYTE
servo_pos_r VAR BYTE
timer1 VAR BYTE
timer2 VAR BYTE
timer3 VAR BYTE
temp1 VAR BYTE
servo_r VAR PORTB.5
servo_l VAR PORTB.6
switch_r VAR PORTA.4
Amphibionics
104
PROGRAM 4.1
frog-test.bas program
listing
Amphibionics 04 3/24/03 8:24 AM Page 104
switch_l VAR PORTA.3
led_l VAR PORTB.1
led_r VAR PORTB.0
piezo VAR PORTB.4
'------------------------------------------------------------------------------------------------------------------------------
low servo_l
low servo_r
start:
for temp1 = 1 to 10
SOUND piezo,[80,4,100,2]
low led_l
low led_r
pause 50
high led_l
high led_r
next temp1
SOUND piezo,[100,4,120,2,80,2,90,2]
low led_l
low led_r
rotate:
servo_pos_r = 170
gosub right_servo
servo_pos_l = 130
gosub left_servo
goto rotate
'------------------------------------------------------------------------------------------------------------------------------
' subroutines to set servos
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
105
PROGRAM 4.1
frog-test.bas program
listing (continued)
Amphibionics 04 3/24/03 8:24 AM Page 105
both_servo,
for timer1 = 1 to 15
pulsout servo_l,servo_pos_l
pulsout servo_r,servo_pos_r
pause 6
next timer1
return
left_servo:
for timer2 = 1 to 10
pulsout servo_l,servo_pos_l
pause 6
next timer2
return
right_servo
for timer3 = 1 to 10
pulsout servo_r,servo_pos_r
pause 6
next timer3
return
end
:100000007B28A0003B200C080D04031976287020E3
:1000100084132008800664000D280E288C0A03191A
:100020008D0F0B28800676288F0022088400200977
:100030003C2084138F0803197628F03091000E08B5
:1000400080389000F03091030319910003198F0359
:10005000031976282B283F2003010C1820088E1F37
:1000600020088E0803190301900F382880061F28E6
:10007000392800002228FF3A8417800576280D08C9
:100080000C0403198C0A80300C1A8D060C198D068D
:100090008C188D060D0D8C0D8D0D76288F018E0020
:1000A000FF308E07031C8F07031C762803308D005A
:1000B000DF305C2050288D01E83E8C008D09FC303B
:1000C000031C65288C07031862288C0764008D0FB9
Amphibionics
106
PROGRAM 4.1
frog-test.bas program
listing (continued)
PROGRAM 4.2
frog-test.hex program
listing
Amphibionics 04 3/24/03 8:24 AM Page 106
:1000D00062280C186B288C1C6F2800006F28080001
:1000E0008C098D098C0A03198D0A080083130313E8
:1000F0008312640008008316FF3085000C308600F0
:100100008312061383160613831286128316861231
:1001100083120130A60064000B3026020318B028B9
:100120000630A2001030A00050308E0004301420A1
:1001300064308E00023014208610831686108312DD
:10014000061083160610323083124E208614831652
:10015000861083120614831606108312A60F8B28AE
:100160000630A2001030A00064308E00043014204D
:1001700078308E000230142050308E00023014206F
:100180005A308E0002301420861083168610831297
:100190000610831606108312AA30A50000218230B3
:1001A000A400ED20CC280130A70064001030270205
:1001B0000318EC2824088C008D01063084004030A0
:1001C000012025088C008D0106308400203001209C
:1001D00006304E20A70FD52808000130A800640083
:1001E0000B3028020318FF2824088C008D010630EC
:1001F00084004030012006304E20A80FEF28080070
:100200000130A90064000B302902031812292508C7
:100210008C008D01063084002030012006304E20F5
:0A022000A90F02290800630013294A
:02400E00F53F7C
:00000001FF
The next experiment will be to read the limit switches,and then
turn on the corresponding LED when a limit switch has been acti-
vated,Compile the limit-switch.basprogram listed in Program 4.3,
and then program the PIC 16F84 with the limit-switch.hex listed in
Program 4.4,Insert the PIC into the 18-pin socket on the con-
troller board and turn on the power,Use your finger to activate the
left limit switch,When the switch is activated,the left LED should
turn on,If the right LED turns on when the left switch is activat-
ed,then switch the pins that the limit switches are attached to on
the controller board,Try the same procedure with the right limit
switch,If the LEDs do not react when the switches are triggered,
then go back and check the wiring.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
107
PROGRAM 4.2
Frog-test.hex program
listing (cotinued).
Amphibionics 04 3/24/03 8:24 AM Page 107
'------------------------------------------------------------------------------------------------------------------------------
' Name,Limit-switch.bas
' Compiler,PicBasic Pro MicroEngineering Labs
' Notes,Program to monitor the status of the leg
',position limit switches and turn on the
',corresponding LED when triggered
'------------------------------------------------------------------------------------------------------------------------------
' set porta to inputs
trisa = %11111111
' set portb pins 2 & 3 to inputs
trisb = %00001100
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
servo_pos_l VAR BYTE
servo_pos_r VAR BYTE
timer1 VAR BYTE
timer2 VAR BYTE
timer3 VAR BYTE
temp1 VAR BYTE
servo_r VAR PORTB.5
servo_l VAR PORTB.6
switch_r VAR PORTA.4
switch_l VAR PORTA.3
led_l VAR PORTB.1
led_r VAR PORTB.0
piezo VAR PORTB.4
low servo_l
low servo_r
'------------------------------------------------------------------------------------------------------------------------------
start:
Amphibionics
108
PROGRAM 4.3
limit-switch.bas program
listing
Amphibionics 04 3/24/03 8:24 AM Page 108
for temp1 = 1 to 5
SOUND piezo,[80,4,100,2]
low led_l
low led_r
pause 50
high led_l
high led_r
next temp1
SOUND piezo,[100,4,120,2,80,2,90,2]
low led_l
low led_r
right:
if switch_r = 1 then
high led_r
else
low led_r
endif
left:
if switch_l = 1 then
high led_l
else
low led_l
endif
goto right
end
:1000000061288F00220884002009282084138F088B
:1000100003195C28F03091000E0880389000F03011
:1000200091030319910003198F0303195C28182801
:100030002B2003010C1820088E1F20088E0803199E
:100040000301900F252880060C28262800000F2881
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
109
PROGRAM 4.3
limit-switch.bas program
listing (continued)
PROGRAM 4.4
limit-switch.hex program
listing
Amphibionics 04 3/24/03 8:24 AM Page 109
:10005000841780055C280D080C0403198C0A803075
:100060000C1A8D060C198D068C188D060D0D8C0D35
:100070008D0D5C288F018E00FF308E07031C8F07CB
:10008000031C5C2803308D00DF3048203C288D01A4
:10009000E83E8C008D09FC30031C51288C070318A6
:1000A0004E288C0764008D0F4E280C1857288C1C86
:1000B0005B2800005B28080083130313831264008D
:1000C00008008316FF3085000C308600831206136B
:1000D000831606138312861283168612831201304A
:1000E000A600640006302602031896280630A200F7
:1000F0001030A00050308E000430012064308E009B
:100100000230012086108316861083120610831693
:100110000610323083123A2086148316861083121A
:100120000614831606108312A60F71280630A2004B
:100130001030A00064308E000430012078308E0032
:100140000230012050308E00023001205A308E00E3
:100150000230012086108316861083120610831643
:10016000061083126400051EBA28061483160610B2
:100170008312BE2806108316061083126400851DA4
:10018000C6288614831686108312CA288610831602
:0A01900086108312B2286300CB280A
:02400E00F53F7C
:00000001FF
Now that everything is running correctly,it is time to put all of the
individual pieces of software together into one program that will
allow the frog robot to jump in a coordinated manner,The pro-
gram will start by monitoring the limit switches that determine
when the legs’ spring-loading mechanisms are set in the proper
position,If the limit switches are not triggered,then the program
will command the servos to rotate forward until both legs are set.
When both legs are in position,the servos are paused for a
moment and then both are commanded to rotate forward at the
same time,The spring mechanisms then let go,and the energy
stored in the springs forces each leg down quickly,causing the
frog’s body to leap forward off the ground,Because it is impossi-
ble to get the two legs perfectly coordinated when the mechanism
Amphibionics
110
PROGRAM 4.4
limit-switch.hex program
listing (continued)
Amphibionics 04 3/24/03 8:24 AM Page 110
lets go,the robot does not always leap forward,This introduces an
interesting random element,and this is the key to actually con-
trolling the robot’s in-flight direction,If you want to add sensors
and direction control to the robot,try writing a routine that will let
one of the legs release,and wait for a predetermined amount of
time before letting the other leg go,These values could be depend-
ent on the information that the microcontroller receives from the
sensor input,Compile frogbotic.bas listed in Program 4.5,and
then program the PIC 16F84 with the frogbotic.hex file listed in
Program 4.6,Insert the PIC 16F84 into the 18-pin socket on the
controller board,Place the robot on a flat surface and turn on the
power,Note that the robot should not be used on hardwood or
other types of flooring that scratches easily.
'------------------------------------------------------------------------------------------------------------------------------
' Name,Frogbotic.bas
' Compiler,PicBasic Pro MicroEngineering Labs
' Notes,Program to coordinate the jumping of
',a robotic frog
'------------------------------------------------------------------------------------------------------------------------------
' set porta to inputs
trisa = %11111111
' set portb pins 2 & 3 to inputs
trisb = %00001100
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
servo_pos_l VAR BYTE
servo_pos_r VAR BYTE
timer1 VAR BYTE
timer2 VAR BYTE
timer3 VAR BYTE
temp1 VAR BYTE
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
111
PROGRAM 4.5
frogbotic.bas program
listing
Amphibionics 04 3/24/03 8:24 AM Page 111
servo_r VAR PORTB.5
servo_l VAR PORTB.6
switch_r VAR PORTA.4
switch_l VAR PORTA.3
led_l VAR PORTB.1
led_r VAR PORTB.0
piezo VAR PORTB.4
low servo_l
low servo_r
'------------------------------------------------------------------------------------------------------------------------------
start:
for temp1 = 1 to 5
SOUND piezo,[80,4,100,2]
low led_l
low led_r
pause 50
high led_l
high led_r
next temp1
SOUND piezo,[100,4,120,2,80,2,90,2]
low led_l
low led_r
right:
if switch_r = 1 then
high led_r
servo_pos_r = 158
gosub right_servo
else
low led_r
servo_pos_r = 200
gosub right_servo
Amphibionics
112
PROGRAM 4.5
frogbotic.bas program
listing (continued)
Amphibionics 04 3/24/03 8:24 AM Page 112
endif
left:
if switch_l = 1 then
high led_l
servo_pos_l = 152
gosub left_servo
else
low led_l
servo_pos_l = 100
gosub left_servo
endif
if switch_l = 1 and switch_r = 1 then
for temp1 = 1 to 6
servo_pos_l = 150
servo_pos_r = 159
gosub both_servo
next temp1
servo_pos_l = 100
servo_pos_r = 200
gosub both_servo
endif
goto right
'------------------------------------------------------------------------------------------------------------------------------
' subroutines to set servos
both_servo,
for timer1 = 1 to 15
pulsout servo_l,servo_pos_l
pulsout servo_r,servo_pos_r
pause 6
next timer1
return
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
113
PROGRAM 4.5
frogbotic.bas program
listing (continued)
Amphibionics 04 3/24/03 8:24 AM Page 113
left_servo:
for timer2 = 1 to 10
pulsout servo_l,servo_pos_l
pause 6
next timer2
return
right_servo
for timer3 = 1 to 10
pulsout servo_r,servo_pos_r
pause 6
next timer3
return
end
:100000009728A4003B200C080D04031992288C208B
:1000100084132408800664000D280E288C0A031916
:100020008D0F0B28800692288F0026088400240953
:100030003C2084138F0803199228F03091000E0899
:1000400080389000F03091030319910003198F0359
:10005000031992282B283F2003010C1824088E1F17
:1000600024088E0803190301900F382880061F28E2
:10007000392800002228FF3A8417800592280D08AD
:100080000C0403198C0A80300C1A8D060C198D068D
:100090008C188D060D0D8C0D8D0D92288F018E0004
:1000A000FF308E07031C8F07031C922803308D003E
:1000B000DF305C2050288D01E83E8C008D09FC303B
:1000C000031C65288C07031862288C0764008D0FB9
:1000D00062280C186B288C1C6F2800006F28080001
:1000E0008D018F018E000230752894000F080D02DB
:1000F000031D7C280E080C0204300318013003197C
:1001000002301405031DFF3092280038031DFF3014
:100110000405031DFF3092288C098D098C0A0319F0
:100120008D0A0800831303138312640008008316EA
:10013000FF3085000C3086008312061383160613E9
:10014000831286128316861283120130AA0064007D
Amphibionics
114
PROGRAM 4.5
frogbotic.bas program
listing (continued)
PROGRAM 4.6
frogbotic.hex program
listing
Amphibionics 04 3/24/03 8:24 AM Page 114
:1001500006302A020318CC280630A6001030A4006E
:1001600050308E000430142064308E000230142091
:1001700086108316861083120610831606103230FE
:1001800083124E208614831686108312061483165B
:1001900006108312AA0FA7280630A6001030A4006C
:1001A00064308E000430142078308E000230142029
:1001B00050308E00023014205A308E00023014204D
:1001C000861083168610831206108316061083127B
:1001D0006400051EF32806148316061083129E3051
:1001E000A9006621FA280610831606108312C8306B
:1001F000A90066216400851D0529861483168610D2
:1002000083129830A80053210C298610831686107B
:1002100083126430A80053210030851901308C000E
:10022000013070209E000030051A01308C00013032
:100230007020A0001E08840020088520A000A100D6
:10024000640020082104031938290130AA00640041
:1002500007302A02031833299630A8009F30A900DE
:100260003921AA0F27296430A800C830A9003921F4
:10027000E8280130AB00640010302B02031852292B
:1002800028088C008D0106308400403001202908A8
:100290008C008D01063084002030012006304E2075
:1002A000AB0F3B2908000130AC0064000B302C027E
:1002B0000318652928088C008D0106308400403021
:1002C000012006304E20AC0F552908000130AD004A
:1002D00064000B302D020318782929088C008D0149
:1002E000063084002030012006304E20AD0F6829F2
:0602F000080063007929FB
:02400E00F53F7C
:00000001FF
All of the code above can be downloaded from the ThinkBotics
Web site located at,www.thinkbotics.com,More Frogbotic exper-
iments will be explored later in the book,Have fun experimenting
with the frog,and don’t be afraid to modify and improve the
designs however you see fit,Figure 4.63 shows Frogbotic leaping
from one leg.
Chapter 4 / Frogbotic,Build Your Own Robotic Frog
115
PROGRAM 4.6
frogbotic.hex program
listing (continued)
Amphibionics 04 3/24/03 8:24 AM Page 115
Amphibionics
116
FIGURE 4.63
Frogbotic leaping from
one leg.
Amphibionics 04 3/24/03 8:24 AM Page 116
117
Snakes
Snakes are characterized by a long,slender body covered in over-
lapping scales,There are approximately 2,800 species of snakes,
most of which are nonvenomous and do not harm humans,They
have no limbs or external ears,Snakes possess a backbone and
ribs that may number in the hundreds,The eyelids do not move,
but are fused to form transparent spectacles,The jaws of the
mouth are not fused,which gives the snake the ability to open its
mouth wide,This allows snakes to eat prey that are much bigger
in diameter than they are,After the snake has swallowed,the
bulge of the newly eaten animal can be seen before the snake’s
digestive process breaks it down,The snake’s forked tongue is
completely retractable,The snake’s organs,such as the heart and
stomach,are long and narrow,Only one lung is functional,with
the left lung being unusable or missing entirely,Some primitive
snakes have teeth only in one jaw,while the egg-eaters have no
teeth at all.
Most snakes achieve locomotion by slithering along an S-shaped
path,On land,a snake presses down and pushes forward from the
Serpentronic,
Build Your Own
Robotic Snake
5
Amphibionics 05 3/24/03 8:43 AM Page 117
Copyright 2003 by The McGraw-Hill Companies,Inc,Click Here for Terms of Use.
curve of its body,The same slithering action also works well in the
water,Sidewinders live much of their lives on sand,These snakes
have developed a sideways movement because the sand slips
away under them if they try to slither,A sidewinder throws a loop
of its body forward,It then shifts its weight,raises its head and
tail,and catches up to itself,Snakes move relatively slowly,and
could not keep up with a person walking at a normal pace,which
is about 4 miles per hour,The scales on a snake’s body give them
better traction as they slide along,They use rippling muscles in
their bellies to shift their wide scales on edge,The edges catch on
the ground and allow the snake to pull itself along.
The snake and its method of locomotion are the inspiration for the
robot in this chapter,Figure 5.1 shows a typical snake (Northern
Death Adder),along with its biologically inspired robotic counter-
part,The robot snake measures 28 inches in length,from head to
tail,and is 2-1/2 inches wide,Figure 5.2 illustrates the size of the
snake relative to a human.
Amphibionics
118
FIGURE 5.1
A snake and its
biologically inspired
robotic counterpart.
Amphibionics 05 3/24/03 8:43 AM Page 118
Overview of the Serpentronic Project
The robot snake that will be built and programmed in this chapter
consists of six segments and a head,with each segment being
powered by an R/C servo,The segments alternate in orientation so
that the first segment moves in a horizontal motion and the next
segment moves in a vertical motion,This sequence repeats itself
for all six segments and the head,as shown in Figures 5.3 and
5.4,This gives the snake enough flexibility to move its body in a
number of different ways in order to achieve locomotion,in much
the same way as a biological snake,The robot is controlled by a
Microchip PIC 16F84 microcontroller,The microcontroller is used
to sequence the movement of each of the snake’s body sections via
servos,The microcontroller also monitors an infrared sensor so
that the snake will avoid obstacles as it explores.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
119
FIGURE 5.2
Robot snake showing
size in relation to its
human creator.
Amphibionics 05 3/24/03 8:43 AM Page 119
Mechanical Construction of Serpentronic
The construction of the robot snake will begin with the mechani-
cal construction of the body,head,and tail,The parts needed for
the mechanical construction are listed in Table 5.1.
Parts Quantity
1/16-inch thick aluminum stock 8-foot H11003 10-foot piece
6/32 H11003 1/2-inch machine screws 98
6/32 locking nuts 98
6/32 nylon washers 6
Standard R/C servo and hardware 6
Amphibionics
120
FIGURE 5.3
Diagram of the robot
snake’s movement
capabilities.
FIGURE 5.4
Close-up view of the
snake’s joints.
TABLE 5.1
Parts List for
Serpentronic’s
Mechanical
Construction
Amphibionics 05 3/24/03 8:43 AM Page 120
The body,head,and tail are constructed using 1/16-inch flat alu-
minum.
Constructing the Body Sections
Start by cutting six pieces of the 1/16-inch aluminum to a size of
7-1/2 inches H11003 2-1/2 inches,These pieces will be identified as
piece A of each of the six body sections,Use Figure 5.5as a guide
to cut the six pieces to the dimensions shown,When the pieces
are cut,use a 5/32-inch drill bit to drill the holes,as indicated in
the diagram,File any rough edges from the pieces,Bend each
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
121
FIGURE 5.5
Cutting,bending,and
drilling guide for body
pieces (A).
Amphibionics 05 3/24/03 8:43 AM Page 121
piece in a table vise or on the edge of a table,as indicated,Each
of the six pieces should look like the one pictured in Figure 5.6.
The next piece that will make up each of the body sections is also
cut from 1/16-inch thick aluminum,Cut six pieces to a size of 2-
1/2 inches H110035-3/4 inches each,These pieces will be identified as
piece B of each of the six body sections,Use Figure 5.7 as a guide
to cut the six pieces to the dimensions shown,When the pieces
are cut,use a 5/32-inch drill bit to drill the holes,as indicated in
the diagram,File any rough edges from the pieces,Bend each
piece in a table vise or on the edge of a table,as indicated,Each
of the six pieces should look like the one pictured in Figure 5.8.
Amphibionics
122
FIGURE 5.6
Finished body piece (A).
Amphibionics 05 3/24/03 8:43 AM Page 122
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
123
FIGURE 5.7
Cutting,bending,and
drilling guide for body
pieces (B).
FIGURE 5.8
Finished body piece (B).
Amphibionics 05 3/24/03 8:43 AM Page 123
Attach pieces A and B together using three 6/32-inch H11003 1/2-inch
machine screws and locking nuts,as shown in Figure 5.9,Note
that piece B is attached so that it is positioned on top of piece A.
Continue the above procedure until all six body segments are
completed.
Attach a standard servo to each body segment using four 6/32-
inch H110031/2-inch machine screws and locking nuts,as illustrated in
Figure 5.10,When the servo is positioned in the body segment,
the servo shaft side of the servo should be attached to piece B,as
shown in Figure 5.10,Add standard servos to the remaining body
segments using the procedure above.
Amphibionics
124
FIGURE 5.9
Completed snake body
segment made up of
pieces A and B.
Amphibionics 05 3/24/03 8:43 AM Page 124
Cut six pieces of 1/16-inch thick aluminum to a size of 4-1/4 inch-
es H110031 inch,Cut,drill,and bend each piece (C) according to Figure
5.11,The finished servo linkage pieces should resemble the one
shown in Figure 5.12.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
125
FIGURE 5.10
Standard servo
attached to body
segment.
Amphibionics 05 3/24/03 8:44 AM Page 125
Amphibionics
126
FIGURE 5.11
Cutting,bending,and
drilling guide for servo
linkage.
FIGURE 5.12
Finished servo linkage.
Amphibionics 05 3/24/03 8:44 AM Page 126
Take the circular,1-inch diameter servo horn that came with your
servo and line the middle mounting hole up with the 1/4-inch hole
in piece C (see Figure 5.11),Mark the position on the servo horn
where the two mounting holes line up,and drill them out with a
5/32-inch bit,as shown in Figure 5.13,Follow this procedure
until a total of six servo horns are complete,Mount each of the
completed servo horns to the six servo linkage pieces (marked C)
using two 6/32-inch H110031/2-inch machine screws and locking nuts
per linkage,as shown in Figure 5.14.
Cut six pieces of 1/16-inch thick aluminum to a size of 3-1/4 inch-
es H11003 1/2-inch and drill as indicated in Figure 5.15,These six
parts are identified as piece D,and are used as mechanical link-
ages to join each of the robot’s body sections,Next,cut six pieces
of 1/16-inch thick aluminum to a size of 1-1/2 inches H110031/2-inch,
identified as piece E in Figure 5.15,Drill and bend each of the six
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
127
FIGURE 5.14
Servo horn attached to
servo linkage.
FIGURE 5.13
Servo horn with
mounting holes.
Amphibionics 05 3/24/03 8:44 AM Page 127
E pieces,as shown in Figure 5.15,This part will be used to mount
the battery holders in each of the body sections of the robot.
Figure 5.16 shows a completed mechanical linkage and battery
pack mount.
Amphibionics
128
FIGURE 5.15
Construction guide for
mechanical linkage and
battery pack mount.
FIGURE 5.16
Completed pieces D
and E.
Amphibionics 05 3/24/03 8:44 AM Page 128
Take one of the 2-cell AA battery holders and drill a hole with a
5/32-inch bit,5/8 of an inch from the edge of the holder without
the battery clip connectors,as shown in Figure 5.17,Do this for
all six of the 2-cell AA battery holders,Secure part E in place with
a 6/32-inch H110031/2-inch machine screw and locking nut so that the
bent part of piece E is to the left side of the battery pack,as shown
in Figure 5.18,Do this for five of the holders,For the other hold-
er that remains,secure part E in place so that the bent tab is ori-
ented to the right,When this battery holder is connected to the tail
section,it will be fastened differently than the rest.
Now that all of the individual mechanical pieces have been con-
structed,we will build the tail and head sections and then put it
all together.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
129
FIGURE 5.17
Battery pack drilling
guide.
Amphibionics 05 3/24/03 8:44 AM Page 129
Constructing the Tail Section
The snake robot will need a tail that will be used to brace the rear
end of the body and provide friction when the robot is moving
forward and turning,as well as for the aesthetic purpose of com-
pleting the body.
The tail section is constructed using 1/16-inch thick aluminum
stock,Cut a piece 2-1/2 inches H11003 8-1/2 inches,File any rough
edges and place the piece on a table,Photocopy the cutting and
bending guide in Figure 5.19,Use the photocopier enlargement
feature so that the dimensions are exactly 2-1/2 inches H11003 8-1/2
inches,Cut the template out and use a glue stick to glue it onto the
piece of aluminum of the same size,Use a metal cutting band saw
or hacksaw to cut the piece,as shown in Figure 5.19,Drill the
mounting holes as indicated,using a 5/32-inch drill bit,Bend the
aluminum in a vise or on the edge of a table,as shown in Figure
5.19,The finished tailpiece is shown in Figure 5.20.
Amphibionics
130
FIGURE 5.18
Battery pack with
mounting piece
attached.
Amphibionics 05 3/24/03 8:44 AM Page 130
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
131
FIGURE 5.19
Cutting,drilling,and
bending guide for the
snake’s tail section.
Amphibionics 05 3/24/03 8:44 AM Page 131
Constructing the Head
The snake’s head will house the controller board that will
sequence all of the servos in each body section and will monitor
the infrared sensor,The infrared sensor will also be mounted at
the front of the head.
Cut a piece of 1/16-inch thick aluminum to a size of 3 inches H11003
6-1/4 inches,Cut,drill,and bend the piece,as shown in Figure
5.21,The finished piece,labeled G,is shown in Figure 5.22.
Amphibionics
132
FIGURE 5.20
Completed tail section.
Amphibionics 05 3/24/03 8:44 AM Page 132
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
133
FIGURE 5.21
Cutting,drilling,and
bending guide for the
bottom head piece G.
FIGURE 5.22
Finished head piece G.
Amphibionics 05 3/24/03 8:44 AM Page 133
Cut a piece of 1/16-inch thick aluminum to a size of 3 inches H110033-
3/4 inches,Cut,drill,and bend the piece,as shown in Figure 5.23.
The finished piece,labeled H,is shown in Figure 5.24.
Amphibionics
134
FIGURE 5.23
Cutting,drilling,and
bending guide for the
top head piece H.
FIGURE 5.24
Finished top head
piece H.
Amphibionics 05 3/24/03 8:44 AM Page 134
Cut two pieces of 1/16-inch aluminum to a size of 1 inch H110033-1/2
inches,Bend and drill each piece according to the dimensions
shown in Figure 5.25,These two pieces are labeled I,The finished
pieces are shown in Figure 5.26 and will be used as the side sup-
ports for the robot’s head.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
135
FIGURE 5.25
Cutting,drilling,and
bending guide for
head support pieces
labeled I.
Amphibionics 05 3/24/03 8:44 AM Page 135
Each of the four head pieces will be assembled to form the robot’s
head,Use five 6/32-inch H11003 1/2-inch machine screws and locking
nuts to assemble the head,as shown in Figure 5.27,Connect the
two pieces labeled I to the bottom head piece labeled G,When
those are secured,attach piece H to piece G,and the two pieces
labeled as I.
Amphibionics
136
FIGURE 5.26
Finished head support
pieces.
FIGURE 5.27
Completed head
assembly.
Amphibionics 05 3/24/03 8:44 AM Page 136
Assembling the Snake’s
Mechanical Structure
Now that all of the individual pieces that make up the snake’s
mechanical body have been constructed,it is time to put them all
together.
Start by connecting the servo horn linkages made up of part C and
a servo horn to each of the servos of each of the six body sections,
as shown in Figure 5.28,Place the servo horn linkage onto the
servo shaft without attaching the mounting screw,Turn the servo
by hand all the way clockwise,and check to see if it is on a 90-
degree angle from the center position,If it is not,then pull the
servo horn linkage off and reattach it to the servo shaft at 90
degrees from the middle position,Turn the servo horn linkage all
the way counterclockwise,and verify that it is also positioned on
a 90-degree angle from the center position,Attach in place with
the servo horn mounting screw that came with the servo,Follow
this procedure for each of the six body sections.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
137
FIGURE 5.28
Servo horn linkage
attached to the servo.
Amphibionics 05 3/24/03 8:44 AM Page 137
Mount the mechanical linkage piece labeled D to each of the six
body sections,as shown in Figure 5.29,This is accomplished by
lining the single hole on the end of piece D up with the single hole
on the body section (piece A) that is opposite to the servo,Secure
in place with a 6/32-inch H11003 1/2-inch machine screw and locking
nut with a 6/32-inch nylon washer between the mechanical link-
age and the body section piece,The nylon washer acts as a bear-
ing,Tighten the locking nut with enough torque to hold the parts
in place,but allowing the piece to move freely,Repeat this same
procedure for each of the six body sections.
Connecting the Body Sections,Tail,and Head
At this point in the robot snake’s construction,the serpent form
starts to take shape,As each of the sections are joined,the battery
packs will be added at the same time,since they will share the
same fastener,Start with the section that will be the tail end of the
snake,Locate the battery holder with the battery mounting con-
nector attached to the opposite side,as all the others,Pick a body
Amphibionics
138
FIGURE 5.29
Mechanical linkage
attached to body
section.
Amphibionics 05 3/24/03 8:44 AM Page 138
section and connect the battery holder,as shown in Figure 5.30.
Remove the locking nut that is connecting piece A and piece B of
the body section,Connect the battery holder,and then secure in
place with the locking nut that was just removed,This will be the
body section that will have the tail section attached to it,and will
be referred to as section 6.
Locate the tail section (piece F) and line it up to body section 6 so
that the 1/2-inch section on either side overlaps on top of the
body section by 1/2 an inch,Mark the location where the holes
line up on the body section,Remove the tailpiece,and then drill
the mounting holes marked on the body section with a 5/32-inch
bit,Secure the tail piece in place with four 6/32-inch H11003 1/2-inch
machine screws and locking nuts,as shown in Figure 5.31.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
139
FIGURE 5.30
Battery pack attached
to body section 6.
Amphibionics 05 3/24/03 8:44 AM Page 139
Locate another one of the body sections and one of the battery
holders,Attach the mechanical linkage and the battery holder to
the body section using two 6/32-inch H110031/2-inch machine screws
and locking nuts,as shown in Figure 5.32,Next,attach the servo
Amphibionics
140
FIGURE 5.31
Tail connected to the
final body section.
FIGURE 5.32
Connected body
sections with battery
holder.
Amphibionics 05 3/24/03 8:44 AM Page 140
linkage to the body section using two 6/32-inch H11003 1/2-inch
machine screws and locking washers,as shown in Figure 5.32.
Follow this same procedure for the rest of the body sections and
battery holders,Note that each alternating body section will have
the servo oriented to the snake’s right side and then to the top,as
illustrated in Figure 5.33.
The body segments alternate in orientation so that the first seg-
ment moves in a horizontal motion,and the next segment moves
in a vertical motion,This sequence repeats itself for all six seg-
ments and the head,This gives the snake enough flexibility to
move its body in a number of different ways in order to achieve
locomotion,much the same way that a biological snake does.
Attach the head to body section 1 with four 6/32-inch H11003 1/2-
inch machine screws and locking nuts,as shown in Figure 5.34.
The head should be positioned so that the 1/4-inch mounting
holes for the power switch and mode select push button are
located on the top,Now that each of the body sections,head,
and tail have been assembled,manually move each section
through its range of motion to ensure that nothing obstructs the
movement,Make any adjustments to the battery holders or
mechanical linkages,if necessary.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
141
FIGURE 5.33
Alternating servo
orientation of
connected body
sections.
Amphibionics 05 3/24/03 8:44 AM Page 141
Fabricate a 9-volt battery holder using 1/16-inch thick aluminum
cut to a size of 4 inches H110031 inch,Figure 5.35is a cutting,drilling,
and bending guide for the battery holder,When the battery hold-
er is completed,attach it to the first body section behind the head.
This is accomplished by positioning it in the top left corner of the
body section and then marking the mounting hole,Drill out the
hole in the body section with a 5/32-inch drill bit,and then mount
the battery holder,as pictured in Figure 5.36,With this finished,
the robot’s mechanical construction is complete,Next,we will
focus on fabricating the robot’s main controller and infrared sen-
sor circuit boards.
Amphibionics
142
FIGURE 5.34
Head section attached
to the robot’s body.
Amphibionics 05 3/24/03 8:44 AM Page 142
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
143
FIGURE 5.35
Cutting,bending,and
drilling guide for 9-volt
battery holder.
FIGURE 5.36
9-volt battery holder
attached to the first
body segment.
Amphibionics 05 3/24/03 8:44 AM Page 143
Serpentronic’s Main Controller Board
This section focuses on the construction of the robot’s main con-
troller circuit and the fabrication of the printed circuit board (PCB).
Table 5.2 lists all of the parts necessary to build the controller
board,All of the robot’s functions are controlled by a Microchip
PIC 16F84 microcontroller,The microcontroller is an entire com-
puter on a chip and makes it possible to eliminate a large amount
of hardware that would otherwise be required,The microcontroller
serves as the robot’s,brain,” controlling and managing all func-
tions,sensors,and reflexes,The 16F84 microcontroller that we are
using will be clocked at 4 MHz and operates on a 5-volt DC sup-
ply,produced from a 78L05 voltage regulator,with the source
being a 9-volt battery,Each of the six servos used to move the
body sections are powered by a separate 6-volt DC power source.
The 6-volt power source is made up of the individual 3-volt bat-
tery packs in each of the body sections,As you can see from the
schematic shown in Figure 5.37,the input/output (I/O) lines are
Amphibionics
144
FIGURE 5.37
Serpentronic’s main
controller board
schematic.
Amphibionics 05 3/24/03 8:44 AM Page 144
used to control the six servos,monitor the infrared sensor board,
turn on two light-emitting diodes (LEDs),and output sound to a
piezo speaker,Each of the controller board’s functions will be cov-
ered in detail when programming the robot.
Part Quantity Description
Semiconductors
U1 1 78L05 5V regulator
U2 1 PIC 16F84 flash microcontroller mounted
in socket
D1 1 Red light-emitting diode
D2 1 Green light-emitting diode
Resistors
R1 1 4.7 KH9024 1/4-watt resistor
R2,R3,R4 3 1 KH9024 1/4-watt resistor
Capacitors
C1 1 0.1 μf capacitor
C2,C3 2 22 pf
Miscellaneous
JP1–JP8 8 3-post header connector—2.5-mm spacing
JP9,JP10 2 1-post header connector—2.5-mm spacing
5-volt power 3 2-post header connector—2.5-mm spacing
Y1 1 4-MHz crystal
Piezo buzzer 1 Standard piezoelectric element
BT1 and BT2 1 4-contact terminal block
I.C,socket 1 18-pin I.C,socket—soldered to PC board U2
Printed 1 See details in chapter.
circuit board
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
145
TABLE 5.2
Parts List for
Serpentronic’s Main
Controller Board
Amphibionics 05 3/24/03 8:44 AM Page 145
Creating the Main Controller
Printed Circuit Board
To fabricate the printed circuit board (PCB),photocopy the art-
work in Figure 5.38 onto a transparency,Make sure that the pho-
tocopy is the exact size of the original,For convenience,you can
download the file from the author’s Web site,located at
www.thinkbotics.com,and simply print the file onto a transparen-
cy using a laser or ink-jet printer with a minimum resolution of
600 dpi,After the artwork has been successfully transferred to a
transparency,use the techniques outlined in Chapter 2 to create a
board,A 4-inch H11003 6-inch presensitized positive copper board is
ideal,When you place the transparency on the copper board,it
should be oriented exactly as in Figure 5.38.
Amphibionics
146
Figure 5.38
Controller board PCB
foil pattern artwork.
Amphibionics 05 3/24/03 8:44 AM Page 146
Circuit board drilling and parts placement,Use a 1/32-inch
drill bit to drill all of the component holes on the PCB,Drill the
holes for the voltage regulator (U1) with a 3/64-inch drill bit,Use
Table 5.2 and Figure 5.39 to place the parts on the component
side of the circuit board,Note that the PIC 16F84 microcontroller
(U2) is mounted in an 18-pin I.C,socket,The 18-pin socket is sol-
dered to the PC board and the PIC is inserted after it has been pro-
grammed,Use a fine-toothed saw to cut the board along the guide
lines,and drill the mounting holes using a 5/32-inch drill bit.
Figure 5.40 shows the finished main controller board.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
147
Figure 5.39
Controller board PCB
component side parts
placement.
Amphibionics 05 3/24/03 8:44 AM Page 147
Check the finished board for any missed or cold soldered con-
nections and verify that all the components have been included.
The board will be tested later when programming the PIC micro-
controller.
The Infrared Sensor Board
An infrared sensor board will be fabricated to give the snake obsta-
cle avoidance capabilities,The sensor board is comprised of an
infrared LED and a Panasonic PNA4602M IR sensor module,A sin-
gle-channel sensor is being used because the sensor board will be
mounted at the front of the robot’s movable head,The snake is able
to move its head in an arc of 180 degrees,allowing it to sense objects
in front,and to either side of its body as it explores the surrounding
environment,The sensor board schematic is shown in Figure 5.41.
Table 5.3 is a list of all the parts needed to construct the board.
The 555 timer in the circuit is used to modulate the infrared LED
at a frequency determined by C1 and R3,R3 is an adjustable 10k
Amphibionics
148
Figure 5.40
Parts soldered to the
finished PCB.
Amphibionics 05 3/24/03 8:44 AM Page 148
potentiometer that will be used to find the optimum frequency
during calibration,In our application,we will use a frequency
between 38 and 42 kHz,so that a meaningful signal will be sent
from the PNA4602 sensor module to the microprocessor.
The PNA4602M shown in Figure 5.42 is designed to detect only
infrared radiation that is modulated at 38 kHz,and rejects all other
light sources,This makes the module an ideal sensor for daylight
conditions,The features include an extension distance of 8 meters
or more,No external parts are required,and a resin filter makes
the module unsusceptible to visible light,Table 5.4 lists the
PNA4602M module’s main characteristics,The output signals
from the module will be processed and filtered by the microcon-
troller with a software routine,described later in the chapter.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
149
FIGURE 5.41
Infrared sensor board
schematic.
Amphibionics 05 3/24/03 8:44 AM Page 149
Part Quantity Description
Semiconductors
U1 1 LM 555 Timer integrated circuit
IR1 1 Panasonic PNA4602M infrared detector
modules
D1 1 Infrared light-emitting diodes
Resistors
R1 1 220 H9024 1/4-watt resistor
R2 1 1 KH9024 1/4-watt resistor
R3 1 10 KH9024-ohm adjustable potentiometer
Capacitors
C1 1,01 μfd capacitor
C2 1,2 μfd capacitor
Miscellaneous
JP1,JP2,1 3-post header connector
and JP3
Printed 1 See details in chapter.
circuit board
I.C,socket 1 8-pin I.C,socket soldered to PC board to
mount U1
Amphibionics
150
TABLE 5.3
Parts List for the
Infrared Sensor Board
Amphibionics 05 3/24/03 8:44 AM Page 150
Parameter Symbol Minimum Typical Maximum Unit
Operating Vcc 4.7 5.0 5.3 V
supply voltage
Current Icc 1.8 2.4 3.0 mA
consumption
Max,reception Lmax 8 10 m
distance
Low-level Vol 0.35 0.5 V
output voltage
High-level Voh 4.8 5.0 Vcc V
output voltage
Low-level Twl 200 400 600 μs
pulse width
High-level Twh 200 400 600 μs
pulse width
Carrier frequency Fo 38.0 kHz
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
151
FIGURE 5.42
Diagram of PNA4602M
infrared sensor module.
TABLE 5.4
Characteristics of the
PNA4602M Module
Amphibionics 05 3/24/03 8:44 AM Page 151
The sensor board works by producing modulated infrared radia-
tion with an infrared LED and using the PNA4602 module to detect
any radiation reflected from the surface of solid objects,The
PNA4602 sensor is designed to respond only to infrared that is
modulated at a frequency somewhere between 38–42 kHz,The
circuit is tuned to modulate the infrared LED at this frequency.
Depending on the proximity of the sensor to the object,a greater
or lesser number of infrared pulses will be reflected back,The
number of reflected,hits” that the sensor receives in a given time
frame allows the robot to determine how close it is to objects,The
higher the number of reflected pulses,the closer the sensor is to
the object,The output pin from the PNA4602 is connected to a
microcontroller input pin,and a software routine is used to mon-
itor the sensor,
Constructing the Infrared Sensor Circuit Board
To fabricate the PCB,photocopy the artwork in Figure 5.43 onto a
transparency,Make sure that the photocopy is the exact size of the
original,After the artwork has been successfully transferred to a
transparency,use the techniques outlined in Chapter 2 to create a
board,A 4-inch H11003 6-inch presensitized positive copper board is
ideal,When you place the transparency on the copper board,it
should be oriented so that it is exactly the same as in Figure 5.43.
Amphibionics
152
FIGURE 5.43
Infrared sensor board
PCB foil pattern
artwork.
Amphibionics 05 3/24/03 8:44 AM Page 152
Circuit board drilling and parts placement,Use a 1/32-inch
drill bit to drill all of the component holes on the PCB,Drill the
holes for the voltage regulator (U1) with a 3/64-inch drill bit,Use
Table 5.3 and Figure 5.44 to place the parts on the component
side of the circuit board,Note that the 555 timer is mounted in an
8-pin I.C,socket,The 8-pin socket is soldered to the PC board and
the 555 is inserted after the board has been soldered,Use a fine-
toothed saw to cut the board along the guide lines,and drill the
mounting holes using a 6/32-inch drill bit,Figure 5.45 shows the
finished main controller board.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
153
FIGURE 5.44
Infrared sensor board
PCB component side
parts placement.
FIGURE 5.45
Parts soldered to the
finished PCB.
Amphibionics 05 3/24/03 8:44 AM Page 153
Calibration
To calibrate the infrared sensor board,a multimeter with frequen-
cy measuring capabilities like the one shown in Figure 5.46 will
be used,Connect a 5-volt DC source to the circuit,as shown in
Figure 5.47,Connect the positive lead of the multimeter to the
point shown in Figure 5.47,and connect the common lead to the
circuit ground,Set the multimeter to read frequency,Use a small
screwdriver to adjust potentiometer R3,until a frequency of
approximately 43 kHz is displayed,This will adjust the circuit so
that the 555 timer is producing a 5-volt square wave that will
modulate the infrared LEDs at a frequency that is close to where
the PNA4602 sensor module will respond,The circuit frequency
will be fine-tuned with a software routine later in the chapter.
Amphibionics
154
FIGURE 5.46
Fluke 87 digital
multimeter with
frequency measuring
capabilities.
Amphibionics 05 3/24/03 8:44 AM Page 154
Mounting the Controller and
Infrared Sensor Board
The main controller circuit board will be mounted in the snake’s
head on three 1/4-inch diameter nylon standoffs cut to a length of
1/2-inch,Position the standoffs over the mounting holes in the
head and place the circuit board on top of the standoffs,Secure the
board in place with three 6/32-inch H11003 1-inch machine screws,
lock washers,and nuts,as shown in Figure 5.48,Table 5.5 lists
all the parts needed to mount the boards and wire the infrared
sensor to the main controller board.
Part Quantity Description
3-strand ribbon wire 1 6 inches
3-connector female header 1 2.5-mm spacing
2-connector female header 1 2.5-mm spacing
1-connector female header 1 2.5-mm spacing
Heat shrink tubing 1 3 inches
1/4-inch diameter nylon standoff 5 1/4-inch length
(continued on next page)
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
155
FIGURE 5.47
Multimeter probe
connection guide.
TABLE 5.5
List of Parts Needed to
Mount the Circuit
Boards
Amphibionics 05 3/24/03 8:44 AM Page 155
Part Quantity Description
6/32 H11003 1-inch machine screws 3
6/32 H11003 1-inch nut 3
6/32 H11003 1-inch lock washer 3
6/32 H11003 1/2-inch machine screw 2
6/32 H11003 1/2-inch locking nut 2
Cut a piece of 3-strand ribbon wire to a length of 6 inches,Strip
the ends and place a 1/2-inch length of heat-shrink tubing over
each wire,Solder the wires at one end to a 3-connector female
header and then shrink the tubing in place over the solder con-
nections,On the other end of the wire,solder a single-connector
female header to one of the outside wires,Solder a 2-connector
Amphibionics
156
TABLE 5.5
List of Parts Needed to
Mount the Circuit
Boards (continued)
FIGURE 5.48
Controller circuit board
mounted in the snake’s
head.
Amphibionics 05 3/24/03 8:44 AM Page 156
female header to the other two wires,Use a heat source to shrink
the tubing over the solder connections,The finished connector
wire should resemble the one shown in Figure 5.49.
Mount the infrared sensor board to the front of the snake’s head
on two 1/4-inch diameter nylon standoffs cut to a length of 1/4-
inch,Use two 6/32-inch H11003 1/2-inch machine screws and locking
nuts to secure the board in place,as shown in Figure 5.50,Figure
5.51 is a wiring diagram showing how the connection wire should
be attached.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
157
FIGURE 5.49
Infrared sensor
connector wire.
FIGURE 5.50
Infrared sensor board
attached to the front of
the snake’s head.
Amphibionics 05 3/24/03 8:44 AM Page 157
Wiring the Robot
Next,the 3-volt battery packs,located in each body segment will
be wired to provide 6 volts to the controller board,The 6-volt sup-
ply will be used to directly power the servos,To accomplish this,
the first two battery packs will be wired in a series to create 6
volts,The next pair of battery packs are also wired in a series to
create 6 volts,as are the last two,Each of these three pairs are
then wired in parallel so that the supply is 6 volts,but capable of
providing higher current and a longer robot operating time,This is
important since the robot will be coordinating the movement of six
servos that may all be in operation at the same time,The 9-volt
supply is from a single battery mounted in the first body segment.
This supply is used to power the controller board,The use of dual
power supplies with a robot is preferred because it provides the
Amphibionics
158
FIGURE 5.51
Infrared sensor board
connection diagram.
Amphibionics 05 3/24/03 8:44 AM Page 158
microprocessor with isolation from the noise introduced by the
direct current motors in the servos,It also allows the robot to run
for a much longer time because the microcontroller can keep oper-
ating from the 9-volt supply,even if the 6-volt supply drops down
to 4 volts,The servos are capable of operating at lower voltages,
but if the PIC’s supply drops below 5 volts,it will go into a reset-
ting loop,By powering the microcontroller with its own 9-volt
source,this problem is eliminated.
Table 5.6 is a list of all the parts needed to complete the wiring of
the robot snake.
Part Quantity Description
Connector wire 1 3 feet
Battery straps,9-volt type 7 Battery straps with 8-inch
leads
DPDT switch 1 Double-pole double-throw
switch
Push button switch 1 Momentary contact switch
12-inch servo connector 3 Male and female
extension connectors
2-connector female header 1 2.5-mm spacing
1-connector female header 1 2.5-mm spacing
1-KH9024 resistor 1 1/4-watt
Rubber grippers 14 Sticky backed nonslip
rubber
AA battery 12 1.5-volt battery
9-volt battery 1 9-volt battery
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
159
TABLE 5.6
List of Parts Required
to Wire the Robot
Amphibionics 05 3/24/03 8:44 AM Page 159
Refer to Figure 5.52 when wiring each of the 3-volt battery packs
and the 9-volt battery to the DPDT switch and the controller
board,Start by mounting the DPDT switch in one of the 1/4-inch
mounting holes on the top of the snake’s head,Wire each of the
3-volt battery packs in the body sections with the battery clips
that attach to each holder,It may be easiest to connect each of the
battery clips together before attaching them to the battery packs.
Make sure that the connections are soldered in place and that
insulating heat-shrink tubing is placed around each connection.
All of the wires should run inside the snake from one section to
another,Use the connector wire to attach the switch to the power
terminal blocks on the controller board,Place a 9-volt battery in
the battery holder that is located in the first body section behind
the head (see Figure 5.36),Attach the negative lead of the 9-volt
battery clip to the 9-volt power terminal connector on the con-
troller board,and solder the positive lead to the switch.
Amphibionics
160
FIGURE 5.52
Electrical wiring diagram
for Serpentronic.
Amphibionics 05 3/24/03 8:44 AM Page 160
Next,connect all of the servos to the robot controller board locat-
ed in the head,Figure 5.53 shows a diagram of the snake and
each servo located in each body section,along with the corre-
sponding connector on the controller board,When attaching each
servo to the connector on the controller board,the servo’s yellow
wire is always to the left,as indicated in Figure 5.53,The middle
wire is red and the wire to the right side is black,The last three
servos labeled servo 4,servo 5,and servo 6 need wire extension
connectors added so that they are long enough to reach the con-
troller board,Use 2-inch servo connector extension wires,like the
one shown in Figure 5.54.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
161
FIGURE 5.53
Servo connection
diagram.
FIGURE 5.54
Servo connector
extension wire.
Amphibionics 05 3/24/03 8:44 AM Page 161
A mode select push button will be added to the top of the robot’s
head so that different functions can be chosen when the robot
starts up,One of the main functions that the push button will
enable is calibrating the infrared sensors.
Fabricate the push button connector using a momentary contact
switch,a 1-KH9024resistor,a 2-connector female header,a 1-connec-
tor female header,some heat-shrink tubing,and three pieces of
connector wire cut to a length of 3 inches each,Use Figure 5.55
as a wiring and soldering guide when creating the connector.
When the push button assembly is finished,mount the push but-
ton in the 1/4-inch mounting hole on the snake’s head and attach
the connectors to the controller board,as shown in Figure 5.56.
Amphibionics
162
FIGURE 5.55
Mode select switch
wiring guide and
finished assembly.
Amphibionics 05 3/24/03 8:44 AM Page 162
To give the snake added friction when moving,rubber gripper
pieces can be added to the underside of the snake’s body,If you
decide not to add the rubber pieces,the robot will still function
properly,but will not move as easily on slippery surfaces like car-
pet,Any sort of rubber nonslip pieces that you can find at a hard-
ware store will be suitable,The ones that I used have a sticky back
and were meant for the bottom of Sun System computers to stop
them from slipping on a desktop,Figure 5.57 shows the positions
that worked well for me,Make sure that the movement of each
body segment is not hindered by the rubber gripper pieces.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
163
FIGURE 5.56
Mode select controller
board connection
diagram.
Amphibionics 05 3/24/03 8:44 AM Page 163
Insert two 1.5-volt,AA type batteries into each of the battery hold-
ers in each body segment,Add a 9-volt battery to the battery hold-
er in the first body segment behind the robot’s head and attach the
battery strap,The robot is now ready to test and calibrate!
Programming and Experiments
with Serpentronic
To test the main controller board,the PIC 16F84 will be pro-
grammed to flash the LEDs,make some random sounds,and cen-
ter all of the servos,This will ensure that all of the components
have been correctly soldered to the circuit board,and that the ser-
vos and batteries are all connected properly,The first program is
called snake-test.bas and is listed in Program 5.1,Type the pro-
gram into your favorite text editor,save,and then compile the pro-
gram with PicBasic Pro,using the instructions in Chapter 3.
Amphibionics
164
FIGURE 5.57
Rubber gripper pieces
added to the underside
of the snake.
Amphibionics 05 3/24/03 8:44 AM Page 164
Program the PIC 16F84 with the snake-test.hex file listed in
Program 5.2,When the chip has been successfully programmed,
insert it into the 18-pin I.C,socket on the main controller board
with the notch and pin 1 facing toward the LEDs and then turn the
power switch to the,ON” position,If everything is working prop-
erly,the LEDs should flash on and off while making random nois-
es,When the light and sound stops,the servos should all move to
the middle position,making the snake straight,If the snake is not
relatively straight,keep the power turned on and readjust each of
the servo horns so that it is straight,If nothing happens when
power is applied,then check all of the battery and circuit board
connections,Also,make sure that the PIC 16F84 was programmed
properly.
'------------------------------------------------------------------------------------------------------------------------------
' Name,Snake-test.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Program to test the main controller
',board by flashing the LEDs,producing
',sounds and setting each of the servos to
',their middle positions
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs
trisa = %00000000
' PortB set as outputs,pins 0-1 inputs
trisb = %00000011
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
led_left VAR PORTA.2
led_right VAR PORTA.3
piezo VAR PORTA.4
servo_1 VAR PORTB.2
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
165
PROGRAM 5.1
snake-test.bas program
listing
Amphibionics 05 3/24/03 8:44 AM Page 165
servo_2 VAR PORTB.3
servo_3 VAR PORTB.7
servo_4 VAR PORTB.6
servo_5 VAR PORTB.5
servo_6 VAR PORTB.4
rand VAR WORD
timer VAR BYTE
temp1 VAR BYTE
i VAR BYTE
servo1 VAR BYTE
servo2 VAR BYTE
servo3 VAR BYTE
servo4 VAR BYTE
servo5 VAR BYTE
servo6 VAR BYTE
low led_left
low led_right
Low servo1
Low servo2
Low servo3
Low servo4
Low servo5
Low servo6
'------------------------------------------------------------------------------------------------------------------------------
' create randon noises and flash LEDs
For temp1 = 1 to 7
High led_left
Low led_right
GoSub randomize
Pause 50
Low led_left
High led_right
GoSub randomize
Pause 50
Amphibionics
166
PROGRAM 5.1
snake-test.bas program
listing (continued)
Amphibionics 05 3/24/03 8:44 AM Page 166
Next temp1
Low led_right
'------------------------------------------------------------------------------------------------------------------------------
' start main execution
start:
servo1 = 150
servo2 = 150
servo3 = 150
servo4 = 150
servo5 = 150
servo6 = 150
GoSub servo
goto start
'Subroutines start here
'------------------------------------------------------------------------------------------------------------------------------
' random sound generator subroutine
randomize:
Random rand
i = rand & 31 + 64
Sound piezo,[i,4]
Return
'------------------------------------------------------------------------------------------------------------------------------
' subroutine to set servos
servo,
For timer = 1 to 20
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
167
PROGRAM 5.1
snake-test.bas program
listing (continued)
Amphibionics 05 3/24/03 8:44 AM Page 167
PulsOut servo_1,servo1
PulsOut servo_2,servo2
PulsOut servo_3,servo3
PulsOut servo_4,servo4
PulsOut servo_5,servo5
PulsOut servo_6,servo6
Pause 12
Next timer
Return
:100000009128A0003F200C080D0403198C2886209D
:1000100084132008800664000D280E288C0A03191A
:100020008D0F0B2880068C288F0022088400200961
:10003000402084138F0803198C28F03091000E089B
:1000400080389000F03091030319910003198F0359
:1000500003198C282B28552003010C1820088E1F0B
:1000600020088E0803190301900F382880061F28E6
:100070003928000022284320FF3A80054028FF3A13
:10008000841780058C28940006309419053084006C
:1000900000308A001408073982070134023404341E
:1000A000083410342034403480340D080C04031913
:1000B0008C0A80300C1A8D060C198D068C188D0652
:1000C0000D0D8C0D8D0D8C288F018E00FF308E074D
:1000D000031C8F07031C8C2803308D00DF30722037
:1000E00066288D01E83E8C008D09FC30031C7B28BE
:1000F0008C07031878288C0764008D0F78280C185B
:1001000081288C1C85280000852808008C098D0911
:100110008C0A03198D0A08008313031383126400E9
:1001200008008316850103308600831205118316AB
:1001300005118312851183168511831227083B2030
:1001400028083B2029083B202A083B202B083B207D
:100150002C083B200130AD00640008302D0203184C
:10016000C92805158316051183128511831685117B
:100170008312DB20323064200511831605118312AF
:100180008515831685118312DB2032306420AD0F74
:10019000AC2885118316851183129630A7009630FE
Amphibionics
168
PROGRAM 5.1
snake-test.bas program
listing (continued)
PROGRAM 5.2
snake-test.hex file
listing
Amphibionics 05 3/24/03 8:44 AM Page 168
:1001A000A8009630A9009630AA009630AB00963091
:1001B000AC00F020CD2824088C0025088D005520A7
:1001C0000C08A4000D08A5005F302405A60005302A
:1001D000A2001030A00026088E0004301420080071
:1001E0000130AE00640015302E02031825292708BF
:1001F0008C008D01063084000430012028088C001A
:100200008D01063084000830012029088C008D0102
:1002100006308400803001202A088C008D010630D1
:100220008400403001202B088C008D0106308400B2
:10023000203001202C088C008D0106308400103005
:0C02400001200C306420AE0FF2280800F2
:02400E00F53F7C
:00000001FF
The next program will be used to calibrate the infrared sensor so
that the robot can safely avoid obstacles,The modulation frequen-
cy of the sensor was set using a multimeter when the circuit board
was initially built,The software calibration routine will be used to
fine-tune the frequency to improve the sensor’s response,The rou-
tine works by taking the input from the sensor and then outputting
the opposite state to the LEDs,The sensor input value is inverted
before being output to the LEDs because the sensor’s output is nor-
mally logic 1 (high) when it is not receiving a signal,and switches
to a state of logic 0 (low) when a signal is received,This will allow
us to visually see how the sensor is responding to the modulated
infrared radiation,and then adjust the modulation frequency
accordingly,The program is called ircal-serpent.bas,and is listed
in Program 5.3,Program the PIC 16F84 with the corresponding
ircal-serpent.hexfile listed in Program 5.4and insert it into the 18-
pin socket on the controller board,When the power is turned on
and nothing is in front of the sensor,the LEDs should be off,To cal-
ibrate the circuit,use a small screwdriver to turn potentiometer R3
counterclockwise until the LEDs are on solid,Figure 5.58 shows
resistor R3 on the infrared circuit board being adjusted,Once the
LEDs are on solid,slowly rotate potentiometer R3 clockwise until
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
169
PROGRAM 5.2
snake-test.hex file
listing (continued)
Amphibionics 05 3/24/03 8:44 AM Page 169
the LEDs flicker and then turn off,Move your hand toward the sen-
sor,With your hand at a distance of approximately 7 inches from
the sensor,the LEDs should start to flicker,With your hand at a
distance between 5 and 6 inches,the LEDs should be turned on
solid.
'------------------------------------------------------------------------------------------------------------------------------
' Name,ircal-serpent.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Infrared sensor calibration program
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs
trisa = %00000000
' PortB set as outputs,pins 0-1 inputs
trisb = %00000011
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
Amphibionics
170
PROGRAM 5.3
ircal-serpent.bas
program listing
FIGURE 5.58
Adjusting the infrared
sensor board.
Amphibionics 05 3/24/03 8:44 AM Page 170
led_left VAR portA.2
led_right VAR portA.3
ir_input VAR portB.1
low led_left
low led_right
ir_cal,
If ir_input = 0 then
high led_left
high led_right
endif
low led_left
low led_right
goto ir_cal
end
:1000000001288316850103308600831205118316AB
:1000100005118312851183168511831264008618D9
:100020001928051583160511831285158316851168
:10003000831205118316051183128511831685110C
:0800400083120E286300222840
:02400E00F53F7C
:00000001FF
Motion Control
The next task will be to coordinate the movement of each of the
snake’s body segments to achieve locomotion,To produce a for-
ward movement,our snake will move its body in a sine wave pat-
tern vertically,with a slight side to side movement of the horizon-
tal segments,The use of servos makes this sort of programming
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
171
PROGRAM 5.3
ircal-serpent.bas
program listing
(continued)
PROGRAM 5.4
ircal-serpent.hex file
listing
Amphibionics 05 3/24/03 8:44 AM Page 171
easy because all that is needed to coordinate this pattern is to give
each of the servos two sets of movement positions,The body seg-
ments will move through the complete range of motion between the
two sets of points determined by the position values,This means
that we really only need to set the servo positions for all of the ser-
vos twice,and then repeat the pattern to get the snake to move for-
ward,The same holds true when sequencing the servos and body
segments for a left or right turning movement,Figure 5.59 shows
the pulsout values for the extreme and middle positions,along with
the microcontroller port address for each servo,This information
will be needed when putting the control program together.
To sequence the forward movement of the snake,a sine wave pat-
tern can be generated by using the servo position values shown in
Table 5.7,The servos that move the horizontal body segments
also move in a slight side to side movement to aid in locomotion.
Figure 5.60 shows the sequence that the snake’s body goes
through when moving in a forward direction,Frame number 1
shows the snake resting before the sequence begins,Frame num-
ber 2 shows the body segment positions that correspond to the
first set of positions in Table 5.7,Frame number 3 shows that the
snake’s body moves through the original position on its way to the
Amphibionics
172
FIGURE 5.59
Microcontroller port
addresses for each of
the body segment
servos.
Amphibionics 05 3/24/03 8:44 AM Page 172
second set of positions in Table 5.7,Frame number 4 shows the
body segment positions that correspond to the second set of posi-
tions in Table 5.7,When the sequence is running,the body moves
in a sine wave pattern,For the snake to continue moving forward,
this entire sequence repeats,In the control program,the servo
positions only need to be set twice,and then the sequence repeats.
If you wish to experiment,you could program sequences with
more intermediate positions for a smoother sine wave.
Body Position 1
Servo and port address Pulsout value
1—PortB.2 157
2—PortB.3 210
3—PortB.7 143
4—PortB.6 100
5—PortB.5 157
6—PortB.4 210
Body Position 2
Servo and port address Pulsout value
1—PortB.2 143
2—PortB.3 100
3—PortB.7 157
4—PortB.6 210
5—PortB.5 143
6—PortB.4 100
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
173
TABLE 5.7
Servo Position Values
to Sequence Forward
Movement of the Snake
Amphibionics 05 3/24/03 8:44 AM Page 173
To make the robot snake turn to the left,the same sine wave pat-
tern will need to occur in the vertical moving body segments,but
the snake’s body will also need to oscillate between the middle
position and a position where the body is arched to the left,The
pulsout values needed to control this movement are listed in Table
5.8,and will be used when programming the snake,Figure 5.61
shows the two positions that the snake’s body will oscillate
between to make a turn to the left,I found that the snake has the
ability to turn to the left or right much faster than it can travel in
the forward direction,Although a side-winding routine will not be
covered in this chapter,with enough experimentation,the snake
can be made to side-wind as its primary mode of locomotion.
When the snake is traveling forward and then moves quickly into
a turn,the effect is quite surprising and very lifelike.
Amphibionics
174
FIGURE 5.60
Sequence of body
positions during forward
movement.
Amphibionics 05 3/24/03 8:44 AM Page 174
Body Position 1
Servo and port address Pulsout value
1—PortB.2 150
2—PortB.3 210
3—PortB.7 150
4—PortB.6 100
5—PortB.5 150
6—PortB.4 210
Body Position 2
Servo and port address Pulsout value
1—PortB.2 100
2—PortB.3 100
3—PortB.7 100
4—PortB.6 210
5—PortB.5 100
6—PortB.4 100
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
175
TABLE 5.8
Servo Position Values
Needed to Sequence a
Left Turn
FIGURE 5.61
Sequence of body
positions during a left
turn.
Amphibionics 05 3/24/03 8:44 AM Page 175
To make the robot snake turn to the right,the same sine wave pat-
tern will need to occur in the vertical moving body segments,but
the snake’s body will also need to oscillate between the middle
position and a position where the body is arched to the right,The
pulsout values needed to control this movement are listed in Table
5.9 and will be used when programming the snake,Figure 5.62
shows the two positions that the snake’s body will oscillate
between to turn to the right,You might have noticed that when
positioning the robot’s body to the right,smaller pulsout values
were used,This is to take into account the extra weight of the ser-
vos that are positioned on the right side of the snake’s body.
Body Position 1
Servo and port address Pulsout value
1—PortB.2 150
2—PortB.3 210
3—PortB.7 150
4—PortB.6 100
5—PortB.5 150
6—PortB.4 210
Body Position 2
Servo and port address Pulsout value
1—PortB.2 190
2—PortB.3 100
3—PortB.7 190
4—PortB.6 210
5—PortB.5 190
6—PortB.4 100
Amphibionics
176
TABLE 5.9
Servo Position Values
Needed to Sequence a
Right Turn
Amphibionics 05 3/24/03 8:44 AM Page 176
Infrared Sensor
The next section outlines conditioning the input received by the
infrared sensor,The motion control algorithms and sensor input
routines will then be put together into one main control program.
The infrared software routine will need to take input from the
infrared sensor so that the robot can change its behavior to safe-
ly avoid any obstacles it may encounter while moving through its
environment,A software subroutine will be developed to monitor
the infrared sensor modules,perform signal processing to clean up
any background noise or transient signals to make the information
more useful,and then return results to the robot’s main program.
In this behavior-based method of artificial intelligence,the robot
will continue on with the dominant behavior of exploring,and will
change that course of action immediately based on sensor input.
We want the main program to call the subroutine and have the
subroutine simply return a value of either a 1 or a 0,with 0 indi-
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
177
FIGURE 5.62
Sequence of body
positions during a right
turn.
Amphibionics 05 3/24/03 8:44 AM Page 177
cating that no object was sensed and 1 indicating that an object is
present,These values will be stored in the variable object_detect.
When the program execution is returned back to the main pro-
gram,certain decisions can easily be made,based on this infor-
mation.
The infrared subroutine takes 40 samples from the module and
counts the number of positive hits received,The number of sam-
ples taken can also be configured by changing the variable
num_samples,Because of stray infrared and signals from the
environment,the module is constantly producing false positive
signals that are referred to as,noise.” The average acceptable
amount of noise picked up by the sensor module is called the noise
floor,The routine needs to set a threshold point above the typical
amount of noise and report a sensed object only if the number of
positive signals received throughout the number of samples taken
exceeds the noise floor.
With the PNA4602M sensor modules,I found that the typical false
positive was actually very low—five for every 40 samples taken,To
be on the safe side,the threshold is set at 25 for every 40 samples,
to ensure that an object is present,By changing the threshold
value,you can change the sensitivity and distance detection
response of the module,If you want a more accurate reading,the
num_samples value can be increased,but will take more time for
the routine to execute.
The last option is using the mode select push button to invoke the
infrared sensor calibration routine,This will enable the user to
simply push the button on the robot’s head to calibrate the sensor,
as described earlier,The experimenter can also develop a software
routine to use the push button to choose different modes of behav-
ior when the robot starts up,When the main software routine
senses that the button has been pushed,it goes into a tight loop
until it senses that the switch has been let up before going to the
Amphibionics
178
Amphibionics 05 3/24/03 8:44 AM Page 178
infrared calibration routine,This is so that when the program exe-
cution jumps to the calibration routine,it does not immediately
jump back to the main routine because the operator still has the
button pushed.
The main robot snake control program is called serpentronic.bas
and is listed in Program 5.5,The program operates by constantly
moving the snake in a forward direction,monitoring the infrared
sensor and then responding by turning either left or right if an
obstacle was sensed,Compile serpentronic.bas and then program
the PIC 16F84 with the serpentronic.hexfile listed in Program 5.6.
The program can be put into the infrared calibration mode by
holding down the push button.
'------------------------------------------------------------------------------------------------------------------------------
' Name,Serpentronic.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Complete control Program for the robot
',snake,Mode select push-button switch
',allows the infrared sensor to be easily
',calibrated,The robot will stop and turn
',if an obstacle is encountered,
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs
trisa = %00000000
' PortB set as outputs,pins 0-1 inputs
trisb = %00000011
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
led_left VAR PORTA.2
led_right VAR PORTA.3
piezo VAR PORTA.4
cal_switch VAR PORTB.0
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
179
PROGRAM 5.5
serpentronic.bas
program listing
Amphibionics 05 3/24/03 8:44 AM Page 179
ir_input VAR PORTB.1
servo_1 VAR PORTB.2
servo_2 VAR PORTB.3
servo_3 VAR PORTB.7
servo_4 VAR PORTB.6
servo_5 VAR PORTB.5
servo_6 VAR PORTB.4
ir_count VAR byte
temp VAR BYTE
object_detect VAR BYTE
num_samples VAR Byte
threshold VAR BYTE
rand VAR WORD
timer VAR BYTE
temp1 VAR BYTE
i VAR BYTE
look_right VAR BYTE
look_left VAR BYTE
turn_count VAR BYTE
servo1 VAR BYTE
servo2 VAR BYTE
servo3 VAR BYTE
servo4 VAR BYTE
servo5 VAR BYTE
servo6 VAR BYTE
low led_left
low led_right
Low servo1
Low servo2
Low servo3
Low servo4
Low servo5
Amphibionics
180
PROGRAM 5.5
serpentronic.bas
program listing
(continued)
Amphibionics 05 3/24/03 8:44 AM Page 180
Low servo6
turn_count = 0
num_samples = 40
threshold = 25
'------------------------------------------------------------------------------------------------------------------------------
' create randon noises and flash LED's
For temp1 = 1 to 5
High led_left
Low led_right
GoSub randomize
Pause 50
Low led_left
High led_right
GoSub randomize
Pause 50
Next temp1
Low led_right
'------------------------------------------------------------------------------------------------------------------------------
' start main execution
start:
If cal_switch = 1 then
pause 50
release_calibrate:
If cal_switch = 1 then
goto release_calibrate
else
Sound piezo,[120,4,90,2,100,2,110,4]
pause 50
goto ir_cal
endif
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
181
PROGRAM 5.5
serpentronic.bas
program listing
(continued)
Amphibionics 05 3/24/03 8:44 AM Page 181
endif
gosub infrared
if object_detect = 1 then
high led_left
high led_right
Sound piezo,[100,4,90,2]
servo1 = 180
gosub servo
servo1 = 120
gosub servo
turn_count = turn_count + 1
if turn_count.0 = 1 then
gosub slide_right
else
gosub slide_left
endif
endif
low led_left
low led_right
gosub forward
goto start
'Subroutines start here
'------------------------------------------------------------------------------------------------------------------------------
' slither forward routine in a sine wave pattern
forward:
servo1 = 157
servo2 = 210
servo3 = 143
servo4 = 100
Amphibionics
182
PROGRAM 5.5
serpentronic.bas
program listing
(continued)
Amphibionics 05 3/24/03 8:44 AM Page 182
servo5 = 157
servo6 = 210
GoSub servo
servo1 = 143
servo2 = 100
servo3 = 157
servo4 = 210
servo5 = 143
servo6 = 100
GoSub servo
return
'------------------------------------------------------------------------------------------------------------------------------
' right turn movement routine
slide_right:
For temp1 = 1 to 3
servo1 = 150
servo2 = 210
servo3 = 150
servo4 = 100
servo5 = 150
servo6 = 210
GoSub servo
servo1 = 190
servo2 = 100
servo3 = 190
servo4 = 210
servo5 = 190
servo6 = 100
GoSub servo
next temp1
return
'------------------------------------------------------------------------------------------------------------------------------
' left turn movement routine
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
183
PROGRAM 5.5
serpentronic.bas
program listing
(continued)
Amphibionics 05 3/24/03 8:44 AM Page 183
slide_left:
For temp1 = 1 to 3
servo1 = 150
servo2 = 210
servo3 = 150
servo4 = 100
servo5 = 150
servo6 = 210
GoSub servo
servo1 = 100
servo2 = 100
servo3 = 100
servo4 = 210
servo5 = 100
servo6 = 100
GoSub servo
Next temp1
return
'------------------------------------------------------------------------------------------------------------------------------
' random sound generator subroutine
randomize:
Random rand
i = rand & 31 + 64
Sound piezo,[i,4]
Return
'------------------------------------------------------------------------------------------------------------------------------
' infrared detection subroutine
infrared:
ir_count = 0
object_detect = 0
Amphibionics
184
PROGRAM 5.5
serpentronic.bas
program listing
(continued)
Amphibionics 05 3/24/03 8:44 AM Page 184
for temp = 1 to num_samples
if ir_input = 0 then
ir_count = ir_count + 1
endif
next
if ir_count >= threshold then
object_detect = 1
endif
return
'------------------------------------------------------------------------------------------------------------------------------
' subroutine to calibrate I.R,sensors
ir_cal,
If ir_input = 0 then
high led_left
high led_right
endif
low led_left
low led_right
If cal_switch = 1 then
pause 50
button_release:
If cal_switch = 1 then
goto button_release
else
Sound piezo,[120,4,90,2,100,2,110,4]
pause 50
goto start
endif
endif
goto ir_cal
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
185
PROGRAM 5.5
serpentronic.bas
program listing
(continued)
Amphibionics 05 3/24/03 8:44 AM Page 185
'------------------------------------------------------------------------------------------------------------------------------
' subroutine to set servos
servo,
For timer = 1 to 20
PulsOut servo_1,servo1
PulsOut servo_2,servo2
PulsOut servo_3,servo3
PulsOut servo_4,servo4
PulsOut servo_5,servo5
PulsOut servo_6,servo6
Pause 12
Next timer
Return
:100000009128A0003F200C080D0403198C2886209D
:1000100084132008800664000D280E288C0A03191A
:100020008D0F0B2880068C288F0022088400200961
:10003000402084138F0803198C28F03091000E089B
:1000400080389000F03091030319910003198F0359
:1000500003198C282B28552003010C1820088E1F0B
:1000600020088E0803190301900F382880061F28E6
:100070003928000022284320FF3A80054028FF3A13
:10008000841780058C28940006309419053084006C
:1000900000308A001408073982070134023404341E
:1000A000083410342034403480340D080C04031913
:1000B0008C0A80300C1A8D060C198D068C188D0652
:1000C0000D0D8C0D8D0D8C288F018E00FF308E074D
:1000D000031C8F07031C8C2803308D00DF30722037
:1000E00066288D01E83E8C008D09FC30031C7B28BE
:1000F0008C07031878288C0764008D0F78280C185B
:1001000081288C1C85280000852808008C098D0911
:100110008C0A03198D0A08008313031383126400E9
:1001200008008316850103308600831205118316AB
:100130000511831285118316851183122C083B202B
Amphibionics
186
PROGRAM 5.5
serpentronic.bas
program listing
(continued)
PROGRAM 5.6
serpentronic.hex file
listing
Amphibionics 05 3/24/03 8:44 AM Page 186
:100140002D083B202E083B202F083B2030083B2069
:1001500031083B20B6012830AA001930B400013024
:10016000B3006400063033020318CE280515831649
:100170000511831285118316851183128721323070
:1001800064200511831605118312851583168511C8
:100190008312872132306420B30FB1288511831672
:1001A000851183126400061CF32832306420640039
:1001B000061CDC28D728F3280530A2001030A00048
:1001C00078308E00043014205A308E000230142013
:1001D00064308E00023014206E308E000430142003
:1001E00032306420B3299C2164002B08013C031D9C
:1001F0001A29051583160511831285158316851195
:1002000005308312A2001030A00064308E0004304C
:1002100014205A308E0002301420B430AC00E82193
:100220007830AC00E821B60A6400361C19293F2159
:100230001A2963210511831605118312851183166E
:10024000851183122421D2289D30AC00D230AD001C
:100250008F30AE006430AF009D30B000D230B100BE
:10026000E8218F30AC006430AD009D30AE00D2305C
:10027000AF008F30B0006430B100E82108000130D9
:10028000B300640004303302031862299630AC00D6
:10029000D230AD009630AE006430AF009630B00082
:1002A000D230B100E821BE30AC006430AD00BE30C9
:1002B000AE00D230AF00BE30B0006430B100E821F3
:1002C000B30F412908000130B30064000430330249
:1002D000031886299630AC00D230AD009630AE00BF
:1002E0006430AF009630B000D230B100E821643005
:1002F000AC006430AD006430AE00D230AF0064308A
:10030000B0006430B100E821B30F6529080024086B
:100310008C0025088D0055200C08A4000D08A500B0
:100320005F302405A6000530A2001030A00026088A
:100330008E00043014200800A701AB010130B20088
:10034000640032082A02031CAB2964008618A9291C
:10035000A70AB20FA029640034082702031CB2299F
:100360000130AB00080064008618BE29051583160D
:1003700005118312851583168511831205118316C5
:100380000511831285118316851164008312061CE2
:10039000E729323064206400061CD029CB29E729E4
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
187
PROGRAM 5.6
serpentronic.hex file
listing (continued)
Amphibionics 05 3/24/03 8:44 AM Page 187
:1003A0000530A2001030A00078308E0004301420F8
:1003B0005A308E000230142064308E000230142037
:1003C0006E308E000430142032306420D228B329DD
:1003D0000130B50064001530350203181D2A2C08C1
:1003E0008C008D0106308400043001202D088C0023
:1003F0008D0106308400083001202E088C008D010C
:1004000006308400803001202F088C008D010630DA
:1004100084004030012030088C008D0106308400BB
:100420002030012031088C008D010630840010300E
:0C04300001200C306420B50FEA29080000
:02400E00F53F7C
:00000001FF
Summary
This concludes the construction and programming of the robot
snake,Much more can be done with this robot than what has been
covered,A remote control can easily be added to this project,since
there are two connectors on the controller board for this purpose.
(Chapter 12 of the first book in this series,Insectronics,has details.)
Other customizations that can be added are:
Use the infrared sensor and the snake’s head movement to
scan the area around the snake for objects,Use this informa-
tion to determine the correct path before moving.
Create a skin for the robot using a waterproof material such
as latex rubber.
Add a wireless video camera.
Develop a side-winding movement routine.
Figure out a routine that will enable the robot to move in
reverse,unlike a real snake.
Amphibionics
188
PROGRAM 5.6
serpentronic.hex file
listing (continued)
Amphibionics 05 3/24/03 8:44 AM Page 188
Add a tilt sensor so that the robot will know when it has
tipped over,and can then right itself.
Write a routine enabling the snake to roll over.
To see movies of the snake in action,go to the author’s Web site
located at www.thinkbotics.com.
Chapter 5 / Serpentronic,Build Your Own Robotic Snake
189
Amphibionics 05 3/24/03 8:44 AM Page 189
This page intentionally left blank.
191
Crocodilians
Crocodiles,alligators,and gharials are all part of a group of rep-
tiles known as the crocodilians,The bodies of animals in this
group are covered in a tough,leathery skin that is strengthened
with plates known as osteoderms,or bone skin,Crocodilians are
unable to sweat through their tough skin,They keep themselves
cool by resting with their mouths open,permitting moisture to
evaporate from the mucous membranes,Although modern croco-
dilians have an almost primeval appearance,they are actually
quite advanced,possessing an elaborate,four-chambered heart
similar to that of a mammal,It is generally accepted by biologists
that birds,rather than other reptiles,are the nearest living rela-
tives of modern crocodilians,All crocodilian species,except for the
American alligator,are endangered in at least part of their ranges,
and some are threatened with extinction as a result of habitat
destruction,hunting,or pollution.
Crocodiles and their method of locomotion are the inspiration for
the robot in this chapter,Figure 6.1shows the Nile crocodile along
with its biologically inspired robotic counterpart,The robot croc-
Crocobot,Build
Your Own Robotic
Crocodile
6
Amphibionics 06 3/24/03 9:02 AM Page 191
Copyright 2003 by The McGraw-Hill Companies,Inc,Click Here for Terms of Use.
odile measures 14 inches in length from head to tail,and is 5 inch-
es wide.
Moving the body from one location to another is one of the most
important everyday tasks for animals,They must be able to move
from place to place during the activities necessary for survival.
These activities include thermoregulation,finding food,social
interactions,nesting,and escape from threats,While crocodiles
spend much of the day motionless or moving very little,it is a mis-
take to think that they are not very active,Crocodiles are capable
of moving at surprising speed when required,Crocodiles have
three basic styles of moving on land,These methods of locomotion
are usually referred to as the belly crawl,the high walk,and the
gallop,The belly crawl is very similar in form to the way that a
lizard moves,The legs are splayed out to the sides and the center
of gravity is low,The belly crawl is used on land and very shallow
water,The crocodile uses its front and hind limbs to achieve loco-
motion,The crocodile’s whole body and tail undulates rapidly
from side to side when walking,The belly crawl is probably the
Amphibionics
192
FIGURE 6.1
A crocodile and its
biologically inspired
counterpart.
Amphibionics 06 3/24/03 9:02 AM Page 192
most commonly used way in which crocodiles move around on
land,It is usually slow,although it can be modified so that the
crocodile reaches speeds of 5 to 10 kilometers per hour when
required,Although the term,belly crawl” implies a certain style of
locomotion,in reality there are several variations on this gait suit-
ed to different situations,and only at very slow speeds does the
crocodile actually crawl,as the name suggests.
The high walk and gallop are unlike a reptilian gait,The crocodile
walks more like a mammal during the high walk,The gallop is very
spectacular to watch,and propels even large crocodiles away from
potential danger at very high speeds,The robotic crocodile in this
chapter will use a method of walking on four legs where the body
is raised completely above the ground.
Overview of the Crocobot Project
The robot crocodile that will be built and programmed in this
chapter is controlled remotely by a human operator via a wireless
data link,The robot and the remote control that will be built are
shown in Figure 6.2,The wireless data is transmitted from the
controller and received by the robot using RF modules built by a
company called Linx Technologies,The robot achieves locomotion
using four legs that are driven by a twin-motor gearbox,The
geared motors operate on voltages between 3 and 6 volts,making
them perfect for small walking robots,The motors are controlled
using the L298 dual full-bridge driver,The motor driver takes its
control signals from a PIC 16F84 microcontroller,The microcon-
troller will also be used to interpret the control commands sent
from the hand held remote control,The remote control uses a PIC
16C71 microcontroller featuring four analog to digital converters.
Two of the analog to digital converters will be used to monitor the
position of the control stick on the remote control device,This is
accomplished by reading the voltages produced by the poten-
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
193
Amphibionics 06 3/24/03 9:02 AM Page 193
tiometers attached to the X and Y axis,When the position of the
control stick is determined,certain control information is trans-
mitted to the robot,Because a wireless data link is being used to
remotely control the robot,the experimenter is not limited to a
certain number of control channels,as are imposed when a regu-
lar model airplane remote control system is used,The experi-
menter has the option of adding any number of other devices.
Mechanical Construction of Crocobot
The construction of the robot crocodile will begin with the
mechanical construction of the body,head,and tail,The parts
needed for the mechanical construction are listed in Table 6.1.
Amphibionics
194
FIGURE 6.2
Crocobot with remote
control device.
Amphibionics 06 3/24/03 9:02 AM Page 194
Parts Quantity
1/16-inch thick aluminum stock 8-foot x 10-foot piece
1/4-inch H11003 1/4-inch aluminum stock 34 inches
6/32 H11003 1/2-inch machine screws 32
6/32 H11003 1-inch machine screws 2
6/32 locking nuts 34
6/32 nylon washers 14
Tamiya twin motor gear box 1
Connector wire 9 feet
Heat-shrink tubing 2 inches
4-post female header connector 3
The body,head,and tail are constructed using 1/16-inch flat alu-
minum.
The construction of the robot crocodile will start with the assem-
bly of the Tamiya twin motor gearbox,It is available from a hobby
robotics supplier called HVW Tech,and can be purchased from its
Web site located at www.hvwtech.com,The gearbox is sold as a
kit and needs to be assembled before it can be used,Figure 6.3
shows the entire kit before assembly.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
195
TABLE 6.1
Parts List for
Crocobot’s Mechanical
Construction
Amphibionics 06 3/24/03 9:02 AM Page 195
Assembling the twin motor gearbox,Take all of the parts out
of the box and unfold the instruction sheet,The gearbox has two
possible configuration options of standard speed with a gear ratio
of 58:1,or low speed with a gear ratio of 203:1,The gearbox will
be assembled for use with the low speed option,The first thing
that needs to be done when assembling the gearbox is to position
a gear hub on each of the two hexagonal output shafts,as shown
in Figure 6.4,Thread a grub screw into each of the gear hubs with
the hex wrench that was supplied with the kit,Use piece M3 to set
the proper position of the gear hubs,and then tighten in place
with the hex wrench.
Amphibionics
196
FIGURE 6.3
Tamiya twin motor
gearbox before
assembly.
Amphibionics 06 3/24/03 9:02 AM Page 196
Break apart each of the gearbox body sections and plastic spacers
from the injection-molded piece,and trim off any rough edges with
a small knife,Locate the gears,eyelets,screws,and output shafts,
then assemble according to Figure 6.5.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
197
FIGURE 6.4
Procedure to attach
gear hubs to the
hexagonal output
shafts.
FIGURE 6.5
Gearbox assembly
diagram.
Amphibionics 06 3/24/03 9:02 AM Page 197
Place a pinion gear onto the end of each motor shaft so that the
end of the shaft is level with the end of the gear,Install each motor
in the gearbox by sliding it into place,as shown in Figure 6.6,The
plastic clips on the gearbox body will snap into place and secure
the motors in position.
When the gearbox is complete,mark each shaft at 5/8 of an inch
from the body and cut with a hacksaw,The finished gearbox,
ready for use with Crocobot,is shown in Figure 6.7.
Amphibionics
198
FIGURE 6.6
Installing motors in the
gearbox.
FIGURE 6.7
Completed twin motor
gearbox with a 203:1
gear reduction.
Amphibionics 06 3/24/03 9:02 AM Page 198
Constructing the Chassis
The main body chassis is constructed using a piece of 1/16-inch
thick flat aluminum,and is labeled as part A,Cut a piece to the
size of 9 inches in length by 2-1/2 inches in width,Use Figure 6.8
as a cutting and drilling guide.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
199
FIGURE 6.8
Cutting and drilling
guide for main body
chassis.
Amphibionics 06 3/24/03 9:02 AM Page 199
Fabricate four leg support brackets using the 1/16-inch aluminum,
as detailed in Figure 6.9,These pieces are identified by the letters
B,C,D,and E,When the pieces are finished,use a file to remove
any rough edges.
Create a single support bracket according to the dimensions
shown in Figure 6.9,This part is labeled piece F,and is also con-
structed using the 1/16-inch aluminum,Fabricate two L-shaped
limit switch mounting brackets identified as pieces G and H in
Figure 6.9,also using the 1/16-inch aluminum.
Attach the leg mounting brackets (pieces B,C,D,and E) to the
body chassis (piece A) using four 6/32-inch H11003 1/2-inch machine
screws and locking nuts,as shown in Figure 6.10,Note that when
pieces B and C are mounted,the 1/4-inch side of each bracket is
attached to the chassis,and when pieces D and E are mounted,
the 1-inch side of each bracket is attached to the chassis,Figure
6.10 shows the mounting brackets attached to the robot chassis.
Amphibionics
200
FIGURE 6.9
Cutting,bending,and
drilling guide for
mounting brackets.
Amphibionics 06 3/24/03 9:02 AM Page 200
Cut four pieces of connector wire to a length of 6-1/2 inches each.
Cut four pieces of heat-shrink insulator tubing to a length of 1/4-
inch each,Use Figure 6.11 to attach the motor to a 4-connector
female header using the connector wire,Use the heat-shrink tub-
ing to protect from shorts at the header.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
201
FIGURE 6.10
Leg mounting brackets
attached to the robot
chassis.
FIGURE 6.11
Motor wiring diagram.
Amphibionics 06 3/24/03 9:02 AM Page 201
When the motor has been wired to the header,attach it to the
robot chassis with the two mounting nuts and bolts that came with
the motor kit,Figure 6.12shows the position of the motor mount-
ed to the chassis.
Constructing the Body Covers and Tail Section
The next step will be to construct the robot’s top body cover,The
body cover is made up of three parts and will also carry three AA
battery holders and batteries that are used as the power supply for
the direct current motors,Cut a piece of the 1/16-inch thick alu-
minum to a size of 2-1/4 inches by 4-1/4 inches,Use Figure 6.13
as a cutting,drilling,and bending guide,This piece is the robot’s
head cover piece,and is identified with the letter I.
Amphibionics
202
FIGURE 6.12
Twin motor gearbox
fastened to the robot
chassis.
Amphibionics 06 3/24/03 9:02 AM Page 202
Cut another piece of the 1/6-inch thick aluminum to a size of 5-
1/2 inches by 6 inches,Cut,drill,and bend the piece,as shown in
Figure 6.14,This piece will make up the body cover,and is
attached to the head cover piece,This piece is identified as J.
Locate mounting bracket (F) and use it to join the head cover piece
(I) to the body cover piece (J) using two 6/32-inch H11003 1/2-inch
machine screws and locking nuts,as shown in Figure 6.15,When
the two pieces are joined,wire three single AA battery holders in
series,as shown in Figure 6.16,so that a total of 4.5 volts are pro-
duced,Solder the negative and positive outputs to a 2-connector
male header,Use a glue gun to glue the battery holders to the top
body cover in the position,as shown in Figure 6.15,Figure 6.17
shows the completed top body cover from the top view.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
203
FIGURE 6.13
Cutting,drilling,and
bending diagram for
head cover piece.
Amphibionics 06 3/24/03 9:02 AM Page 203
Amphibionics
204
FIGURE 6.14
Cutting,drilling,and
bending diagram for
body cover piece.
FIGURE 6.15
Pieces I and J attached
with mounting
bracket—underside
view.
Amphibionics 06 3/24/03 9:02 AM Page 204
The robot’s tail section will be added to the end of the chassis and
will contain the 9-volt battery holder and 9-volt battery,The tail
will swing from side to side as the robot walks,adding to the rep-
tilian realism of the robot,To construct the tail section,cut two
pieces of 1/16-inch thick aluminum to a size of 6-3/4 inches by 2-
1/4 inches,Use the diagrams in Figure 6.18 (piece K) and Figure
6.19 (piece L) to cut,drill,and bend the pieces,Construct the 9-
volt battery holder (piece M) using 1/16-inch thick aluminum,as
detailed in Figure 6.20,Assemble each of the pieces,as shown in
Figure 6.21,using three 6/32-inch H11003 1/2-inch machine screws
and locking nuts.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
205
FIGURE 6.16
Motor power supply
wiring diagram.
FIGURE 6.17
Completed top body
cover—top view.
Amphibionics 06 3/24/03 9:02 AM Page 205
Amphibionics
206
FIGURE 6.18
Upper tail section
cutting,drilling,and
bending diagram.
Amphibionics 06 3/24/03 9:02 AM Page 206
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
207
FIGURE 6.19
Lower tail section
cutting,drilling,and
bending diagram.
Amphibionics 06 3/24/03 9:02 AM Page 207
Amphibionics
208
FIGURE 6.20
Battery holder cutting,
drilling,and bending
guide.
FIGURE 6.21
Completed tail section
with battery holder.
Amphibionics 06 3/24/03 9:02 AM Page 208
Wiring the Limit Switches
Mount the leg limit switches to the mounting brackets labeled G
and H with appropriately sized machine screws and nuts,orient-
ed as shown in Figure 6.22,Cut four wires to a length of 8 inch-
es,Solder two of these wires to a 2-connector female header.
Locate another 2-connector female header and solder the other
two wires to it,Protect each of the connections with a 1/4-inch
length of heat-shrink tubing,Cut two more wires to a length of 5
inches,Wire up the leg limit switches,as shown in Figure 6.22.
The finished leg limit switches with connectors and mounting
brackets are shown in Figure 6.23,Attach the mounting brackets
with the limit switches to the bottom of the chassis using four
6/32-inch H110031/2-inch machine screws and locking nuts,as shown
in Figure 6.24.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
209
FIGURE 6.22
Limit switch wiring
diagram.
Amphibionics 06 3/24/03 9:02 AM Page 209
Amphibionics
210
FIGURE 6.23
Completed limit
switches wired and
attached to mounting
brackets.
FIGURE 6.24
Limit switches and
mounting brackets
attached to chassis.
Amphibionics 06 3/24/03 9:02 AM Page 210
Constructing the Legs
The legs,feet,and motor shaft mounts will be created using 1/4-
inch H11003 1/4-inch aluminum square stock,Start by fabricating two
motor output shaft mounts according to the dimensions shown in
Figure 6.25,The two parts are identified as N and O,When the
pieces are finished,thread a 6/32-inch H110031/4-inch machine screw
into the hole that has been threaded with a 6/32-inch tap,Figure
6.26 shows a completed motor shaft mount.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
211
FIGURE 6.25
Motor output shaft
mount fabrication
diagram.
FIGURE 6.26
Completed motor
output shaft mount.
Amphibionics 06 3/24/03 9:02 AM Page 211
Using the 1/4-inch H110031/4-inch aluminum stock,fabricate the four
leg pieces (P,Q,R,and S) and the mechanical linkage pieces (T
and U),as detailed in Figure 6.27,Construct the mechanical link-
age pieces V and W and the four feet (X1,X2,X3,and X4),as
outlined in Figure 6.28,When all of these pieces are complete,the
robot’s legs will be assembled.
Amphibionics
212
FIGURE 6.27
Leg and mechanical
linkage construction
diagram.
Amphibionics 06 3/24/03 9:02 AM Page 212
Assembling the Legs
Start by connecting the motor shaft mounts (pieces N and O) to
the motor shafts so that the motor shafts are flush with the outer
sides of the mounts when they are placed,Tighten the screw on
the mounts so that each mount is secure on the motor’s hex
shafts,Use Figure 6.29 and Figure 6.30 as a guide to assembling
the legs,Note that the leg pieces attached to the motor shaft
mounts use 6/32-inch H110031-inch machine screws and locking nuts.
All of the others use 6/32-inch H11003 3/4-inch machine screws and
locking nuts,The foot piece machine screws and locking nuts
should be as tight as possible,All of the other joints should have
a 6/32 nylon washer between metal pieces,and the locking nuts
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
213
FIGURE 6.28
Feet and mechanical
linkage construction
diagram.
Amphibionics 06 3/24/03 9:02 AM Page 213
Amphibionics
214
FIGURE 6.29
Leg parts placement for
the robot’s left side.
FIGURE 6.30
Leg mechanism parts
placement.
Amphibionics 06 3/24/03 9:02 AM Page 214
should be fastened with just enough pressure to allow the parts to
move freely without any resistance.
Cut six connector wires to a length of 6 inches each,Wire the
power switch,9-volt battery strap,and three female header con-
nectors,as indicated in Figure 6.31,When the switch and con-
nectors are finished,mount the switch in the 1/4-inch hole in the
robot chassis with the switch mechanism facing down toward the
bottom of the robot,and the 9-volt battery strap facing toward the
back,Now that the mechanical and electrical systems are in place,
the next step is to add the electronics.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
215
FIGURE 6.31
Power switch wiring
diagram.
Amphibionics 06 3/24/03 9:02 AM Page 215
The Controller Circuit Board
The robot’s main controller will integrate a PIC 16F84 microcon-
troller,a Lynx radio receiver module,and an L298 dual motor con-
troller chip all on a 1-1/2 inch by 2-1/2 inch circuit board,The
schematic for the controller board is shown in Figure 6.32.
The PIC 16F84 microcontroller is used to interpret the serial infor-
mation that is received from the Lynx radio receiver module,mon-
itor the leg limit switches,and control the motors via the L298
motor controller I.C,The 16F84 microcontroller is clocked at 4
MHz and operates from a 5-volt direct current (DC) supply that is
produced from a 78L05 voltage regulator,with the source being a
9-volt battery in the robot’s tail section,The motors operate from
their own 4.5-volt supply contained in the robot’s top cover,Six of
the PIC 16F84 port B pins will be connected to the L298 to control
the motors,The parts necessary to construct the main board are
listed in Table 6.2.
Amphibionics
216
FIGURE 6.32
Crocobot’s main
controller board.
Amphibionics 06 3/24/03 9:02 AM Page 216
Part Quantity Description
Semiconductors
U1 1 78L05 5V regulator
U2 1 PIC 16F84 flash microcontroller mounted
in socket
U3 1 L298 dual full-bridge driver
RX1 1 Lynx RXM-433-LC-S RF receiver module
D1 1 Red light-emitting diode
D2—D9 8 Diodes 1N4001
D10 1 Green light-emitting diode
Q1 1 2N3904 NPN transistor
Resistors
R1,R2 2 470 H9024 1/4-watt resistor
R3 1 10 KH9024 1/4-watt resistor
R4 1 4.7 KH9024 1/4-watt resistor
Capacitors
C1 1 0.1 μf
C2,C3 2 22 pf
C4,C5 2,01 μf
Miscellaneous
JP1—JP4 4 2-post male header connector—2.5-mm
spacing
JP5—motors 1 4-post male header connector—2.5-mm
spacing
JP6—RF 1 4-post female header connector—2.5-mm
module spacing
(continued on next page)
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
217
TABLE 6.2
Parts List for
Crocobot’s Main
Controller Board
Amphibionics 06 3/24/03 9:02 AM Page 217
Part Quantity Description
Y1 1 4-MHz crystal
W1-W4 4 Jumper wire
Piezo buzzer 1 Standard piezoelectric element
I.C,socket 1 18-pin I.C,socket—soldered to PC board U2
Printed 1 See details in chapter.
circuit board
L298 Dual Full-Bridge Driver
This robot is a departure from the previous two robots detailed in
this book because it uses a twin DC motor gearbox as its source
of power,instead of RC servos,In order to safely control the
motors with the microcontroller,the L298 dual full-bridge driver
will be used,and is shown in Figure 6.33,The L298 is an inte-
grated monolithic circuit in a 15-lead multiwatt package,It is a
high-voltage,high-current dual full-bridge driver designed to
accept standard TTL logic levels and drive inductive loads such as
relays,solenoids,DC,and stepping motors,Two enable inputs are
provided to enable or disable the device independently of the input
signals,The emitters of the lower transistors of each bridge are
connected together,and the corresponding external terminal can
be used for the connection of an external sensing resistor,An addi-
tional supply input is provided so that the logic functions at a
lower voltage.
Amphibionics
218
TABLE 6.2
Parts List for
Crocobot’s Main
Controller Board
(continued)
Amphibionics 06 3/24/03 9:02 AM Page 218
How it works,The L298 contains two motor control circuits that
are referred to as the,H-Bridge.” This method of controlling DC
motors gets its name because the four transistors used to control
the motors are configured to form an,H” with the motor being at
the center,Figure 6.34 shows the basic schematic for a typical H-
Bridge,The H-Bridge works by having the control circuitry or
microcontroller turn on only two of the transistors at a time,In this
example,when transistors Q1 and Q4 are turned on,the motor will
spin in one direction,When transistors Q2 and Q3 are turned on,
the motor will spin in the opposite direction,When all of the tran-
sistors are turned off,the motor is stopped,Table 6.3 is a truth
table showing the state of each transistor and the motor direction.
Note that if transistors Q1 and Q3 (or Q2 and Q4) were turned on
at the same time,there would be a short circuit across the battery.
For this reason,the L298 has internal logic that prevents this from
happening.
Motor direction Q1 Q2 Q3 Q4
Stopped 0000
Forwad 1001
Reverse 0110
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
219
FIGURE 6.33
L298 bidirectional
motor controller.
TABLE 6.3
H-Bridge Truth Table
Amphibionics 06 3/24/03 9:02 AM Page 219
With the L298,each bridge has three control inputs made up of an
enable line and two control lines,In our robot application,these
inputs will be controlled by the programmable interface controller
(PIC),The PIC will interpret the data received by the radio link and
then issue the proper motor commands,depending on the infor-
mation sent from the hand remote control,An external bridge of
diodes is required when inductive loads like DC motors are being
driven,The specifics of controlling the motors will be described
during the programming section.
Radio transmitter and receiver modules,The robot will be
remotely controlled using a pair of 433-MHz transmitter and
receiver modules,The modules that will be used are the TXLC-434
transmitter and the RXLC-434 receiver,available from Reynolds
Electronics at www.rentron.com,The modules are based around
Linx Technologies’ (www.linxtechnologies.com) LC series trans-
mitter modules,The staff at Reynolds Electronics have made using
Amphibionics
220
FIGURE 6.34
A typical H-Bridge DC
motor control
configuration.
Amphibionics 06 3/24/03 9:02 AM Page 220
these devices very easy by mounting the modules on small circuit
boards with connectors and a place to solder on the antennas
(which are included with the modules).
The LC Series is ideally suited for volume use in applications such
as remote control,security,identification,robotics,and periodic
data transfer,Packaged in a compact SMD package,the LC trans-
mitter utilizes a highly optimized SAW architecture to achieve an
unmatched blend of performance,size,efficiency,and cost,When
paired with a matching LC series receiver,a highly reliable wire-
less link is formed,capable of transferring serial data at distances
in excess of 300 feet,No external RF components,except an
antenna,are required,making design integration straightforward.
The features include,low cost,no external RF components
required,ultra-low power consumption,compact surface-mount
package,stable SAW–based architecture,support data rates to
5,000 bps,wide supply range (2.7-5.2 vdc),direct serial interface,
low harmonics,and no production tuning,The receiver module
pinout diagram is shown in Figure 6.35,Using the module to
receive information from the transmitter will be described when
programming is covered.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
221
FIGURE 6.35
Receiver module pinout
diagram.
Amphibionics 06 3/24/03 9:02 AM Page 221
Creating the Main Controller
Printed Circuit Board
To fabricate the controller printed circuit board (PCB),photocopy
the artwork in Figure 6.36 onto a transparency,Make sure that
the photocopy is the exact size of the original,For convenience,
you can download the file from the author’s Web site,located at
www.thinkbotics.com,and simply print the file onto a transparen-
cy using a laser or ink-jet printer with a minimum resolution of
600 dpi,After the artwork has been successfully transferred to a
transparency,use the techniques outlined in Chapter 2 to create a
board,A 4-inch H11003 6-inch presensitized positive copper board is
ideal,When you place the transparency on the copper board,it
should be oriented exactly the same as in Figure 6.36,It would be
a good idea to create the circuit board for the remote control at the
same time.
Amphibionics
222
FIGURE 6.36
Controller board PCB
foil pattern artwork.
Amphibionics 06 3/24/03 9:02 AM Page 222
Circuit board drilling and parts placement,Use a 1/32-inch
drill bit to drill all of the component holes on the PCB,Drill the
holes for the voltage regulator (U1) and the diodes (D2–D9) with
a 3/64-inch drill bit,Use Table 6.2 and Figure 6.37 to place the
parts on the component side of the circuit board,The PIC 16F84
microcontroller (U2) is mounted in an 18-pin I.C,socket,The 18-
pin socket is soldered to the PC board,and the PIC is inserted after
it has been programmed,Note that Figure 6.37 also shows four
jumper wires labeled W1–W4 that are not shown in the schemat-
ic,These jumpers were needed due to routing conflicts when
designing the PCB,Use a fine-toothed saw to cut the board along
the guide lines,and drill the mounting holes on the corners using
a 5/32-inch drill bit,Use 1/4-inch standoffs to mount the board.
Figure 6.38 shows the finished main controller board.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
223
FIGURE 6.37
Controller board PCB
component side parts
placement.
Amphibionics 06 3/24/03 9:02 AM Page 223
Check the finished board for any missed or cold soldered connec-
tions,and verify that all the components have been included,The
board will be tested later when programming the PIC microcon-
troller.
Adding the radio receiver module,Locate the radio receiver
module (RXLC-434) and flip it over so that the back is facing
upward,Solder the 7-inch antenna wire that was included with the
module to the tinned area on the board where there is no solder
mask,Figure 6.39 shows the antenna soldered to the board.
The next step is to bend all of the connector pins of the receiver
module on 90-degree angles toward the back of the module,Use
a pair of needle nose pliers to carefully bend each pin,This is
needed so that the module will sit parallel to the controller board
when it is plugged into its connector,Figure 6.40 illustrates how
Amphibionics
224
FIGURE 6.38
Parts soldered to the
finished PCB.
Amphibionics 06 3/24/03 9:02 AM Page 224
the pins should be bent,Once the pins have been bent,insert the
module into the 4-pin female connector (JP6) located in front of
the diode array,Orient the module so that it sits above the diodes
when it is plugged in,Figure 6.41show the module plugged into
the circuit board.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
225
FIGURE 6.39
Antenna soldered to the
receiver module PCB.
FIGURE 6.40
Receiver module
connector pins bent 90
degrees.
Amphibionics 06 3/24/03 9:02 AM Page 225
Putting It All Together
Now that the mechanical,electronics,and electrical systems are
all finished,it is time to integrate them all together into a working
robot,Start by mounting the circuit board to the chassis at the
head of the robot,Attach the robot’s tail section to the chassis with
a 6/32-inch H11003 1/2-inch machine screw and locking nut,Tighten
the nut with enough torque to let the tail swing freely,Plug each
of the connectors into the main controller,as indicated in Figure
6.42,Note that the motor power supply battery pack can’t be
connected until the top cover has been attached to the chassis.
Place a new AA battery into each of the three battery holders
located on the top cover,Figure 6.43shows the robot with the tail
section attached and all of the connecting wires plugged into the
controller board,Place a 9-volt battery into the battery clip locat-
ed in the tail section,Attach the battery strap to the battery,Feed
the antenna through the hole in the head section,then use three
6/32-inch H11003 1/2-inch machine screws and nuts to attach the top
cover,Plug in the motor power connector before you fasten the
cover in place,Figure 6.44 shows the completed robot with the
Amphibionics
226
FIGURE 6.41
Receiver module
inserted into connector
on the main board.
Amphibionics 06 3/24/03 9:02 AM Page 226
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
227
FIGURE 6.42
Robot connection
diagram.
FIGURE 6.43
Robot with tail section
attached and all wiring
connected.
Amphibionics 06 3/24/03 9:02 AM Page 227
top cover attached,The PIC microcontroller will be programmed a
little later,during experimentation,Now that the robot is complete,
the remote control transmitter will be built.
Constructing the Remote
Control Transmitter
The remote control transmitter will be used to control the robot’s
movements and may be customized to control other devices as
well,The hand held remote control device uses an analog X and Y
axis control stick as the input to two analog-to-digital converters
residing on a PIC 16C71,The remote control is pictured in Figure
6.45.
Amphibionics
228
FIGURE 6.44
Completed robot with
cover attached.
Amphibionics 06 3/24/03 9:02 AM Page 228
The schematic for the transmitter remote control is shown in Figure
6.46,The circuit functions by using the PIC 16C71 to monitor the
position of the control stick and then send serial commands to the
transmitter module,When the control stick moves along the X and
Y axis,the resistance values of two 100K H9024potentiometers are var-
ied,The control stick and the two attached potentiometers are
shown in Figure 6.47,Each potentiometer is configured as a volt-
age divider so that a unique voltage represents each position along
the X- and Y-axis,The voltages from the potentiometers are con-
verted to 8-bit values by the internal analog to digital converters on
the PIC 16C71 and then interpreted by the microcontroller.
Depending on the values,certain movement commands are sent in
a serial format from the transmitter to the robot,The remote control
also has a programmable push-button switch and a light-emitting
diode (LED) that can be turned on when certain events occur,such
as during the transmission of a movement command,The transmit-
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
229
FIGURE 6.45
Robot remote control
device.
Amphibionics 06 3/24/03 9:02 AM Page 229
ter module is the TXLC-434 transmitter,available from Reynolds
Electronics at,www.rentron.com,The modules are based around
Linx Technologies’ (www.linxtechnologies.com) LC series transmit-
ter modules,as discussed earlier,The transmitter module pinout
diagram is shown in Figure 6.48,The only external part needed for
the module to function is a 430 H9024resistor that is connected from the
VADJ line to ground for 5-volt operation,If the resistor is not includ-
ed,then the device will operate at 3 volts,Using the module to
transmit information to the receiver will be discussed when pro-
gramming is covered.
Amphibionics
230
FIGURE 6.46
Remote control
schematic diagram.
Amphibionics 06 3/24/03 9:02 AM Page 230
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
231
FIGURE 6.47
Control stick with X and
Y axis potentiometers.
FIGURE 6.48
Transmitter module
pinout diagram.
Amphibionics 06 3/24/03 9:02 AM Page 231
PIC 16C71
The Microchip PIC 16C71 is very similar to the PIC 16F84 that has
been used throughout the book,The pinouts are identical,The dif-
ference is that the pins on PortA of the 16C71 can be configured to
take advantage of four on-chip analog-to-digital converters.
Another difference is that the chip is erased by exposure to ultra-
violet light,A small window on the top of the device allows light to
get at the chip,After the chip has been programmed,the window
should be covered with a sticker so that it does not get erased if it
is exposed to sunlight or fluorescent lighting,The 8-bit resolution
of the 4-channel high-speed 8-bit A/D is ideally suited for appli-
cations requiring a low-cost analog interface,Use of the A/D con-
verters will be discussed when the software routines are covered.
Although the 16C71 device was used in the book,Microchip now
manufactures an 18-pin,flash erasable device with analog-to-dig-
ital converters,identified as the PIC 16F818,Figure 6.49 shows
the PIC 16C71 with its ultraviolet erase window,The parts needed
to build the transmitter are listed in Table 6.4.
Amphibionics
232
FIGURE 6.49
Microchip PIC 16C71.
Amphibionics 06 3/24/03 9:02 AM Page 232
Part Quantity Description
Semiconductors
U1 1 78L05 5V regulator
U2 1 PIC 16C71 microcontroller mounted in
socket
TX1 1 Lynx TXM-433-LC-R RF transmitter module
D1 1 Red light-emitting diode
D2 1 Red light-emitting diode
Resistors
R1,R2,R6 3 470 H9024 1/4-watt resistor
R3 1 4.7 KH9024 1/4-watt resistor
R4,R5 2 Control stick with two 100 KH9024
potentiometers
R7 1 1 KH9024 1/4-watt resistor
Capacitors
C1 1 0.1 μf
C2,C3 2 22 pf
Miscellaneous
JP1 1 2-post male header connector—2.5-mm
spacing
JP2,JP6,JP7 3 2-post female header connector—2.5-mm
spacing
JP3 1 4-post female header connector—2.5-mm
spacing
JP4,JP5 2 3-post female header connector—2.5-mm
spacing
(continued on next page)
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
233
TABLE 6.4
List of Parts Needed to
Build the Transmitter
Amphibionics 06 3/24/03 9:02 AM Page 233
Part Quantity Description
Y1 1 4-MHz crystal
I.C,socket 1 18-pin I.C,socket—soldered to PC board U2
Project box 1 3 inches wide x 1-1/2 inches deep
Battery strap 1 9-volt battery strap
S1—switch 1 SPST switch
S2—switch 1 Momentary contact—normally open
pushbutton
Antenna 1 6-3/4 inch whip antenna with threaded
mount
Enclosure connectors
JP1 1 2-post female header connector—2.5-mm
spacing
JP2,JP6,JP7 3 2-post male header connector—2.5-mm
spacing
JP3 1 4-post male header connector—2.5-mm
spacing
JP4,JP5 2 3-post male header connector—2.5-mm
spacing
Creating the Remote Control
Printed Circuit Board
To fabricate the PCB,photocopy the artwork in Figure 6.50 onto a
transparency,Make sure that the photocopy is the exact size of the
original,For convenience,you can download the file from the
author’s Web site,located at www.thinkbotics.com,and simply
print the file onto a transparency using a laser or ink-jet printer
with a minimum resolution of 600 dpi,After the artwork has been
Amphibionics
234
TABLE 6.4
List of Parts Needed to
Build the Transmitter
(continued)
Amphibionics 06 3/24/03 9:02 AM Page 234
successfully transferred to a transparency,use the techniques out-
lined in Chapter 2 to create a board,A 4-inch H11003 6-inch presensi-
tized positive copper board is ideal,When you place the trans-
parency on the copper board,it should be oriented so that it is
exactly the same as in Figure 6.50.
Circuit board drilling and parts placement,Use a 1/32-inch
drill bit to drill all of the component holes on the PCB,Drill the
holes for the voltage regulator (U1) with a 3/64-inch drill bit,Use
Table 6.4and Figure 6.51to place the parts on the component side
of the circuit board,Note that female sockets are used where cer-
tain components will be plugged in,This is to make it easier to
mount the control potentiometers,LEDs,and switches to the top
cover of the project box,The PIC 16C71 microcontroller (U2) is
mounted in an 18-pin I.C,socket,The 18-pin socket is soldered to
the PC board,and the PIC is inserted after it has been programmed.
Use a fine-toothed saw to cut the board along the guide lines.
Check the finished board for any missed or cold soldered connec-
tions,and verify that all the components have been included,The
board will be tested later when programming the PIC microcon-
troller.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
235
FIGURE 6.50
Remote control PCB foil
pattern artwork.
Amphibionics 06 3/24/03 9:02 AM Page 235
Remote control project enclosure,Choose a project box that is
at least 3 inches wide,5 inches in length,and 1-1/2 inches deep.
Depending on the control stick that you are using,the box may
need to be larger or smaller than the dimensions above,I used a
project box that had removable top and bottom panels to make it
easier to work with.
Locate the 6-3/4 inch whip antenna and cut the coaxial cable to a
length of 2-1/2 inches in length,Strip 1/2-inch of the shielding off
the end of the wire,and then strip the middle wire as well,Drill a
1/4-inch hole in the top,right side of the case,and mount the
antenna,Solder the antenna lead wire to the small area on the
back (the area without any solder mask) of the transmitter mod-
ule,Bend the connector pins of the transmitter module 90 degrees
downward,This is the same procedure that was performed on the
receiver module,Place the remote control circuit board in the case,
and then plug the transmitter module into the female connector
(JP3),Move the circuit to the top of the case,1/2-inch from the
top,Use hot glue to secure the board in place,Figure 6.52 shows
the finished transmitter circuit board,with the antenna attached to
the case and the transmitter module.
Amphibionics
236
FIGURE 6.51
Remote control PCB
component side parts
placement.
Amphibionics 06 3/24/03 9:02 AM Page 236
Mount the control stick,power switch,two LEDs,and push-but-
ton switch to the top cover of the project box in similar positions,
as shown in Figure 6.53,You will have to drill a 3/4-inch hole for
the control stick,Depending on the project box that you are using,
you may have to find the best positions for each of the compo-
nents,When the parts are mounted in the cover,use Figure 6.54
to wire the parts to the board,I used wires with a length of 3-1/2
inches to connect each component to the appropriate connector.
Figure 6.55 shows the components wired to the connectors,Once
the parts are wired to the connectors,attach a 9-volt battery,but
move the cover to the side to leave access to the 18-pin socket,so
that the PIC 16C71 can easily be inserted and removed during the
programming,debugging,and experimentation stages,We are
now ready to start programming the robot and transmitter.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
237
FIGURE 6.52
Remote control circuit
board with antenna
connected.
Amphibionics 06 3/24/03 9:02 AM Page 237
Amphibionics
238
FIGURE 6.53
Mounting placement of
control stick,switches,
and light emitting
diodes.
FIGURE 6.54
Transmitter wiring
diagram.
Amphibionics 06 3/24/03 9:02 AM Page 238
Programming Crocobot
To bring the crocodile robot to life,the leg sensor switches will be
checked to make sure that they are working properly,The leg sen-
sor switches will be used to coordinate the walking gait of the
robot,With the two-motor,four-leg design that has been used,it
is necessary for one set of legs to be in the forward position when
the other set of legs are in motion,Otherwise,the robot does not
get maximum body lift or forward/reverse motion,The first pro-
gram that will be written is called crocobot-switch.bas and is list-
ed in Program 6.1,Enter the program into your favorite text edi-
tor,then compile and program the PIC 16F84 using the crocobot-
switch.hexfile listed in Program 6.2,Insert the PIC into the 18-pin
socket on the main board,Move the legs by hand so that the limit
switches are not triggered,and then turn on the power,The robot
should make a start-up sound and then go silent,If tones are
being produced without the switch being pushed,then turn the
power off,Make sure that the polarity of JP2 is correct,with H110015
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
239
FIGURE 6.55
Transmitter components
wired to connectors.
Amphibionics 06 3/24/03 9:02 AM Page 239
being connected to the middle connector of the limit switches (see
Figure 6.42),Turn the power back on,and push the limit switch
on the robots right side with your finger,The PIC should produce
alternating high and low tones from the piezo speaker,Trigger the
left switch with your finger,A steady pulsing tone should be heard.
If the tones being produced do not correspond to the correct
switch,then reverse connector JP4 (Figure 6.42).
'------------------------------------------------------------------------------------------------------------------------------
' Name,croco-switch.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Program to test the leg limit switches
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs,pins 0 and 1 inputs
trisa = %00000011
' PortB set as outputs,pin 1 input,
trisb = %00000001
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
include "modedefs.bas"
limit_left VAR PORTA.0
limit_right VAR PORTA.1
piezo VAR PORTA.3
SOUND PIEZO,[115,10,50,10]
start:
If limit_left = 1 then
SOUND PIEZO,[100,10]
pause 20
endif
Amphibionics
240
PROGRAM 6.1
crocobot-switch.bas
program listing
Amphibionics 06 3/24/03 9:02 AM Page 240
If limit_right = 1 then
SOUND PIEZO,[80,20]
pause 40
SOUND PIEZO,[110,20]
pause 40
endif
goto start
end
:1000000061288F00220884002009282084138F088B
:1000100003195C28F03091000E0880389000F03011
:1000200091030319910003198F0303195C28182801
:100030002B2003010C1820088E1F20088E0803199E
:100040000301900F252880060C28262800000F2881
:10005000841780055C280D080C0403198C0A803075
:100060000C1A8D060C198D068C188D060D0D8C0D35
:100070008D0D5C288F018E00FF308E07031C8F07CB
:10008000031C5C2803308D00DF3048203C288D01A4
:10009000E83E8C008D09FC30031C51288C070318A6
:1000A0004E288C0764008D0F4E280C1857288C1C86
:1000B0005B2800005B28080083130313831264008D
:1000C0000800831603308500013086000530831256
:1000D000A2000830A00073308E000A3001203230B8
:1000E0008E000A3001206400051C80280530A20023
:1000F0000830A00064308E000A30012014303A200D
:100100006400851C97280530A2000830A0005030FC
:100110008E001430012028303A200530A20008302B
:10012000A0006E308E001430012028303A20732851
:0401300063009828A8
:02400E00F53F7C
:00000001FF
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
241
PROGRAM 6.1
crocobot-switch.bas
program listing
(continued)
PROGRAM 6.2
crocobot-switch.hex file
listing
Amphibionics 06 3/24/03 9:02 AM Page 241
The next program will test the robot leg motors and will ensure that
the motor connector is oriented correctly,Compile motor-test.bas,
listed in Program 6.3,Program the PIC 16F84 with the
motor-test.hex file listed in Program 6.4,and then insert it into the
18-pin socket on the main board,When the power is turned on,the
left leg motor should rotate in a forward direction for 3 seconds,
and then turn off,The right leg motor should then rotate forward
for 3 seconds,The whole sequence will then repeat itself,If either
the left or right leg motors are rotating in the reverse direction dur-
ing this test,then de-solder the wires connected to the offending
motor,reverse them,and re-solder the connections,If the first
motor to run is the right motor,then unplug the motor connector
(JP3),turn it around,and plug it back in,The motors are controlled
by first setting the L298 enable pins high on the desired channels.
The forward or reverse pins for each channel are then set high,
depending on the direction in which you want the motor to travel.
If both the forward and reverse pins are set high,then the chip will
perform a fast motor stop.
'------------------------------------------------------------------------------------------------------------------------------
' Name,motor-test.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Program to test the leg motors
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs,pins 0 and 1 inputs
trisa = %00000011
' PortB set as outputs,pin 1 input,
trisb = %00000001
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
include "modedefs.bas"
Amphibionics
242
PROGRAM 6.3
motor-test.bas program
listing
Amphibionics 06 3/24/03 9:02 AM Page 242
enable_right VAR PORTB.1
forward_right VAR PORTB.2
reverse_right VAR PORTB.3
enable_left VAR PORTB.4
reverse_left VAR PORTB.5
forward_left VAR PORTB.6
limit_left VAR PORTA.0
limit_right VAR PORTA.1
piezo VAR PORTA.3
low enable_left
low forward_left
low reverse_left
low enable_right
low forward_right
low reverse_right
SOUND PIEZO,[115,10,50,10]
start:
high enable_left
high forward_left
pause 3000
low enable_left
low forward_left
high enable_right
high forward_right
pause 3000
low enable_right
low forward_right
goto start
end
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
243
PROGRAM 6.3
motor-test.bas program
listing (continued)
Amphibionics 06 3/24/03 9:02 AM Page 243
:1000000061288F00220884002009282084138F088B
:1000100003195C28F03091000E0880389000F03011
:1000200091030319910003198F0303195C28182801
:100030002B2003010C1820088E1F20088E0803199E
:100040000301900F252880060C28262800000F2881
:10005000841780055C280D080C0403198C0A803075
:100060000C1A8D060C198D068C188D060D0D8C0D35
:100070008D0D5C288F018E00FF308E07031C8F07CB
:10008000031C5C2803308D00DF3048203C288D01A4
:10009000E83E8C008D09FC30031C51288C070318A6
:1000A0004E288C0764008D0F4E280C1857288C1C86
:1000B0005B2800005B28080083130313831264008D
:1000C0000800831603308500013086008312061273
:1000D00083160612831206138316061383128612E2
:1000E00083168612831286108316861083120611D9
:1000F000831606118312861183168611053083122A
:10010000A2000830A00073308E000A300120323087
:100110008E000A3001200616831606128312061777
:100120008316061383120B308F00B8303B20061263
:10013000831606128312061383160613831286147F
:1001400083168610831206158316061183120B3050
:100150008F00B8303B20861083168610831206115C
:0C0160008316061183128B286300B4285C
:02400E00F53F7C
:00000001FF
In the next program,the robot’s four basic walking subroutines
will be developed,The robot will walk forward,turn to the left,
walk in reverse,and then turn to the right,As described earlier,
in order for a two-motor,four-legged robot to walk successfully,
it is necessary for one set of legs to be in the forward position
when the other set of legs are in motion,This ensures static sta-
bility,Otherwise,the robot does not get maximum body lift or
forward/reverse motion with each leg cycle,For example,when
the crocodile robot moves in a forward direction,the microcon-
troller first turns on the left leg motor,A small delay is intro-
duced so that the leg has time to move past the leg position
Amphibionics
244
PROGRAM 6.4
motor-test.hex file
listing
Amphibionics 06 3/24/03 9:02 AM Page 244
switch,since that was possibly the position that is was stopped
at during the last cycle,The program goes into a tight while loop
to monitor the leg switch,When the leg makes a complete cycle,
the leg switch is activated,program execution breaks out of the
while loop,and the leg motor is turned off,The microcontroller
then goes through the same logic with the right leg moving in a
forward direction,With both the left leg and the right leg moving
for one cycle in the forward direction,the robot’s body is moved
forward,This logic works for most cases,but depending on the
position of the leg during the last leg cycle,the leg may actually
trigger the switch right away,and a full leg cycle does not occur.
This is taken care of by having each routine run twice,so that if
a cycle was missed on the first time through,it will occur the
second time through.
Each of the walking routines uses the logic stated above,In order
for the robot to walk in reverse,both legs move in the reverse
direction,To turn the robot to the right,the left leg moves forward
and the right leg moves in reverse,To turn the robot to the left,the
left leg moves in reverse,while the right leg moves forward,Any of
the four walking routines can be combined to diversify the move-
ment,An example of this would be if you wanted the robot to move
forward and to the right,This would be accomplished by calling
the forward subroutine and then the right subroutine,alternating
between the two.
Program 6.5is called walk-routines.bas,This program demonstrates
each of the four walking routines that will be used later with the
remote control,Program the PIC 16F84 with the walk-routines.hex
file listed in Program 6.6,When the program executes,the robot will
run through the forward routine five times,for a total of 10 leg cycles.
It will then turn to the left,walk in reverse,and then turn to the right.
Now that the walking routines have been developed,the radio
remote control can be added.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
245
Amphibionics 06 3/24/03 9:02 AM Page 245
'------------------------------------------------------------------------------------------------------------------------------
' Name,walk-routines.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,various walking subroutines
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs,pins 0 and 1 inputs
trisa = %00000011
' PortB set as outputs,pin 1 input,
trisb = %00000001
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
include "modedefs.bas"
enable_right VAR PORTB.1
forward_right VAR PORTB.2
reverse_right VAR PORTB.3
enable_left VAR PORTB.4
reverse_left VAR PORTB.5
forward_left VAR PORTB.6
limit_left VAR PORTA.0
limit_right VAR PORTA.1
piezo VAR PORTA.3
temp VAR BYTE
low enable_left
low forward_left
low reverse_left
low enable_right
low forward_right
low reverse_right
SOUND PIEZO,[115,10,50,10]
start:
Amphibionics
246
PROGRAM 6.5
walk-routines.bas
program listing
Amphibionics 06 3/24/03 9:02 AM Page 246
'------------------------------------------------------------------------------------------------------------------------------
' walking subroutines
walk_forward:
For temp = 1 to 5
' move left leg
high enable_left
high forward_left
pause 300
while limit_left = 0
wend
low enable_left
low forward_left
' move right leg
high enable_right
high forward_right
pause 300
while limit_right = 0
wend
low enable_right
low forward_right
next temp
'------------------------------------------------------------------------------------------------------------------------------
turn_left:
For temp = 1 to 5
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
247
PROGRAM 6.5
walk-routines.bas
program listing
(continued)
Amphibionics 06 3/24/03 9:02 AM Page 247
' move left leg
high enable_left
high reverse_left
pause 300
while limit_left = 0
wend
low enable_left
low reverse_left
' move right leg
high enable_right
high forward_right
pause 300
while limit_right = 0
wend
low enable_right
low forward_right
next temp
'------------------------------------------------------------------------------------------------------------------------------
walk_reverse:
For temp = 1 to 5
' move left leg
high enable_left
high reverse_left
pause 300
Amphibionics
248
PROGRAM 6.5
walk-routines.bas
program listing
(continued)
Amphibionics 06 3/24/03 9:02 AM Page 248
while limit_left = 0
wend
low enable_left
low reverse_left
' move right leg
high enable_right
high reverse_right
pause 300
while limit_right = 0
wend
low enable_right
low reverse_right
next temp
'------------------------------------------------------------------------------------------------------------------------------
turn_right:
For temp = 1 to 5
' move left leg
high enable_left
high forward_left
pause 300
while limit_left = 0
wend
low enable_left
low forward_left
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
249
PROGRAM 6.5
walk-routines.bas
program listing
(continued)
Amphibionics 06 3/24/03 9:02 AM Page 249
' move right leg
high enable_right
high reverse_right
pause 300
while limit_right = 0
wend
low enable_right
low reverse_right
next temp
goto start
end
:1000000061288F00220884002009282084138F088B
:1000100003195C28F03091000E0880389000F03011
:1000200091030319910003198F0303195C28182801
:100030002B2003010C1820088E1F20088E0803199E
:100040000301900F252880060C28262800000F2881
:10005000841780055C280D080C0403198C0A803075
:100060000C1A8D060C198D068C188D060D0D8C0D35
:100070008D0D5C288F018E00FF308E07031C8F07CB
:10008000031C5C2803308D00DF3048203C288D01A4
:10009000E83E8C008D09FC30031C51288C070318A6
:1000A0004E288C0764008D0F4E280C1857288C1C86
:1000B0005B2800005B28080083130313831264008D
:1000C0000800831603308500013086008312061273
:1000D00083160612831206138316061383128612E2
:1000E00083168612831286108316861083120611D9
:1000F000831606118312861183168611053083122A
:10010000A2000830A00073308E000A300120323087
:100110008E000A3001200130A40064000630240261
:100120000318C428061683160612831206178316B0
Amphibionics
250
PROGRAM 6.5
walk-routines.bas
program listing
(continued)
PROGRAM 6.6
walk-routines.hex file
listing
Amphibionics 06 3/24/03 9:02 AM Page 250
:100130000613831201308F002C303B206400051819
:10014000A2289E280612831606128312061383160F
:1001500006138312861483168610831206158316DF
:100160000611831201308F002C303B20640085186B
:10017000BA28B628861083168610831206118316B5
:1001800006118312A40F8D280130A40064000630EC
:1001900024020318FD2806168316061283128616FB
:1001A00083168612831201308F002C303B206400AE
:1001B0000518DB28D728061283160612831286122A
:1001C00083168612831286148316861083120615F0
:1001D00083160611831201308F002C303B206400FF
:1001E0008518F328EF2886108316861083120611CF
:1001F000831606118312A40FC6280130A4006400E0
:1002000006302402031836290616831606128312B6
:10021000861683168612831201308F002C303B2005
:100220006400051814291029061283160612831279
:100230008612831686128312861483168610831202
:10024000861583168611831201308F002C303B20D7
:10025000640085182C29282986108316861083129D
:100260008611831686118312A40FFF280130A40083
:1002700064000630240203186F290616831606123E
:100280008312061783160613831201308F002C3059
:100290003B20640005184D294929061283160612D1
:1002A0008312061383160613831286148316861090
:1002B0008312861583168611831201308F002C302D
:1002C0003B206400851865296129861083168610F5
:1002D00083128611831686118312A40F38298B2866
:0402E000630070291E
:02400E00F53F7C
:00000001FF
The Lynx LC series transmitter and receiver modules were
designed to facilitate a highly reliable wireless serial data link.
Once the units are powered up,serial data can be sent on a single
pin of the transmitter and received on a single pin of the receiver.
This makes it very easy to use the modules with a microcontroller
and a programming language like PicBasic Pro.
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
251
PROGRAM 6.6
walk-routines.hex file
listing (continued)
Amphibionics 06 3/24/03 9:02 AM Page 251
When using the serin command to receive data,PicBasic Pro lets
you define a qualifier enclosed within brackets before any more
data is received,Serin must receive these bytes in exact order
before receiving any data items,If any bytes received do not match
the next byte in the qualifier sequence,the qualification process
starts over (i.e.,the next received byte is compared to the first item
in the qualifier list),This makes it easy for us to program an iden-
tification code for each device or robot that we are going to con-
trol,It also ensures that good data are being sent,and cuts down
on erroneous interpretation of the received serial data,Once the
qualifiers are satisfied,serin begins storing data in the variables
associated with each item,If the variable name is used alone,the
value of the received ASCII character is stored in the variable.
For our test program,we will use the qualifier,Z” to identify that
the received data is coming from our transmitter,Once the char-
acter,Z” has been received,the next byte of information will be
stored in a variable,We can then compare this information to cer-
tain control commands and carry out the tasks associated to them.
The line of code that will receive the serial data looks like this:
serin rxmit,rx_baud,["Z"],control
The serial data is received on pin rxmit(PORTB.0) at a baud rate
of rx_baud (2400),The program execution will remain in a tight
loop,receiving serial data and comparing each received byte to the
character,Z.” When the character,Z” is received,the next data
byte is stored in the variable named control,We will then compare
the contents of the variable control to the character,A.” If the
comparison is true,then the microcontroller will produce a couple
of tones on the piezo speaker,The receiver program is called
receive-test.bas and is listed in Program 6.7,Program the PIC
16F84 with the receive-test.hex file listed in Program 6.8,Place
the PIC in the 18-pin socket on the robot’s main board.
Amphibionics
252
Amphibionics 06 3/24/03 9:02 AM Page 252
'------------------------------------------------------------------------------------------------------------------------------
' Name,receive-test.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Program to test the wireless data link
',between the Lynx 433LC series
',transmitter and receiver.
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs,pins 0 and 1 inputs
trisa = %00000011
' PortB set as outputs,pin 0 input,
trisb = %00000001
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
include "modedefs.bas"
rx_baud CON N2400
rxmit VAR PORTB.0
piezo VAR PORTA.3
control VAR BYTE
SOUND PIEZO,[115,10,50,10]
start:
serin rxmit,rx_baud,["Z"],control
if control = "A" then
SOUND PIEZO,[115,10,80,20]
pause 100
endif
goto start
end
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
253
PROGRAM 6.7
receive-test.bas
program listing
Amphibionics 06 3/24/03 9:02 AM Page 253
:100000009F2864001120031801281C2008308F004D
:100010001D2011208E0C0C288F0B08281D200E0887
:100020000800220884002008841780048413000537
:100030001F192006FF3E08001F171F0D06398C00F0
:100040002B208D008C0A2B201F1F7E281F138C0055
:10005000023095207E2800308A000C088207013487
:1000600075340334153400343C340C34D9348F00E7
:100070002208840020095E2084138F0803199A281F
:10008000F03091000E0880389000F0309103031991
:10009000910003198F0303199A284E286120030148
:1000A0000C1820088E1F20088E0803190301900FDA
:1000B0005B28800642285C280000452884178005BC
:1000C0009A280D080C0403198C0A80300C1A8D062E
:1000D0000C198D068C188D060D0D8C0D8D0D9A2822
:1000E0008F018E00FF308E07031C8F07031C9A2898
:1000F00003308D00DF307E2072288D01E83E8C00B9
:100100008D09FC30031C87288C07031884288C0772
:1001100064008D0F84280C188D288C1C91280000F9
:100120009128080003108D0C8C0CFF3E03189228B8
:100130000C089A28831303138312640008008316A3
:10014000033085000130860005308312A20008309C
:10015000A00073308E000A30372032308E000A3013
:1001600037200630A2000130A00004309F0001209B
:100170005A3C031DB7280120A40064002408413C18
:10018000031DD0280530A2000830A00073308E0077
:100190000A30372050308E00143037206430702001
:0601A000B1286300D12824
:02400E00F53F7C
:00000001FF
The corresponding transmit-test.bas for the PIC 16C71 microcon-
troller used in the remote control is listed in Program 6.9,This
program uses the serout command to send serial data to the
transmitter,The baud rate is also set at the same rate as the
receiver program,Notice that the qualifier character,Z” is sent
first,and then our control character,in this case,A.” Program the
PIC 16C71 with the transmit-test.hex file listed in Program 6.10.
Amphibionics
254
PROGRAM 6.8
receive-test.hex file
listing
Amphibionics 06 3/24/03 9:02 AM Page 254
Insert the 16C71 into the 18-pin socket on the remote control cir-
cuit board,Turn the power on at the robot,and then turn on the
power to the remote control,When the button on the remote con-
trol is pushed,the LED above the button will light up,indicating
that a transmission has been sent,At the same time,the piezo
speaker on the robot will make a couple of tones each time the
button is pushed,You should also notice that the LED next to the
receiver module on the robot’s controller board will flash on and
off rapidly,as data comes through,If nothing happens when the
button is pushed,check all of your wiring and battery supplies.
Once the units are working together correctly,you can check the
range of the transmitter by walking away from the robot and hold-
ing the push button on the remote control down,For later experi-
mentation,you can program this button for other tasks.
'------------------------------------------------------------------------------------------------------------------------------
' Name,transmit-test.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Program to test wireless link using the
',Linx 433LC series transmitter and receiver
'------------------------------------------------------------------------------------------------------------------------------
' set PortA inputs
trisa = %00011111
' PortB set as outputs,pin 2 input
trisb = %00000100
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
include "modedefs.bas"
tx_baud CON N2400
txmit VAR PORTB.0
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
255
PROGRAM 6.9
transmit-test.bas
program listing
Amphibionics 06 3/24/03 9:02 AM Page 255
txmit_led VAR PORTB.1
push_button VAR PORTB.2
start:
low txmit_led
If push_button = 1 then
serout txmit,tx_baud,["ZA"]
high txmit_led
pause 200
endif
goto start
:1000000063289200220884000930930003100D2019
:10001000920C930B072803140D2884139F1D1C2892
:10002000000820041F1D20068000841700082004FB
:10003000031C20068000272800082004031C20063B
:100040001F192006800084172009800527281F0D0E
:1000500006398C0030208D008C0A302000004A28A0
:1000600000308A000C0882070134753403341534DB
:1000700000343C340C34D9348F018E00FF308E07AD
:10008000031C8F07031C5E2803308D00DF304A20DD
:100090003E288D01E83E8C008D09FC30031C53285E
:1000A0008C07031850288C0764008D0F50280C18FB
:1000B00059288C1C5D2800005D2808008313031359
:1000C00083126400080083161F3085000430860008
:1000D000831286108316861064008312061D802802
:1000E0000630A2000130A00004309F005A300120E9
:1000F00041300120861483168610C83083123C20BC
:0201000069286C
:02400E00F53F7C
:00000001FF
At this stage,we can bring all of the subroutines together into one
set of robot remote control programs,The only thing left to discuss
is the use of the analog-to-digital (A/D) converters on the PIC
Amphibionics
256
PROGRAM 6.9
transmit-test.bas
program listing
(continued)
PROGRAM 6.10
transmit-test.hex file
listing
Amphibionics 06 3/24/03 9:02 AM Page 256
16C71,These A/D converters will be used to convert the voltages
from the control stick potentiometers to 8-bit digital values,Each
potentiometer is configured as a voltage divider so that a unique
voltage represents each position along the X and Y axis,The
PicBasic Compiler also makes using the A/D converters very easy.
Using the ADCIN command,it is easy to set the number of bits in
the result,set the clock source,set the sampling rate,and set the
port pins to analog,Once that has all been set up,simply read the
channel value and store the result in a variable,I have listed all of
the A/D converter registers in the comments of the transmitter
code if you are interested in exactly what is happening.
The program for the robot is called rx-remote.bas and is listed in
Program 6.11,Compile the code and then program the PIC 16F84
with the rx-remote.hex file listed in Program 6.12,Insert the pro-
grammed 16F84 into the 18-pin socket on the robot’s main board.
The program for the remote control is called tx-remote.bas and is
listed in Program 6.13,Make sure that the PIC 16C71 has been U.V.
erased,Compile the code and then program the PIC 16C71 with the
tx-remote.hex file listed in Program 6.14,Insert the programmed
16C71 into the 18-pin socket on the remote control circuit board.
Place the robot on the floor and turn on the power,Turn on the
power to the remote control,Push the button on the front of the
remote,The robot should make a sound,Try controlling the robot’s
direction using the control stick,When everything is working cor-
rectly,place the top on the transmitter project enclosure and secure
it in place with the screws that came with the box.
With the control stick sitting in the middle position,the robot will
be stopped,With the stick pushed all the way forward,the robot
will walk forward,When the control stick is pulled backwards,the
robot will walk in reverse,When the control stick is positioned to
the right,the robot will turn to the right,and when the stick is
positioned to the left,the robot will turn to the left,The poten-
tiometer values were determined by taking the A/D readings and
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
257
Amphibionics 06 3/24/03 9:02 AM Page 257
then outputting the values to an LCD display,You can check the
program listing for the values,Feel free to make any changes or
improvements,By using a serial wireless data link,the options are
unlimited,so have fun with it.
'------------------------------------------------------------------------------------------------------------------------------
' Name,rx-remote.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Robot remote control using the Linx
',433LC series transmitter and receiver,
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs
trisa = %00000000
' PortB set as outputs,pin 0 input,
trisb = %00000001
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
include "modedefs.bas"
rx_baud CON N2400
rxmit VAR PORTB.0
enable_right VAR PORTB.1
forward_right VAR PORTB.2
reverse_right VAR PORTB.3
enable_left VAR PORTB.4
reverse_left VAR PORTB.5
forward_left VAR PORTB.6
limit_left VAR PORTA.0
limit_right VAR PORTA.1
piezo VAR PORTA.3
control VAR BYTE
temp VAR BYTE
Amphibionics
258
PROGRAM 6.11
rx-remote.bas program
listing
Amphibionics 06 3/24/03 9:02 AM Page 258
low enable_left
low forward_left
low reverse_left
low enable_right
low forward_right
low reverse_right
SOUND PIEZO,[115,10,50,10]
start:
serin rxmit,rx_baud,["Z"],control
if control = "A" then
gosub walk_forward
endif
if control = "B" then
gosub walk_reverse
endif
if control = "C" then
gosub turn_left
endif
if control = "D" then
gosub turn_right
endif
if control = "E" then
sound piezo,[115,10,50,10]
endif
if control = "F" then
low enable_left
low forward_left
low reverse_left
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
259
PROGRAM 6.11
rx-remote.bas program
listing (continued)
Amphibionics 06 3/24/03 9:02 AM Page 259
Amphibionics
260
low enable_right
low forward_right
low reverse_right
endif
goto start
'------------------------------------------------------------------------------------------------------------------------------
' walking subroutines
walk_forward:
' move left leg
high enable_left
high forward_left
pause 300
while limit_left = 0
wend
low enable_left
low forward_left
' move right leg
high enable_right
high forward_right
pause 300
while limit_right = 0
wend
low enable_right
low forward_right
return
PROGRAM 6.11
rx-remote.bas program
listing (continued)
Amphibionics 06 3/24/03 9:02 AM Page 260
'------------------------------------------------------------------------------------------------------------------------------
turn_left:
' move left leg
high enable_left
high reverse_left
pause 300
while limit_left = 0
wend
low enable_left
low reverse_left
' move right leg
high enable_right
high forward_right
pause 300
while limit_right = 0
wend
low enable_right
low forward_right
return
'------------------------------------------------------------------------------------------------------------------------------
walk_reverse:
' move left leg
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
261
PROGRAM 6.11
rx-remote.bas program
listing (continued)
Amphibionics 06 3/24/03 9:02 AM Page 261
high enable_left
high reverse_left
pause 300
while limit_left = 0
wend
low enable_left
low reverse_left
' move right leg
high enable_right
high reverse_right
pause 300
while limit_right = 0
wend
low enable_right
low reverse_right
return
'------------------------------------------------------------------------------------------------------------------------------
turn_right:
' move left leg
high enable_left
high forward_left
pause 300
while limit_left = 0
wend
low enable_left
Amphibionics
262
PROGRAM 6.11
rx-remote.bas program
listing (continued)
Amphibionics 06 3/24/03 9:02 AM Page 262
low forward_left
' move right leg
high enable_right
high reverse_right
pause 300
while limit_right = 0
wend
low enable_right
low reverse_right
return
end
:100000009F2864001120031801281C2008308F004D
:100010001D2011208E0C0C288F0B08281D200E0887
:100020000800220884002008841780048413000537
:100030001F192006FF3E08001F171F0D06398C00F0
:100040002B208D008C0A2B201F1F7E281F138C0055
:10005000023095207E2800308A000C088207013487
:1000600075340334153400343C340C34D9348F00E7
:100070002208840020095E2084138F0803199A281F
:10008000F03091000E0880389000F0309103031991
:10009000910003198F0303199A284E286120030148
:1000A0000C1820088E1F20088E0803190301900FDA
:1000B0005B28800642285C280000452884178005BC
:1000C0009A280D080C0403198C0A80300C1A8D062E
:1000D0000C198D068C188D060D0D8C0D8D0D9A2822
:1000E0008F018E00FF308E07031C8F07031C9A2898
:1000F00003308D00DF307E2072288D01E83E8C00B9
:100100008D09FC30031C87288C07031884288C0772
:1001100064008D0F84280C188D288C1C91280000F9
:100120009128080003108D0C8C0CFF3E03189228B8
:100130000C089A28831303138312640008008316A3
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
263
PROGRAM 6.11
rx-remote.bas program
listing (continued)
PROGRAM 6.12
rx-remote.hex file listing
Amphibionics 06 3/24/03 9:02 AM Page 263
:10014000850101308600831206128316061283127F
:1001500006138316061383128612831686128312E1
:1001600086108316861083120611831606118312D9
:1001700086118316861105308312A2000830A00074
:1001800073308E000A30372032308E000A3037202C
:100190000630A2000130A00004309F0001205A3C2C
:1001A000031DCE280120A40064002408413C031D47
:1001B000DA281B2164002408423C031DE0287D212D
:1001C00064002408433C031DE6284C2164002408F5
:1001D000443C031DEC28AE2164002408453C031D6B
:1001E000FD280530A2000830A00073308E000A30D0
:1001F000372032308E000A30372064002408463C15
:10020000031D1A290612831606128312061383167B
:1002100006138312861283168612831286108316A3
:100220008610831206118316061183128611831617
:1002300086118312C8280616831606128312061723
:1002400083160613831201308F002C307120640056
:1002500005182B2927290612831606128312061366
:1002600083160613831286148316861083120615CE
:1002700083160611831201308F002C307120640028
:10028000851843293F29861083168610831206118C
:1002900083160611831208000616831606128312AF
:1002A000861683168612831201308F002C3071203F
:1002B000640005185C295829061283160612831259
:1002C0008612831686128312861483168610831272
:1002D000061583160611831201308F002C30712011
:1002E000640085187429702986108316861083127D
:1002F00006118316061183120800061683160612CD
:100300008312861683168612831201308F002C30DA
:100310007120640005188D2989290612831606129A
:100320008312861283168612831286148316861011
:100330008312861583168611831201308F002C30AC
:10034000712064008518A529A129861083168610BE
:1003500083128611831686118312080006168316EF
:1003600006128312061783160613831201308F00BC
:100370002C30712064000518BE29BA290612831694
:10038000061283120613831606138312861483162D
:1003900086108312861583168611831201308F0012
Amphibionics
264
PROGRAM 6.12
rx-remote.hex file listing
(continued)
Amphibionics 06 3/24/03 9:02 AM Page 264
:1003A0002C30712064008518D629D2298610831636
:1003B000861083128611831686118312080063004B
:0203C000DF2933
:02400E00F53F7C
:00000001FF
'------------------------------------------------------------------------------------------------------------------------------
' Name,tx-remote.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Robot control using the Linx 433LC series
',transmitter and receiver.
',Using the PIC 16C71 on-chip analog to digital
',converters to read the position of
',the two control stick potentiometers,
'------------------------------------------------------------------------------------------------------------------------------
' PIC 16C71 A/D converter registers
'
' PORTA = 05 hex = 5 dec
' five I/O lines RA0 RA1 RA2 RA3 RA4
'
' TRISA = 85 hex = 133 dec
' data direction register
' ---1 1111 inputs
' ---0 0000 outputs
'
' ADCON1 = 88 hex = 136 dec
' configure as A to D converter or digital I/O
' bits RA0,RA1 RA2 RA3 Vref
' ---- --00 analog analog analog VDD
' ---- --01 analog analog ref input RA3
' ---- --10 analog digital digital VDD
' ---- --11 digital digital digital VDD
'
' ADCON0 = 08 hex = 8 dec
' A/D control and status register - 8 bits
' bit7 - ADCS1
' bit6 - ADCS0
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
265
PROGRAM 6.12
rx-remote.hex file listing
(continued)
PROGRAM 6.13
tx-remote.bas program
listing
Amphibionics 06 3/24/03 9:02 AM Page 265
' bit5 - reserved
' bit4 - CHS1
' bit3 - CHS0
' bit2 - GO/DONE
' bit1 - ADIF
' bit0 - ADON
' ADCS1 and ADCS2 - bit7 and bit6
' A/D conversion clock select:
' ADCS1,0 = 00,fosc/2
' 01,fosc/8
' 10,fosc/32
' 11,f rc (derived from internal
' rc oscillator)
' bit5 - reserved
' Analog channel select - bit4 and bit3
' CHS1,CHS0 = 00,channel 0 (AIN0)
' 01,channel 1 (AIN1)
' 10,channel 2 (AIN2)
' 11,channel 3 (AIN3)
' GO/DONE - bit2,must be set to begin a
' conversion,It is automatically
' reset in hardware when conversion
' is done.
' ADIF - bit1,A/D conversion complete interrupt flag bit,Set
' when conversion is completed,Reset in software.
' ADON - bit0,If ADON = 0 A/D converter module is shut off and
' consumes no operating current,ADON = 1 A/D
' converter module is on.
'
' ADRES = 09 hex = 9 dec
' A/D conversion result register
'
' INTCON = 0B hex = 11 dec
' interupt control register
'------------------------------------------------------------------------------------------------------------------------------
' set PortA inputs.
trisa = %00011111
Amphibionics
266
PROGRAM 6.13
tx-remote.bas program
listing (continued)
Amphibionics 06 3/24/03 9:02 AM Page 266
' PortB set as outputs,Pin 2 input
trisb = %00000100
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
include "modedefs.bas"
tx_baud CON N2400
pot_y VAR PORTA.0
pot_x VAR PORTA.1
txmit VAR PORTB.0
txmit_led VAR PORTB.1
push_button VAR PORTB.2
val_y VAR BYTE
val_x VAR BYTE
control VAR BYTE
'------------------------------------------------------------------------------------------------------------------------------
' Set up the analog to digital converters
DEFINE ADC_BITS 8 ' Set number of bits in result
DEFINE ADC_CLOCK 3 ' Set clock source (rc = 3)
DEFINE ADC_SAMPLEUS 10 ' Set sampling time in microseconds
ADCON1 = 2 ' Set porta pins 0 and 1 to analog
start:
low txmit_led
ADCIN 0,val_y ' read A/D converter - porta.pin 0
ADCIN 1,val_x ' read A/D converter - porta.pin 1
If val_y < 20 then
high txmit_led
serout txmit,tx_baud,["ZA"]
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
267
PROGRAM 6.13
tx-remote.bas program
listing (continued)
Amphibionics 06 3/24/03 9:02 AM Page 267
endif
If val_y > 200 then
high txmit_led
serout txmit,tx_baud,["ZB"]
endif
If val_X < 20 then
high txmit_led
serout txmit,tx_baud,["ZC"]
endif
If val_X > 200 then
high txmit_led
serout txmit,tx_baud,["ZD"]
endif
If push_button = 1 then
high txmit_led
serout txmit,tx_baud,["ZE"]
endif
If ((val_y > 25) and (val_y < 190)) or ((val_x > 25) and (val_x < 190))
then
serout txmit,tx_baud,["ZF"]
endif
goto start
end
:100000008C2892002A0884000930930003100D20E8
:10001000920C930B072803140D288413A71D1C288A
:1000200000082804271D28068000841700082804DB
:10003000031C28068000272800082804031C280623
:100040002719280680008417280980052728270DEE
:1000500006398C0030208D008C0A302000004E289C
:1000600000308A000C0882070134753403341534DB
Amphibionics
268
PROGRAM 6.13
tx-remote.bas program
listing (continued)
PROGRAM 6.14
tx-remote.hex file listing
Amphibionics 06 3/24/03 9:02 AM Page 268
:1000700000343C340C34D9348C008C0D8C0D0C0DB8
:100080003839C138880000308D000A304E200815FC
:10009000081948288D01090887288D01E83E8C0041
:1000A0008D09FC30031C57288C07031854288C0733
:1000B00064008D0F54280C185D288C1C61280000EA
:1000C000612808008D018F018E0001306C288D01A0
:1000D0008F018E0004306C2894000F080D02031D60
:1000E00073280E080C020430031801300319023083
:1000F0001405031DFF3087280038031DFF30040559
:10010000031DFF3087280404031DFF308728831355
:10011000031383126400080083161F308500043027
:100120008600023088008312861083168610003005
:1001300083123C20AE0001303C20AD00640014303E
:100140002E020318B12886148316861006308312F7
:10015000AA000130A8000430A7005A300120413025
:1001600001206400C9302E02031CC42886148316A3
:10017000861006308312AA000130A8000430A700C0
:100180005A30012042300120640014302D0203183F
:10019000D72886148316861006308312AA000130F1
:1001A000A8000430A7005A30012043300120640029
:1001B000C9302D02031CEA288614831686100630E7
:1001C0008312AA000130A8000430A7005A30012091
:1001D000443001206400061DFB2886148316861017
:1001E00006308312AA000130A8000430A7005A305C
:1001F0000120453001202E088C00193062209E001D
:100200002E088C00BE306720A0001E088400200845
:100210007C20A000A1002D088C0019306220A200D3
:100220002D088C00BE306720A4002208840024081A
:100230007C20A400A50020082104840024082504B3
:100240008320A400A5006400240825040319322992
:100250000630AA000130A8000430A7005A3001205F
:0602600046300120942845
:02400E00FD3F74
:00000001FF
Chapter 6 / Crocobot,Build Your Own Robotic Crocodile
269
PROGRAM 6.14
tx-remote.hex file listing
(continued)
Amphibionics 06 3/24/03 9:02 AM Page 269
This page intentionally left blank.
271
Turtles and Tortoises
There are more than 270 living species of turtles and tortoises.
These creatures are found in terrestrial,fresh water,and marine
habitats,and in both temperate and tropical regions,The term
“turtle” usually refers to a freshwater or marine species,while the
term,tortoise” is normally used for terrestrial species.,Terrapin”
is the informal name for a freshwater turtle.
Turtles and tortoises belong to the order Testudines,which is divid-
ed into two suborders,The primitive sideneck turtles (suborder
Pleurodira) cannot fully retract their long necks,When they are at
rest,they must lay their heads sideways along the inside of their
shells,All of the 70 or so species of sideneck turtles live in fresh-
water,The more advanced straightneck turtles (suborder
Cryptodira) are a much larger group that lives on land and in water.
They are able to withdraw their heads completely into their shells.
Turtles and tortoises vary greatly in size,from the tiny Speckled
Padloper,2-1/2 inches long,to the massive Leatherback Sea
Turtle,which can reach up to 6 feet in length.
Turtletron,
Build Your Own
Robotic Turtle
7
Amphibionics 07 3/24/03 9:13 AM Page 271
Copyright 2003 by The McGraw-Hill Companies,Inc,Click Here for Terms of Use.
The turtle and its behavior is the inspiration for the robot in this
chapter,At first I wanted the turtle to be a walking robot,much like
the biological version,but decided that an inexpensive,wheeled
robot would be a great platform on which to base experiments.
Figure 7.1 shows a real turtle and the robotic version that will be
built during this chapter.
Overview of the Turtletron Project
The robot turtle that will be built and programmed in this chapter
has a circular base and achieves locomotion using two wheels,
each one powered by direct current (DC) motors and gearboxes.
The robot will operate in autonomous mode or under remote con-
trol by a human operator,Turtletron will use an ultrasonic range
finder and a linear shaft encoder to map its surrounding area dur-
ing autonomous mode,and will also use the sonar to inhibit move-
ment if an operator is directing the robot into an obstacle during
remote control,The robot will also be equipped with a linear shaft
encoder that will give it the ability to keep track of the distance that
Amphibionics
272
FIGURE 7.1
A turtle and its robotic
counterpart.
Amphibionics 07 3/24/03 9:13 AM Page 272
it has traveled and to create maps of its surroundings,To save time
and money on construction,this robot will use the same main con-
troller circuit board and transmitter device that we built during the
last crocodile robot project,The only difference with the main con-
troller board will be with the software of the PIC 16F84,The robot
will also adopt the wireless data link that was utilized in the last
chapter,The robot with the remote control is shown in Figure 7.2.
The History of Robotic Turtles
William Grey Walter built the first robotic turtles in the late 1940s.
His work in robotics was an extension of his research in neuro-
physiology,Walter’s studies of the brain and its neural networks
led him to wonder about what type of behavior could be created
using just a few neurons,To experiment with this concept,in
1948,Walter built a three-wheeled turtle-like mobile robot that
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
273
FIGURE 7.2
Turtletron with remote
control.
Amphibionics 07 3/24/03 9:13 AM Page 273
measured 12 inches in height and 18 inches in length,Amazingly
this robot used just two electronic neurons,but exhibited interest-
ing and complex behaviors,The first two robots were named Elmer
and Elsie (ELectroMEchanical Robot,Light Sensitive),He later
named the style of robots Machina Speculatrix after observing the
complex behavior they exhibited.
The robot’s nervous system consisted of two sensors connected to
two neurons,One sensor was a light-sensitive resistor mounted
onto the shaft of the front wheel steering-drive assembly,This
arrangement ensured that the photosensitive resistor was always
facing in the direction that the robot was moving,The second sen-
sor was a bump switch attached to the robot’s outer cover,The
three wheels of the robot were arranged in a triangular configura-
tion,The front wheel had a motorized steering assembly that
could rotate a full 360 degrees in one direction,The front wheel
also contained a drive wheel for propulsion,Figure 7.3 shows a
robot turtle built by Walter during the 1940s,This robot is now on
display at the Smithsonian.
Amphibionics
274
FIGURE 7.3
Robot tortoise built by
robotics pioneer William
Grey Walter in 1948.
Amphibionics 07 3/24/03 9:13 AM Page 274
The robot exhibited four modes of operation described below.
1,Search,The room is at low light level or darkness,The robot
responds by searching for a light source,The steering motor
is on full speed and the drive motor is at half speed.
2,Move,The robot found light,The robot responds by turning
the steering motor off and the drive motor on at half speed.
3,Dazzle,The robot encounters bright light,The robot
responds by setting the steering motor to half speed,while
the drive motor is reversed.
4,Touch,The robot hits an obstacle,The robot responds by
setting the steering motor to full speed,with the drive motor
reversed.
In the 1950s,W,Grey Walter wrote two Scientific American articles
(“An Imitation of Life,” May 1950;,A Machine That Learns,”
August 1951) and a book titled The Living Brain (Norton,New York,
1963),Walter reported,“The strange richness provided by this
particular sort of permutation introduces right away one of the
aspects of animal behavior—and human psychology—that
Machina Speculatrix is designed to illustrate,the uncertainty,ran-
domness,free will or independence so strikingly absent in most
well designed machines.”
Although the robot we will be building is turtle-like,it is not
intended to recreate any of the experiments of W,Grey Walter,
although you could easily implement the sensors and program the
microcontroller to do so.
Mechanical Construction of Turtletron
The parts needed for the mechanical construction of the turtle
robot are listed in Table 7.1.
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
275
Amphibionics 07 3/24/03 9:13 AM Page 275
Parts Quantity
18 3/4-inch diameter Frisbee 2
3-inch diameter model airplane wheels 2
1-1/2 inch casters 2
#4-40 H11003 3/4-inch machine screws 4
#4-40 H11003 1-inch machine screws 4
#4-40 nuts 8
6/32 H11003 1/2-inch machine screws 32
6/32 H11003 1-inch machine screws 2
6/32 locking nuts 34
Power switch DPDT 1
Tamiya high power gear box H.E,2
Connector wire 9 feet
Heat-shrink tubing 2 inches
4-post female header connector 3
The construction of the robot turtle will start with the assembly of
two Tamiya high power gearboxes,They are available from HVW
Tech and can be purchased at their Web site,located at
www.hvwtech.com,The gearboxes are sold as kits and need to be
assembled before they can be used,Figure 7.4 shows the Tamiya
high power gearbox kit.
Amphibionics
276
TABLE 7.1
List of Parts Needed for
Turtletron’s Mechanical
Construction
Amphibionics 07 3/24/03 9:13 AM Page 276
Assembling the Gearboxes and
Attaching the Wheels
Take all of the parts out of the box and unfold the instruction
sheet,The gearbox has two possible configuration options of a
64.8:1 or 41.7:1,The gearbox will be assembled for use with the
64.8:1 ratio using one green and two red gears,Follow the instruc-
tions included with the kits to assemble both gearboxes.
Locate two,3-inch diameter model airplane wheels and two gear-
box horns labeled as A3 that are included with the gearbox kits.
Place a wheel on the table and line up the center hole in one of the
gearbox horns with the center of the wheel,Use a pencil to mark
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
277
FIGURE 7.4
Tamiya high power
gearbox kit.
Amphibionics 07 3/24/03 9:13 AM Page 277
the position of the two holes where they line up on the wheel,as
shown in Figure 7.5,Follow this procedure for the second wheel,
Amphibionics
278
FIGURE 7.5
Gearbox horn A3 with
mounting holes
indicated.
FIGURE 7.6
Wheel attached to
gearbox.
Amphibionics 07 3/24/03 9:13 AM Page 278
and then drill the holes with a 5/32-inch drill bit,Attach an A3
gearbox horn to each of the gearboxes with the washers and
securing nuts that came with the kits,Use two #4-40 H11003 3/4-inch
machine screws and nuts to attach each wheel to each gearbox
horn as,shown in Figure 7.6.
Constructing the base,The robot’s body will be constructed
using two common Frisbees that can be obtained at most depart-
ment stores,Starting with the base,use the dimensions shown in
Figure 7.7 to cut two recesses in the plastic disk,using a hack
saw,The gearboxes will be mounted so that the wheels are posi-
tioned in the recessed areas,Use a file to smooth any rough edges
where the plastic was cut.
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
279
FIGURE 7.7
Cutting dimension for
wheel recesses in the
robot base.
Amphibionics 07 3/24/03 9:13 AM Page 279
Drill the motor mounting holes and power switch hole,as indicat-
ed in Figure 7.8,Center the casters at the front and back of the
underside of the Frisbee,and mark the mounting holes with a pen-
cil,as shown in Figure 7.8,No dimensions for drilling were shown
in the figure because the exact position of the caster mounting
holes may vary,depending on the casters,When the holes have
been marked,drill with the bit sizes indicated.
Amphibionics
280
FIGURE 7.8
Drilling guide for robot
base.
Amphibionics 07 3/24/03 9:13 AM Page 280
Mount the wheeled gearboxes onto the robot base using the
machine screws and nuts that came with the gearbox kits,Mount
each caster onto the base using four 6/32-inch H11003 1/2-inch
machine screws and locking nuts,Mount the power switch in the
1/4-inch hole toward the back of the base,Use Figure 7.9to posi-
tion the gearboxes,casters,and switch when mounting them to
the base.
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
281
FIGURE 7.9
Gearboxes,wheels,
casters,and switch
mounted to the robot
base.
Amphibionics 07 3/24/03 9:13 AM Page 281
Cut four pieces of 1/2-inch aluminum stock to a size of 2-1/2
inches in length,These pieces will be used to support the top
cover and antenna,Use Figure 7.10as a cutting and drilling guide.
Mount the aluminum pieces on the Frisbee base,Position each
piece 1/2 of an inch beside the wheel recesses and mark the
mounting holes,Drill each mounting hole with a 5/32-inch drill
bit,and attach each piece with a 6/32-inch H11003 1/2-inch machine
screw and locking nut,Figure 7.11 shows two of the supports
attached around one of the wheel recesses.
Amphibionics
282
FIGURE 7.10
Cutting and drilling
guide for cover
supports.
FIGURE 7.11
Two cover supports
mounted to robot base
around wheel recesses.
Amphibionics 07 3/24/03 9:13 AM Page 282
Differential drive system,Turtletron employs what is called the
differential drive system,It is one of the least complicated loco-
motion systems from a construction and programming standpoint.
The differential drive scheme consists of two wheels on a common
axis,with each wheel driven independently,This arrangement
allows the robot to drive straight,to turn in place,and to move in
an arc.
In order to ensure balance,some additional support beside the two
drive wheels must be provided to prevent the robot from tipping
over,This is usually done by arranging one or two caster wheels
in a diamond or triangle pattern,Turtletron uses the diamond pat-
tern,as illustrated in Figure 7.9,One of the problems with using
this configuration is that when the caster wheels are attached
rigidly to the robot body,undulations in terrain can leave the robot
supported only by the casters,The drive wheels may lose contact
with the surface and become unable to move the robot,To improve
on this design,a suspension system could be added that would
allow the casters to move up and down relative to the drive
wheels.
Electronics
To simplify the design and construction of Turtletron,the main
controller board and remote control that were built for the croco-
dile robot in the last chapter will be used,The circuits are identi-
cal,except that the software of the PIC 16F84 will be changed.
This robot will also include an ultrasonic range finder for room
mapping and obstacle avoidance,along with a linear shaft
encoder to keep track of distance,The main controller schematic
is shown in Figure 7.12,If you did not build the crocodile robot,
or would like to build a separate circuit board for Turtletron,fol-
low the instructions in Chapter 6,The parts needed to complete
the electronics are listed in Table 7.2.
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
283
Amphibionics 07 3/24/03 9:13 AM Page 283
Part Quantity Description
Semiconductors
U1 1 78L05 5V regulator
U2 1 PIC 16F84 flash microcontroller mounted
in socket
U3 1 L298 dual full-bridge driver
RX1 1 Lynx RXM-433-LC-S RF receiver module
D1 1 Red light-emitting diode
D2–D9 8 Diodes 1N4001
D10 1 Green light-emitting diode
Q1 1 2N3904 NPN transistor
Resistors
R1,R2 2 470 H9024 1/4-watt resistor
R3 1 10 KH9024 1/4-watt resistor
R4 1 4.7 KH9024 1/4-watt resistor
(continued on next page)
Amphibionics
284
FIGURE 7.12
Schematic of
Turtletrons main
controller board.
TABLE 7.2
List of Parts Needed for
Turtletron’s Electronics
Amphibionics 07 3/24/03 9:13 AM Page 284
Part Quantity Description
Capacitors
C1 1 0.1 μf
C2,C3 2 22 pf
C4,C5 2,01 μf
Miscellaneous
JP1–JP4 4 2-post male header connector—2.5-mm
spacing
JP5–Motors 1 4-post male header connector—2.5-mm
spacing
JP6–RF module 1 4-post female header connector—2.5-mm
spacing
Y1 1 4-MHz crystal
W1-W4 4 Jumper wire
Piezo buzzer 1 Standard piezoelectric element
I.C,socket 1 18-pin I.C,socket—soldered to PC board U2
Whip antenna 1 6-3/4 inch whip antenna
9-volt battery 2 Battery connector
strap
4 AA-battery 1 4 AA-battery holder with 6-volt output
holder
Printed 1 See details in Chapter 6.
circuit board
Mount the main board on four 1/2-inch threaded standoffs,Turn
the robot over so that it is right side up,with the wheels facing
downward,Place the main controller circuit board at the center of
the robot base,mark the positions of the standoffs,and then drill
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
285
TABLE 7.2
List of Parts Needed for
Turtletron’s Electronics
(continued)
Amphibionics 07 3/24/03 9:13 AM Page 285
the holes with a 5/32-inch bit,Mount the circuit board to the robot
base using machine screws that match the threaded standoffs.
Ultrasonic Range Finding
An ultrasonic range finder will be added to Turtletron so that the
robot will be able to avoid obstacles while roaming in autonomous
mode or to inhibit movement when under remote control,The
robot will be able to determine the distance to an object from itself,
and then make decisions based on that information,The robot will
also have the ability to create a rudimentary map of the surround-
ing area before movement through the environment begins.
Devantech SRF04 ultrasonic range finder,A low-cost solution
is the Devantech SRF04 ultrasonic range finder,pictured in Figure
7.13,This device offers precise ranging information from 3 cm to
3 m,is easy to interface,and its minimal power requirements make
it an ideal ranger for mobile robotics applications,It is available
from Acroname Robotics Inc.,and can be purchased from their
Web site at www.acroname.com.
Amphibionics
286
FIGURE 7.13
Devantech SRF04
ultrasonic range finder.
Amphibionics 07 3/24/03 9:13 AM Page 286
The SRF04 range finder is a small printed circuit board (PCB) that
measures 1-3/4 H11003 3/4-inches,with two ultrasonic transducers
mounted on the front,The ranger requires a 5V power supply capa-
ble of handling roughly 50 mA of continuous output,One transduc-
er is used to send an ultrasonic signal,and the other transducer
receives the signal reflection from nearby objects,The SRF04 will
output a 100-microsecond to 18-millisecond detection pulse that is
proportional to range when a reflected signal is detected,Table 7.3
is a list of the parts that will be needed to add the sonar ranger,The
SRF04 range finder specifications are listed in Table 7.4.
Part Quantity Description
SRF04 ultrasonic ranger module 1 Sonar distance
measuring device
5-post male header connector 1 2.5-mm spacing
4-strand ribbon cable 1 8-1/2 inches
2-connector female header 2 2.5-mm spacing
1/16-inch thick aluminum 1 2-inches H11003 4-inches
Hot glue — Hot glue and gun
Specification Value
Voltage 5v
Current 30 mA Typical 50 mA
Frequency 40 kHz
Maximum range 3 meters
Minimum range 3 centimeters
Sensitivity Can detect a 3-cm diameter broom handle at 2 meters
Input trigger 10 μS minimum TTL level pulse
Echo pulse Positive TTL level signal,width proportional to range
Size 1-3/4 H11003 3/4-inches
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
287
TABLE 7.3
Parts Required for the
Addition of the SRF04
Ultrasonic Range Finder
TABLE 7.4
Table of Specifications
for the SRF04
Amphibionics 07 3/24/03 9:13 AM Page 287
Theory of operation,The SRF04 works by sending a pulse of
sound outside the range of human hearing,This pulse travels at the
speed of sound (1.1 ft/ms) away from the ranger in a cone shape.
If any objects are in the path of the pulse,the sound is reflected off
the object and back to the ranger,The ranger is paused for a brief
interval after the sound is transmitted and then awaits the reflect-
ed sound in the form of an echo,The controller driving the ranger
requests the device to create a 40-kHz sound pulse,and then waits
for the return echo,If the echo is received,the ranger reports this
echo to the controller,and the controller can then compute the dis-
tance to the object,based on the elapsed time.
Connections,The ranger requires four connections to operate.
The first two are the power and ground lines,The ranger requires a
5-volt power supply capable of handling roughly 50 mA of continu-
ous output,The other two lines are the signal connections,The first
signal connection is the pulse trigger input line,and the second is
the echo output line,These two pins will be connected to two
input/output (I/O) lines of the microcontroller,Figure 7.14 shows
the connection pins on the back of the device,Note that the ground
pin is on the far right and is marked with the letter,G” beside it.
Amphibionics
288
FIGURE 7.14
SRF04 pin connections.
Amphibionics 07 3/24/03 9:13 AM Page 288
Basic timing,There are a couple of requirements to consider
about the input trigger and the output pulse generated by the
ranger,The input line should be held low (logic 0),and then
brought high for a minimum of 10 μsec to initiate the sonic pulse.
The pulse is generated on the falling edge of the input trigger,The
ranger’s receive circuitry is held in a short blanking interval of 100
μsec to avoid noise from the initial ping,and then it is enabled to
listen to the echo,The echo line is logic low until the receive cir-
cuitry is enabled,Once the receive circuitry is enabled,the falling
edge of the echo line signals either an echo detection or the time-
out of 36 ms if no object is detected,Figure 7.15 illustrates the
timing sequence of the initial trigger input,the 40 kHz sonic burst
that is generated,and the echo output pulse.
The microcontroller will begin timing on the falling edge of the
trigger input pulse,and end timing on the falling edge of the echo
line,This duration determines the distance between the sonar
module and the object from which the echo is bounced back,If no
object is detected,a time-out will occur,which is indicated by the
echo output line going high for approximately 36 ms.
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
289
FIGURE 7.15
SRF04 timing diagram.
Amphibionics 07 3/24/03 9:13 AM Page 289
Connecting the ultrasonic ranger to the robot,First,solder
four male header pins to the ranger,as shown in Figure 7.16,This
is probably the best way to connect the ranger to the controller
because the robot could possibly move the wires around during
locomotion,Wires soldered directly to PCBs have a tendency to
fray at the solder joints and become disconnected,The use of
header pins eliminates this problem.
Fabricate a jumper wire made up of 4-strand ribbon wire cut to a
length of 8-1/2 inches,The end of the wire attached to the ranger
uses a 5-connector female header,Solder the wires to the female
header connector,Skip the pin that is not used and clip it off with
wire cutters,On the other end of the wire,use a pair of 2-con-
nector female headers and solder the 5-volt and ground to one
connector,and the trigger input and echo output to the other.
Figure 7.17 illustrates what the connector wire should resemble
when it is finished.
Amphibionics
290
FIGURE 7.16
Header pins soldered to
the SRF04 ultrasonic
ranger.
Amphibionics 07 3/24/03 9:13 AM Page 290
To secure the ultrasonic ranger to the robot,a housing to mount
the unit will be fabricated,Use Figure 7.18 as a guide to cut,drill,
and bend the housing,using 1/16-inch thick aluminum,Drill the
mounting hole with a 5/32-inch drill bit,The aluminum can be
bent on the edge of a table by hand or in a table vise,Figure 7.19
shows the finished housing so that you can get an idea of how the
aluminum should be bent,Next,place the ranger unit inside the
housing at the front and secure it in place by tightening the alu-
minum around the circuit board by hand,Apply a small amount of
hot glue on the inside at the corners where the circuit board and
aluminum housing meet,This will ensure that the circuit board
does not move out of position.
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
291
FIGURE 7.17
Completed SRF04
connector wire.
Amphibionics 07 3/24/03 9:13 AM Page 291
Amphibionics
292
FIGURE 7.18
Cutting,drilling,and
bending guide for the
SRF04 housing.
Amphibionics 07 3/24/03 9:13 AM Page 292
Figure 7.20 shows the SRF04 ranger mounted in the housing with
the jumper wire plugged into the header connector,Use 1/16-inch
thick aluminum stock to construct the neck mount that will con-
nect the ranger housing to the robot body,Follow the cutting,
bending,and drilling guide in Figure 7.21,When the neck mount
is completed,attach it to the front of the robot with a 6/32-inch H11003
1/2-inch machine screw and locking nut,as shown in Figure 7.22.
Note that the 1-1/2 inch section of the neckpiece is attached to the
robot base,Attach the ultrasonic ranger housing to the neck using
a 6/32-inch H11003 1/2-inch machine screw and locking nut.
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
293
FIGURE 7.19
Finished SRF04
housing.
Amphibionics 07 3/24/03 9:13 AM Page 293
Amphibionics
294
FIGURE 7.20
SRF04 ranger mounted
in housing with
connector wire
attached.
FIGURE 7.21
Cutting,bending,and
drilling guide for neck
mount.
Amphibionics 07 3/24/03 9:13 AM Page 294
Attaching the antenna to the RF module,Locate the 6-3/4 inch
whip antenna and strip 1/2-inch of the insulator and shielding
material from the connector wire,Drill a hole in the second
Frisbee,toward the edge,using a 1/4-inch bit,Mount the whip
antenna to the Frisbee by feeding the connector lead through the
hole and then fastening the mounting nut,Solder the wire to the
antenna mount area on the back of the Lynx RXM-433-LC-S
receiver module,Bend the pins on the receiver module 90 degrees
downward,if this was not done earlier in Chapter 6,The finished
top cover with the antenna and receiver module attached is shown
in Figure 7.23.
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
295
FIGURE 7.22
Neck mount and sonar
ranger attached to
Turtletron’s body.
Amphibionics 07 3/24/03 9:13 AM Page 295
Now that all of the components are in place,it is time to wire
everything together,Use the diagram in Figure 7.24 to connect all
of the components to the main controller board,Drill a 5/32-inch
hole in the base in front of each of the motors to feed the motor
wires through to the controller board,Plug the RF receiver module
into the 4-connector female header on the controller board,Attach
the top cover with the antenna toward the back of the robot,The
top cover should fit snugly on the four aluminum cover support
pieces,Figure 7.25 shows the robot with all of the components
and batteries connected to the main controller board,Attach a
fresh 9-volt battery and a 6-volt battery pack containing four AA
batteries to the proper battery clips,as indicated in Figure 7.24.
Amphibionics
296
FIGURE 7.23
Antenna and receiver
module attached to top
cover.
Amphibionics 07 3/24/03 9:13 AM Page 296
In the next section,we will program the PIC 16F84 to control the
motors,interpret the information from the radio receiver module,
and obtain distance measurements from the sonar ranger for obsta-
cle avoidance and room mapping,The final experiment will be to
add an optical shaft encoder so that the robot will be able to keep
track of the distance that it has traveled,This will also be necessary
when the robot is creating maps of its surrounding environment.
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
297
FIGURE 7.24
Turtletron wiring
diagram.
Amphibionics 07 3/24/03 9:13 AM Page 297
The Remote Control Transmitter
The first objective will be to control Turtletron’s differential drive,
using the remote control transmitter that was built in Chapter 6.
The hand held remote control device uses an analog X and Y axis
control stick as the input to two analog-to-digital converters resid-
ing on a PIC 16C71,To make the project easier,we will not change
any of the programming for the remote control transmitter,If you
wish to create another remote control,follow the instructions in
chapter 6,To make Turtletron respond only to the second remote
control,simply change the qualifier in the serial transmit and
receive code of the robot and transmitter,The schematic for the
transmitter remote control is shown in Figure 7.26.
The circuit functions by using a PIC 16C71 to monitor the position
of the analog control stick and then send serial commands to the
transmitter module,When the control stick moves along the X and
Y axis,the resistance values of two 100KH9024potentiometers change
proportionally,The control stick and the two attached poten-
Amphibionics
298
FIGURE 7.25
Turtletron with all
components attached.
Amphibionics 07 3/24/03 9:13 AM Page 298
tiometers are shown in Chapter 6 (Figure 6.47),Each poten-
tiometer is configured as a voltage divider,so that a unique volt-
age represents each position along the X and Y axis,The voltages
from the potentiometers are converted to 8-bit values by the inter-
nal analog-to-digital converters on the PIC 16C71,and then inter-
preted by the microcontroller,Depending on the values,certain
movement commands are sent in a serial format from the trans-
mitter to the robot,The remote control also has a programmable
push-button switch and a light-emitting diode (LED) that can be
turned on when certain events occur,such as during the trans-
mission of a movement command,The transmitter module is the
TXLC-434 transmitter,available from Reynolds Electronics at
www.rentron.com.
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
299
Figure 7.26
Remote control
schematic diagram.
Amphibionics 07 3/24/03 9:13 AM Page 299
Programming Turtletron
The first program to be written will receive commands from the
hand held remote control via the RF receiver module,This infor-
mation will be used to control the drive motors,as required,It will
not be necessary to reprogram the transmitter because the same
transmission codes that were implemented for the final remote
control program in Chapter 6 will be used,The robot control pro-
gram will use the serin command to collect the data from the
receiver module,and then make movement decisions based on
that information,The differential drive allows the robot to move
forward,reverse,turn left,or turn right on the spot,and to move
in an arc,The control program is called turtle-receive.bas and is
listed in Program 7.1,Compile turtle-receive.bas,and then pro-
gram the PIC 16F84 with the turtle-receive.hex file listed in
Program 7.2,Place the PIC 16F84 into the 18-pin socket on
Turtletron’s main board.
If you reprogrammed the PIC 16C71 in the transmitter circuit since
Chapter 6,then compile turtle-trans.bas listed in Program 7.3.
Program the 16C71 with the turtle-trans.hex file listed in Program
7.4,and then insert the PIC back into the 18-pin socket on the
transmitter circuit board,Move the control stick on the remote
control to the middle position,and then turn the power on,Turn
the robot on and place it on the ground,When the control stick is
moved to the forward position,the robot will move forward,With
the stick moved backwards,the robot will respond by moving in
reverse,With the control stick moved to the left,the robot will
rotate left on the spot,The ability to rotate on the spot is one of
the great things about using a differential drive system,Rotating
on the spot is accomplished by rotating one wheel forward,while
the other wheel rotates in reverse,With the stick moved to the
right,the robot will rotate to the right on the spot,Try moving the
control stick to the forward-right position,The code will alternate
Amphibionics
300
Amphibionics 07 3/24/03 9:13 AM Page 300
transmitting forward and turn-right commands to the robot,The
robot will respond by moving in a forward-right arc.
'------------------------------------------------------------------------------------------------------------------------------
' Name,turtle-receive.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Robot remote control using the Linx 433LC
',series transmitter and receiver,
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs.
trisa = %00000000
' PortB set as outputs,pin 0 input,
trisb = %00000001
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
include "modedefs.bas"
rx_baud CON N2400
rxmit VAR PORTB.0
enable_right VAR PORTB.1
forward_right VAR PORTB.2
reverse_right VAR PORTB.3
enable_left VAR PORTB.4
reverse_left VAR PORTB.5
forward_left VAR PORTB.6
piezo VAR PORTA.3
control VAR BYTE
temp VAR BYTE
low enable_left
low forward_left
low reverse_left
low enable_right
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
301
PROGRAM 7.1
turtle-receive.bas listing
Amphibionics 07 3/24/03 9:13 AM Page 301
low forward_right
low reverse_right
SOUND PIEZO,[115,10,50,10]
start:
serin rxmit,rx_baud,["Z"],control
if control = "A" then
gosub forward
endif
if control = "B" then
gosub backwards
endif
if control = "C" then
gosub turn_left
endif
if control = "D" then
gosub turn_right
endif
if control = "E" then
sound piezo,[115,10,50,10]
endif
if control = "F" then
low enable_left
low forward_left
low reverse_left
low enable_right
low forward_right
low reverse_right
endif
Amphibionics
302
PROGRAM 7.1
turtle-receive.bas listing
(continued)
Amphibionics 07 3/24/03 9:13 AM Page 302
goto start
'———————————————————————————
' movement subroutines
forward:
high enable_left
high forward_left
high enable_right
high forward_right
return
'------------------------------------------------------------------------------------------------------------------------------
turn_left:
high enable_left
high forward_left
high enable_right
high reverse_right
return
'------------------------------------------------------------------------------------------------------------------------------
backwards:
high enable_left
high reverse_left
high enable_right
high reverse_right
return
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
303
PROGRAM 7.1
turtle-receive.bas listing
(continued)
Amphibionics 07 3/24/03 9:13 AM Page 303
'------------------------------------------------------------------------------------------------------------------------------
turn_right:
high enable_left
high reverse_left
high enable_right
high forward_right
return
end
:10000000922864001120031801281C2008308F005A
:100010001D2011208E0C0C288F0B08281D200E0887
:100020000800220884002008841780048413000537
:100030001F192006FF3E08001F171F0D06398C00F0
:100040002B208D008C0A2B201F1F71281F138C0062
:1000500002308820712800308A000C0882070134A1
:1000600075340334153400343C340C34D9348F00E7
:100070002208840020095E2084138F0803198D282C
:10008000F03091000E0880389000F0309103031991
:10009000910003198F0303198D284E286120030155
:1000A0000C1820088E1F20088E0803190301900FDA
:1000B0005B28800642285C280000452884178005BC
:1000C0008D280D080C0403198C0A80300C1A8D063B
:1000D0000C198D068C188D060D0D8C0D8D0D8D282F
:1000E0008D01E83E8C008D09FC30031C7A288C07BA
:1000F000031877288C0764008D0F77280C18802848
:100100008C1C842800008428080003108D0C8C0CA3
:10011000FF3E031885280C088D28831303138312D0
:1001200064000800831603308500013086008312C6
:100130000612831606128312061383160613831201
:1001400086128316861283128610831686108312F7
:100150000611831606118312861183168611053047
:100160008312A2000830A00073308E000A303720BE
:1001700032308E000A3037200630A2000130A00055
Amphibionics
304
PROGRAM 7.1
turtle-receive.bas listing
(continued)
PROGRAM 7.2
turtle-receive.hex file
listing
Amphibionics 07 3/24/03 9:13 AM Page 304
:1001800004309F0001205A3C031DC2280120A40016
:1001900064002408413C031DCE280F21640024087C
:1001A000423C031DD428312164002408433C031D34
:1001B000DA28202164002408443C031DE028422161
:1001C00064002408453C031DF1280530A2000830D6
:1001D000A00073308E000A30372032308E000A3093
:1001E000372064002408463C031D0E29061283169E
:1001F00006128312061383160613831286128316C1
:1002000086128312861083168610831206118316B7
:10021000061183128611831686118312BC280616D6
:10022000831606128312061783160613831286148A
:100230008316861083120615831606118312080092
:1002400006168316061283120617831606138312E8
:1002500086148316861083128615831686118312E0
:100260000800061683160612831286168316861257
:1002700083128614831686108312861583168611C0
:10028000831208000616831606128312861683163A
:10029000861283128614831686108312061583161F
:0A02A00006118312080063005329C1
:02400E00F53F7C
:00000001FF
'------------------------------------------------------------------------------------------------------------------------------
' Name,turtle-trans.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Robot control using the Linx 433LC series
',transmitter and receiver.
',Using on-chip analog to digital converters
',of the PIC 16C71 to read the position of
',the two control stick potentiometers,
'------------------------------------------------------------------------------------------------------------------------------
' set PortA inputs.
trisa = %00011111
' PortB set as outputs,Pin 2 input
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
305
PROGRAM 7.2
turtle-receive.hex file
listing (continued)
PROGRAM 7.3
turtle-trans.bas listing
Amphibionics 07 3/24/03 9:13 AM Page 305
trisb = %00000100
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
include "modedefs.bas"
tx_baud CON N2400
pot_y VAR PORTA.0
pot_x VAR PORTA.1
txmit VAR PORTB.0
txmit_led VAR PORTB.1
push_button VAR PORTB.2
val_y VAR BYTE
val_x VAR BYTE
'------------------------------------------------------------------------------------------------------------------------------
' Set up the analog to digital converters
DEFINE ADC_BITS 8 ' Set number of bits in result
DEFINE ADC_CLOCK 3 ' Set clock source (rc = 3)
DEFINE ADC_SAMPLEUS 10 ' Set sampling time in microseconds
ADCON1 = 2 ' Set porta pins 0 and 1 to analog
start:
low txmit_led
ADCIN 0,val_y ' read A/D converter - porta.pin 0
ADCIN 1,val_x ' read A/D converter - porta.pin 1
If val_y < 20 then
high txmit_led
serout txmit,tx_baud,["ZA"]
endif
If val_y > 200 then
high txmit_led
Amphibionics
306
PROGRAM 7.3
turtle-trans.bas listing
(continued)
Amphibionics 07 3/24/03 9:13 AM Page 306
serout txmit,tx_baud,["ZB"]
endif
If val_X < 20 then
high txmit_led
serout txmit,tx_baud,["ZC"]
endif
If val_X > 200 then
high txmit_led
serout txmit,tx_baud,["ZD"]
endif
If push_button = 1 then
high txmit_led
serout txmit,tx_baud,["ZE"]
endif
If ((val_y > 25) and (val_y < 190)) or ((val_x > 25) and (val_x < 190))
then
serout txmit,tx_baud,["ZF"]
endif
goto start
end
:100000008C2892002A0884000930930003100D20E8
:10001000920C930B072803140D288413A71D1C288A
:1000200000082804271D28068000841700082804DB
:10003000031C28068000272800082804031C280623
:100040002719280680008417280980052728270DEE
:1000500006398C0030208D008C0A302000004E289C
:1000600000308A000C0882070134753403341534DB
:1000700000343C340C34D9348C008C0D8C0D0C0DB8
:100080003839C138880000308D000A304E200815FC
:10009000081948288D01090887288D01E83E8C0041
:1000A0008D09FC30031C57288C07031854288C0733
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
307
PROGRAM 7.3
turtle-trans.bas listing
(continued)
PROGRAM 7.4
turtle-trans.hex file
listing
Amphibionics 07 3/24/03 9:13 AM Page 307
:1000B00064008D0F54280C185D288C1C61280000EA
:1000C000612808008D018F018E0001306C288D01A0
:1000D0008F018E0004306C2894000F080D02031D60
:1000E00073280E080C020430031801300319023083
:1000F0001405031DFF3087280038031DFF30040559
:10010000031DFF3087280404031DFF308728831355
:10011000031383126400080083161F308500043027
:100120008600023088008312861083168610003005
:1001300083123C20AD0001303C20AC006400143040
:100140002D020318B12886148316861006308312F8
:10015000AA000130A8000430A7005A300120413025
:1001600001206400C9302D02031CC42886148316A4
:10017000861006308312AA000130A8000430A700C0
:100180005A30012042300120640014302C02031840
:10019000D72886148316861006308312AA000130F1
:1001A000A8000430A7005A30012043300120640029
:1001B000C9302C02031CEA288614831686100630E8
:1001C0008312AA000130A8000430A7005A30012091
:1001D000443001206400061DFB2886148316861017
:1001E00006308312AA000130A8000430A7005A305C
:1001F0000120453001202D088C00193062209E001E
:100200002D088C00BE306720A0001E088400200846
:100210007C20A000A1002C088C0019306220A200D4
:100220002C088C00BE306720A4002208840024081B
:100230007C20A400A50020082104840024082504B3
:100240008320A400A5006400240825040319322992
:100250000630AA000130A8000430A7005A3001205F
:0602600046300120942845
:02400E00FD3F74
:00000001FF
Testing the SRF04 Ultrasonic Ranger
As described previously,the ranger works by emitting a short burst
of sound and then listening for the echo,Under the control of the
PICmicro MCU 16F84,the SRF04 will emit an ultrasonic (40 kHz)
sound pulse,The pulse travels through the air,hits an object,and
Amphibionics
308
PROGRAM 7.4
turtle-trans.hex file
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 308
then bounces back,Since we know that sound travels through air
at approximately 1129 feet per second when the temperature is 21
degrees Celsius,we can accurately determine distance by measur-
ing the amount of time between the transmission of the pulse and
the return echo,When the temperature drops,the speed of sound
through air slows down,If a temperature sensor was added,an
algorithm to determine distance based on the speed of sound
through air could take the surrounding temperature into account
and adjust for differences.
The PicBasic Pro command called PULSIN returns the round trip
echo time in 10 μs units when using a 4-MHz oscillator,Since the
pulse width has a 10 μs resolution per increment,that means that
if PULSIN returns a value of 1,then 10 μs have elapsed,The fac-
tors to convert the raw data to inches and centimeters given in the
SRF04 manual are 74 for inches (73.746 μs per 1 inch) and 29 for
centimeters (29.033 μs per 1 cm) based on the Basic Stamps
PULSIN command returning values in 2 μs increments,In the
SRF04 manual,the calculation to determine the distance is not
divided in half to take into account the return time of the pulse
because the sample program is for the Basic Stamp II,which
returns PULSIN values in 2 μs increments,Because the PULSIN
command with PicBasic Pro is returning values in increments of 10
μs,the conversion factor will need to be divided by 5,so that we
get the correct value based on our 10 μs increment,Taking the
PULSIN increment timing difference into account gives us an
approximate conversion factor of 15 for inches and 6 for centime-
ters,Testing with the ranger indicated that the raw value returned
by PULSIN when an object was 12 inches away was 180,One hun-
dred and eighty divided by the inch conversion factor of 15 gives
us the correct distance of 12 inches.
In order to test the SRF04 sonar ranger,a program will be written
to produce audible tones,based on the distance of an object from
the device,Compile the sonar-test.bascode listed in Program 7.5,
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
309
Amphibionics 07 3/24/03 9:13 AM Page 309
and then program the PICmicro MCU 16F84 with the
sonar-test.hex file listed in Program 7.6,When the PIC is insert-
ed into the 18-pin socket on the main controller board and power
is applied,move your hand slowly toward the ranger and notice
that the tones produced by the PIC get lower the closer your hand
gets to the device,If no tones are produced when power is applied,
then check to make sure that none of the connections from the
sonar module to the controller board have been mixed up.
'------------------------------------------------------------------------------------------------------------------------------
' Name,sonar-test.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Program control of the Devantech SRF04
',ultrasonic module,Convert the raw distance
',data to a frequency and output to the piezo
',element,
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs,Pin 1 input.
trisa = %00000010
' PortB set as outputs,
trisb = %00000000
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
trigger VAR PORTA.0
echo VAR PORTA.1
piezo VAR PORTA.3
dist_raw VAR WORD
dist_inch VAR WORD
dist_cm VAR WORD
freq VAR WORD
conv_inch CON 15
conv_freq CON 6
Amphibionics
310
PROGRAM 7.5
sonar-test.bas program
listing
Amphibionics 07 3/24/03 9:13 AM Page 310
SOUND PIEZO,[115,10,50,10]
start:
main:
gosub sr_sonar
if freq > 47 then main
sound piezo,[80 + freq,10]
Goto main
'------------------------------------------------------------------------------------------------------------------------------
sr_sonar:
pulsout trigger,1 ' send a 10us trigger pulse to
the SRF04
pulsin echo,1,dist_raw ' start timing the pulse width
on echo pin
dist_inch = (dist_raw/conv_inch) ' Convert raw data into inches
freq = (dist_raw/conv_freq) ' Convert raw data into a
frequency
pause 10 ' wait for 10ms before
returning to main
return
end
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
311
PROGRAM 7.5
sonar-test.bas program
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 311
:10000000C828A2008417800484138E010C1C8E0063
:1000100023200319C32823200319C3282320C3281E
:10002000A20059200C080D040319C328BD20841315
:100030002208800664001C281D288C0A03198D0FD5
:100040001A288006C32822088E0601308C008D01F4
:10005000000822050E06031D08008C0A03198D0FE7
:10006000282808008F002408840022095A208413BD
:100070008F080319C328F03091000E0880389000D3
:10008000F03091030319910003198F030319C3285A
:1000900049285D2003010C1822088E1F22088E08B3
:1000A00003190301900F562880063D2857280000A9
:1000B0004028FF3A84178005C3280D080C04031953
:1000C0008C0A80300C1A8D060C198D068C188D0642
:1000D0000D0D8C0D8D0DC3288F018E00FF308E0706
:1000E000031C8F07031CC32803308D00DF307A20E8
:1000F0006E288D01E83E8C008D09FC30031C83289E
:100100008C07031880288C0764008D0F80280C183A
:1001100089288C1C8D2800008D2808008E00013055
:10012000912894000F080D02031D98280E080C0258
:10013000043003180130031902301405031DFF3089
:10014000C32891019001103092000D0D900D910D7A
:100150000E0890020F08031C0F0F91020318B72816
:100160000E0890070F0803180F0F910703108C0D4E
:100170008D0D920BA5280C08C3288C098D098C0ABB
:1001800003198D0A08008313031383126400080007
:100190008316023085000130860005308312A400EA
:1001A0000830A20073308E000A30322032308E00C8
:1001B0000A303220F4202C088C002D088D008F018D
:1001C0002F308E20031DDA280530A4000830A2004D
:1001D00050302C079E002D080318013E9F001E087A
:1001E0008E000A303220DA2801308C008D01053073
:1001F00084000130102001308C0005308400023072
:1002000001200C08AA000D08AB002A088C002B085E
:100210008D000F308E008F01A120A8000D08A900CD
:100220002A088C002B088D0006308E008F01A1203B
:10023000AC000D08AD000A306C20080063001E29D8
:02400E00F53F7C
:00000001FF
Amphibionics
312
PROGRAM 7.6
sonar-test.hex file
listing
Amphibionics 07 3/24/03 9:13 AM Page 312
Obstacle Avoidance Using the
Ultrasonic Range Finder
In the next experiment,the robot will explore its environment and
will react to obstacles based on the distance information obtained
from the SRF04 sonar module,The robot will normally travel in a
forward direction while sonar distance measurements are taken.
When it is determined that the robot is within 12 inches of an
object,it will reverse,and then alternate between rotating to the
left and rotating to the right each time an obstacle is sensed,The
distance that the robot travels in reverse and how far it rotates in
either direction is determined by the amount of time that the
motors are activated,The robot will rotate a further distance to the
right than to the left so that it does not get stuck in corners,You
can try experimenting with the pause values to change the behav-
ior,When the avoidance maneuver is complete,the robot will con-
tinue moving forward,Compile the avoidance.bas code listed in
Program 7.7,and then program the PICmicro MCU 16F84 with the
avoidance.hex file listed in Program 7.8,After watching the robot
behavior,it is obvious that a better system to track the distance
that the robot has traveled or rotated is needed,Later in the chap-
ter,a linear optical shaft encoder will be added to track distance
traveled,and to develop a more precise motor control method.
'------------------------------------------------------------------------------------------------------------------------------
' Name,avoidance.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Obstacle avoidance using the sonar ranger
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs,Pin 1 input.
trisa = %00000010
' PortB set as outputs,
trisb = %00000000
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
313
PROGRAM 7.7
avoidance.bas program
listing
Amphibionics 07 3/24/03 9:13 AM Page 313
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
trigger VAR PORTA.0
echo VAR PORTA.1
piezo VAR PORTA.3
enable_right VAR PORTB.1
forward_right VAR PORTB.2
reverse_right VAR PORTB.3
enable_left VAR PORTB.4
reverse_left VAR PORTB.5
forward_left VAR PORTB.6
dist_raw VAR WORD
dist_inch VAR WORD
conv_inch CON 15
turn VAR BYTE
low enable_left
low forward_left
low reverse_left
low enable_right
low forward_right
low reverse_right
SOUND PIEZO,[115,10,50,10]
turn = 0
start:
gosub sr_sonar
if dist_inch < 12 then
turn = turn + 1
gosub backwards
if turn.0 = 1 then
gosub turn_left
else
Amphibionics
314
PROGRAM 7.7
avoidance.bas program
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 314
gosub turn_right
endif
endif
gosub forward
goto start
'------------------------------------------------------------------------------------------------------------------------------
' movement subroutines
forward:
high enable_left
high forward_left
high enable_right
high forward_right
pause 50
low enable_left
low forward_left
low enable_right
low forward_right
return
'------------------------------------------------------------------------------------------------------------------------------
turn_left:
high enable_left
high forward_left
high enable_right
high reverse_right
pause 300
low enable_left
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
315
PROGRAM 7.7
avoidance.bas program
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 315
low forward_left
low enable_right
low reverse_right
return
'------------------------------------------------------------------------------------------------------------------------------
backwards:
SOUND PIEZO,[115,5,90,2,80,4,50,10]
high enable_left
high reverse_left
high enable_right
high reverse_right
pause 300
low enable_left
low reverse_left
low enable_right
low reverse_right
return
'------------------------------------------------------------------------------------------------------------------------------
turn_right:
high enable_left
high reverse_left
high enable_right
high forward_right
pause 600
low enable_left
Amphibionics
316
PROGRAM 7.7
avoidance.bas program
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 316
low reverse_left
low enable_right
low forward_right
return
'------------------------------------------------------------------------------------------------------------------------------
sr_sonar:
pulsout trigger,1
pulsin echo,1,dist_raw
dist_inch = (dist_raw/conv_inch)
pause 10
return
end
:10000000C828A0008417800484138E010C1C8E0065
:1000100023200319C32823200319C3282320C3281E
:10002000A00059200C080D040319C328BD20841317
:100030002008800664001C281D288C0A03198D0FD7
:100040001A288006C32820088E0601308C008D01F6
:10005000000820050E06031D08008C0A03198D0FE9
:10006000282808008F002208840020095A208413C1
:100070008F080319C328F03091000E0880389000D3
:10008000F03091030319910003198F030319C3285A
:1000900049285D2003010C1820088E1F20088E08B7
:1000A00003190301900F562880063D2857280000A9
:1000B0004028FF3A84178005C3280D080C04031953
:1000C0008C0A80300C1A8D060C198D068C188D0642
:1000D0000D0D8C0D8D0DC3288F018E00FF308E0706
:1000E000031C8F07031CC32803308D00DF307A20E8
:1000F0006E288D01E83E8C008D09FC30031C83289E
:100100008C07031880288C0764008D0F80280C183A
:1001100089288C1C8D2800008D2808008E00033053
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
317
PROGRAM 7.7
avoidance.bas program
listing (continued)
PROGRAM 7.8
avoidance.hex file
listing
Amphibionics 07 3/24/03 9:13 AM Page 317
:10012000912894000F080D02031D98280E080C0258
:10013000043003180130031902301405031DFF3089
:10014000C32891019001103092000D0D900D910D7A
:100150000E0890020F08031C0F0F91020318B72816
:100160000E0890070F0803180F0F910703108C0D4E
:100170008D0D920BA5280C08C3288C098D098C0ABB
:1001800003198D0A08008313031383126400080007
:100190008316033085000130860083120612831611
:1001A0000612831206138316061383128612831611
:1001B0008612831286108316861083120611831608
:1001C0000611831286118316861105308312A20050
:1001D0000830A00073308E000A30322032308E009A
:1001E0000A303220A801AD2124088C0025088D009A
:1001F0008F010C308E20031D0529A80A4F216400B1
:10020000281C04292A21052988210721F3280616FC
:10021000831606128312061783160613831286149A
:100220008316861083120615831606113230831248
:100230006C20061283160612831206138316061309
:1002400083128610831686108312061183160611F8
:1002500083120800061683160612831206178316E9
:10026000061383128614831686108312861583164E
:100270008611831201308F002C306D2006128316F8
:100280000612831206138316061383128610831632
:10029000861083128611831686118312080005309A
:1002A000A2000830A00073308E00053032205A3092
:1002B0008E000230322050308E0004303220323036
:1002C0008E000A3032200616831606128312861616
:1002D000831686128312861483168610831286155F
:1002E00083168611831201308F002C306D20061288
:1002F00083160612831286128316861283128610C4
:1003000083168610831286118316861183120800C5
:100310000616831606128312861683168612831219
:10032000861483168610831206158316061183120F
:1003300002308F0058306D20061283160612831289
:1003400086128316861283128610831686108312F5
:100350000611831606118312080001308C008D01EE
:10036000053084000130102001308C0005308400FD
:10037000023001200C08A6000D08A70026088C00FA
Amphibionics
318
PROGRAM 7.8
avoidance.hex file
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 318
:1003800027088D000F308E008F01A120A4000D08DA
:0C039000A5000A306C2008006300CC2996
:02400E00F53F7C
:00000001FF
Now that radio remote control and sonar obstacle avoidance has
been covered,a program will be written to incorporate both,An
operator will determine the robot movements,via the remote con-
trol,Based on distance measurements taken from the sonar mod-
ule,the microcontroller will inhibit movement if the robot is in
danger of crashing into an obstacle,Since the sonar is mounted to
the front of the robot,this will help protect the device,Compile the
program called remote-sonar.bas,listed in Program 7.9,Program
the PIC 16F84 with the corresponding remote-sonar.hex file,listed
in Program 7.10.
This kind of human/machine interaction is valuable in situations
where a robot is operated over large distances (teleoperated).
Because the complexity of machines has increased,it is impossi-
ble for humans to control all of the small aspects of robotic behav-
ior,With teleoperated robotics,the human gives basic control
commands and the robot carries out the tasks all on its own.
Another problem with controlling machines over large distances,
because of slow radio signals,is that time delays are introduced
between the human control commands and the robot’s actions,If
a human operator makes a mistake,the robot will compensate to
avoid a catastrophic failure.
'------------------------------------------------------------------------------------------------------------------------------
' Name,remote-sonar.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Remote control with sonar avoidance.
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs,Pin 1 input.
trisa = %00000010
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
319
PROGRAM 7.8
avoidance.hex file
listing (continued)
PROGRAM 7.9
remote-sonar.bas
program listing
Amphibionics 07 3/24/03 9:13 AM Page 319
' PortB set as outputs,pin 0 input,
trisb = %00000001
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
include "modedefs.bas"
rx_baud CON N2400
rxmit VAR PORTB.0
enable_right VAR PORTB.1
forward_right VAR PORTB.2
reverse_right VAR PORTB.3
enable_left VAR PORTB.4
reverse_left VAR PORTB.5
forward_left VAR PORTB.6
trigger VAR PORTA.0
echo VAR PORTA.1
piezo VAR PORTA.3
control VAR BYTE
temp VAR BYTE
dist_raw VAR WORD
dist_inch VAR WORD
conv_inch CON 15
low enable_left
low forward_left
low reverse_left
low enable_right
low forward_right
low reverse_right
SOUND PIEZO,[115,10,50,10]
start:
serin rxmit,rx_baud,["Z"],control
Amphibionics
320
PROGRAM 7.9
remote-sonar.bas
program listing
(continued)
Amphibionics 07 3/24/03 9:13 AM Page 320
if control = "A" then
gosub sr_sonar
if dist_inch < 8 then start
gosub forward
endif
if control = "B" then
gosub backwards
endif
if control = "C" then
gosub turn_left
endif
if control = "D" then
gosub turn_right
endif
if control = "E" then
sound piezo,[115,10,50,10]
endif
if control = "F" then
low enable_left
low forward_left
low reverse_left
low enable_right
low forward_right
low reverse_right
endif
goto start
'------------------------------------------------------------------------------------------------------------------------------
' movement subroutines
forward:
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
321
PROGRAM 7.9
remote-sonar.bas
program listing
(continued)
Amphibionics 07 3/24/03 9:13 AM Page 321
high enable_left
high forward_left
high enable_right
high forward_right
pause 500
low enable_left
low forward_left
low enable_right
low forward_right
return
'------------------------------------------------------------------------------------------------------------------------------
turn_left:
high enable_left
high forward_left
high enable_right
high reverse_right
return
'------------------------------------------------------------------------------------------------------------------------------
backwards:
high enable_left
high reverse_left
high enable_right
high reverse_right
return
'------------------------------------------------------------------------------------------------------------------------------
Amphibionics
322
PROGRAM 7.9
remote-sonar.bas
program listing
(continued)
Amphibionics 07 3/24/03 9:13 AM Page 322
turn_right:
high enable_left
high reverse_left
high enable_right
high forward_right
return
'------------------------------------------------------------------------------------------------------------------------------
sr_sonar:
pulsout trigger,1
pulsin echo,1,dist_raw
dist_inch = (dist_raw/conv_inch)
pause 10
return
end
:100000000629A0008417800484138E010C1C8E0026
:100010002320031901292320031901292320012961
:10002000A0008F200C080D0403190129FB20841364
:100030002008800664001C281D288C0A03198D0FD7
:100040001A288006012920088E0601308C008D01B7
:10005000000820050E06031D08008C0A03198D0FE9
:100060002828080064004220031832284D20083058
:100070008F004E2042208E0C3D288F0B39284E20B9
:100080000E080800220884002008841780048413C6
:1000900000051F192006FF3E08001F171F0D063917
:1000A0008C005C208D008C0A5C201F1FB0281F1361
:1000B0008C000230C720B02800308A000C0882076C
:1000C000013475340334153400343C340C34D934E1
:1000D0008F00220884002009902084138F080319C0
:1000E0000129F03091000E0880389000F030910323
:1000F0000319910003198F03031901297F28932005
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
323
PROGRAM 7.9
remote-sonar.bas
program listing
(continued)
PROGRAM 7.10
remote-sonar.hex file
listing
Amphibionics 07 3/24/03 9:13 AM Page 323
:1001000003010C1820088E1F20088E080319030114
:10011000900F8C28800673288D2800007628FF3ADF
:100120008417800501290D080C0403198C0A8030FE
:100130000C1A8D060C198D068C188D060D0D8C0D64
:100140008D0D01298F018E00FF308E07031C8F0754
:10015000031C012903308D00DF30B020A4288D015D
:10016000E83E8C008D09FC30031CB9288C0703186D
:10017000B6288C0764008D0FB6280C18BF288C1C7D
:10018000C3280000C328080003108D0C8C0CFF3E10
:100190000318C4280C0801298E000430CF289400CD
:1001A0000F080D02031DD6280E080C020430031898
:1001B0000130031902301405031DFF30012991019C
:1001C0009001103092000D0D900D910D0E089002CF
:1001D0000F08031C0F0F91020318F5280E08900753
:1001E0000F0803180F0F910703108C0D8D0D920B44
:1001F000E3280C0801298C098D098C0A03198D0A42
:10020000080083130313831264000800831602306E
:1002100085000130860083120612831606128312AF
:100220000613831606138312861283168612831210
:100230008610831686108312061183160611831208
:1002400086118316861105308312A2000830A000A3
:1002500073308E000A30682032308E000A306820F9
:100260000630A2000130A00004309F0032205A3C2A
:10027000031D36293220A80064002808413C031DD4
:100280004C29E52124088C0025088D008F010830B9
:10029000CC20031D30298D2164002808423C031D19
:1002A0005229C32164002808433C031D5829B22168
:1002B00064002808443C031D5E29D42164002808FA
:1002C000453C031D6F290530A2000830A0007330A3
:1002D0008E000A30682032308E000A3068206400B8
:1002E0002808463C031D8C29061283160612831229
:1002F0000613831606138312861283168612831240
:100300008610831686108312061183160611831237
:10031000861183168611831230290616831606125B
:10032000831206178316061383128614831686100B
:100330008312061583160611831201308F00F430E4
:10034000A3200612831606128312061383160613C1
:1003500083128610831686108312061183160611E7
Amphibionics
324
PROGRAM 7.10
remote-sonar.hex file
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 324
:1003600083120800061683160612831206178316D8
:10037000061383128614831686108312861583163D
:10038000861183120800061683160612831286163B
:10039000831686128312861483168610831286159E
:1003A000831686118312080006168316061283121E
:1003B000861683168612831286148316861083127D
:1003C0000615831606118312080001308C008D017A
:1003D000053084000130102001308C00053084008D
:1003E000023001200C08A6000D08A70026088C008A
:1003F00027088D000F308E008F01DF20A4000D082C
:0C040000A5000A30A22008006300042AB6
:02400E00F53F7C
:00000001FF
Distance Measurement
Using an Optical Shaft Encoder
A shaft encoder is a sensor that measures the position or velocity
of a shaft,Shaft encoders are generally inexpensive devices that
are most often mounted on the output shaft of a drive motor or on
the axle,The signal that is produced by this sensor can be either
a code that corresponds to a particular position of the shaft (called
absolute encoders),or it may be a pulse train,Shaft encoders that
produce a pulse train are called incremental encoders,The
encoder is typically a disk that has numerous holes or slots along
its outside edge,An infrared LED is placed on one side of the disk
and an infrared-sensitive phototransistor is positioned directly
opposite the LED,As the shaft rotates,the holes pass the light
intermittently and the state of the phototransistor output changes
from high to low or vise versa,producing a pulse train,The rate at
which the pulses are produced corresponds to the rate at which
the shaft turns,By using a microprocessor to count the pulses,the
robot can determine how far its wheels have rotated,The combi-
nation of an infrared LED emitter and a phototransistor,packaged
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
325
PROGRAM 7.10
remote-sonar.hex file
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 325
for the purpose of being mounted on either side of a shaft
encoder’s disk,is called a photointerrupter,as shown in Figure
7.27.
The device that we will use to track the distance that Turtletron’s
motor has traveled is a photodarlington optical interrupter switch
with part number H22B1,shown in Figure 7.28,The H22B1 con-
sists of a gallium arsenide infrared LED,coupled with a silicon
photodarlington in a plastic housing,The packaging system is
designed to optimize the mechanical resolution,coupling efficien-
cy,ambient light rejection,cost,and reliability,The gap in the
housing provides a means of interrupting the signal with an
opaque material,switching the output from an,ON” to an,OFF”
state,The interrupter will be mounted on a small circuit board and
placed around the encoder disk that was included with the motor
kits.
Amphibionics
326
FIGURE 7.27
Optical encoder and
photointerrupter
attached to motor
shaft.
Amphibionics 07 3/24/03 9:13 AM Page 326
Fabricating the Shaft Encoder
Start by locating the plastic motor mount with six evenly spaced
holes along its outside edge,It is shown in Figure 7.29 and will
function as the encoder disk,Mount it to the end of the robot’s left
motor shaft,opposite to the wheel,using the washer and nut that
were supplied,This small disk only has six holes and six opaque
areas,giving us a rotational accuracy of 30 degrees per state
change,which is sufficient for a small robot like Turtletron,If the
microcontroller is monitoring the interrupter switch and counts 12
state changes,from high to low or vice versa,then the wheel has
made one full rotation,The parts needed to construct the shaft
encoder are listed in Table 7.5.
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
327
FIGURE 7.28
H22B1 interrupter
switch package
dimensions and
schematic.
Amphibionics 07 3/24/03 9:13 AM Page 327
Part Quantity Description
H22B1 Optical 1 Photodarlington transistor
interrupter switch
R1,R2 2 1 KH9024 1/4-watt resistor
R3 1 470 KH9024 1/4-watt resistor
D1 1 Red light-emitting diode
Three-strand ribbon wire 7 inches Connector wire
header 1 4-post male connector—
2.5-mm spacing
Hot glue — Hot glue and gun
The schematic to interface the interrupter switch to the PIC 16F84
is shown in Figure 7.30,The circuit operates by using the transis-
tor as a switch,Cut a piece of perfboard to a size of 1-1/2 inches
H11003 3/4 of an inch,Create an aluminum mounting bracket by fol-
lowing the cutting,drilling,and bending instructions in Figure
7.31,Use 1/16-inch thick aluminum to construct the mounting
bracket,When it is complete,position the 3/4-inch side of the
mount on the left side of the perfboard and mark the mounting
hole,Drill the hole with a 5/32-inch bit,Attach the mount to the
perfboard with a 6/32-inch H11003 1/2-inch machine screw and lock-
Amphibionics
328
FIGURE 7.29
Encoder disk.
TABLE 7.5
Optical Encoder Parts
List
Amphibionics 07 3/24/03 9:13 AM Page 328
ing nut,Mount the interrupter to the upper left side of the board
and secure it in place with hot glue,Because the circuit is so sim-
ple,use point to point wiring to solder all of the parts together.
Mount the LED with the leads bent on a 90-degree angle so that it
is pointing upwards,The LED will indicate when the infrared light
beam has been interrupted by the opaque parts of the disk,Cut a
piece of 3-strand ribbon wire to a length of 7 inches,Solder the
end of one wire to the 5-volt connection point,another wire to ter-
minal 3 of the H22B1,and the last wire to the common ground
point,The finished interface board is shown in Figure 7.32.
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
329
FIGURE 7.30
Schematic to interface
the H22B1 interrupter
switch to PIC 16F84.
FIGURE 7.31
Encoder board
mounting bracket.
Amphibionics 07 3/24/03 9:13 AM Page 329
Place the interface board on the bottom of the robot so that the
encoder disk is positioned in between the H22B1 interrupter,Make
sure that the disk does not touch either side of the interrupter and
can rotate freely when the tire is turned by hand,Mark the posi-
tion of the two mounting holes on the robot base,Drill the two
holes with a 5/32-inch bit,and then secure the interface board
with two 6/32-inch H11003 1/2-inch machine screws and locking nuts.
Rotate the tire by hand,Make any necessary position adjustments
of the interface board if the disk is not centered,A close-up of the
encoder disk and interface board is shown in Figure 7.33,To get
an idea of the overall positioning,refer to Figure 7.34,Drill a hole
in the robot base and feed the 3-strand connector wire through.
Disconnect the RF receiver module from the main controller board.
The interrupter circuit will use the connector that the RF module
was plugged into,Follow the wiring diagram in Figure 7.35 to
connect the interface board to the main controller.
Amphibionics
330
FIGURE 7.32
Finished encoder
interface board.
Amphibionics 07 3/24/03 9:13 AM Page 330
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
331
FIGURE 7.33
Optical encoder disk
centered between the
interrupter.
FIGURE 7.34
Interrupter interface
board mounted to robot
base.
Amphibionics 07 3/24/03 9:13 AM Page 331
When the photointerrupter is connected to the main controller,
take the PIC microcontroller out of the 18-pin socket and turn on
the power,Slowly rotate the tire by hand,The LED will be on when
an opaque section of the encoder disk is between the optical inter-
rupter,When it comes across a hole in the disk,the LED will be
off,The next program will test the connection of the device to the
PIC 16F84 microcontroller,Compile encode-test.bas,listed in
Program 7.11,and then program the PIC 16F84 with the encode-
test.hex file listed in Program 7.12,Place the PIC in the 18-pin
socket and then turn on the power,When you rotate the tire and
encoder disk by hand,the PIC will produce a sound each time a
hole is encountered,The program stays in a tight loop until the
transistor changes state again; otherwise the PIC would continu-
ously produce the tone sequence while the disk was on the same
hole,This method will be used when counting the number of times
the transistor switches from one state to another,or an event is
being triggered,If a counter is being incremented,this method
ensures that only one count will occur during a state transition.
Amphibionics
332
FIGURE 7.35
Wiring diagram to
connect interface board
to main controller.
Amphibionics 07 3/24/03 9:13 AM Page 332
'------------------------------------------------------------------------------------------------------------------------------
' Name,encode-test.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Program to test the optical interrupter
',photodarlington switch
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs.
trisa = %00000000
' PortB set as outputs,pin 0 input,
trisb = %00000001
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
switch VAR PORTB.0
enable_right VAR PORTB.1
forward_right VAR PORTB.2
reverse_right VAR PORTB.3
enable_left VAR PORTB.4
reverse_left VAR PORTB.5
forward_left VAR PORTB.6
piezo VAR PORTA.3
control VAR BYTE
temp VAR BYTE
low enable_left
low forward_left
low reverse_left
low enable_right
low forward_right
low reverse_right
SOUND piezo,[115,10,50,10]
start:
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
333
PROGRAM 7.11
encode-test.bas
program listing
Amphibionics 07 3/24/03 9:13 AM Page 333
If switch = 0 then
SOUND piezo,[80,5,110,5,50,10,120,2]
while switch = 0
wend
endif
goto start
:100000003F288F00220884002009282084138F08AD
:1000100003193A28F03091000E0880389000F03033
:1000200091030319910003198F0303193A28182823
:100030002B2003010C1820088E1F20088E0803199E
:100040000301900F252880060C28262800000F2881
:10005000841780053A280D080C0403198C0A803097
:100060000C1A8D060C198D068C188D060D0D8C0D35
:100070008D0D3A288313031383126400080083163E
:100080008501013086008312061283160612831240
:1000900006138316061383128612831686128312A2
:1000A000861083168610831206118316061183129A
:1000B00086118316861105308312A2000830A00035
:1000C00073308E000A30012032308E000A30012059
:1000D0006400061883280530A2000830A0005030C4
:1000E0008E00053001206E308E0005300120323048
:1000F0008E000A30012078308E000230012064002A
:08010000061883287F286828F7
:02400E00F53F7C
:00000001FF
Room Mapping Using the Shaft Encoder
and Ultrasonic Range Finder
The robot now has the ability to keep track of how far the left
wheel has traveled using the incremental shaft encoder,This will
be necessary when the robot is mapping an area before it starts to
move,In previous programs where the robot used the sonar
ranger,it avoided obstacles in a reactionary way because it did not
have an internal representation of the outside world,It wandered
Amphibionics
334
PROGRAM 7.11
encode-test.bas
program listing
(continued)
PROGRAM 7.12
encode-test.hex file
listing
Amphibionics 07 3/24/03 9:13 AM Page 334
around the room until distance readings from the sonar module
alerted the robot that an evasive maneuver was needed to avoid
crashing into an obstacle.
To improve this situation,the robot will need to create a rudimen-
tary map of the area surrounding its current position,A robot’s
ability to create an internal representation of the external world
can be thought of as the first measure of machine intelligence,and
is a necessary evolutionary step to self awareness and conscious-
ness,The final program in this chapter will take advantage of the
optical shaft encoder and the ultrasonic range finder to give the
robot the ability to map the area around itself and store the results
internally,Based on this information,the robot can then make an
intelligent decision about where to move.
This is accomplished by having the robot take a series of distance
measurements in a 180-degree arc to the front and sides of its cur-
rent location,From where the robot is facing,it will rotate 90
degrees to the left and then start taking distance measurements as
it rotates back in the opposite direction for 180 degrees,The dis-
tance measurements are stored in a one-dimensional array called
position,made up of 12 elements,To make sure that the robot is
consistently moving the same distance for each sonar measure-
ment taken,the output from the optical encoder circuit is used.
The motor control algorithm works by first reading the current
state of the sensor,The initial state of the sensor doesn’t matter;
we are concerned with when the sensor changes from its current
state,indicating that the wheel has moved 1/12 of a complete
rotation,Using this method makes motor control and wheel track-
ing uncomplicated,The program takes the current state of the sen-
sor and stores it in a variable,The motor is then moved by a very
small amount,and the stored sensor state is then compared to the
current state,If the two states are the same,then the motor is
moved again by a small amount,This continues until the sensor
has changed from its original state,at which time the motor is
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
335
Amphibionics 07 3/24/03 9:13 AM Page 335
stopped and the next sonar distance reading is taken,This indi-
cates that the motor has moved the wheel by 1/12 of a complete
rotation.
When all of the sonar distance measurements have been taken,a
sorting algorithm determines which position contains the distance
measurement with the highest value,The robot is then rotated
back to the position with the greatest amount of free space,and
then moves forward to map out the surrounding area,If an obsta-
cle is encountered while moving forward,the robot backs up and
makes another map to determine the best route to take,Compile
sonar-map.bas,listed in Program 7.13,and then program the PIC
16F84 with the corresponding sonar-map.hex file,listed in
Program 7.14,
I find this final experiment to be a lot of fun because of the speed
at which the robot scans the area while making maps,and how
fast it can travel through a room,It is very surprising to see how
well the robot can maneuver through rooms and consistently pick
the areas with the most free space.
To develop robotic room mapping further,write a program that
stores the distance readings in a two-dimensional array,This way
the robot would be able to quickly backtrack without having to
take sonar readings for an area that it has already explored.
'------------------------------------------------------------------------------------------------------------------------------
' Name,sonar-map.bas
' Compiler,PicBasic Pro - MicroEngineering Labs
' Notes,Room mapping using the sonar ranger and
',incremental shaft encoder,
'------------------------------------------------------------------------------------------------------------------------------
' PortA set as outputs,Pin 1 input.
trisa = %00000010
' PortB set as outputs,pin 0 input,
Amphibionics
336
PROGRAM 7.13
sonar-map.bas program
listing
Amphibionics 07 3/24/03 9:13 AM Page 336
trisb = %00000001
'------------------------------------------------------------------------------------------------------------------------------
' initialize variables
trigger VAR PORTA.0
echo VAR PORTA.1
piezo VAR PORTA.3
switch VAR PORTB.0
enable_right VAR PORTB.1
forward_right VAR PORTB.2
reverse_right VAR PORTB.3
enable_left VAR PORTB.4
reverse_left VAR PORTB.5
forward_left VAR PORTB.6
dist_raw VAR WORD
dist_inch VAR WORD
conv_inch CON 15
I VAR BYTE
temp VAR BYTE
state VAR BYTE
best_pos VAR BYTE
most_space VAR BYTE
position VAR WORD[12]
low enable_left
low forward_left
low reverse_left
low enable_right
low forward_right
low reverse_right
SOUND PIEZO,[115,10,50,10]
start:
' rotate robot to the left
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
337
PROGRAM 7.13
sonar-map.bas program
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 337
For I = 1 to 5
state = switch
while switch = state
gosub turn_left
wend
Next I
position[11] = 0
' take 11 distance measurements and store the
' results in the distance[11] array
For I = 0 to 10
gosub sr_sonar
position[I] = dist_inch
state = switch
while switch = state
gosub turn_right
wend
Next I
' sort the distance array to find the location
' with the most free space
best_pos = 11
For I = 0 to 10
If position[I] >= position[best_pos] then
best_pos = I
Endif
Next I
most_space = 11 - best_pos
' rotate the robot so that it is pointing towards
' the area with the most free space
Amphibionics
338
PROGRAM 7.13
sonar-map.bas program
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 338
For I = 1 to most_space
state = switch
while switch = state
gosub turn_left
wend
Next I
' Move the robot forward into the area that was
' determined to be the most free of obstacles.
' Check for any obstacles while moving forward.
' Move in reverse and then scan for area with
' most space if an obstacle was encountered.
For I = 1 to 24
gosub sr_sonar
If dist_inch < 8 then
SOUND PIEZO,[115,5,90,2,80,4,50,10]
For temp = 1 to 6
state = switch
while switch = state
gosub backwards
wend
Next temp
goto start
Endif
state = switch
while switch = state
gosub forward
wend
Next I
goto start
end
'———————————————————————————
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
339
PROGRAM 7.13
sonar-map.bas program
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 339
' movement subroutines
forward:
high enable_left
high forward_left
high enable_right
high forward_right
pause 20
low enable_left
low forward_left
low enable_right
low forward_right
pause 20
return
'------------------------------------------------------------------------------------------------------------------------------
turn_left:
high enable_left
high forward_left
high enable_right
high reverse_right
pause 5
low enable_left
low forward_left
low enable_right
low reverse_right
pause 5
Amphibionics
340
PROGRAM 7.13
sonar-map.bas program
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 340
return
'------------------------------------------------------------------------------------------------------------------------------
backwards:
high enable_left
high reverse_left
high enable_right
high reverse_right
pause 20
low enable_left
low reverse_left
low enable_right
low reverse_right
pause 10
return
'------------------------------------------------------------------------------------------------------------------------------
turn_right:
high enable_left
high reverse_left
high enable_right
high forward_right
pause 5
low enable_left
low reverse_left
low enable_right
low forward_right
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
341
PROGRAM 7.13
sonar-map.bas program
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 341
pause 5
return
'------------------------------------------------------------------------------------------------------------------------------
sr_sonar:
pulsout trigger,1
pulsin echo,1,dist_raw
dist_inch = (dist_raw/conv_inch)
pause 2
return
end
:10000000CB28A4008417800484138E010C1C8E005E
:1000100023200319C62823200319C6282320C62815
:10002000A40059200C080D040319C628C02084130D
:100030002408800664001C281D288C0A03198D0FD3
:100040001A288006C62824088E0601308C008D01EF
:10005000000824050E06031D08008C0A03198D0FE5
:10006000282808008F002608840024095A208413B9
:100070008F080319C628F03091000E0880389000D0
:10008000F03091030319910003198F030319C62857
:1000900049285D2003010C1824088E1F24088E08AF
:1000A00003190301900F562880063D2857280000A9
:1000B0004028FF3A84178005C6280D080C04031950
:1000C0008C0A80300C1A8D060C198D068C188D0642
:1000D0000D0D8C0D8D0DC6288F018E00FF308E0703
:1000E000031C8F07031CC62803308D00DF307A20E5
:1000F0006E288D01E83E8C008D09FC30031C83289E
:100100008C07031880288C0764008D0F80280C183A
:1001100089288C1C8D2800008D2808008E00033053
:1001200094288E000430942894000F080D02031DBB
:100130009B280E080C02043003180130031902300A
Amphibionics
342
PROGRAM 7.13
sonar-map.bas program
listing (continued)
PROGRAM 7.14
sonar-map.hex file
listing
Amphibionics 07 3/24/03 9:13 AM Page 342
:100140001405031DFF30C628910190011030920064
:100150000D0D900D910D0E0890020F08031C0F0F4E
:1001600091020318BA280E0890070F0803180F0F02
:10017000910703108C0D8D0D920BA8280C08C62832
:100180008C098D098C0A03198D0A08008313031347
:100190008312640008008316023085000130860057
:1001A0008312061283160612831206138316061391
:1001B0008312861283168612831286108316861087
:1001C0008312061183160611831286118316861177
:1001D00005308312A6000830A40073308E000A3068
:1001E000322032308E000A3032200130C5006400E7
:1001F0000630450203180A29003006180130C700EE
:10020000640047080618013C031D0829DB2100296A
:10021000C50FF728BE01BF01C50164000B304502C0
:1002200003182A294A220310450D283E840040085D
:100230008000840A41088000003006180130C700A1
:10024000640047080618013C031D2829252220299F
:10025000C50F0D290B30C400C50164000B304502E9
:10026000031852290310450D283E840000089E0003
:10027000840A00089F000310440D283E84000008F3
:10028000A000840A0008A1001E088C001F088D0031
:1002900021088F0020089120031D50294508C40023
:1002A000C50F2D2944080B3CC6000130C500640071
:1002B00045084602031C6A29003006180130C700B1
:1002C000640047080618013C031D6829DB216029EA
:1002D000C50F57290130C5006400193045020318C5
:1002E000B3294A2240088C0041088D008F01083054
:1002F0008E20031DA5290530A6000830A400733008
:100300008E00053032205A308E00023032205030BC
:100310008E000430322032308E000A30322001301C
:10032000C8006400073048020318A42900300618EA
:100330000130C700640047080618013C031DA229CC
:1003400000229A29C80F9129F5280030061801309B
:10035000C700640047080618013C031DB129B621F7
:10036000A929C50F6C29F5286300B4290616831640
:100370000612831206178316061383128614831639
:1003800086108312061583160611143083126C2012
:10039000061283160612831206138316061383129F
Chapter 7 / Turtletron,Build Your Own Robotic Turtle
343
PROGRAM 7.14
sonar-map.hex file
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 343
:1003A00086108316861083120611831606111430E8
:1003B00083126C2008000616831606128312061795
:1003C00083160613831286148316861083128615ED
:1003D00083168611053083126C20061283160612CE
:1003E0008312061383160613831286108316861053
:1003F0008312861183168611053083126C20080043
:100400000616831606128312861683168612831228
:10041000861483168610831286158316861114306F
:1004200083126C200612831606128312861283161C
:100430008612831286108316861083128611831605
:1004400086110A3083126C200800061683160612E5
:1004500083128616831686128312861483168610DC
:100460008312061583160611053083126C200612BE
:100470008316061283128612831686128312861042
:100480008316861083120611831606110530831217
:100490006C20080001308C008D0105308400013093
:1004A000102001308C0005308400023001200C083F
:1004B000C2000D08C30042088C0043088D000F30B5
:1004C0008E008F01A420C0000D08C10002306C20F6
:0604D00008006300692A28
:02400E00F53F7C
:00000001FF
Amphibionics
344
PROGRAM 7.14
sonar-map.hex file
listing (continued)
Amphibionics 07 3/24/03 9:13 AM Page 344
345
After building some or all of the biologically inspired robots in this
book,you may have thought of a number of ways to improve or
enhance each of the projects,You may have even come up with
ideas for completely new robots,If that is the case,then
Amphibionics has achieved its goal,Listed below are some ideas to
take each of the robot projects further.
Frogbotic
1,Add an infrared or ultrasonic range finder to the robot so that
it can avoid obstacles before leaping.
2,Add a servo to the front legs so that they can be turned to the
left or right,This will make navigation control much easier
when combined with the timed release of the back legs.
3,Waterproof the frog by creating a latex outer skin,Rubber
latex can be applied to a mold with a paintbrush,and is
available at most model hobby shops,It can be built up in
layers until the required thickness is achieved.
Taking It
Further
8
Amphibionics 08 3/24/03 9:15 AM Page 345
Copyright 2003 by The McGraw-Hill Companies,Inc,Click Here for Terms of Use.
Serpentronic
1,Create a scaled surface for the underside of the robot that will
allow the snake to slide forward,but produce friction in the
opposite direction,much like the skin of a real snake,The
skin could be fabricated out of very thin sheets of aluminum,
overlapping by 1/8 of an inch.
2,Interface a model airplane transmitter and receiver system for
human control of the robot,The use of a long-range remote
control system will allow the robot to be guided to exact
remote locations,Because the robot snake has a low profile
and stealthy nature,it has many uses such as espionage
applications,military reconnaissance,safe land mine search,
and removal,along with locating survivors in disaster areas.
3,Interface various environmental and weather sensors to
monitor remote,rough terrain areas accessible only to small
animals,such as a snake,Sensors that can measure temper-
ature and humidity can be added so that readings can be
taken at different locations and the information radioed back
to a main computer or stored in the robot’s memory,to be
retrieved at a later date.
4,Interface a global positioning system (GPS) module to the
PicMicro MCU,and have the robot move from one defined
area to another.
Crocobot
1,Include an obstacle avoidance sensor so that the robot can
operate autonomously,Try using a method other than
infrared or ultrasonic detection,like a simple whisker switch.
2,Add a gripper so that the robot can pick up objects via the
remote control,Program the microcontroller so that when a
Amphibionics
346
Amphibionics 08 3/24/03 9:15 AM Page 346
push-button command is received from the transmitter,the
control stick will then be used to operate the gripper.
3,Install a miniature video/audio camera and transmitter for
remote visual operation.
4,Incorporate a digital compass or gyroscope into the control
system so that the robot can keep its bearing when it is com-
manded to walk in a straight line.
Turtletron
1,Add a line-following circuit to the underside of the robot con-
sisting of two sets of light-emitting diodes and phototransis-
tors,The robot can be programmed to follow a predetermined
white line that has been placed on the floor,This type of nav-
igation is used in some factories,The reflective tape method
is preferred,so that the track can easily be changed.
2,Use rechargeable batteries,and then add a battery charger
station so that the robot can recharge its batteries when they
run low,It could use line-following capability to find its
recharging station.
3,Install a small vacuum system on the bottom of the robot.
Use the information from the shaft encoder sensor,and pro-
gram the robot to start moving in a spiral pattern from the
center of the room outward,When the ultrasonic sensor indi-
cates that it is near a wall,program the robot to navigate
around the edges of the room and under the furniture.
4,Add a light sensitive resistor to the front of the robot,and
interface it to the microcontroller,Have the robot search for
the brightest areas of the room or the darkest,If solar panels
were added to recharge the batteries,this sort of behavior
would be desirable.
Chapter 8 / Taking It Further
347
Amphibionics 08 3/24/03 9:15 AM Page 347
This page intentionally left blank.
349
Anita M,Flynn,Joseph L,Jones,Mobile Robots,Inspiration to
Implementation,A K Peters,Massachusetts,1993,ISBN 1-56881-
011-3
H.R,Everett,Sensors for Mobile Robots,A K Peters,Massachusetts,
1995,ISBN 1-56881-048-2
Karl Williams,Insectronics—Build Your Own Walking Robot,
McGraw-Hill,New York,2003,ISBN 0-07-141241-7
Rodney Brooks,Flesh and Machines,Random House,New York,
2002,ISBN 0-375-42079-7
Ed Rietman,Experiments in Artificial Neural Networks,1988,TAB
BOOKS Inc,PA,ISBN 0-8306-0237-2
Gordon Mccomb,The Robot Builder’s Bonaza,McGraw-Hill,New
York,1987,ISBN 0-8306-2800-2
John Iovine,Robots,Androids,and Animatrons,McGraw-Hill,New
York,2002,1998,ISBN 0-07-137683-6
Geoff Simons,Robots,The Quest For Living Machines,Sterling
Publishing,New York,1992,ISBN 0-304-34414-1
Bibliography
Amphibionics Biblio 3/24/03 9:18 AM Page 349
Copyright 2003 by The McGraw-Hill Companies,Inc,Click Here for Terms of Use.
Steven Levy,Artificial Life,Random House,New York,1992,ISBN
0-679-74389-8
Daniel Crevier,AI—The Tumultuous History of the Search for Artificial
Intelligence,HarperCollins,New York,1993,ISBN 0-465-00104-1
Amphibionics
350
Amphibionics Biblio 3/24/03 9:18 AM Page 350
351
Note,Boldface numbers indicate illustrations.
@ command,32
ADCIN,32,257
aluminum stock,12–15,12,13,14
analog to digital converters,25,30,256–257
antenna,Turtletron,295–296,296
arithmetic logic unit,25
artificial intelligence,273–275
ASM...ENDASM,32
assembler,38
avoidance.bas/avoidance.hex,Turtletron,313–319
band saw,1,2
BAS extension on source files,36
BASIC,29,35
BASIC Stamps,29,41
battery pack holder
Crocobot,203–208,208
Frogbotic,92,93,94
Turtletron,296–297
Serpentronic,128–129,128,129,130,139,139,142,143
battery power supply
Crocobot,226
Frogbotic,94–95,101,102
Serpentronic,144–145,158–164
BRANCH,32
Index
Amphibionics Index 3/24/03 9:21 AM Page 351
Copyright 2003 by The McGraw-Hill Companies,Inc,Click Here for Terms of Use.
BRANCHL,32
BUFFERs setting,31
BUTTON,32
calibration of infrared sensor board,154–155,154,155,178–179
CALL,32
capacitors,29
central processing unit (CPU),25,26
CLEAR,32
CLEARWDT,32
clock speed,PIC 16F84 MCU and 26–27
code file,38
Code Protect setting,EPIC Programmer and,43
command/statements listing for PicBasic Pro Compiler,32–35
compiler (See also PicBasic Pro Compiler),28
CONFIG.SYS file,31
continuous rotation modification for servo motors,55–66,57–66
controller board
Crocobot,216–226,216,222,223,224
Frogbotic,94–98,95,101,102
Serpentronic,144–148,144
testing,44–45
Turtletron,283–286,284
controlling modified servo motors,66–68
copper boards for PCB,18–20,19
COUNT,32
Crocobot,191–269
analog to digital converters in,256–257
battery pack holder for,203–208,208
battery power supply for,226
body covers and tail section for,202–208,203–208
chassis construction for,199–202,199–202
component connection and assembly steps in,226–228,227,228
control stick for,231,257–269
controller board for,216–226,216,222,223,224
crocobot-switch.bas/crocobot-switch.hex for,239–241
crocodilian biology and,191–193,192
gearbox assembly for,195–198,196,197,198
L298 dual full-bridge driver in,218–221,219
leg assembly in,213–215,214
leg construction in,211–212,212,213
limit switch wiring in,209,209,210
mechanical construction of,194–198
modifications and customizations for,346–347
motion programming and control in,244–269
Amphibionics
352
Amphibionics Index 3/24/03 9:21 AM Page 352
Crocobot (continued)
motor output shafts for legs in,211–212,211
motor-test.bas/motor-test.hex for,242–244
motors for,193
overview of,193–215
parts list for,195,217–218,233–234
PIC 16C71 in,232–234,232
power switch wiring for,215,215
programming for,239–269
radio transmitter and receiver modules for,220–221,221,224–239,
225,226,238,239
receive-test.bas/receive-test.hex for,252–254
remote control printed circuit board,234–239,235,236,237
remote control transmitter for,228–239,229–231
remote controller for,193–194,194
rx-remote.bas/rx-remote.hex in,257,258–265
serial data link in,251–269
transmit-test.bas/transmit-test.hex in,254–256
tx-remote.bas/tx-remote.hex in,257,265–269
walk-routines.bas/walk-routines.hex for,245–251
wiring for,201,201,238
crocobot-switch.bas/crocobot-switch.hex for,239–241
DATA,32
DEBUG,32
debugging,30
DEBUGIN,32
Devantech SRF04 ultrasonic range finder,286–298,286
developing PCB,18–20,19
differential drive system,Turtletron,283
digital multimeter,10–11,10,154–155,154
digital–to–analog converters,25
DISABLE,32
distance measurement using optical shaft encoder in,325–344,326,
327
DOS EDIT,35
drilling and parts placement on PCB,21–22,22,23
drills and drill presses,3–5,4,5
DTMFOUT,32
EEPROM command,32
ENABLE,32,33
encode-test.bas/encode-test.hex,Turtletron,332–334
END FOR...NEXT,33
endmill,5,5
Index
353
Amphibionics Index 3/24/03 9:21 AM Page 353
EPIC Programmer,40–43,41
Code Protect setting in,43
DOS users,41–42
graphical user interface of,43,43
opening file in,42–43
plugging in,41–42
programming process in,43
Windows users,41
epoxy,9,10
erasing and reprogramming PICmicros,30
etching the PCB,20–21
exposing PCB,19–20
fasteners,14,15
ferric chloride for PCB,18,19,20–21
file,9
FILES setting,31
flash memory,26,30
FOR...NEXT,33
FREQOUT,33
friction pads,Serpentronic,163,164
frog-test.asm,38,39
frog-test.bas,36–38,39,103,104–106
frog-test.hex,38,39–40,104,106–107
Frogbotic,51–116,103
battery pack holder for,92,93,94
battery power supply for,94–95,101,102
component connections,100–103,101
controller board for,94–98,95,101,102
controlling the modified servo in,66–68
cutting and bending guides for,69,69
drilling guide for,70
feet,76,76,77
frog and toad biology and,51–52,52
frog-test.bas/frog-test.hex for,103,104–107
frogbotic.bas/frogbotic.hex for,111–115
front leg construction and attachment in,90,90
jumping motion,programming and controlling,110–113,116
leg assembly for,77–82,78–81
leg attachment to body for,82–83,82,83
leg pieces for,74,75
leg position sensors in,91,91
leg stops for,74,74,76,76
limit switch wiring in,91–94,92,93
limit-switch.bas/limit-switch.hex for,107–110
Amphibionics
354
Amphibionics Index 3/24/03 9:21 AM Page 354
Frogbotic (continued)
mechanical construction of,68–77
modifications and customizations for,345
modifying servos for continuous rotation in,55–66,57–66
mounting brackets for,72,73,73
overview of project for,52–66
parts lists for,68,95–96,99
potentiometers in,54–55
power connector for,98–99,100
printed circuit board fabrication for,96–98,97,98
programming and experiments with,103–116
pulse width setting for,55,56,67–68,67
resistor network in,62–63,62,63
servo gear placement in,65,65
servo motor mounts in,84–89,85,89
servo motors for,52,54,54–55
springs and spring-loading mechanisms in,52,53,54,82–83,83,
86,86,87,88,89
frogbotic.bas/frogbotic.hex,111–115
gears,gearboxes
Crocobot,195–198,196,197,198
Frogbotic,65,65
Turtletron,276,277
GOSUB,33
GOTO,33
H-Bridge,in L298 dual full-bridge driver,219–220,219,220
hacksaw,1,2
hammer,9,9
Harvard architecture,26
HEX machine code,39
HIGH,33
hot glue gun and glue,7,9
HSERIN/HSEROU,33
I2CREAD/I2CWRITE,33
IF..THEN..ELSE..ENDIF,33
In Circuit Debugging (ICD),MicroCode Studio and,45,48–49
infrared sensor board,Serpentronic,148–153,149,151,152,153
ircal-serpent.bas/ircal-serpent.hex in,169–171
adjustment in,169–170,170
calibration of,154–155,154,155,178–179
connector wires and wiring diagram for,156–157,157,158
Index
355
Amphibionics Index 3/24/03 9:21 AM Page 355
infrared sensor board,Serpentronic (continued)
programming routines for,177–188
ink-jet printers for PCBs,17–18
INPUT,33
input/output (I/O) ports,25,27
integrated development environment (IDE) (See MicroCode Studio)
ircal-serpent.bas/ircal-serpent.hex in,169–171
jumping motion,programming and controlling,110–113,116
L298 dual full-bridge driver,Crocobot,218–221,219
laser printers for PCBs,17–18
LCDIN/LCDOUT,33
leg assembly,Frogbotic,77–82,78–81
LET,33
limit switch wiring
Crocobot,209,209,210
Frogbotic,91–94,92,93
limit-switch.bas/limit-switch.hex,107–110
LOOKDOWN/LOOKDOWN2,33
LOOKUP/LOOKUP2,33
LOW,33
M.G,Chemicals,18
materials,12–15
Mecanique (See MicroCode Studio)
memory,25,26
Metal Supermarket,The,14
MicroCode Studio IDE,45–47,46
compiler setup in,46,47
editor in,45–46
In Circuit Debugging (ICD) in,45,48–49
MPLAB programmers and,46
one-button compile and programming use,48,49
PICStart Plus programmers and,46
programmer use with,47–49,48
microcontrollers,25
MicroEngineering Labs,28
miter box,1,2
mode select switch,Serpentronic,162,162,162
motor-test.bas/motor-test.hex,Crocobot,242–244
motors
Crocobot,193
L298 dual full-bridge driver in,218–221,219
MPLAB programmers,MicroCode Studio and,46
Amphibionics
356
Amphibionics Index 3/24/03 9:21 AM Page 356
multimeter,10–11,10,154–155,154
NAP,33
neural networks,273–275
NOTEPAD,35
obstacle avoidance routine,Turtletron,313–325
ON DEBUG,34
ON INTERRUPT,34
one time programmable (OTP) chips,30
optical shaft encoder (See also Turtletron),distance measurement using,
325–344,326,327
oscilloscopes,11–12,11
OUTPUT,34
parts lists
Crocobot,195,217–218,233–234
Frogbotic,68,95–96,99
Serpentronic,120,145,150,155–156,159
Turtletron,276,284–285,287,328
PAUSE,34
PAUSEUS,34
PEEK,34
PIC (See programmable interface controller)
PIC 16877,30
PIC 16C71 in,232–234,232
PIC 16F84,26–28,26,30
clock speed of,26–27
controller board connection for,44
input/output (I/O) ports in,27
pinouts for,26,26
port A and B connection table for,28
registers in,27
PIC 16F876,30
PicBasic Pro Compiler,28–40,29
assembler in,38
BAS extension on source files for,36
BASIC source files for,35
code file in,38
command/statements listing for,32–35
compiling a program in,35–40
EPIC Programmer and,40–43,41
frog-test.bas program listing for,36–38
HEX machine code for,39
non-16F84 chips,compiling code for,38–39
Index
357
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PicBasic Pro Compiler (continued)
software installation for,31–35
testing code in,38
text editors and word processors for source file creation in,35–36
uncompressing files for,31
PICStart Plus programmers,MicroCode Studio and,46
pliers,6,6
PNA4602M module in infrared sensor board,Serpentronic,148,151,
152
POKE,34
ports,25,30
position sensors,Frogbotic,91,91
POT,34
potentiometers,Frogbotic,54–55
power connector,Frogbotic,98–99,100
power supplies,30,44
presensitized copper boards for PCB,19–20,19
printed circuit board fabrication,17–23
developing,18–20,19
drilling and parts placement on,21–22,22,23
etching,20–21
exposing the board for,19–20
ferric chloride for,18–21,19
Frogbotic,96–98,97,98
presensitized copper boards for,19–20,19
printers for reproducing,laser and ink-jet,17–18
remote control device,234–239,235,236,237
resist removal in,22
Serpentronic,146–148,146,147
setup for,19
soldering,22
transparency for,17–18,18
programmable interface controller (PIC),26
programmer use with MicroCode Studio,47–49,48
pulse width setting,Frogbotic,55,56,67–68,67
PULSIN,34,309
PULSOUT,34
PWM,34
radio transmitter and receiver modules,Crocobot,220–221,221,
224–239,225,226,238,239
RANDOM,34
random access memory (RAM),25,26
RCTIME,34
READ,30,34
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read only memory (ROM),25
READCODE,34
README.TXT file,31
receive-test.bas/receive-test.hex,Crocobot,252–254
reduced instruction set computer (RISC),26
registers,PIC 16F84 MCU,27
remote controller
Crocobot,193–194,194,228–239,229–231
Turtletron (See also Crocobot),272–273,273,298–299,299
remote-sonar.bas/remote-sonar.hex,319–325
resist removal from PCB,22
resistor network,Frogbotic,62–63,62,63
resistors,30
RESUME,34
RETURN,34
REVERSE,34
Reynolds Electronics,220,299
room mapping,Turtletron,334–344
rulers and squares,7,9
rx-remote.bas/rx-remote.hex,Crocobot,257,258–265
safety glasses,9,10
screwdrivers,6,6
serial data link,Crocobot,251–269
SERIN/SEROUT,34,252
Serpentronic,117–189
alternating servo orientation in body sections of,141,141
assembling mechanical structure for,137–138,138
battery pack holders for,128–129,128,129,130,139,139,142,143
battery power supply for,144–145,158–164
body section construction in,121–130,121–125
calibration of infrared sensor board in,154–155,154,155,178–179
connecting body,tail,and head together,138–143,140,141,142
connector wires and wiring diagram for infrared sensors in,
156–157,157,158
controller board for,144–148,144
friction pads for,163,164
head construction in,132–136,133–136
infrared sensor adjustment in,169–170,170
infrared sensor board for,148–153,149,151,152,153
infrared sensor routine programming in,177–188
ircal-serpent.bas/ircal-serpent.hex in,169–171
joints in,120
mechanical construction of,120–121
microcontroller for,119
Index
359
Amphibionics Index 3/24/03 9:21 AM Page 359
Serpentronic (continued)
mode select switch in,162,162,163
modifications and customizations for,188–189,346
motion programming and control in,171–176,172,173,174,175,
176,177
mounting controller board and infrared sensor board in,155–158,
156,157
movement of,119,120
movie of,on web site,189
overview of,119–136
parts lists for,120,145,150,155–156,159
PNA4602M module in infrared sensor board for,148,151,152
printed circuit board fabrication for,146–148,146,147
programming and experiments with,164–177
serpentronic.bas/serpentronic.hex for,179–188
servo horn linkage for,137,137
servo linkage attachment to,124–130,125,126,127,128
servo motor wiring in,161–164,161
servo motors in,119
size of,118,119
snake biology and,117–118,118
snake-test.bas/snake-test.hex for,164,165–169
soldering connections in,147–148,148
tail section construction in,130–131,131,132
wiring in,158–164,160,161
serpentronic.bas/serpentronic.hex,179–188
servo motors
continuous rotation modification to,55–66,57–66
control of modified,66–68
Frogbotic,52,54,54–55
Frogbotic,control of,66–68
Frogbotic,modifying for continuous rotation in,55–66,57–66
mounts for,84–89,85,89
Serpentronic,119,161–164,161
SHIFTIN/SHIFTOUT,35
SLEEP,35
snake-test.bas/snake-test.hex,164,165–169
software installation,31–35
soldering,6–7,7,8,22
sonar-map.bas/sonar-map.hex,336–344
sonar-test.bas/sonar-test.hex for,309–312
SOUND,35
springs and spring-loading mechanisms,52,53,54,82–83,83,86,
86–89
SWAP,35
Amphibionics
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Tamiya gearboxes
Crocobot,195–198,196,197,198
Turtletron,276,277
test equipment,10–12
testing controller boards,44–45
text editors and word processors for source file creation in,35–36
Thinkbotics web site,17
timers,25,30
TOGGLE,35
tools,1–10
transmit-test.bas/transmit-test.hex,Crocobot,254–256
TRIS register,PIC 16F84 MCU and,27
turtle-receive.bas/turtle-receive.hex,300,301–305
turtle-trans.bas/turtle-trans.hex,300,305–308
Turtletron,271–344
avoidance.bas/avoidance.hex for,313–319
base for (Frisbee),279–281,279,280,281
battery pack holder for,296–297
controller board and electronics of,283–286,284
cover supports for,282,282
differential drive system in,283
distance measurement using optical shaft encoder in,325–344,326,
327
encode-test.bas/encode-test.hex for,332–334
gearbox assembly and attaching wheels to,276,277,277–283,278
history of robotic turtles and,273–275,274
mechanical construction of,275–299
modifications and customizations for,347
obstacle avoidance routine for,313–325
optical shaft encoder in
encode-test.bas/encode-test.hex for,332–334
fabrication of,327–334,328,329,330,331
mounting of,331
parts list for,328
room mapping using,334
sonar-map.bas/sonar-map.hex for,336–344
wiring diagram for,332
overview of,272–273
parts lists for,276,284–285,287
programming,300–325
remote controller for (See also Crocobot),272–273,273,298–299,
299
remote-sonar.bas/remote-sonar.hex for,319–325
room mapping for,334–344
sonar-map.bas/sonar-map.hex for,336–344
Index
361
Amphibionics Index 3/24/03 9:21 AM Page 361
Turtletron (continued)
sonar-test.bas/sonar-test.hex for,309–312
turtle and tortoise biology and,271–272,272
turtle-receive.bas/turtle-receive.hex for,300,301–305
turtle-trans.bas/turtle-trans.hex for,300,305–308
ultrasonic range finder in,272,286–298,286
antenna attachment to,295–296,296
avoidance.bas/avoidance.hex for,313–319
connecting to robot,290–291,290,291
connections for,288,288
housing for,292,293,293,294
neck mount for,294,295
obstacle avoidance routine for,313–325
operation of,288
pulse width setting in,309
remote-sonar.bas/remote-sonar.hex for,319–325
room mapping using,334–344
sonar-map.bas/sonar-map.hex for,336–344
sonar-test.bas/sonar-test.hex for,309–312
testing,308–312
timing of,289,289
wheels for,277–283,278
wiring diagram for,297
tx-remote.bas/tx-remote.hex,Crocobot,257,265–269
Ultraedit,35
ultrasonic range finder (See Turtletron)
ultraviolet erasable chips,30
uncompressing PicBasic Pro files,31
vise,1,3,3
Von Neumann architecture,26
walk-routines.bas/walk-routines.hex,Crocobot,245–251
Walter,William Grey,273–275
WHILE..WEND,35
wire strippers,6,7
wiring
Crocobot,201,201
Crocobot,transmitter,238
optical shaft encoder (Turtletron),332
Serpentronic,158–164,160,161
Turtletron,297
word processors for source file creation in,35–36
wrenches,6,6
Amphibionics
362
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WRITE,30,35
WRITECODE,35
XIN,35
XOUT,35
Index
363
Amphibionics Index 3/24/03 9:21 AM Page 363
Karl Williams is an independent robotics researcher,electronics
experimenter,and software developer,He is with Mitra Imaging,
a leading medical imaging software company just acquired by
AGFA HealthCare Informatics,He is the author of Insectronics—
Build Your Own Walking Robot and has written for Nuts and Volts
magazine,A resident of Ontario,Canada,Karl has hosted a robot-
ics and electronics Web site for four years,and received an IBM
regional computer technology award for building a computer-
controlled robotic arm.
About the Author
Amphibionics Index 3/24/03 9:21 AM Page 364
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