Servo magazine 02 2008

Tạp chí Servo

SERVO Magazine (ISSN 1546-0592/CDN Pub Agree#40702530)

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08 Robytes by Jeff Eckert

Stimulating Robot Tidbits

10 GeerHead by David Geer

Robot Leaves Breadcrumbs

14 Ask Mr Roboto by Pete Miles

Your Problems Solved Here

62 Robotics Resources

by Gordon McComb

The Recycled Robot

67 Lessons From The Lab

by James Isom

NXT Packbot: Part 3

76 Appetizer by Kevin Berry

The Door Into Spring

78 Then and Now by Tom Carroll

Personal Robots: From Science Fiction

To Reality

PAGE 48

VOL 6 NO 2

ENTER WITH CAUTION!

22 The Combat Zone

31 The RoboCooler

by Jerry Reed

Find a few design tidbits in this embedded “appliance” application

to use in your next build.

39 The MechBash Traveling

Robot Show

by Jon Vandervelde

See what happens when you combine Mechwars robot combat with BotBash into one event.

43 Maker Faire

by R Steven Rainwater

Pleos, horses, monkeys, and parrots were just a few of the robotic pets that Faire attendees had the opportunity to get up close and personal with.

48 Building a Stepper Motor

Controller: Part 1

by Fred Eady

This controller is based on the STMicroelectronics L6208, which is a single-IC DMOS driver.

54 Capacity: The Key to

Battery Runtime

by Isidor Buchmann

Take a quick look at emerging rapid-test technologies for deep-cycle, lead-acid batteries.

57 Reviving an Androbot BOB

by Robert Doerr

Get your BOB rolling again.

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PUBLISHER

Larry Lemieux

publisher@servomagazine.com ASSOCIATE PUBLISHER/

Jeff Eckert Tom Carroll Gordon McComb David Geer Pete Miles R Steven Rainwater Fred Eady Kevin Berry James Isom Robert Doerr Isidor Buchmann Jon Vandervelde Jerry Reed Russ Barrow

Chris Olin

CIRCULATION DIRECTOR

Tracy Kerley

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ADMINISTRATIVE ASSISTANT

Debbie Stauffacher Copyright 2008 by

T & L Publications, Inc.

All Rights Reserved

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REFLEX CONTROL

Although fully autonomous

robots are often viewed as the

pinnacle of robotics, sometimes it’s

desirable for robots to follow specific

directions, under direct user control

For example, a surgeon controlling a

surgical robot may want to exactly

specify the location of an incision

The cost of full user control is the

demand placed on the operator As

experienced with the MQ-1 Predator

and other drone combat aircraft has

shown, the control of a single robot

can require the full attention of

several humans – the basic crew for a

Predator is one pilot and two sensor

operators Similarly, if you’ve ever

controlled a mobile or air-borne robot

with an R/C unit through a video link

— or even an R/C battle-bot in direct

sight — you know that the task

requires focus and concentration,

leaving little room for other activities

Controlling robots — wearable or

otherwise — through neuromuscular

signals is an obvious, albeit challenging,

approach to freeing the operator to

focus on other tasks Instead of handling

a joystick, the operator simply moves an

arm or leg and the exoskeleton follows,

using the electrical signals activating the

muscles as a trigger (Watch for Kazuo

Kiguchi’s article on “Control of ExoSuits

with Biological Signals” coming in the

March issue.)

One of the issues in biological

control of robots is how to handle

reflexes — semi-autonomous movements

that are not consciously directed To

understand the relevance of reflexes to

robotics, consider your normal reflexes

If you accidentally brush your hand

against the hot tip of a soldering iron,your hand will instinctively and —without conscious control — instantlyrecoil from the heat source If you arefast enough, you might get away with aminor reddening of the skin that quicklydissipates Without the reflex, you’d beleft with a serious burn, possibleinfection, and a permanent scar

The reflex arc illustrated in Figure 1involves sensors in your skin and muscle,

a neurological pathway from the sensors

to your spinal cord, a connection withinthe cord to the outbound motor neuronscontrolling muscles in your hand andarm, and neuromuscular innervation

The brain isn’t normally part of a reflex

When it is involved, it’s usually to inhibit

the reflex — you don’t want to rip yourarm away from a nurse giving you avaccination, for example

A practical advantage of a reflexaction is speed Conscious controlinvolving hundreds or thousands ofneural synapses is simply slower than areflex arc involving a few neurons Ifyou had to consciously blink every timesomething headed for you eyes, you’dprobably be blind by now Anotheradvantage of reflexes is that theyenable you to avoid danger or at leastminimize damage while maintainingconscious focus on the task at hand

Given the advantage of nearinstantaneous reflexes in biologicalsystems, it’s reasonable to assume thatexoskeletons and other forms of robotscan benefit from similar capabilities

However, a dilemma faced by developers

of wearable robotic systems is thedegree to which the wearer should beinsulated from the environment

At one extreme, the wearer isunaware of extreme heat, impact, and

Mind / Iron

by Bryan Bergeron, Editor Œ

other dangers in the environment It’s up to exoskeletons

and built-in protective reflexes to keep the wearer from

danger The downside to this scenario is that the wearer

would have to adapt to sudden reflex movements of the

exoskeleton, and the movements would have to be

controlled to avoid joint or muscle damage At the other

extreme, the wearer of a robotic exoskeleton would be

exposed to whatever forces contact the exoskeleton, with

fidelity determined by the available sensors and transducers

Somewhere in the middle seems reasonable for many

applications For example, a soldier with a bulletproof

robotic exoskeleton should be protected from the physical

damage of bullets or shrapnel, but not necessarily from a

modest sting of impact The modest pain would result in

biological reflexes, and the exoskeleton could respond to

the associated neuromuscular activity Pain is often a

reliable indicator that something is wrong and that action

is necessary to avoid injury

The impact of shrapnel or a bullet on a soldier’s

bulletproof exoskeleton could be translated into a mildly

uncomfortable sensation on the wearer’s skin just beneath

the point of impact Along this line of reasoning, variants of

Immersion’s TouchSense technology (www.immersion.

com/industrial/touchscreen/) could be used to synthesize

sensations through tactile transducers excited by signals of

varying frequency, intensity, duration, and wave shapes

Tactile synthesis for wearers of sensor-studded

exoskeletons, socks, or shoes has potential medical value, as

well Wearable sensors coupled with tactile synthesizers can

replace and supplant the desensitized peripheral sensory

organs of diabetics and other sufferers of peripheral

neuropathy It’s not unusual for sufferers of diabetes to tear

a toenail or cut their foot, only to discover the damage hours

later, when they happen to notice a blood-soaked sock A

thin, lightweight, flexible sensory exoskeleton that generates

synthetic tactile feedback on the wearer’s back or other area

not affected by neuropathy could provide life-saving feedback

to diabetics, as well as advance the field of robotics

If you want to take up the challenge, start by exploring

the computer literature on virtual reality and the psychological

literature on perception and the synthesis of sensation SV

Spinal Cord

MuscleHeat

FIGURE 1.

Reflex Arc.

Perform proportional speed, direction, and steering with

only two Radio/Control channels for vehicles using twoseparate brush-type electric motors mounted right and leftwith our mixing RDFR dual speed control Used in manysuccessful competitive robots Single joystick operation: upgoes straight ahead, down is reverse Pure right or left twirlsvehicle as motors turn opposite directions In between stickpositions completely proportional Plugs in like a servo toyour Futaba, JR, Hitec, or similar radio Compatible with gyrosteering stabilization Various volt and amp sizes available.The RDFR47E 55V 75A per motor unit pictured above.www.vantec.com

STEER WINNING ROBOTS

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Order at (888) 929-5055

UAV Imitates Sea Birds

So one day Guy Meadows, director

of the Marine Hydrodynamics Labs at

the University of Michigan (www.

umich.edu), was floating around and

saw a flying fish pop out of the water

and soar over the waves He was so

impressed and inspired that he said,

“Wow I’ll bet I can build one of those,”

hence the name of the UAV that he and

some engineering researchers designed

and built Somehow the concept

evolved away from fish and focused on

sea birds, but the name stuck

In any event, Meadows and his

colleagues did a study of things that

go flap and discovered that many of

them have some traits in common,

such as weighing about 20 lb and

having a 2 m wingspan It turns out

that this is pretty much the ideal

aerodynamic design for skimming

close to the surface, so the Flying Fish

is physically similar to a large,

mechan-ical pelican It is also believed to be the

first seaplane that can initiate and

perform its own takeoffs and landings

It may sound like all fun and

games, and a good excuse to escape

Ann Arbor for some quality time in

Monterey, CA, testing the thing, but

project funding came from the DoD’s

Defense Advanced Research Projects

Agency (DARPA), with the aim of

advancing the agency’s Persistent

Ocean Surveillance program

In operation, the electric-powered

UAV drifts along until its onboard GPS

tells it that it has floated too far The

takeoff sequence is then triggered, andFlying Fish goes airborne in about 10 m

When it reaches the proper GPS nates, it lands using a shallow descent

coordi-The next step will be to fit the plane withsolar power and an array of sensors

Bots to Fight Fires in London

Apparently, there are a seriousnumber of incidents in the Londonarea involving fire, acetylene cylinders,and railroad tracks Such incidentscause great consternation among railtravelers, as the lines have to be shutdown until the danger has been eliminated As a result, Network Rail, inconjunction with the London FireBrigade, has commissioned QinetiQ Ltd

to provide and operate some specializedfirefighting ROVs for a six-month trial

The plan is to use the bots’ cameras

to identify whether any acetylene cylinders are present when firebreaks out near the tracks and —using thermal imaging — gaugewhether such cylinders havecooled off enough to allow humanfirefighters to approach them

Three types of ROVs areincluded in the trial: Talon, asmall tracked vehicle used in Iraqfor bomb disposal and here fittedwith video and thermal imagecameras; Black Max, basically asquirtbot; and Brokk 90, a heavy-duty mini-digger designed to

remove debris and gain access to burning vehicles and structures

According to a companyspokesman, “QinetiQ has already beencalled to deploy the ROVs on a number

of occasions, and they have eachproved useful in assisting the FireBrigade in dealing with the incidents.”Sounds like a bit of all right

Also sponsored by the folks atDARPA is BigDog, billed as the most advanced quadruped robot on Earth Built by Boston Dynamics, it

is a major part of the agency’s Biodynotics (biologically inspireddynamic robots) program, which aims

to apply biological principles to

devel-op robots that can better movethrough difficult terrain, travel moreefficiently, and recover from stumbles.The BigDog portion of the program aims to replace tracked andwheeled systems with legged ones,eventually demonstrating mule-sized,200-lb platforms that can carry payloads of supplies, ammunition,weapons, and other items that soldiersnow have to tote

At present, BigDog measures 1 m(3.3 feet) long, is 0.7 m (2.3 feet) tall,and weighs 75 kg (165 lb) The dogfood this guy consumes is gasoline,which feeds an engine that drives the hydraulic actuation system An on-

The Flying Fish UAV Photo courtesy

of the University of Michigan.

ROVs fire robots in action.

Photo courtesy of QinetiQ Ltd.

The BigDog quadruped robot Photo courtesy

of the US Department of Defense.

by Jeff Eckert

board computer controls locomotion,

the legs, and a complex variety of

sensors So far, BigDog has trotted 5.3

km/hr (3.3 mph), climbed a 35° slope,

and carried a 54-kg (120-lb) load For a

fascinating video, visit www.boston

dynamics.com/content/sec.php?

section=BigDog.

It might look like a model airplane

that you would fly in the park on

Sunday, but the RQ-11B Raven is a

serious little cousin of the MQ-1

Predator and MQ-9 Reaper The little

UAV weighs only about 4 lb and has

just a 55-in (1.4-m) wingspan, but it

can conduct visual reconnaissance up

to 10 miles from its launch point and

climb to 10,000 feet above sea level

It sends live footage back to the

operator for later evaluation

According to a spokesman,the Raven B is particularly useful during convoy operations,because it can travel at 17 to 44knots and keep up with mosttrucks It is also good for targetacquisitioning, battle damageassessment, and detection assess-ment for ground-based threats

Raven carries a camera thatprovides high-res imagery up to

500 feet above the terrain, withlocation coordinates shown onthe display It can remain air-borne for 1.5 hours on a charge

Perhaps its most interestingcharacteristic is that it has no landinggear; it is designed to break apart,undamaged, on impact, and it can bereassembled in a matter of minutes

The exact cost of the little bird was not disclosed, but the Danish Army

recently ordered 12 systems (includinglogistics support and training) at a cost

of $2.4 million, which would price it at

$200,000 Yes, nothing you’ll be flying

in the park for fun SV

R o b y t e s

Staff Sgt Marie Garcia launches an RQ-11B Raven at Bagram Air Base, Afghanistan US Air Force photo by Staff Sgt Mike Andriacco.

Moravian College student and

roboticist Wesley Moser (class

of ‘08) built a robot thatcould trace its steps and map them out

on a computer screen, albeit with a lot

of help from Moser’s own software,

which he programmed using multiple

languages

The robot was the result of

Moser’s Student Opportunity for

Academic Research (SOAR) project at

Moravian Ben Coleman, assistant

professor of computer science at the

academic institution, guided Moser

The robot uses a variety of sensors

to traverse the boundaries of its given

landscape; in this case, a box Along

with the ability to avoid obstacles —

without which it would be quite clumsy

— its sensors and computer technology

enable it to record where it has been

The robot then distributes the

information to a computer, which draws

a line duplicating the robot’s path

Mapping and Maneuvering the Robot’s Intelligence

Technically, the robot itself doesn’tactually know where it has been,according to Moser As the robot rollsaround inside its little playpen, it keeps a heading Every few parts of asecond, it sends its heading back to acomputer (laptop)

The heading is simply informationabout whether it is turning or not and

in which direction, according to Moser

Along with the heading, the robotreturns its recent sensor readings andgives the computer the exact timesince its last update, Moser explains

The computer then compiles all ofthese readings in real-time and generates a single-line mapping

of where the robot has been “Inthis case, the robot is really the

‘explorer’ and the laptop has to

do all the work of knowing wherethe robot was,” continues Moser

The robot houses its intelligence in a Handy Board TheHandy Board consists of aMotorola MC68HC11 processor,32K of RAM, and a variety of sen-sor inputs It also supports fourmotors Despite its comparablyslow clock speed, the 2 MHz

Moser had developed for it “We werecoming up on its limit when trying tosend data to the computer, collect datareadings, and determine the next heading all at once,” Moser notes

Moser used a programming language called Interactive-C to enablethe robot’s ‘cranium’ so it could ‘think.’Through this programming, the robotcould complete tasks like polling sensors for data, controlling its motors,and doing direct access calls to the on-board RAM

Moser first programmed the robotwith a path-finding ability, with both therobot and sonar facing straight ahead.But he quickly discovered that the robotcollided with walls when approachingthem from an angle Moser needed therobot to be able to see obstacles from allsides, and so he added a servo to turnthe sonar side to side Still, the robotcrashed into walls, so Moser addedinfrared sensors so the robot could sensewhen it was too close to the walls of itsbox, whether the sonar agreed or not!Once Moser had decided to savethe robot’s path and record it, he real-ized he had to do more programming

“I added some programming routines

to get the robot to remember what ithad done, but the robot only hadenough memory to remember the previous 30 seconds,” Moser says.Moser had to clear that memoryand move that data off the robot toanother computer to make room for

Contact the author at geercom@alltel.net

by David Geer

Robot Leaves Breadcrumbs

A trailblazer that traces its own steps

This is a front and side angle view of

the fully assembled robot.

move the data, this would be

cost-prohibitive and too much extra

processing work for the robot’s brain

So, Moser wrote a program that

moved the data to the laptop via cable

According to Moser, it’s easy to

program the Handy Board He simply

wrote his code on a computer and

downloaded it to the board “Our

partic-ular Handy Board had an expansion

board on it, which allowed us to use the

sonar, the servo, and gave a few extra

sensor inputs The Handy Board also has

a small, 16 x 2 LCD screen for displaying

the status of the robot,” Moser says

The board supports three infrared

sensors, a sonar and control box, and a

servomotor for turning the sonar

The laptop runs a program of

Moser’s design, written in C++ and

OpenGL This program uses the

robot’s data to draw the map on the

computer screen

“The program parses the robot’s

data and determines where the robot

would be if it were situated on a

Cartesian coordinate plane The

program assumes that the robot starts

positioned at (0,0) When the robot

sends its data, the program takes the

current direction and projects a circle in

front of the robot with a radius that is

dependent on how much the robot is

turning,” says Moser

Then, the program calculates the

next point on the plane or map (the

robot’s next location) by using the speed

of the robot and the time that has

passed to determine how far the robot

has traveled The process repeats itself

starting from the newly plotted point

The mapping process works better

in theory than in practice, due to a few

factors First, the motors don’t always

run at the same speed So, using speed

and time to calculate the robot’s new

location is inaccurate Speed also

varied at times as the batteries ran low

“An improvement to our design

would be to add an odometer to each

rear wheel to actually tell how far the

wheel has turned, but with our current

design the robot could not handle yet

another task — it would slow down the

robot’s processing time too much,”

Moser says

Communications between therobot and computer were particularlychallenging The robot sent data across

a cable to the computer in the form of

a stream of characters The computerreceived and parsed the data in order

to interpret it

But the computer had to mine when and whether it hadreceived a complete and uncorrupteddata stream before it could act on thedata “Occasionally the computerwould end up in an endless loop collecting data because one part of thedata got corrupted, and the computerwas waiting for the rest of it I supposethis is par for the course with datacommunication, but this was my firstexperience with it,” Moser explains

deter-Around, Not Through

The robot gets around objectsusing its sonar Another technician created the sonar for Moser from aPolaroid camera “I believe Polaroid usedthis particular sonar to determine thedistance from their camera to the object

it was shooting,” Moser suggests

The sonar estimates the distancebetween the robot and other objects Itdoes a good job of estimating these dis-tances and detecting objects if they arebetween one and eight feet away fromthe robot The sonar turns 62 degrees

to the right or left of the robot to detectobjects that come within range oneither side, according to Moser

“However, the sonar is notoriously liable, as it will occasionally see some-thing that is not there,” Moser says

unre-Moser wrote some programmingroutines to help the sonar see withinone foot of the robot, but at about sixinches away, the sonar’s capabilitiesreally fell off

The way the sonar works, Mosertells it to ping by setting a bit on theHandy Board, and the sonar returns anumber between 0 and 32768 repre-senting the distance away, with 0 being

This is the robot as it is about to be disassembled Here, the sonar speaker has been removed from the servomotor Moser has his hand on the Handy Board

on top, about to peel it away from

the robot.

This mostly head-on view of the robot reveals its sonar “speaker” and grill-like covering up top (black) The robot uses this speaker to send and receive sonar pings.

The nearly transparent box on the side houses the sonar control box This is the mechanism that actually sends and receives the pings through the speaker element.

Beneath the sonar speaker is a black servo motor and housing, which looks a lot like printer cartridges in form factor But rather than printing with ink, this motor turns the sonar to map out obstacles in the robot’s path Directly beneath the servo motor inside the blue rectangle of LEGOs, is the front infrared sensor.

right in front (one foot away) and 32768

being infinity, or about eight feet away

for the robot/sonar, according to Moser

To allow the sonar to see things

clos-er than one foot, Mosclos-er had to suppress

something called a blanking feature onthe sonar The blanking feature preventsthe robot from hearing the exact pingthat it had just sent out before it hearsthe echo that returns; in this way, it does-n’t recognize its own sound as being thereturning sound, which would negatethe distance calculations “By inhibitingthis blanking feature and implementing

my own (smaller) blanking interval, therobot was able to detect things thatwere closer to it,” says Moser

The robot also facilitates obstacledetection and avoidance by use of its

three infrared sensors, which are

locat-ed on the front and to the right andleft These infrared sensors can pick upobjects up to three inches away Theyalso return a number within a range ofnumbers to determine the distance theobject is away (in this case, the numberreturned is between 0 and 255).While these sensors take up theslack for the sonar at the closest ranges,they are less effective in sun light,detecting the natural light’s infrared rays

as being something close to the bot “Iwrote an algorithm to work around this,which decreases the sensitivity of theinfrared sensors (or disables them com-pletely) if it appears that the robot is sur-rounded by natural light,” says Moser.The laptop computer combines theinput from the infrared sensors and thesonar and weighs them when determin-ing what path the robot should take SV

An Interactive C programming language manual/resource

www.owlnet.rice.edu/~elec201/ Book/icmanual.html

A C++ programming language tutorial

RESOURCES

The path of the robot is projected

back into the image for us to see As

the path of light demonstrates, the

robot frequently miscalculates the

distance between itself and the sides

of the box As a result, it repeatedly

gets very close to things before turning

off in another direction.

Here is the robot nearly in pieces At the bottom is the interface box and cable Directly above it are the Handy Board and expansion board The expansion board drives the sonar and offers a few more sensor inputs for the robot’s use The sonar control box is visible with the sonar speaker attached “I am holding the frame of the robot, which is essentially made of LEGOs In the bottom of the frame are two LEGO-style motors, which drive the wheels through a series of gears,” says Moser.

Q.This might sound like a stupid question, but how

do you display numbers on a serial LCD? I have a

serial LCD from Parallax that was given to me at

this year’s FLL (FIRST LEGO League) tournament, and it

works great for printing characters, but when I send it a

number it prints what looks like a random number Yeah, I

know, it’s an ASCII character So, how do you convert a

byte size number into a three digit number to display on the

serial LCD? I don’t suppose that you would be willing to

explain how to convert that same byte into an eight digit

binary number?

— Pat Smith

A.Like I always say, there is no such thing as a stupid

question The only reason you are asking is because

you don’t know, and I am sure that there are a lot of

other people that have the same question in the back of their

minds It is great to hear that you are participating in the

FIRST LEGO League (www.firstlegoleague.org) I think

everyone reading this magazine should get involved with the

different FIRST activities The Parallax serial LCD (www.

parallax.com) is a really simple LCD module to get up and

running Only one wire, plus power and ground is needed

to control it

This isn’t that difficult, and many microcontrollerswill automatically do this for you, such as the BASICStamps from Parallax Basically, all you have to do is takeyour number and divide it by 100 The integer part ofthe result is the first digit to be displayed Then take theremainder of that division and divide it by 10, and theinteger part of that result is the second digit to bedisplayed And what is remaining, is the third digit to bedisplayed The LCD_DEC programming example shownhere is a short and simple BASIC Stamp 2 program that will display a single byte value as a three digit number onthe serial LCD

TxPin CON 0 LCD_Baud CON 32 ‘9600 baud on a BS2

temp1 VAR Byte temp2 VAR Byte temp3 VAR Byte temp4 VAR Byte

temp1 = 195

LCD_DEC:

temp2=temp1/100 temp2 = temp2 + 48 Serout TxPin, LCD_Baud, [temp2]

temp2=temp1//100 temp3=temp2/10 temp3=temp3 + 48 Serout TxPin, LCD_Baud, [temp3]

temp4=temp2//10 temp4=temp4 + 48 Serout TxPin, LCD_Baud, [temp4]

Temp1 is some number that I have randomly chosen

Tap into the sum of all human knowledge and get your questions answered here! From software algorithms to material selection, Mr Roboto strives to meet you where you are — and what more would you expect from a complex service droid?

returns the remainder of a division operation For example,

in regular division, 195/100 = 1 (BASIC Stamps use

integer math, so all the decimal places are truncated/lost)

Now, 195//100 = 95 Then, 95/10 = 9 and 95//10 = 5

Thus, these are the three digits that will be displayed — 1,

9, and 5 The Parallax serial LCD doesn’t actually display

numbers but rather ASCII characters So to convert these

numbers into the appropriate ASCII character digits, the

decimal 48 is added to each digit Forty eight is the

ASCII character for the number 0 (zero), and by adding 48

to the digit, it will map this digit to the appropriate

number character on the ASCII table which will then be

displayed properly

Now, converting a single byte into an eight character

binary number requires reading all eight bits of the byte,

one at a time To do this, a simple loop is used Since

writing to the LCD is like writing by hand (from left

to right) each bit must be read from left to right (most

significant bit, MSB to the least significant bit, LSB) and

then displayed on the LCD in that order The sample

routine, LCD_BIN, demonstrates how this is done The key

function in this routine is the rotate left operator, << This

function will shift every bit in the byte to the left Temp2

<< 1 means that every bit in the byte is shifted to the left

by one place If temp2 << 2 was used, it would shift all the

bits by two places The bits don’t wrap around, thus the

temp2 variable is destroyed in the process of reading each

bit This is why temp2 = temp1 is used Temp1 is the

primary variable, and temp2 is just a copy of it so that the

original variable isn’t changed in the process of reading

each of its bits The IF-THEN statement checks the MSB of

temp2 and will display its result on the serial LCD That’s all

Now, just in case you were wondering how to display

hexadecimal numbers, the LCD_HEX routine shown here

demonstrates how to do this This routine is very similar to

the LCD_DEC routine, except that instead of dividing the

number by 100 and 10, you are only dividing the number

once by 16 As with the LCD_DEC routine, the numbers

need to be mapped to the ASCII character set Adding 48

to the decimal numbers will display the decimal characters

When the number is greater than nine, i.e., 10, 11, 12,

etc., it is actually A, B, C, etc., in hexadecimal To map

this properly, we add 55 to the numbers so that the

prop-er charactprop-ers are displayed on the LCD The conditional

IF-THEN statement in this routine performs the mapping

operation

LCD_HEX:

temp2=temp1/16

IF temp2 > 9 THEN temp2 = temp2 + 55 ELSE

temp2 = temp2 + 48 ENDIF

SEROUT TxPin, LCD_Baud, [temp2]

temp2=temp1//16

IF temp2 > 9 THEN temp2 = temp2 + 55 ELSE

temp2 = temp2 + 48 ENDIF

SEROUT TxPin, LCD_Baud, [temp2]

The BASIC Stamp and many other microcontrollers havespecial built-in functions that do this for you, but if yourmicrocontroller doesn’t have them, then these routines willshow you how to do it So, how would you write a routine todisplay Octal numbers?

++++++++++++++++++++++++++++++++++++++++++++++

Q.I am writing to you in hopes that you can show me

how to make my RoboNova robot a remote controlled robot with something like a Playstation 2controller When I saw your article last October about turning a Playstation 2 controller into a remote control, I gotexcited about this The Robonova robot has a lot of reallycool moves that can’t be controlled with a regular aircraftR/C system, but the Playstation 2 controller has 16 buttonsand two joysticks that can be used to control all the robot’sfunctions I don’t like the IR remote that comes with itbecause you practically have to be on top of the robot inorder for it to work, and then it only works sometimes Anyhelp here would be greatly appreciated

— Lance Alberts

A.You’re in luck! I recently did the same thing with my

robot The work to prepare for the October ‘07 issue of

SERVO Magazine inspired me to see if I could convert

my RoboNova (www.hitecrobotics.com) into a remote

control robot My goal was to see if I could get this robot tocompete in the remote control division of the 3 kg robot

sumo contest at Robothon (www.robothon.org) that is hosted by the Seattle Robotics Society (www.seattlerobot ics.org) Needless to say, it didn’t win, but it sure was a

crowd pleaser Especially when one of his opponents gotstuck between his legs — a true wrestling match

The BlueSMiRF serial modem (see Figure 1) from

SparkFun Electronics (www.sparkfun.com) makes this a

fairly straightforward upgrade You will need two of them:one for the robot and the other for your Playstation 2 controller Figure 2 shows a schematic drawing for wiring theBlueSMiRF serial modem to a SX28 microcontroller fromParallax Figure 3 shows a schematic cable for connecting the BlueSMiRF serial modem to the MR-C3024 controller onthe RoboNova

You may want to purchase a special adapter cable from

Lynxmotion (www.lynxmotion.com) called the Sony

Playstation Controller Cable For $4.95, it is well worth the

money for obtaining the special cable that connects to

the Playstation 2 controller and has convenient connectors

for connecting to your projects I do not know of any other

place that sells the special connector that the Playstation 2

controller uses

The MR-C3024 controller

on the RoboNova has two dedicated serial data ports thatmake life really easy for wiringthe BlueSMiRF to the MR-C3024 One port is for transmitting serial data, andthe other is for receiving serialdata Each port has threewires: a signal wire, +5V, andGND The +5V wire (centerpin) is used to power theBlueSMiRF serial modem Figure 4 shows a photo of theseports Notice the three port labels (ETX, ERX, and LCD)immediately to the left of the programming port at thecenter of the MR-C3024 WARNING: The ETX and ERXports are mislabeled on the circuit board The ERX (serialreceive) port is actually immediately adjacent to the serialprogramming port, and the ETX (serial transmit) port isactually between the ERX and the LCD ports This is

RB.4 RB.3

RB.7 RB.6 RB.5

RC.0

RC.3 RC.2 RC.1

RC.5 RC.6 RC.4 RC.7

RA.3

RA.0

RA.2 RA.1

MCLR OSC2 OSC1 RTCC

4 MHz

+9V FOR VIBRATION MOTOR POWER

NOT CONNECTED ACKNOWLEDGE

Vdd (+3V to +5V) ATTENTION CLOCK

GROUND

COMMAND DATA

LYNXMOTION PS2 CONTROLLER ADAPTER CABLE AS VIEWED FROM THE FEMALE END

GREEN

BROWN ORANGE

BLACK

YELLOW RED/SHIELD BLUE

VIOLET N/C

DATA CMD ATTN CLOCK

Vdd GND +9V ACK

4.7 KΩ 4.7 KΩ

10 KΩ

+5V

+5V +5V

GND TX-0 PWR CTS-I

Modem BlueSMiRF

N/C RX N/C

+5V TX GND

+5V GND

TO ETX ON THE MR-C3024

TO ERX ON THE MR-C3024

Figure 3 Cable drawing for connecting a BlueSMiRF to the RoboNova.

Figure 4 Serial communication ports on the MR-C3024 Note the

ETX and ERX labels are labeled incorrectly They should be reversed! Figure 5 The BlueSMiRF serial modem cable

connected to the ERX and ETX ports.

opposite to what is labeled on the circuit board The LCD

port is for an LCD display that is available for the robot

Figure 5 shows the two plugs for the BlueSMiRF cable

attached to these ports Figure 6 shows the BlueSMiRF

mounted inside the plastic housing on the back of the

RoboNova The BlueSMiRF serial modem is held in place

with a piece of double-sided foam tape Double-sided

foam tape works very well

As you can see, by using the BlueSMiRF serial modem

there isn’t a lot of wiring or additional circuits needed to turn

the RoboNova into a truly remote controlled robot The bulk

of the work is modifying the software on the RoboNova and

establishing a wireless serial link between the RoboNova and

the Playstation 2 controller

The key to maintaining a good reliable communication

link between the Playstation 2 controller and the

RoboNova is making sure that the two devices are

synchronized so that the data is properly transmitted and

received as expected The loop structure in the RoboNova

is slower because it has to process the commands and

execute the servo motions By the time it has finished a

particular command, the time lapse can be from a few

milliseconds to several seconds The Playstation 2 controller

can cycle through reading the states of the different pins

many orders of magnitude faster Because both systems

are running independently at different internal loop cycle

rates, there needs to be a way to synchronize the wireless

connection so that the data can be transmitted and

received properly

There are many methods that can be used to

synchro-nize the wireless link For example, using the RTS and CTS

features on the BlueSMiRF serial modem However, I chose

more of a brute force method When the RoboNova has

completed a particular command and is ready for the next

motion command, it will transmit a four character string,

!PSX This is to tell the Playstation 2 controller that it is ready

to receive the next motion command The Playstation 2

controller sits in a loop looking for the !PSX string When it

finally receives this command, it will then read the current

state of the controller’s buttons and joystick positions, and

then transmit the results to the RoboNova with a simple

data checksum In the meantime, the RoboNova is waiting

until it receives the next command The four character

string, !PSX, is the synchronization command between the

two systems You can change this to whatever you want I

just happened to use this since it is the same

synchroniza-tion method that Jon Williams used in the original

Playstation 2 controller software that helped me figure out

how all this works

In the main RoboBasic program that the RoboNova

uses, it will have to be modified slightly so that you can use

the BlueSMiRF serial modem The following is a portion of

the MAIN startup/loop routines from the “Overall Template

Program.bas” (or you can use the Action_Auto.bas

program) that comes with the RoboNova This program

will need to be modified to send and receive data instead of

its current configuration to respond to commands from the

GOTO main_exit

MAIN1:

‘——————————————-A = REMOCON(1)

A = A - ID

ON A GOTO MAIN,K1,K2,K3,K4,K5,K6,K7,K8,K9,K10,K11,K12,K13,K14,K15,K 16,K17,K18,K19,K20,K21,K22,K23,K24,K25,K26,K27,K28,K29,K3 0,K31,K32

GOTO MAIN

action_proc:

‘————————————————————————-A = RR - 50

ON A GOTO MAIN,K1,K2,K3,K4,K5,K6,K7,K8,K9,K10,K11,K12,K13,K14,K15,K 16,K17,K18,K19,K20,K21,K22,K23,K24,K25,K26,K27,K28,K29,K3 0,K31,K32

RETURN

main_exit:

‘——————————————-IF RR > 50 THEN RETURN

RR = 0 GOTO MAIN

‘================================================

Since I wasn’t using a gyroscope or monitoring the battery voltage, I removed the robot_voltage and robot_tiltcall routines from the MAIN program I removed two of thethree ON n GOTO MAIN,K1, K2,… command sections,

and removed the action_proc subroutine and the main_exitroutine (I pretty much gutted the main routines.)

The following shows the changes to the MAIN routinethat enable serial communications with the BlueSMiRF serialmodem The DELAY 5000 is just a five second delay that Iadded so that it will allow me some time to turn on thePlaystation 2 controller after I turned on the RoboNova This

Figure 6 The BlueSMiRF serial modem mounted to

the inside of the RoboNova’s back body panel.

can be eliminated or changed It doesn’t matter The ETX

command sends only one character at a time, and the

character definition must be in a variable So, to send the

synchronization command !PSX requires eight lines of code

I am sending the commands at 19200 baud This was

arbitrarily chosen I just happened to have configured the

BlueSMiRF serial modems to operate at 19200 baud You can

choose any other speed Keep in mind that slower speeds are

more reliable in ensuring proper data transfer, but it also

takes longer to transmit You may begin to notice a lag time

between transmission and reaction You will need to

experiment to see which baud rate works best for you and

the RF noise environment that you are in

Immediately after sending the !PSX synchronization

command, I read in the next two bytes of data As with the

ETX, the ERX can only read in one byte of data at a time The

variable, A, is the variable that contains the actual RoboNova

motion command This will be a number between 0 and 31

The Playstation 2 controller will convert the controller

commands into a number between 0 and 31 The second

variable, tmp, that is read from the ERX command is a simple

checksum command Here, I arbitrarily chose to send a byte

value of 126 as a checksum to verify that the data was sent

properly There are much better checksum methods that

should be used, but like I said before, I used a brute force

method to make this work If the checksum value is not 126,

then the RoboNova will consider the data set invalid, and will

begin the loop structure all over again

I also removed the following lines from earlier in the

program since the robot is no longer using the IR remote:

‘== Action command check (50 - 82)

‘IF RR > 50 AND RR < 83 THEN GOTO action_proc

Then I added the following line to the variable tion set so that it will know that “tmp” was a byte variable:DIM tmp AS BYTE

declara-That’s all there is to make the RoboNova program workwith the BlueSMiRF serial modem The next step is to makesure that the BlueSMiRF Playstation 2 controller software isconfigured to receive and transmit the proper data The following is the MAIN routine in the SX28 microcontroller

READ_PSX endif

RoboNova_cmd = 0

if psxJoyRY > 220 then ‘walk forward RoboNova_cmd = 12

TX_Out RoboNova_cmd TX_Out 126

goto Main endif

if psxJoyRY < 25 then ‘walk backwards RoboNova_cmd = 11

TX_OUT RoboNova_cmd TX_Out 126

goto Main endif

if psxJoyRX < 25 then ‘turn left RoboNova_cmd = 22

TX_OUT RoboNova_cmd TX_Out 126

goto Main endif

if psxJoyRX > 220 then ‘turn right RoboNova_cmd = 24

TX_OUT RoboNova_cmd TX_Out 126

goto Main endif GOTO Main

The beginning part of this routine is an endless loop thatlooks for the !PSX synchronization command Once itreceives this command, the current state of the Playstation 2controller is read and stored into a set of joystick and pushbutton variables Then, the RoboNova command vari-able RoboNova_cmd is reset to zero From this point on, thedifferent joystick positions and button states are convertedinto a single byte with a value between 0 and 31 The reason

the numbers 0 to 31 via the ON n GOTO

instruc-tion in the RoboBasic demo program So to keep

things simple, I kept the same data structure

Once the RoboNova_cmd is determined, it is

transmitted to the RoboNova via the BlueSMiRF

serial modem Then the checksum value, 126, is

transmitted to tell the RoboNova that the entire

data set transmission is complete

The entire programs for the SX28

microcon-troller for reading the Playstation 2 conmicrocon-troller

and commanding the RoboNova robot, along

with the RoboBasic program for the RoboNova

robot can be downloaded from the SERVO

website (www.servomagazine.com) Table 1

shows which Playstation 2 controller

button/joy-stick position controls which built-in RoboNova

motion command The October ‘07 issue of

SERVO Magazine has a long discussion on how

to configure the BlueSMiRF serial modem for

automatic connection between two devices, or

you can obtain the configuration instructions

from Sparkfun Electronics Autoconnect is the

best way to configure both of the BlueSMiRF

serial modems, otherwise you will have to add

some more code to both programs to tell the

BlueSMiRF modems to search for each other

and then to connect to each other

Table 1 shows a list of the Playstation 2

command sequences and the resulting

RoboNova motion command These are what I

happened to use from the 32 built-in commands

to choose from In the Playstation 2 SX/B

program, combination key functions can easily

be programmed in With the single command

byte that is sent, up to 256 separate commands

can be configured Modifying the

pro-grams to send two bytes of data can be

used to send over 65 thousand unique

commands And yes, the Playstation 2

controller has far more command

options than a regular R/C transmitter

There are a lot of better ways to

do this This is just what I did, and it

worked well enough for the robot to

compete in the robot Sumo contest at

Robothon It is also good enough for

the robot to compete in the Robo-One

competitions (www.robo-one.com).

Some of you may be wondering how

my robot survived the competitions It

did just fine, and still works like it did

before the contest A few scratches

here and there, but no damage So,

have fun with this, and let the SERVO

readers know how things go with your

experiments Many of us really enjoy

learning about what other people are

doing with their humanoid robots SV

Playstation 2 Controller RoboNova Command Command Description

Right Joystick Up 12 Walk Forward Right Joystick Down 11 Walk Backward Right Joystick Right 24 Turn Right Right Joystick Left 22 Turn Left Left Joystick Up 21 Forward Tumble Left Joystick Down 31 Backward Tumble Left Joystick Right 30 Right Cartwheel Left Joystick Left 28 Left Cartwheel Left Arrow 14 Shift Left

Up Arrow 10 Walk Fast Right Arrow 13 Shift Right Down Arrow 8 Shoot Pistols Start Button 2 Raise Arms Press Down on Left Joystick 19 Backward Standup Press Down on Right Joystick 25 Forward Standup

Select Button 1 Bow Square Button 15 Left Attack Triangle Button 29 Front Attack Circle Button 20 Right Attack

X Button 7 Flap like a bird R1 Button 9 Handstand L1 Button 26 Toggle between sit or stand R2 Button 4 Sit with raised arms, wait one

second, then stand L2 Button 3 Sit, wait one second, then stand

Table 1 Playstation 2 wireless controls for the RoboNova robot.

Drobo — the World’s First

Storage Robot

Data Robotics has developed Drobo — the world’s first

storage robot Drobo is a striking black desktop

device that connects via any USB 2.0 port on a Mac

or Windows PC Under its magnetically attached

faceplate are four bays that can accept any brand, size,

speed, or capacity mix of standard 3.5” SATA internal

hard drives (sold separately and available at most

electronics stores)

Drobo has gained a following of enthusiasts including

creative professionals such as graphic designers,

photographers, and video editors, as well as users in the

education sector and small business owners

Drobo works like any external USB drive and installing

it is as easy as pulling it out of the box and plugging it into

a USB port However, unlike competitive solutions, Drobo

requires no software, no configuration, and no computer

expertise to start reliably storing important data In a

ddition, Drobo users benefit from the extensive reliability

features of the storage device, which uses patent-pending

RAID-like proprietary software Drobo boasts data

redundancy features normally associated with RAID such

as mirroring and data striping, but without the hassle of

RAID Drobo creates one large pool of protected storage

out of the available drives, enabling users to get rid of

multiple external drives

Julian Terry, chief architect of Data Robotics and

20-year-veteran of the storage industry, said he was

inspired to create Drobo after losing irreplaceable

personal data from a system crash at home “After

inventing enterprise storage technologies and building

entire data centers, I understand how to store and protect

data better than most,” Barrall said “When I investigated

what solutions were out there, the only options were

managing a growing number of external hard drives or

managing RAID That’s when I realized there needed to be

an easier solution, and I began the development of Drobo

four years ago.”

Drobo is distributed in Sweden by FixIT and is available

immediately

For further information, please contact:

Sub-50 Cent Eight-Bit Flash Microcontroller Family

STMicroelectronics now offers a new ultra-low-costseries of Flash microcontrollers (MCUs) intended forhighly cost-sensitive products such as electric bicycles(ebikes), air conditioning, small appliances, and sensors The ST7FOX series includes devices with from 2KB to 8KB of on-chip Flash memory, and with eight to

32 pins, all of which are priced below the critical 50 cent($0.50) threshold

Part of the well-established ST7 family of MCUs built

on an industry-standard eight-bit architecture, the newdevices achieve their low unit cost with a simplified featureset, while maintaining the benefits of a robust and proventechnology ST7FOX operates with +5V (±10%) powersupply, and includes a relaxed RC oscillator which can becalibrated within the application

The CISC (complex instruction set computer) architecture is a significant advantage for the production

of compact code matching the small memory footprint ofthe family’s devices, with nested interrupt managementand a variety of addressing modes in the core architecturesimplifying high level language coding

ST7FOX is designed to satisfy the increasing needs in the industry for reliable low-end and verylow-cost MCUs for use in cost-critical applications.However, its upgrade path to the easy-to-use ST7Litefamily — itself a cost-effective solution — also enablesmanufacturers to build scalable product families toaddress broader markets

The very low pricing enables designers to implement

a microcontroller solution to replace electromechanical orlogic-based control, and for the same cost as ROM devices,this Flash-based family will ease inventory managementand simplify the supply-chain A free integrated development environment (IDE) including a C compilerminimizes costs for developers

Samples of ST7FOX are available now in eight-pin DIP

or SO-8 packaged devices with 2KB of Flash, and 32-pinDIP or LQFP devices with 4KB of Flash All are priced at lessthan $0.50 in large quantities

For further information, please contact:

Website: www.drobo.se

Rugged, Low-Cost Motorized

Robot Platform

The new wheeled robot

platform from Electronix

Express is made from

0.1 inch industrial-grade

aluminum It features

two seven-inch octagonal

plates separated by four

pre-drilled 2.5 inch riser brackets

You can use the bracket holes to

mount sensors and other accessories The plates have

grommeted holes for passing cable, and are thick and

strong enough to drill and tap additional mounting holes

The platform includes an industrial-grade ball-caster

and two reversible 12 VDC gear-head motors with

neoprene foam wheels It comes assembled, and includes

hex keys for the socket-head chassis-screws and the

set-screws on the wheels A dual H-bridge is available for

separate purchase The platform is catalog number

01BRPL and sells for $109.95 each (quantity discounts

are available)

For further information, please contact:

Digitizing Probe

Tormach offers a touch-trigger CNC Digitizing Probe

that mounts in a machine spindle for fast and accurate

electronic measurement of parts and fixtures

The probe features a robust detachable ruby tipped

stylus and will connect directly to the Tormach PCNC 1100

auxiliary socket The probe enables accurate measurement

of parts and sets up jobs quickly Probe features include:

• Capable of generating a point cloud for reverse

engineering and repair applications

• Works with Tormach machine control software to

automate many probing operations

• Compatible with standard Tormach Tooling System

geometry, allowing setup consistent with TTS tool

changes

By mounting the probe in a machine spindle and

connecting it to the control computer with the propersoftware, the machine can be used for measuring instead

of cutting

The measurements can be used to set work offsets,measure features, or to generate a 3D “point cloud”describing a complex surface

The Tormach machine control software has interactivescreens to automate standard probing operations such asfinding the center of a bore, finding a plane surface, orfinding the corner of a vise jaw or workpiece

The probe interfaces directly with the TormachPCNC 1100 It can be used with many other machines provided the electrical interface is configured properly

Detailed information on using the probe isavailable in Chapter 8 of the PCNC 1100 manual It is

available online at www.tormach.com/documents.htm

The stylus with the ruby tipped sphere is very accurateand wear resistant, but not inexpensive Tormach offers aless expensive steel stylus training kit with a breakawaysection called the Practice Probe Tip (PN 30695) that

is helpful when learning how to operate the probe The Probe Wrench Set (PN 30673) is necessary to swap probes

For further information, please contact:

TOOLS & TEST EQUIPMENT

CONTROLLERS & PROCESSORS

Is your product innovative, less expensive, more functional,

or just plain cool? If you have a new product that you

would like us to run in our New Products section, please

email a short description (300-500 words) and a photo ofyour product to:

newproducts@servomagazine.com

Show Us What You’ve Got!

365 Blair Rd.

Avenel, NJ 07001 Tel: 800•972•2225 or 732•381•8020 (in NJ) Website: www.elexp.com

Electronix

Express

204 Moravian Valley Rd., Ste N Waunakee, WI 53597 608•849•8381 Fax: 209•885•4534 Website: www.TORMACH.comTORMACH

Featured This Month:

Features

22 The Holy Grail of Combat

Robotics — Usable Melty

ROBOT PROFILE – Top

Ranked Robot This Month:

29 Bounty Hunter by Kevin Berry

One of the classic trade-offs incombat design is armor vs

platform vs weapon weight Atruly efficient, traditional spinningweapon bot might devote25–30% of total weight to theweapon The next “step up” inefficiency is a full body spinner,where weapon and armor arecombined, and 50% or more ofthe weight gets applied towardsoffensive capability

A method sometimes used toget 100% offense is the “thwack-bot,” where the entire bot is spunand a protruding hammer or spikeimparts the built-up momentuminto the opponent The only problem with a thwack style bot isthat it basically must spin in place,

hoping the opponent moves intoits kill zone

Obviously, the optimum solution is to spin the whole botcontinuously, while also chasingdown the opponent To do this, avery complex driving schemeemerges, known as “translationaldrift,” or in the vernacular, “meltybrain.” This means inputting slightspeed changes to one set ofwheels, resulting in a drifting move-ment rather than spinning in place.Few, if any, drivers have donethis successfully by hand.Attempts to automate thisfunction exhibit much technicalcreativity, and some limitedsuccess Searching the variouscombat forums reveals periodic

● by Kevin Berry

Usable Melty Brain Part 1: Profiles of (Nearly) Successful Attempts

THE HOLY GRAIL

OF COMBAT ROB TICS

and interesting threads on the

topic, beginning back in 2001, and

continuing up to today There is also

a Wikipedia article of some interest

on the topic

Blade Runner

The first credited attempt at

building a melty brain bot belongs to

Team Carnivore, which competed at

the first, Long Beach BattleBots

event, and many others Ilya Polyakov

contributed his remembrances on

the naming of the technology, and

what drove it

“My middleweight Carnivore

got beaten really bad by Christian

Carlberg’s thwack-bot Knee Breaker

at the Long Beach BattleBots The

thwack-bot design intrigued me and

really got stuck in my head, perhaps

reinforced by flashbacks of the

nasty and unnecessary loss to Knee

Breaker The design is brutally

simple and perhaps the most

effi-cient conversion of stored electrical

energy to kinetic impact energy

while maintaining reliability,

minimizing moving parts and

maximizing defensive capabilities.Only

one drawback — mobility Because

the robot relies on a tank style drive

train, the robot can only spin in one

spot Blade Runner 1 was designed

to take advantage of this system

The concept was to use this robot in

conventional pushy or “hand to

hand” combat while having the

ability to spin up and attack the

opponent like a full body spinner

The melty brain system was given

that name as a result of a late night

conversation with one of my

teammates who reported his brain

melting when I tried to explain the

math behind it.”

Next month’s article will discuss

the technical aspects of the

transla-tional drift implementation in all four

featured bots For this issue, we’ll

focus on the more traditional

config-uration items on each machine Ilya

gives a short history of Blade Runner:

“BR1 was driven mostly as a

pushy bot with some minor

side-ways thwacking Blade Runner

2 was an all composite version

of BR1 powered by two fourinch Magmotors This crammed

a 8HP+ drive train into a dleweight The bot was amaz-ingly powerful and destructive,but keeping the wheels fromlosing traction during normaldriving was a feat In the end,the all composite nature of this robot was its un-doing

mid-Lightweight armor and ture was critical for meeting the

struc-120 lb weight limit with some 80 lb

of just motors and batteries Thearmor and structure were com-bined into a single monocoqueKevlar shell The all composite construction entailed fabricatingeverything out of Kevlar, includingbearing mounts, motor mounts,and battery mounts The Kevlarworks great as armor where hightolerances are okay, however, trying

to line up motor mount holes andbearing mounts in Kevlar was toomuch The project ran weeks lateresulting in the final robot assemblytaking place in the back of aSuburban on the drive between SanJose and Treasure Island! We didnot have time to implement themelty brain system Blade Runnercompeted unfinished in both sea-son 5 and 6 of BattleBots Season 5had a few wins but a forgotten clipresulted in a lost wheel and a loss

Season 6 was ended by an amazingfight against Hazard where one ofthe hits penetrated 3/8” thick lami-nated Kevlar armor and cut through

a Magmotor — sick!

BotRank lists Blade Runner as 5-5 across all fights, from BattleBots1.0 through 5.0

CycloneBot

Next up in ourmelty brain hit list isCycloneBot from CMRobotics This is a 220pound Heavyweightwhich fully implementsthe translational drift

strategy with a sophisticated

comput-er system The backbone of the bot is

an oblong, one piece shell, madefrom 1/2” welded titanium The botfeatures impressive craftsmanship,along with a proprietary systemcalled “TauntWare” which allowsreal-time, marquee style messages

to be displayed on the side of the rotating bot during a fight The teamhas termed their drive scheme

“Cyclone Drive,” and has garneredmuch interest among the computerand electronics industry for theirimplementation

Michael Worry from the teamdescribes the platform and someinteresting problems: “We’ve gonethrough a few different iterations

on the system The melty brain is continuously accelerating and braking the motors which is very hard on the motor controllers,batteries, and wiring

“Today, we use Odyssey 12VSLAs, two in series and run a 24Vbus into two MC1-HVs We find weneed to use the “dry cell” SLAs, asany sort of liquid in the batteriescauses battery failures when spinning at 300 gs

Blade Runner

CycloneBot

We’ve actually taken batteriesout of the robot that are visibly

bulged on one side We started with

NiCds and NiMHs, but kept burning

them up due to insufficient power

density

“The MC1-HVs are fed from acustom board that CM Robotics built

that provides isolation between the

digital and power electronics The

digital electronics are a ruggedized

NIOS development board from

Altera

“On motors, the originalCycloneBot used two Etek motors

which worked awesomely However,

we found the power density of the

system was limited by the power

from the batteries rather than the

power output of the motors Plus,

we wanted to go to a much smaller

chassis to permit thicker armor

We changed to four longmag motors

— two on each side into a Whyachi

gearbox These longmags have

worked reasonably well, though

we have problems with the impact

forces dislodging the magnets in

the casing

“We use carefree tires,machined down to our desired diam-

eter Armor and chassis are all

titani-um Blades are hardened tool steel

CycloneBot’s BotRank record is11-20, fighting in a wide variety

of the sport’s most prestigious

events since 2003 Their website is

www.maccanikill.com

Melty B

A recent addition to the meltyfleet is “Melty B,” an antweight

meeting with some success in the

box Team SpamButcher’s builder,

Rich Olson, built many test platformsand a 1.0 version before hitting suc-cess, winning Robothon’s antweightdivision in September 2007

Rich Olson describes Melty B’sguts “It uses Ever Motor’s ERS-365S-3033s They’re similar to a Speed

400 — except they’re a bit shorterand lighter They’re rated at 6V with16,340 no-load RPM I’m runningthem at 7.4V — and getting about8,000 RPM (there’s a lot of load —and they’re only on about 75% ofthe time due to the melty brainstuff) The battery is a 7.4V 910 mAThunderpower LiPo

“For motor controllers in themost recent (1 lb) version, I actuallyused Darlington drivers (ST Power’sBU941ZT) These are inexpensive(about $2.50 each) and I was able toconnect them directly to the micro-controller I am using one Darlingtondriver per motor Since the drivers areonly on/off (no reverse) — the robot

is only translational drift — it has no

“normal” drive mode

“The shell is a custom cut 7”

aluminum (6061) pipe segment

(1/8th” thick) I got this from www.

onlinemetals.com for under $10!

The “knockers” are titanium andDelrin The Delrin held up pretty well

— but did eventually crack in one of

my final matches Most of the electronics in the bot are connectedusing wire wrapping, and the topand bottom are made of 03” thickgarolite (fiberglass)

A nice historical build page —including the total software load and

videos — is available at www.spam butcher.com.

BotRank shows that Melty B 2.0went 4-0 at Robothon 2007

Scary-Go-Round

The last in our line-up ofbots using this drive scheme

is Scary-Go-Round, a 30 lbFeatherweight from Dale’sHomemade Robots DaleHeatherington, a recognizedinnovator and master craftsman,got interested in the translation-

al drift schema, after followingCycloneBot’s successes He started,

as did Rich, with models and prototypes before turning out a finely crafted machine

Three modular motor/gearboxunits were built on a CNC mill, pow-ered by Team Orion 13 turn R/C carmotors, driving 4” wheels A 23:1ratio in the gearbox ensures compli-ance with Robot Battle’s 20 fps maximum for spinning weapons Theunique three legged “Y” configura-tion puts maximum mass out at theperimeter to maximize Moment OfInertia After experimenting withspring bumpers intended to launchthe opponent (but, which proved to

be more effective launching Scary),

he turned to wedges To get aroundthe inherent problem of zero clearance wedges (hanging up andlaunching on arena floor bumps), hecame up with a “smart wedge” thatretracts upon hitting an obstacle.Robot Battles features 1/4” aluminum bars all over the platform.Shop trials showed that Scary could-n’t translate over the bars, so Dalewas forced to come up with anotherinnovation: an automatic conversionfrom melty drive to standard tankdrive A rotatable skid falls under

a wheel when the bot is spun inreverse, converting it to tank drive.Dale has posted a superb buildreport with photos and videos, at his

CM Robotics; and Dale Heatherington, Dale’s Homemade Robots

Weight is perhaps the single most

difficult challenge in the

devel-opment of any robotic system While

this design aspect may not seem the

top concern for your robotic system, it

will influence every part of it, from

materials used, to mobility, speed, and

power In addition, for each robotic

design, there is the builder’s need to

design something unique or artistic

For me, designing with minimal

weight requirements is simply part of

the creation process To accomplish

this, it is important to understand the

simple concept of a form

In combat robotics, the form or

exterior design is paramount to the

defensive and offensive strategy

employed, but in general the exterior

design of any robot must match the

requirements of the task A brilliant

electrical design or application can

be lost in an ordinary black box

Formed shapes and complex angles

can provide not only a more pleasing

or natural shape, but they can also

dramatically increase material rigidity

and deformation resistance Building

such designs does require more

planning and the willingness to

potentially abandon familiar CAD

programs for initial development

Although each builder should employ

techniques that they are comfortable

with, I will discuss several techniques

I have used to convert flat sheet

metal into dynamic sculptures

Often, when many people build

a robot or machine, they think about

familiar dimensional characteristics

such as a top, bottom, right side, left

side, front, and back Then they take

their measurements and cut their

materials to match these dimensions

Joining the material is often an afterthought accomplished withwelding, fasteners, and too oftenglue Unfortunately, these solutionsoften result in a joint that is not asstrong as the material used or severe-

ly weakens the material throughirregular heat zones, dissimilar metals, cuts, or holes at the joints

Another issue is that mostdesigns use flat planar lengths of thematerial that do not provide strength

in multiple axis This often causes alack of rigidity across the materialrequiring weight inducing reinforce-ment Simply creating an edge in thematerial will significantly improverigidity along the edge To demon-strate this, imagine a single sheet ofpaper Unfolded, the paper will sagregardless of where it is held, butfold the paper and create a crease,and the sheet will now have a rigidspan along the crease This edge isimportant since it demonstrates theinherent advantage of forming andthe continuity of the material thatdoes not require fasteners or otherjoining techniques (Photo 1)

Angular bends are not the onlyway to improve material rigidity andmultiple axis strength Roundedforms can also create very strongshapes such as domes and cylinders

Although a dome cannot easily bedemonstrated with paper, most plastics and metals can be stretchedalong the interior of the materialusing a hammer, heat, and/or rolling(using a tool such as an Englishwheel) A half dome is anothershape that can be formed by using

half of a circle or ellipse By bendingthe shape perpendicular to the halfcut, an even curve in the material willproduce a domed shape that directsenergy away from the center of theform toward the edges (Photo 2).Now that the ideas of foldingthe material have been understood,the next step is to see how a designcould be created in this manner Ifyou are more comfortable creatingeach component separately, scalethe parts and create them on paper.Now, with a little tape, join theircommon edges Slowly, the connect-

ed pieces should take on a singlepiece form One note: The connectededges should match the placeswhere the most strength is required.There are CAD tools that can createthese forms as well, however, paper

This article provides just a peek

into the history of attempts at ing translational drift driven bots Inthe interest of magazine sales, I’ve

build-withheld all the juicy technical detailsfor Part 2, “Looking Under The Hood:The Technology Of Melty Brain.” SV

PHOTO 1

PHOTO 2

Nov 12-Dec 16, 2007

Roaming Robots held their Winter

Tour Grand Finals in Nottingham,

England at the Harvey Hadden SportsComplex on December 1st Go

is a cheap and easy way to prove out

an idea (Photos 3 and 4)

Next, we need to form the flatsheet based on the type of material

used An industrial brake press is a

handy tool that many of us will not

have access to, however, some

materials can be formed by hand or

a common vise with the use of heat

or brute force

Angular bends work well with avise and a block material that evenly

distributes the force you are

applying The block can be metal,

wood, or plastic, but typically is flat

and more rigid than the material

being bent Rounded forms (such as

the half doom example above) are

best shaped by holding down a

corner or mid section and applying

force to the end of the piece,

there-fore curving the material as needed

As an example, I have placed ametal sheet in an expansion joint

between two sections of concrete,and then used the brute force of myweight by leaning or stepping on thematerial to get the shape I wanted(Photo 5)

Plastics and some metals willrespond well to being bent withoutheat, but some materials do not easily stretch and will actually fatigue

if bent Titanium and aluminum arematerials that will greatly benefitfrom a large radius rolled edge orsharp crease of less than 30 degrees

If a tighter bend is necessary withthese materials, or you cannot easilybrute force thicker metals or thermoplastics, then the application of heatmay be necessary

Heat can be crated from manysources, including a blow torch,propane gas torch, or even a smallcylinder of Mapp Gas The key here is

to let the heat do the work Securelymount the material and use the hottest

part of the flame (generally the blue tip

of the flame) to heat the material.Titanium and steel will become adark red when they are ready to beformed Aluminum and plastics aremore difficult to determine when the best forming temperature isachieved, so keep continual force onthe material until it begins to softenand bend For lengthy angularedges, keep the torch moving overthe material along the edge, and use

a block to apply consistent force.Heat can also be used to transfer

a shape or form to the sheet of

materi-al To create a radius bend, you cansecure the material and use pipe ortubing placed against the sheet withthe needed radius to create a roll in thematerial Once again, keep the torchmoving back and forth along the bendedge to keep the radius consistent.Transferring other shapes can bedone by placing the material over theform and allowing the heat to sagthe material to match the form usingnothing more than gravity or lightforce from a hammer or pliers(Photos 6 and 7)

It will take some time to masterthe techniques above, but with a littlepatience, you can make somethingthat is both stronger and more aesthet-ically pleasing than a joined box SV

5, Team Iron Awe, Rob and Gilbert

Grimm; 2nd: Kan Opener, Team

Kan Opener, Andy and Tom

Kane; 3rd: Tilly Ewe 2, Team Tilly,

Shane Lale

● Featherweights — 1st: Beauty 2,

Team Beast, John and John Jr

Lear; 2nd: Mini Mighty Mouse,

Team Mouse, Trevor Wright; 3rd:

Skink, Team Windbags, Mike

org for more information.

Upcoming Events for

for more information The event will

be held at the Monroe County

Fairgrounds (near Seattle); www.

nwmodelhobbyexpo.com/Directi

ons.html The event will be

held from 11:30am-6:00pm, safety

inspection from 9:00am-11:00am If

a lot of robots register, they may

start safety and fights earlier

Classes: 1, 3, 12, and 30* poundrobots (*30 lb spinning-weapons notallowed) Format: Double Elimination

or Round Robin (RFL Rules) NoICE or open flames Entry Fee: $40for first 30lb or 12lb robot $25 forfirst 3lb or 1lb robot Additionalrobots are half price Special entryfee considerations for builderswho are under 18 Arena: 12 x 12with 18” x 18” pit in one cornersurrounded by a 2” high wall making

it very difficult to accidentally driveinto it

Robots Live will present an event

at the Hermitage Leisure Centre,Whitwick, Leicestershire on February

2nd and 3rd, 2008 Go to www.

robotslive.co.uk for more information For the first event of theyear, Robots Live heads back to their home town of Whitwick inLeicestershire Not only is this theirhome town, but also their birthday!

Come and celebrate two years ofRobots Live!

Motorama 2008 will be

present-ed by North East RoboticsClub, Inc., in Harrisburg, PA, from2/15/2008 through 2/17/2008 Go

to www.nerc.us/ for more information This will be an 150 g to

30 lb combat event Fairies and Antsfight in 8’ box on Friday; Beetlesthrough Featherweights fight in16x16 box on Saturday and Sunday

All completed forms and entry fees

must be received by 1/2/07 This isgoing to be another awesome event

at the Farm Show Complex!

Roaming Robots will present

an event on February 17th, 2008

at The Metro Dome in Barnsley, UKand another on March 22nd and 23rd, 2008 at Colchester Leisure World in Colchester, UK Go

to www.roamingrobots.co.uk for

more information

Central Illinois Bot Brawl 2008 will

be presented by Central IllinoisRobotics Club in Peoria, IL on March

29th, 2008 Go to http://circ mtco.com for more information.

Categories will be: RC Combat (1 lbAnts only), Autonomous Sumo (3 kg,

500 g, LEGO), Line Following, LineMaze Entry fee is $7 per entry if youpre-register, $10 per entry for walk-ins Free admission for spectators

BotsIQ will hold a RegionalCompetition on March 28th and29th, 2008 in Pittsburg, PA Go

to www.botsiq.org for moreinformation SV

On Saturday, November 3rd, the

Ohio Robotics Club (ORC) in

association with the Robot Fighting

League (RFL) held their 6th insect

weight combat robot event, “House

of Robotic Destruction, Fall 2007”

(HORD) at the Cuyahoga ValleyCareer Center (CVCC)

This event helped kick offCVCC’s new robotics program

Students in this program will bebuilding ant weight robots for thenext ORC/CVCC event to be heldnext spring

Eleven teams brought a total of

● by Chris Olin

20 robots to compete in three

weight classes; 150 g Flea Weight, 1

lb Ant Weight, and 3 lb Beetle

Weight Teams came from across

Ohio, as well as Pennsylvania,

Indiana, and most notably, Team

Mechanical Advantage flew in all the

way from Kansas

Action started with three FleaWeight robots fighting a double

round robin tournament Little Buzz,driven by Richard Kelley of BoilingSpring, PA, dominated the classwinning four straight matches 0-2,driven by Evan Gandola of OmstedTownship, OH, exceeded expecta-tions by finishing 2-2; while I.R.D

(Improvised Robotic Device), driven

by Chris Olin of Perry Township, OH,failed to win a single match, largelydue to a lack of reliable batteries

In Ant Weight action, eight robots fought through a dou-ble elimination tournament Dustythe Evil Dustpan, driven by Jeff Gier

of Kansas City, KS, managed to comeback from an early defeat and fight

his way to the finals

Heman I, driven by EvanGandola muscled his

way through the winners’ bracket tothe finals, but not even the power ofGreyskull could stand against thedetermined dustpan Dusty pittedHeman and claimed first prize.Moving on to the BeetleWeights, nine robots clashed in adouble elimination tournament D2,driven by David Timothy of BrookPark, OH, tore a path of destructionthrough the winners’ bracket all theway to the finals Meanwhile, TheBox, driven by Richard Kelley, afterlosing in the second round pushedback through the losers bracket tothe finals But, his comeback washalted by the 1 lb spinning drum ofD2 D2 K.O.s The Box and took homethe first prize honors

In rumble action, Heman Iprevailed over four other contenders

to win the Ant Weight rumble, whileSweaver, driven by Greg Shay ofGarrettsville, OH, beat out fiveother robots to win the BeetleWeight rumble

Prizes and other considerationswere provided by: Dimension

Engineering (www.dimensionengi neering.com); Micro Bot Parts (www.microbotparts.com);

SERVO Magazine (www.servo

magazine.com); and Cuyahoga Valley Career Center (www cvccworks.com).

ORC’s next event will beApril 19th at Cuyahoga Valley

Career Center See www ohiorobotclub.org for more

details SV

Left to right: Richard Kelley, Team Kelley,

Boiling Spring, PA, driver of Little Buzz Evan

Gandola, Team Probotics, Omsted Township,

OH, driver of 0-2.

D2 Little Buzz

Dusty The Evil Dustpan

Left to right: Evan Gandola, Team Probotics, Omsted Township, OH, driver of Heman I Jeff Gier, Team Mechanical Advantage, Kansas City, KS, driver of Dusty the Evil Dustpan.

Greg Shay, Team Fishneck, Garrettsville, OH, driver of Sweaver Richard Kelley, Team Kelley, Boiling Spring, PA, driver of The Box David Timothy, Team D2, of Brook Park, OH, driver of D2.

Evan Gandola, Team Probotics, Omsted

Township, OH Jeff Gier, Team Mechanical

Advantage, Kansas City, KS Greg Shay,

Team Fishneck, Garrettsville, OH Richard

Kelley, Team Kelley, Boiling Spring, PA.

David Timothy, Team D2, Brook Park, OH.

Bounty Hunter has competed in

Motorama 2007 and Franklin

Institute 2007 Details are listed below:

• Frame: Internal frame work is

aluminum

• Base plate: 3/16” aluminum with

lots of large holes to save weight

• Drive train: Four wheel drive, Black

and Decker 9.6V drill motors

• Voltage: 12.0 volts

• Wheels: 4’ x 0.75’ Colson

• Configuration: Wheels narrower in

front than rear to keep inside armor

• Drive ESC: Two IFI Victors

• Drive batteries: Saft 3.2 Ah

• Armor: All titanium, very thin

• Future plans: Needs more power, larger ram, go to two wheel driveset-up to save weight

• Design philosophy: “Flippers win” SV

Photos and information are courtesy of Jerrk Clarkin and Brian Benson All fight statistics

are courtesy of BotRank (www.botrank.com) as

of December 11, 2007 Event attendance data is

courtesy of The Builder’s Database (www.

Historical Ranking is calculated by

perfomance at all events known to

BotRank

Current Ranking is calculated by performance at all known events, using data from the last 18 months

History Score Ranking

Historical Ranking: #1 Weight Class: 30 lb Sportsman's Class Team: Hammertime

Builder: Jerry Clarkin Location: Malvern, PA

BotRank Data Total Fights Wins Losses

Know of any robot competitions I’ve missed? Is your

local school or robot group planning a contest? Send an

email to steve@ncc.com and tell me about it Be sure to

include the date and location of your contest If you have a

website with contest info, send along the URL as well, so we

can tell everyone else about it

For last-minute updates and changes, you can always

find the most recent version of the Robot Competition FAQ

at Robots.net: http://robots.net/rcfaq.html

— R Steven Rainwater

Fe bru ar y

24-28 APEC Micromouse Contest

Austin Convention Center, Austin, TX

Amazingly fast little autonomous robot critters race

to solve a maze in this competition If you’ve neverseen one of these events, go see this one Youwon’t believe how fast these things are

www.apec-conf.org

28- Pragyan

Mar 2 National Institute of Technology, Trichy, India

Events include standard Micromouse and Sym-Bot,

a contest in which a remote controlled robot mustguide an autonomous robot to the starting line

of a course — then the autonomous robot must complete the course by itself

www.pragyan.org/08/home/events/

robovigyan

M arc h

7-8 AMD Jerry Sanders Creative Design Contest

University of Illinois at Urbana-Champaign, IL

Check the website for the details of this year’s contest

http://dc.cen.uiuc.edu

8 Fort Collins Robot Fire Fighting Challenge

Discovery Science Center, Fort Collins, CO

This is a regional for the Trinity College Fire FightingRobot contest Autonomous robots must locateand extinguish a flame in a scale model of a home

15-16 Manitoba Robot Games

Tec Voc High School, Winnipeg, Manitoba, Canada

Included in this competition are a mix of events for autonomous and remote-controlled robotsincluding Japanese style mini-Sumo, Western styleSumo, a robot Mini-Tractor Pull, Super Scramble,line-following, and the Robo-Critters contest for kids

www.scmb.mb.ca

29 CIRC Central Illinois Bot Brawl

Lakeview Museum, Peoria, IL

This event includes RC combat, autonomous Sumo,line-following, line maze Autonomous and remote-control robots

http://circ.mtco.com

30 Boonshoft Museum Robot Rumble

Boonshoft Museum, Dayton, OH

This event includes robot building and competition

www.boonshoftmuseum.org

TBA Penn State Abington Mini Grand Challenge

Penn State Abington, Abington, PA

This event includes outdoor autonomous mobilerobot navigation

http://www.ecsel.psu.edu/~avanzato/robots/ contests/outdoor/contest05.htm

TBA DPRG RoboRama

Dallas, TX

This event includes quick trip: an entry-level eventwhere the robot moves from A to B and back; line-following: the robot must follow a line on thefloor; T-time: the robot moves through three points

on a T-shaped course; and can can: the robot mustlocate and retrieve empty soda cans

www.dprg.org/competitionsApri

26 RoboFest

Lawrence Technological University, Southfield, MI

This event includes game competition —two autonomous robots work together Also robotexhibition, RoboSumo, RoboFashion show, andmini urban robot challenge

Send updates, new listings, corrections, complaints, and suggestions to: steve@ncc.com or FAX 972-404-0269

I’ve tried various simple control

projects before and sometimes

the devices themselves were not

spectacularly successful A disastrously

blind line-following robot that

challenged both my mechanical skills

and my patience comes to mind Still,

my students found these projectsinteresting and motivating, much more so than the usual static sort ofclass project

When I ran across Velleman’sK8055 USB Experiment Interface Boardkit, I realized it could form the basis of

a simple, PC-based control system Ihad used various embedded micro-controllers before, but the USB/PC combination had some definite advantages We wouldn’t need a cross-compiler, there were no serial links to(mis)configure, and we could use the

FIGURE 1 RoboCooler Block Diagram This shows the major components of the cooling and heating system, including the PC, the K8055 controller, the interface board, the sensor, and the output devices Devices shown within the large rectangle are integral to the K8055 board; all other components are externally connected.

I teach introductory programming classes at a local community college

and I’m always looking for an involving project for my students One of the

problems with entry-level programming classes is that many students find the

example programs they construct boring and somewhat removed from the real world It’s hard for anyone — myself included — to get too excited about coding a bubble sort, for instance.

Microsoft Visual C++ compiler installed

in the classroom lab with which the

stu-dents were already becoming familiar

This article recounts how we

created and tested the “RoboCooler,”

essentially a model heating and air

conditioning system based around a

disused Igloo cooler, the Velleman

interface board, and a handful of

sur-plus parts While the control algorithm

we implemented is elementary, readers

may find some of the techniques and

technology useful in more

sophisticat-ed systems of their own devising

System Overview

Figure 1 provides an overview of

the system The Velleman board

con-nects via USB 1.0 to a PC running

either Microsoft Windows or Linux The

controller’s Analog-to-Digital Converter

(ADC) samples the temperature in the

cooler using a thermistor Pulse Width

Modulation (PWM) outputs on the

controller board feed a driver board

that, in turn, drives a Thermoelectric

Cooler (TEC) and a pair of low voltage

heating elements A single digital

output controls a fan that circulates

heated or cooled air within the cooler

Controller Board

Velleman’s board comes eitherfully assembled or as a kit I chose thekit to save money and found it was easily constructed The construction isall through-hole, with socketed ICs and

no surface-mount parts The boardcomes solder-masked and silk-screenedfor easy assembly Screw connectorsare provided for the five digital inputs,two analog inputs, two PWM outputs,and eight digital outputs

If you’ve never assembled one ofVelleman’s kits before, you may bepleasantly surprised at how easy it is tofollow their almost completely pictorialinstructions The box is printed in four languages, but the assemblyinstructions just show the order inwhich the parts should be installed AnEnglish PDF manual available from theVelleman website explains the providedsoftware drivers [1]

The design of the board is simplebut efficient Basically, all the input andoutput functions the board providesare handled using a PIC16C745 microcontroller that also handles theUSB interface This microcontroller isnot user re-programmable, but it is

on the board are LEDs on all outputs,Normally Open (NO) pushbuttons totest the inputs, op-amps to buffer theanalog inputs and outputs, and acounter function on two of the digitalinputs Not bad for about $45

Figure 3 shows the assembled controller board

Temperature Sensor

For the temperature sensor, Ichose a Negative TemperatureCoefficient (NTC) thermistor I found at

a local surplus electronics outlet Theresistance of an NTC thermistor goesdown as temperature goes up in a negatively accelerated, decreasingfunction If you can measure the resistance accurately and if you knowthe non-linear characteristic curve relating resistance to temperature inyour particular thermistor, then you caninfer temperature

Because our thermistor’s specificcharacteristics were unknown, we initially attempted a crude calibration

by comparing measured resistance values against an available electronic thermometer Coupled with a softwaretable lookup, this yielded acceptable

FIGURE 2 The RoboCooler System Modified Igloo cooler.

The TEC and its external fan are mounted on the side facing

the camera The box containing the interface board is

partially hidden on the right side of the unit Not visible

are the controller (unplugged) and the heater (inside).

FIGURE 3 Assembled K8055 USB Experiment Interface Board Wires at the right carry PWM and digital outputs to the cooler interface assembly Analog inputs are on the left, near

my thumb The variable resistors near the alligator clip at the top of the board are replaced with a fixed resistor as

described in the text.

somewhat better

accu-racy If you don’t have

access to a calibration

lab and you have to

calibrate your own

thermistor, you have a

couple of options First,

you can purchase

thermistors with known

and guaranteed

charac-teristics These will

come with data

indicat-ing the appropriate coefficients for

resistance to temperature conversion

Even if you’re dealing with an

unknown thermistor, determining the

Steinhart-Hart coefficients for your

particular thermistor empirically is a bit

tedious, but not difficult

The technique has been detailed a

number of places, including Circuit

Cellar [2], so I’ll spare you the detail, but

it can be done by measuring the

resist-ance at three or more known, widely

separated temperatures, and solving for

the appropriate coefficients using a

spreadsheet or a dedicated program

Fortunately, one of my students

works in an applied metrology lab and

ran a complete calibration of our

unknown thermistor over the range of

45 to 90 degrees Fahrenheit The most

interesting part of the calibration

results is the determination of the

four coefficients needed to compute

the Steinhart-Hart equation relating

thermistor resistance to temperature

With these coefficients in hand,computing the temperature directlyfrom the inferred resistance of the thermistor was easy to realize as a Cfunction Figure 4 shows a snippet of Ccode to convert an ADC count into aFahrenheit temperature, using the values from calibration Figure 5 showsthe calibrated relationship betweenresistance and temperature for thesample thermistor

Input Interfacing

Thermistor resistance, and hence

temperature, is inferred by insertingthe thermistor into a voltage dividerconnected to the input of an ADC Thevoltage divider circuit uses a knownresistance as one half of the divider,and applies a reference voltage to thetop end of the divider

The ADC measures the voltage

at the divider junction, which is proportional to the resistance of thethermistor

The thermistor can be placed ineither the upper or lower arm of thedivider, with a resulting alteration inavailable range Selection of the fixed

// Convert ADC count to Degrees F // Based in part on: http://www.maxim-ic.com/appnotes.cfm/an_pk/1753 double countToTemp ( long count, double gain, double r1 )

{

// These are computed via calibration static const double a = 0.00393401767 ; static const double b = 0.000252561203 ; static const double c = -0.000000252514329 ; static const double d = -0.000000672358356 ;

double tempK = 0.0 ; double tempF = 0.0 ; double ohms = 0.0 ;

// Compute thermistor resistance (in megaohms) from voltage divider formula ohms = ( ( ( ( 256.0 / ( ( double ) count ) ) * gain ) - 1.0 ) * r1 ) / 1000000.0 ;

// Apply Steinhart-Hart to get reciprocal of temp (Kelvin) tempK = a + ( b * log ( ohms ) ) + ( c * pow ( log ( ohms ), 2 ) )

+ ( d * pow ( log ( ohms ), 3 ) ) ;

// Temp K tempK = 1.0 / tempK ;

//Convert to degrees F tempF = ( tempK - 273.16 ) * ( 9.0 / 5.0 ) + 32.0 ;

return ( tempF ) ; }

and the calibration

data obtained for our

thermistor, this function computes the

temperature in degrees

Fahrenheit Count is the

raw count from the ADC

(0 to 255), gain is equal

to 2.0 in this design, and

R1 is equal to 47K.

FIGURE 5 Relationship between

thermistor resistance and temperature.

This graph was generated by stepping

through a range of resistance values and

computing the temperature predicted

by the equation implemented in the

code snippet of Figure 4.

resistor for the divider is subject to a

number of trade-offs, including

thermistor self-heating that you can

find detailed in other sources I placed

the thermistor on the high side of the

divider, and selected a fixed resistor

value of 47K These are compromises

and almost certainly not optimal, but

they yield satisfactory results over

the range of temperature covered by

the system

To make the circuit simpler and

a bit more stable against changes inboard temperature or mis-adjustment,

I re-wired the analog input circuit

of the Velleman board as shown inFigure 6

The modifications relative to theoriginal schematic consist of replacingRV1 with a fixed 47K resistor, andbypassing R3 by connecting the thermistor directly across the SK2

jumper Gain of the op-amp is set totwo by installing a 10K resistor as R8.Since the 47K resistor was a 5% part, Iused its measured value of 47,500 inthe program calculations Calculation

of temperature from the ADC count isbased on the techniques described inreference [3]

Over a range of 45 to 90 degreesFahrenheit and coupled with the eight-bit range of the Velleman ADC,this combination of values yields anaverage step of a little less than onehalf degree per count, as shown inEquation 1

EQUATION 1

V 45 = R1/(R1+RT 45 )*Vref*Gain = 47500/(47500+232400)*5*2 =

1.7 volts

V 90 = 47500/(47500+70500)*5*2 =

4.03 volts Counts per degree = (90-45)/(((V 90 -V 45 )/Vref)*256) = 45/(2.33/5)*256 = 0.38 degrees/count

V45is the predicted voltage at theinput to the ADC at 45 degrees F Itdepends on the value of the voltagedivider formed by the fixed resistor andthe thermistor, and it is scaled relative

to the reference voltage applied to thetop of the divider and to the gain ofthe op-amp feeding the ADC The fixedresistor is 47,500 ohms, and the resistance of the thermistor at thespecified temperature is calculatedfrom the calibration data using theSteinhart-Hart formula V90 is the voltage present at the same pointwhen the thermistor is at 90 degrees F.Given the other factors (such as

FIGURE 6 Revised AIN circuit for the K8055 This revision replaces RV1 with

a fixed resistor and shows where the thermistor is connected to the board R8 and R11 establish the op-amp gain

at 2.0.

FIGURE 7 Schematic of the TEC, heater,

self-heating affecting thermistor

calibration), the assumed accuracy

of this system is probably around

±1 degree Fahrenheit over this

temperature range While this isn’t

high precision, it does compare

favorably with the precision of the

electro-mechanical thermostat this s

ystem replaces

Output Interfacing

Figure 7 shows the schematic of

the interface board

The PWM outputs on the Velleman

board are buffered with discrete

tran-sistors, arranged in an open-collector

configuration Since the heaters draw a

little over one amp and the TEC draws

four to five amps, driving the cooler’s

output devices directly is not a good

option Therefore, the controller

board’s PWM outputs drive a couple of

hefty MOSFETs

The PWM outputs that drive the

interface board from the Velleman

controller are open collector, so in this

simple design, the sense of the PWM is

reversed In other words, when the

PWM pulses are off, the transistors on

the controller board are essentially

open-circuited, allowing the MOSFET

gates to be pulled up to the 12 volt rail

and turning on the load Similarly,

when the PWM pulse goes high, the

transistors on the controller turn on,

pulling the MOSFET gate down and

shutting off the load

This inversion of PWM duty cycle is

a bit odd, but is easily compensated for

by reversing the sense of the 0 to

100% values passed to the controller

board for each PWM channel

There are several fans in the

design, but only one is uniquely under

program control The fan inside the

cooler responsible for stirring the air to

better distribute the heating and

cooling load is controlled by a relay

operated off two paralleled digital

controller outputs I used a fairly

current-hungry surplus relay because

that is what I had on hand, so I chose

to parallel a couple of the

open-collector outputs from the ULN2803

chip on the controller The fan on theoutside of the TEC to help cool the

“hot side” is wired to the same PWMoutput as the TEC itself and goes onand off with the TEC

Figure 8 shows the constructiondetails for the interface board

The MOSFETs are rated for morethan enough current in this application, but the one driving theTEC does get fairly warm over time,since with its on resistance of about0.1 ohms, the five amp load of the TECdissipates up to 2.5 watts In view ofthis and a good bit of caution, I addedhome-made heatsinks to the MOSFETs,

as well as a tiny fan to force airthrough the housing covering theinterface board

The heatsinks are leftover copperelectrical connectors salvaged from acircuit breaker box Each is screwed toone edge of the MOSFET’s TO-204 canafter the application of thermalgrease Since it wasn’t practical to isolate these heatsinks from the transistor’s cases, and since the casesare electrically connected to the MOSFET drains, I elected to tie theheatsinks into the interface controllerwith a bit of heat shrink tubing andnylon strain-relief fasteners Thisexplains the odd, sloping angle atwhich the interface board is mounted

Wiring on the cooler was donepoint-to-point using screw terminalblocks where possible While these are not the most reliable sort of connection under vibration and strain,they have the saving grace of making iteasy to test the individual

components with a ter and rewiring as necessary

multime-It is pretty obviouswhen the TEC is running,since its fan makes a fair

amount of noise But since theheaters don’t dissipate enoughwattage to glow (a safety considera-tion in the classroom), I added an LEDthat illuminates the inside of the cooler when the heat is turned on.(The LEDs I used had integral current-limiting resistors for 12V operation,and these are not shown in theschematic.) A window in the coolerlets the curious peer inside withoutdisrupting the thermal operation

I fused the primary 12 volt lineswith automotive “mini-ATC” style fuses

Of course, like all fuses, these are mostly a protection against fire in theevent of a wiring short, and can’t provide much protection for theMOSFETs, given the relatively slowspeed at which a fuse blows, compared to the speed at which aMOSFET dies

Software

My students jointly designed,coded, and validated the basic thermostat algorithm by simulating theprogram’s inputs and outputs withconsole input and output underMicrosoft Visual C++ This enabled us

to get a prototype version of the ware completed while the hardwarewas still under development

soft-The temperature control algorithm is the simplest possible one:Measure the temperature and if it differs from the setpoint, turn thecooling or the heating full on, asappropriate This is sometimes

FIGURE 8 RoboCooler Interface Board Construction.

On the left of the enclosure

is the fan relay The two MOSFETs and their heatsinks are immediately to the right of the fan relay The small fan on the right-hand side of the box just provides cooling insurance

of the heatsinks.

referred to as “Bang-Bang” control,

reputedly from the noise that

mechanical actuators driven by this

method would make as the system

changes state This is exactly what the

electro-mechanical thermostat in most

household heating and cooling

systems does, so the RoboCooler is a

faithful — if limited — emulation of the

sort of heating and cooling problem

with which everyone is familiar

Originally, conversion of the

raw ADC count to temperature

was done using a simple table lookup

This is quick to execute, easy to code,

and provides a good example of

employing and searching arrays for

the students

If the host here were a

microcon-troller with limited memory and

integer math, then retaining the

table lookup method for count to

temperature conversion would likely

be a good idea But as we are blessedhere with a fast processor (the PC),lots of memory, and full floatingpoint, I rewrote the temperature conversion to apply the Steinhart-Hartequation directly, as shown in the listing This is not terribly efficient, but

it strikes me as more aestheticallypleasing and easier to understandthan the former table lookup

Bang-Bang control could oscillaterather rapidly about the setpoint, sothe program we developed adds simpledamping in the form of moving average Successive raw temperaturereadings are shifted through a 10-sample window in the form of an arrayand averaged Since the samples aretaken at one second intervals, the average value used for comparisonwith the setpoint is a 10-second average This is really just a very basiclow-pass filter, but it seems sufficient to

damp the system effectively

The software also tries to steal a little more efficiency at the end of cooling or heating cycles by keepingthe fan running for a programmabletime after the TEC or the heaters arecut off This is rather like what some airconditioning systems do to “scavenge”cold or hot air from the ductwork.The hardware would supportmuch more intelligent and powerfulcontrol algorithms, of course Since theTEC and the heaters are driven withPWM, they can be varied proportional-

ly and not just switched fully on or fullyoff This would allow more sophisticat-

ed software to implement say, aProportional Integral Derivative (PID)algorithm for smoother and more accurate temperature control For thebenefit of my first-time programmingstudents, we stuck to a basic softwarecontrol approach even though this doesn’t take full advantage of thehardware capability

One of the less pleasant aspects ofthe system software which I faced wasmaking the Velleman-supplied VisualBasic (VB) Dynamic Link Library (DLL)work with a C or C++ program.Adopting a layered approach, I was able to structure a reasonably programmer-friendly function libraryfor the cooler system, with mnemonicfunctions such as TurnOnHeat(),TurnOffCooling() and ReadADCCount()that could be incorporated to replacethe stub functions in the student-developed simulation

But the lower layer — essentiallythe bridge from this function library tothe VB DLL — proved challenging andlacked portability While the code available for this project on the SERVO

website (www.servomagazine.com)

will work under Microsoft Visual Studio6.0, the code would not compile or link

FIGURE 9 A sample cooling run

The top line shows the TEC turning

on and off, and the bottom line shows the temperature in the cooler.

FIGURE 10 A sample heating run The top line shows the heating element

against the newest version of Visual

Studio Apparently, this has to do

with the way that linkage between

dynamic libraries compiled in different

languages has been altered in later

compilers

The solution was to port the code

to Linux This turned out to be much

quicker and much less painful than my

efforts to that point in linking later

versions of the Microsoft tools to the

K8055 DLL

The Linux drivers do not require

any DLL and instead supply a shared

library that understands how to talk

directly to the Velleman K8055

hardware via another library of USB

routines I rewrote the upper layer of

our hardware interface in terms of the

new library functions and the

student-developed code compiled under Linux

with gcc, required few changes

The Linux library faithfully

emulates each function from Velleman’s

VB DLL and so you can still use the

documentation that came with the

board for a guide in understanding the

capabilities of the board [4]

One late — but useful — addition to

the software was the ability to log

information about cooler operation to a

disk file while the system is running This

facilitated checking the operation of the

system when heating and cooling

Results

With the luxury of a Linux-hosted

computer dedicated to running and

monitoring the cooler, I was able to

gather some data showing how the

system performs These data were

written to a log file in

comma-separated values (CSV) format and

then read into and graphed from Excel

or OpenOffice

Figure 9 shows a typical cooling

run for the RoboCooler The top trace

shows the status of the TEC, with 1

being fully on and 0 being fully off The

bottom trace shows the temperature

declining from a starting value of 88F

down to the desired temperature of

70F in about 30 minutes Note that

over time the temperature bounces

around the setpoint and the coolingturns on and off as the cooler reheats,with a period of about four minutes

This is the Bang-Bang algorithm inaction

Figure 10 shows a heating test

The interpretation of the graph is muchthe same as for cooling Note that achange in temperature of about 18Ftakes almost twice as long as for cooling I attribute this to the low-powered heating elements employed,which total about 15 watts

Modifications and Extensions

As with any project, experience indeveloping and testing the RoboCoolerleads to a number of suggestions forextension and improvement

First and foremost, the interface

logic should be improved so that the hardware comes up in a “safe”configuration As readers may alreadyhave surmised from the discussion ofthe inversion of the PWM logic, wheninitially plugged into the USB cable,the cooler comes up with both heating and cooling fully on If wewere talking about say, a piece ofrotating machinery, this would beobjectively dangerous, while in a cooler it is just annoying The software

we developed does attempt to

Special thanks to the students in the Spring 2007 section of Introduction To Programming Concepts, and the help and dedication of the computer lab staff, without whom this project would not have happened.

Thank Yous

Almost all the parts I used are surplus, but similar items remain widely available in both new and used versions.

1 The Velleman USB Experiment Interface Board is available as either a kit or pre-assembled from Apogee Kits at www.

apogeekits.com/usb_interface.htm

2 The TEC I used is actually a surplus item originally designed for cooling — what else — picnic coolers But TECs, with and without integral heatsinks are available from sources such as:

http://skycraftsurplus.com/index.asp www.goldmine-elec-products.com/prod info.asp?number=G2201

www.allelectronics.com/cgi-bin/item/

PJT-6/search/40_MM_SQUARE_THERMO ELECTRIC_COOLER_.html

www.alltronics.com/cgi-bin/category.

cgi?item=04U003

(You may have more success when searching for these items by using their scientific name: Peltier devices.)

3 There are a lot of options for heaters.

You could use a 12 volt halogen lamp, for instance, which consumes up to 50W and puts off a lot of heat Another possibility

is a set of resistors in series/parallel to yield the sort of dissipation you need One heater resource is:

www.goldmine-elec-products.com/prod info.asp?number=G4554

4 Thermistors are available from:

www.allelectronics.com/cgi-bin/item/ THR-19/search/THERMISTOR,_30K_ PREPPED_.html

www.goldmine-elec-products.com/prod info.asp?number=G1929

www.mouser.com/search/refine.aspx? Ntt=thermistor

5 A wide range of MOSFET devices will work in this and similar systems One source for MOSFETs in the same family as the IRF143 is:

www.mouser.com

Mouser also stocks appropriate relays for fan control.

Parts Sources

compensate for this condition, bysteering the outputs to a safe stateboth when it initially loads and as theprogram terminates This, however isfar from foolproof and a hardwaresolution would be much superior.

Second, it would be fun to try outsome more sophisticated control algorithms on the system by implementing some form of propor-tional or even PID control in lieu of thesimple Bang-Bang approach used here

I’m planning to let my next C ming class take a shot at implementingthat improvement

program-Lastly, we could further improvethe software so that it can automatically switch from heating tocooling and back again as environmen-tal conditions change As currentlyimplemented, the software — like yourliving room thermostat — is either inheating or in cooling mode andrequires manual intervention to switch.This was a fun and simple projectbut my hope is that readers will find

at least a few tidbits that may be of use

in their own, and likely more sophisticated designs If you are aneducator, perhaps you’ll consider howembedded “appliance” applicationsmight be used to increase your student’s involvement, not just in digital hardware courses, but in computer science and programmingclasses, as well SV

Jerry Reed holds a Masters Degree in Computer Science from Webster University and is an Adjunct Professor

of Computer Programming and Applications at Valencia Community College in Orlando, FL In his day job, he works as Senior Systems Analyst for the college, and spends much of his spare time involved with amateur radio and microcontrollers.

About the Author

[1] Velleman’s documentation for the

K8055 board is at www.apogeekits.

com/PDF_Files/Manual_K8055.

pdf and www.apogeekits.com/PDF_

Files/Usermanual_K8055_DLL.pdf

[2] Brian Miller’s Temperature

Calibration System in the May 2007

Circuit Cellar, does an excellent job of

explaining both TECs and thermistors

[3] Maxim’s Application Note entitled

A Simple Thermistor Interface to an

ADC explains how to calculate the

sensitivity and range of thermistors

connected to ADCs via voltage

dividers; go to www.maxim-ic.com/

appnotes.cfm/an_pk/1753

[4] Linux software for the K8055,

including source code and build/

installation instructions is available

at http://libk8055.sourceforge.net/

References

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Needless to say, with the sheer,

concentrated weight of genius

crammed into that tiny, bamboo

paneled Tiki bar, answers to these

questions and many more besides were

soon flowing thick and fast And from

these ramblings MechBash was born

Mechwars Robot Combat in

Minneapolis (which has been holding

both combat tournaments and

entertainment events since 1999) and

BotBash LLC in Arizona (holding

combat tourneys since the misty days of

antiquity) decided to team up and put

together a traveling show to push the

idea of robot combat, and emphasize

the educational aspect of the activity

This new entity — the MechBash

Robot Combat Show — would be

expensive to operate, but not as

expen-sive as an actual robot tournament,

and the entertainment and

education-al content could be more reliably

managed It would be attractive

mostly to large clients like state fairs

and big trade-shows

A format was hammered out and

after knocking on many doors, a

booking agency was finally willing to

take a flier on the idea

However, after weeks of frantic

tap-dancing and heroic efforts on thepart of myself, Bob Pitzer, and our long-suffering agent, we had one single,magical, this-either-turns-the-tap-of-success-or-buries-our-efforts forever book-ing — the 2007 South Carolina StateFair in Columbia, SC We all bore downand got working to make it a success

One of the problems that a robotcombat promoter faces is the sheerweight and sophistication of the infra-structure required to stay one step ahead

of the builders in the arms-race betweenthe robots and the containment system

And in terms of doing live shows, there

is the added complication of time

The cage has to go up and comedown in about a day, and the econom-ics of a show (or tournament) simplydon’t work out It’s all very well to build

a super massive mega-cage, but if ittakes five days to set up, the promoterhas to pay four more days of StaplesCenter level rent, and consequentlyloses $80,000 on the show The result

is either a quick bankruptcy for the promoter or — if outside sources ofincome can be found to delay theinevitable — a slow and ugly death.The Mechwars cage — rated to han-dle even mega-weight combat robots(390 lbs) — goes up in about 10 hours

Newton launches a washer.

“how can we get robot combat — with all its associated cultural and educational benefits — back into the public eye?” Another question that came up was “how

can I get paid to blow things up, and yet stay out of jail?”

by Jonathan Vandervelde

One night, a gaggle of robot builders were posing questions like

with a crew of 12 Each individual

com-ponent is designed to be man-portable

The floor plane acts as a tensile

membrane from barrier to barrier, and

the under-floor support structure is

light-ened by using the truss-and-plate model

rather that the far heavier four-legged

sub-unit concept of stage design

It goes up relatively quickly, but in

the case of an east coast show

thousands of miles from its Minneapolis

home base, it’s still a bit dicey in terms of

time/effort Luckily, MechBash also has

Bob’s Mobile Automated Robot Combat

Arena (MARCA) While not rated for

full-on combat with robots above

middle-weight size, it has plenty of strength for

the kind of entertainment event we wereholding in SC, and it is super trick in bothappearance and functionality

So, after six months of prep andorganization, at 3:00 pm on Monday,October 9th, the MARCA finished up

an 1,800 mile journey by rolling ontothe SC Fairgrounds in Columbia Wepulled a few pins, hit the hydraulics,and by 9:00 that night, three guys hadlargely assembled a fully functional 24’

by 40’ robot arena with integratedhalogen lighting and P.A., electronical-

ly controlled pneumatic drop-pits andflame projectors, and two roof mount-

ed video screens (David Therrien’s tribution to the effort) to show close-

con-ups of the action in the cage

The MARCA is essentiallyits own 40’ trailer, with afolded width of approx 8’

and a folded height of 13’

The central section of ceiling

is fixed, with longitudinalsupport trusses running fromfront to back, while the sides

of the ceiling fold down tojust past the centerline of theroad wheels

The cage floor also has afixed central section, withsides that fold up inside thewhole package At the event,the ceiling “wings” are raised

to the horizontal position,locked into place by support

members which reach the ground,then a flexible curtain of steel-framedlexan panels is clipped together andsuspended from the perimeter

The floor then folds down cally The wall “curtain” hangs 18 inches outboard to the edge of thecombat floor and acts to soak up energy from a flying piece of robot inmuch the same way the netting behindthe goal posts soak up the energy from

hydrauli-a kicked footbhydrauli-all, drhydrauli-agging it to hydrauli-a hhydrauli-alt

We had numerous occasions toverify this useful property of thedesign, as quite a few 35 poundmicrowave ovens, smaller pieces ofshrapnel, and even one complete robotmade it over the barrier into the wall,only to be gathered in and dumped onthe ground harmlessly Throwing stuffagainst the glass is — as it turns out —

a big hit with an audience

Eventually, we started to actuallystage our robot bits in such a way that ahigh speed spinbot would throw shrap-nel directly onto the front wall, causingparents to jump six inches in their seatsand the kids to laugh themselves silly.The MARCA is perfect for this purpose

as the battlefloor is relatively narrowand therefore confines the action to aspot fairly close to the bleachers

With the MARCA in place, the ond wave could come rolling in and by8:00 am, the Minneapolis MechBashcrew had backed up another truck andoffloaded 12 big robots with the entireMechBash educational robot program.This includes a horde of individual R/Cand chassis components for kids toassemble, and an ant/beetle cage withfunctional hazards Then came thepiece de resistance Bob unveiled therobot co-host and mascot that he andpartner Chris Harriman had been working on back at his Arizona lair:Gizmotronic, a 5’ 8” humanoid (more

sec-or less) with articulated arms, head,and waist, a video screen “face” thatechoes a miked voice, and enoughsophisticated safety code to allow us todrive it around and interact directlywith kids in the audience

A robot display area was set upalong with a hands-on small-bot area

The MechBash Traveling Robot Combat Show

Big Bots on display between shows.