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Vol. 6 N
o. 7
SERV
OM
AG
AZIN
ERO
BOTICS H
ISTORY
•EN
COD
ER M
ATCH
ING
•BIG
MA
MA
GEA
R M
OTO
R•
CES ROU
ND
UP
July 2008
Cover.qxd 6/4/2008 7:36 PM Page 1
Let your geek shine.Meet Leah Buechley, developer of LilyPad—a sew-able microcontroller—and fellow geek. Leah used SparkFun products and services while she developed her LilyPad prototype.
The tools are out there, from LEDs to conductive thread, tutorials to affordable PCB fabrication, and of course Leah’s LilyPad. Find the resources you need to let your geek shine too.
©2008 SparkFun Electronics, Inc. All rights reserved.
»Sharing IngenuityS P A R K F U N . C O M
Full Page.qxd 3/5/2008 4:10 PM Page 2
Features28 BUILD REPORT
Apollyon
30 MANUFACTURINGHigh-Performance Drill Motor Modification
32 PARTS IS PARTSMag Motor Upgrades and Repairs
Events33 Results and Upcoming Competitions
Robot Profile31 Billy Bob
06 Mind/Iron
07 Bio-Feedback
22 Events Calendar
24 Robotics Showcase
26 New Products
70 Robo-Links
71 SERVO Webstore
81 Advertiser’s Index
Columns08 Robytes by Jeff Eckert
Stimulating Robot Tidbits
12 GeerHead by David Geer
Lewis, the Robot Photographer
16 Ask Mr. Roboto by Dennis Clark
Your Problems Solved Here
58 Twin Tweaksby Bryce and Evan Woolley
There’s a New Humanoid on the Block
64 Robotics Resources by Gordon McComb
Stocking Up with Surplus Electronics
67 Different Bitsby Heather Dewey-Hagborg
Random Bits
74 Appetizerby Kym Graner
Dusting Robots
77 Then and Now by Tom Carroll
Robotics — A Historical Perspective
PAGE 12
4 SERVO 07.2008
THE COMBAT ZONE ...
Dep
artm
ents
TOC Jul08.qxd 6/4/2008 3:41 PM Page 4
07.2008VOL. 6 NO. 7
SERVO 07.2008 5
34 CES 2008 Robot Roundupby Ted LarsonThe annual Consumer Electronics Show does not disappoint with itscoverage of robotics in theTech Zone.
39 Encoder Matchingby Robert DoerrScaling and inverting encoder values to fit your particular application.
44 Big Mama Gear Motorsby Fred EadyLearn what it takes to design, build,and code a heavy duty DC motordriver module.
50 Loki Crosses the Pond — Part 2by Alan MarconettThis final installment examines the QwikFlash controller board and the software that runs Loki.
SERVO Magazine (ISSN 1546-0592/CDN Pub Agree#40702530) is publishedmonthly for $24.95 per year by T & L Publications, Inc., 430 Princeland Court, Corona,CA 92879. PERIODICALS POSTAGE PAID AT CORONA, CA AND AT ADDITION-AL ENTRY MAILING OFFICES. POSTMASTER: Send address changes to SERVOMagazine, P.O. Box 15277, North Hollywood, CA 91615 or StationA, P.O. Box 54,Windsor ON N9A 6J5; [email protected]
PAGE 44PAGE 39
PAGE 34
Features & Projects
TOC Jul08.qxd 6/4/2008 3:42 PM Page 5
Published Monthly By T & L Publications, Inc.
430 Princeland CourtCorona, CA 92879-1300
(951) 371-8497FAX (951) 371-3052
Webstore Only 1-800-783-4624www.servomagazine.com
SubscriptionsToll Free 1-877-525-2539
Outside US 1-818-487-4545P.O. Box 15277
North Hollywood, CA 91615
PUBLISHERLarry Lemieux
ASSOCIATE PUBLISHER/VP OF SALES/MARKETING
Robin [email protected]
EDITORBryan Bergeron
CONTRIBUTING EDITORSJeff Eckert Tom CarrollGordon McComb David GeerDennis Clark R. Steven RainwaterFred Eady Kevin BerryRobert Doerr Ted LarsonAlan Marconett Kym GranerBryce Woolley Evan WoolleyHeather Dewey-Hagborg Nick MartinMike Jeffries Bryan Ruddy
CIRCULATION DIRECTORTracy Kerley
MARKETING COORDINATORWEBSTORE
Brian [email protected]
WEB CONTENTMichael Kaudze
PRODUCTION/GRAPHICSShannon Lemieux
Joe Keungmanivong
ADMINISTRATIVE ASSISTANTDebbie Stauffacher
Copyright 2008 by T & L Publications, Inc.
All Rights ReservedAll advertising is subject to publisher’s approval.We are not responsible for mistakes, misprints,or typographical errors. SERVO Magazineassumes no responsibility for the availability orcondition of advertised items or for the honestyof the advertiser.The publisher makes no claimsfor the legality of any item advertised in SERVO.This is the sole responsibility of the advertiser.Advertisers and their agencies agree toindemnify and protect the publisher from anyand all claims, action, or expense arising fromadvertising placed in SERVO. Please send alleditorial correspondence, UPS, overnight mail,and artwork to: 430 Princeland Court,Corona, CA 92879.
Small is Big
When it comes to robot
components, small is big. If you’ve
followed the robotics news lately, you
know that academic and military
R&D communities are busy at work
developing robots that mimic – in
form and function – small crawling
and flying insects. Need to locate
survivors in the rubble of a collapsed
building? Simply release a swarm of
heat-seeking crawling robots that can
squeeze through cracks without
disrupting the rubble and
endangering trapped victims. Need
an up-close view of a hostage
situation? A swarm of flying
microbots with photosensors could
provide police with a composite,
real-time image of the victims and
their captors.
Despite ongoing advances in
research laboratories, there are
numerous challenges that must be
overcome before practical
autonomous insect swarms can
become a reality. There are issues
of how to provide communications
between each insect-sized robot and
their human masters, local
computation, sensors, power, and
of course, powerful, lightweight,
controllable micromotors. And there’s
the underlying issue of cost.
A recent advance in the area
of micromotors has been the
commercial availability of linear
micromotors from New Scale
Technologies (www.newscaletech.
com). Their series of Squiggle motors
fills the void between the microscopic
nanomotors and the miniature servos
and electronic/pneumatic linear
actuators popular among robotics
enthusiasts.
I had the opportunity to evaluate
New Scale’s mid-sized offering — the
Squiggle SQL-1.8-6 linear motor —
shown in the photo. As the name
suggests, the motor is a mere 1.8
mm in width. The rectangular motor
body is 6 mm long, with a 12 mm
axial screw running through its
center. The 160 milligram SQL 1.8 is
capable of handling a 30 g load
when driven by a 400 mW, 40V, 171
kHz pulse. The even smaller SQL 1.5
linear motor can work with a 20 g
load. As illustrated in the photo, the
electrical connection to the Squiggle
motor is via a flex printed circuit
strip.
With a PC-based control
application and USB-to-Squiggle
interface, I was able to vary the travel
rate from micrometers per second to
millimeters per second, with an
impressive 0.5 micrometer resolution.
Although the relatively fragile motor
was glued to a polycarbonate mount
Mind / Iron
by Bryan Bergeron, Editor
Mind/Iron Continued
6 SERVO 07.2008
Piezoelectric Squiggle micro motor onpolycarbonate mount shown next to a six-pin DIP for size comparison.
Mind-Iron Jul08.qxd 6/4/2008 2:22 PM Page 6
for evaluation purposes, I could easily envision a
spider-sized eight-legged walker, powered by 16
skeleton-mounted Squiggles.
The size of the peripherals that accompanied the
motor — a wall wart power supply, a USB driver card, and
a three-foot USB cable — not to mention the desktop PC
and software — explains why the robotics shops aren’t
offering autonomous robots sporting Squiggle-based
grippers and actuators. Even a six-pin DIP dwarfs the
Squiggle, much less a PIC or BASIC Stamp. However, the
control issue should be partially solved by the time you
read this. New Scale has a miniature ASIC driver under
development that could form the heart of a Squiggle
spider robot.
Power issue is another matter. The smallest battery
packs that I’ve used are thin-film lithium-polymer cells
designed for miniature indoor R/C aircraft. The thin,
dime-sized cells power a single-motor aircraft for about
five minutes. As such, an autonomous eight-legged
Squiggle spider would likely have a lifespan measured
in seconds with current battery technology. Even so,
in some applications, 20-30 seconds of operation
could be worth the cost of a swarm of insect-sized
microbots.
On the topic of microsensors, with the exception of
Hall-effect devices, I haven’t seen any commercial sensor
offerings that come close to the level of miniaturization
required for an insect-sized microbot. I’d like to have an
affordable ultrasonic or IR rangefinder comparable in
relative size to the Squiggle. However, consider the
challenge in creating a suitable IR rangefinder with
standard components. A typical IR LED alone is about the
size of an insect’s head. And the available ultrasound
rangefinders require even more volume. Clearly, when it
comes to microsensors for autonomous microbots, it’s time
for a new generation of SMT devices.
Although autonomous microbots made completely of
commodity — read affordable and readily available —
components may be a few years away, there are myriad
applications of micromotors in other areas of robotics. The
most obvious applications range from the manipulation of
camera optics and R/C mini helicopter control surfaces, to
control of microvalves in implantable drug delivery devices
to surgical robots. Although I expect to see the first
large-scale applications of micromotors in the consumer
electronics industry, the medical applications will likely
have the most profound effect on quality of life.
Consider that current surgical robotics rely on
standard-sized motors connected to scalpels and other
instruments through cables. Although these robotic
systems enable surgeons to operate with greater efficiency
and effectiveness than traditional methods, because of the
physical arrangement of cables and instruments, the
working area is constrained to only a few inches across.
The use of micromotors connected directly to instruments
would allow for a much larger work area for tele-surgeons,
as well as lighter, mechanically simpler surgical robots. Size
and weight can be critical factors if the remote patient
happens to be an astronaut on Mars, or a critically injured
US soldier in a remote area of the world. SV
SERVO 07.2008 7
Dear SERVO:
The “analog” servo block diagram, Figure 5, of the
Servo Buddy article in May 2008, is missing the velocity
feedback path from the motor to the local pulse
generator. Without this damping feedback, the servo will
oscillate. After the stretched drive pulse has ended, the
motor back EMF is used to modify the next local pulse.
In servos that use the NE544 IC, this feedback is from
pin 9 to pin 1 via a resistor. For the NJM2611 IC, from
pin 11 to pin 15.
It is interesting to note that years ago what is
now called an analog servo was called a digital servo.
Back then, an analog servo required an analog VOLTAGE
input.
— William J. Kuhnle
RESPONSE: While I tried to keep the diagram simple,
it might have been good to include that. Thanks for
pointing it out.
— Jim Stewart
SchmartBoard Is Looking forBeta TestersNew Website will be Social Networkfor Electronics Enthusiasts
SchmartBoard is looking for people to beta-test a soon
to be opened web space call Solder By Numbers™.
The website, which is due to launch in late summer,
will be a social network for electronics enthusiasts.
SchmartBoard is looking for all levels of testers from
professional engineers to novices who have an interest
in electronics. They are looking for people from around
the world.
According to SchmartBoard’s VP of Sales &
Marketing, Neal Greenberg, “SchmartBoard is not yet
ready to reveal specific details about the website,
except that it is web 2.0 for electronics enthusiasts.
Solderbynumbers.com will be a place to design and
build your electronic circuits while you create a worldwide
network of peers. The site will be much more than a
social network. It will be a place to collaborate, create,
communicate, and learn.”
To sign up to be a beta-tester, go to www.solder
bynumbers.com.
Mind-Iron Jul08.qxd 6/4/2008 2:23 PM Page 7
8 SERVO 07.2008
The Vulture Seldom ComesHome to Roost
On a more celestial level, DARPA
is also funding a competition to
develop an unmanned aerial vehicle
that will shatter endurance records.
The bird will draw 5 kW of power,
carry a 1,000 lb (450 kg) payload,
stay aloft for at least five years, and
remain in its assigned airspace 99
percent of the time while fighting
winds encountered at operating
altitudes, reportedly ranging from
60,000 to 90,000 ft (18,000 to
27,000 m). The goal is to provide
long-term intelligence, surveillance,
reconnaissance, and communication
missions over locations of interest.
Contractors for phase one are
Aurora Flight Sciences (www.aurora.
aero), Boeing (www.boeing.com),
and Lockheed Martin (www.lock
heedmartin.com). A variety of
propulsion approaches — including
solar and internal combustion — will
be considered; however, nuclear and
lighter-than-air designs have been
ruled out. The winning design must
comply with space — not aviation —
industry standards, because only a
“pseudo-satellite” will handle the
demanding requirements. A supervi-
sory engineer at NASA observed,
“What you don’t want to build is a
fragile, expensive pain in the butt.”
The Aurora offering will be based
on its “Odysseus”
design, which uses solar
power during daylight
hours and stored energy
at night. It combines
three “constituent
aircraft” in a 500 ft
(150 m), intriguing
Z-wing configuration.
Boeing is expected to
field a design based on
the existing British-built
Zephyr high-altitude,
long-endurance UAV,
from partner QinetiQ
(www.qinetiq.com).
Lockheed Martin is still
mum on the subject.
The competitors have 12 months
to come up with their initial designs
for DARPA review. Phase two will end
with a three-month flight test of a
subscale demonstrator, and the final
phase will require a 12-month test of
a full-scale vehicle.
Mini Network BotsAlso pulling down government
funding — in this case, up to $3
million over three years from the
Defense Advanced Research Projects
Agency (www.darpa.gov) — is
iRobot (www.irobot.com). Under
the grant, the company will develop
the LANdroid robot, a portable com-
munications relay device. According
to the contractor, “This robot will be
small enough that a single dismounted
warfighter can carry multiple robots,
inexpensive to the point of being
disposable, robust enough to allow
the warfighter to drop and throw
them into position, and smart enough
to autonomously detect and avoid
obstacles while navigating in the
urban environment.”
The objective is to enable
networking in urban areas where
buildings and other pesky objects
can block wireless operations. In
operation, each of the little guys will
wander around until it finds a good
spot to function as a node and then
join the rest of the swarm to form
the network. If one is destroyed, the
others will adjust their positions to
keep the system up and running.
New Touch TechnologyOne of the perennial problems in
robotics is improving the machine’s
Aurora’s Odysseus design:A possibleconfiguration of the Vulture UAV.
Photo courtesy of Aurora Flight Sciences.
Sneak peak at what the LANdroid robot will look like. Photo courtesy of DARPA.
by Jeff EckertRobytes
Robytes.qxd 5/29/2008 2:20 PM Page 8
sense of touch, and what could be a
better way to solve it than to learn
from our touchy-feely friend, the rat?
Enter BIOTACT (BIOmimetic Technology
for vibrissal ACtive Touch, www.
biotact.org), a project funded by the
European Union and involving nine
research groups in seven countries.
The goal is to emulate how such
mammals as rats and Etruscan shrews
can rapidly sweep their whiskers
back and forth to gather information
about their surroundings. Thus, a bot
fitted with hundreds of whisker-like
sensors may be able to seek, identify,
and track fast-moving target objects,
even in poorly lit places where machine
vision doesn’t get you anywhere.
The challenge is to develop new
biomimetic computational methods
and technologies that enable the
technology. But the consortium
has been granted four years and
$11.6 million to do it, so the odds
look good.
Showcase of RobotendersIt’s beginning to look like the
Germanic tribes have a curious
fetish about linking robotics with
such ostensibly unrelated fields as
sociology, philosophy, and art (see
last month’s Robytes). In this vein, the
upcoming 10th anniversary of the
RoboExotica conference recently
came to light. According to the
event’s Vienna-based
creator (www.robo
exotica.com), “Until
recently, no attempts
had been made to
publicly discuss the
role of cocktail
robotics as an index
for the integration
of technological
innovations into the
human Lebenswelt
[environment], or
to document the
increasing occurrence of radical
hedonism in man-machine
communication.” Imagine that.
But you can stop worrying, because
“RoboExotica is an attempt to fill
this vacuum.”
RoboExotica generally consists
of a series of events (exhibition,
conference, workshops, music, and
film presentations) held at various
locations in Vienna. But this year,
sometime after the December 4th
kickoff in Austria, it will be presented
in San Francisco, as well, “thus
facilitating the already existing
exchange of ideas between the West
Coast’s very much alive technology/
art scene and the RoboExotica
mother ship in Vienna.”
Unfortunately, the US incarnation
will not include the annual cocktail
robot awards, where you can enter a
machine in one of five categories:
serving cocktails, mixing cocktails,
bartending conversation, smoking
culture, and other achievements in
the sector of cocktail culture. To
participate, you’ll have to show up at
the Rote Bar/Volkstheater Wien
(www.volkstheater.at/rotebar
.html). The program is still under
development, so check the website
from time to time for details.
Bot Assists Endoscopy
This month’s device for taunting
the squeamish is EndoAssist, a robotic
endoscope manipulator offered by
Prosurgics Ltd. Used in invasive
thoracic and abdominal surgery, it is
particularly useful for ardiothoracic,
urological, bariatric, ob/gyn, and
general surgery. Perhaps the most
interesting feature is that the surgeon
controls camera angles simply by
moving his head. Glance left, and the
camera moves left, and so on. You
Robytes
Artist’s concept of the “ScratchBot”employing the BIOTACT sensor.
Photo courtesy of the BIOTACT project.
The EndoAssist robotic manipulator.Photo courtesy of Prosurgics.
A contestant from RoboExotica 2007.Photo courtesy of Roboexotica.com.
SERVO 07.2008 9
Robytes.qxd 5/29/2008 2:23 PM Page 9
can also pan, zoom, or modify the
view in any direction. For a video
demonstration that may affect your
ability to keep lunch down, visit
www.prosurgics.com/prosurgics_
endoassist.htm.
Uribot Tends Kobe AirportFinally, the strangest application
of robotics of late would be Dasubee,
a bot designed specifically to clean
urinals. One is already operating in
the Kobe, Japan airport. An astute
observer will note that it resembles
an elephant. Designer Susumu Kanai
revealed that this design was inspired
by the pachyderm’s trunk, which
resembles the powerful water cannon
employed by the bot. The ears are
handles, the eyes are the start and
stop buttons, and its little yellow hat
is the filler cap for the 13 gal (50 l)
tank. Reportedly, using
specially developed
antibacterial detergent,
Dasubee can shine up
a fouled privy in only
10 seconds.
If you’re still
reluctant to buy one,
consider that Kanai
has included “a
vacuum function to
breathe in a scraper
and the water of the
floor to be able to
wash the dirt scattered
to the floor together
on the function side.”
(Something may have
been lost in the
translation.) You can
pick one up for only
one million yen (about
$9,500). SV
Robytes
10 SERVO 07.2008
Dasubee, the urinal bot and its proud operator.Photo courtesy of Impress Watch Corp.
Perform proportional speed, direction, and steering withonly two Radio/Control channels for vehicles using two
separate 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
WITHOUT SERVOS!
Order at (888) 929-5055
Robytes.qxd 5/29/2008 2:24 PM Page 10
12 SERVO 07.2008
When Lewis the Robot
Photographer first enters a
crowded room, it gets atten-
tion. But, once people have adjusted
to its roaming around, looking here
and there, they forget all about it.
After all, it’s just a machine, another
object in their environment.
Lewis’ ability to blend in keeps
it from creating the kind of
apprehension that comes with a
live photographer who roams around
snapping candid pictures of people
(as a wedding photographer might
do, for example).
Because Lewis captures people at
ease, it can take a much higher quality
of photos — no blinking, phony smiles,
or stiff or awkward poses. Because
Lewis recognizes faces and quickly
snaps only the best photos, it takes
many more quality pictures in the
same period at gatherings, functions,
and on special occasions.
Looking for Faces
Lewis starts by scanning the room
for pairs of what appear to be legs.
This way, he can identify people and
then look up to find and identify
their faces. Then, Lewis uses face-
recognition technology that identifies
parts of images with lots of skin tones
grouped closely together.
Lewis separates real faces from
things that may look like faces to the
robot eye. Lewis eliminates anything
that is too big, too low, or the wrong
shape. Anything left is assumed to
be a face.
Lewis can take front-on and side
angle pictures of people. It continually
scans images for the criteria that
predict a face or group of faces. Once
it has detected a suitable image, it
adjusts the camera to take a quality
photo, moving it into position via
a series of zooming, tilting, and
panning.
The robot uses object avoidance
technology to guide itself around
objects and people, and maintains its
position within the mass of subjects
by recognizing a given object and
centering itself in the group based on
the position of that object.
Forming Pictures
How does Lewis form pictures of
faces? By following rules. One such
rule is the rule of thirds. The rule of
thirds says that if you split a picture
into thirds, first horizontally, then also
vertically, the primary point of visual
interest in the photo should be where
the lines cross. Lewis makes human
faces the points of greatest interest,
placing them at these cross points.
Contact the author at [email protected] David Geer
Lewis, the RobotPhotographer
At first brush, a robot that snaps people’s pictures might not imbue the mind with
a novel image. But, a photographer that sets its subjects at ease, circumvents their
shy and self-conscious natures and related facial reactions, and captures the essence
of the subject unawares, now that’s a wonder to see!
Full side view of Lewis.
Geerhead.qxd 5/30/2008 10:07 AM Page 12
Photographers try to avoid empty
space in their photos. This helps
ensure that photos contain as much
relevant visual information as possible.
Lewis weighs the rule of thirds and
the rule around empty space one
against the other whenever they
conflict, to take the best pictures.
Lewis can also think for himself
when taking photos. He is free to
break the rules altogether and take
feedback about his images. He uses
this information to learn which rules
to break and when in order to deliver
great photos based on a sort of
photographic instinct.
Live Test
Researchers tested the Lewis
robot photographer on a group of
5,000 subjects over a period of 40
hours. Lewis took 3,000 pictures in
that period. During this 40 hour run,
people (guests at a large technology
event) either ignored the robot
completely or tried to interact with it.
Because the robot wasn’t instilled
with the ability to interact, people
quickly dispensed with it and began
socializing with other people in
the crowd. Because people ignored
the robot, they relaxed and acted
naturally, enabling the robot to take
candid, natural pictures.
Results
Among other things, researchers
determined that the robot should
have a sort of bi-modal capability. If
someone is trying to interact with it,
it should stop what it is doing and
interact with those people, taking
their pictures where possible. If no
one is trying to interact with the
robot, it should blend into the
background and continue to take
candid shots. This version of the robot
is only capable of blending in. So, the
robot will ignore people who want to
interact with it or who specifically look
to have their picture taken.
People will be more likely to
interact with the robot on some level
if they know what it is up to. What’s
it there for? In this version
of the robot it made a noise,
sounding an alarm or signal
when it had taken a picture. However,
the sound wasn’t loud enough for
most people to hear.
If the signal were louder, this
would communicate to people in the
robot’s proximity that it had just taken
a picture. This would form some level
of communication between the robot
and those people, and provide some
simple basis for interaction.
The robot had no way of telling
people to hold still or say cheese. It
took four seconds for the robot to line
up shots, in which time people might
hold still to get their picture taken, or
they might move around. After the
robot’s test run, people suggested
that the robot actually say cheese or
show a picture of a “birdie” (as in,
look at the birdie) to signal that it was
about to take a picture.
People waiting in front of the
robot hoping to have their pictures
taken were often disappointed when
the robot was navigating, getting its
bearings, or homing in on a landmark
instead of taking pictures at that
particular moment. However, the
Sharing a more whimsicalmoment with Lewis are members of the Media andMachines Lab (from left):Assistant Professor WilliamSmart; Assistant Professor CindyGrimm (seated): two of thelab’s founders, ShannonLieberg, Engineering Class of ‘04and research assistant MichaelDixon, B.S./M.A. ‘03; and NikMelchior, a fifth year B.S./M.S.student in computer scienceand engineering. Members areshowing off the “playful props”used by Lewis in the lab.
Lewis close-up head shot with camera. Lewis has workedphotographing at a real live
wedding reception.
SERVO 07.2008 13
GEERHEAD
Geerhead.qxd 5/30/2008 10:10 AM Page 13
14 SERVO 07.2008
robot was programmed to take
frequent pictures of human faces even
when it may not have had the
opportunity to focus in for a good
picture. To better interact with
subjects, the robot should have the
ability to communicate which mode or
“state” it is in to the subjects. So, if
the robot is available to interact, it can
communicate that, and so on.
Photographic subjects expected
the robot to respond when waved at,
like a human being would. However,
the robot didn’t have this capacity
either. When the robot did seem to
react — because it turned toward
someone by sheer coincidence when
someone had waved at it, for example
— people thought this meant it was
more intelligent than it actually was.
In particular, when the camera
pointed in their direction coinci-
dentally in response to trying to
hail the robot, this was mistaken
for eye contact.
Lewis seemed intelligent to
people when he did what
appeared to be a double take.
Because the robot face detection
code was not optimized, the cam-
era panned past the faces and
beyond by the time the software
determined it had detected a
face. The camera then returned to
focus on the face for the picture.
This apparent “double take”
humanized the robot in the eyes
of on-lookers, attracting people to
interact with the robot.
Likewise, other robot
behaviors made the robot appear
not so smart, even though these
behaviors were quite intelligent
for a robot in what they
accomplished. One such behavior
was looking at the wall (pointing its
camera toward the wall) or moving
along a wall in order to aid in its
navigation. While the robot was
trying to get its bearings, it appeared
not to “see” anyone around it, and so
looked dumb.
Conclusion
Continued research based on
Lewis should address whether Lewis
truly functions in two separate modes,
whether the level of sophistication of
the people interacting with Lewis has
an impact, and whether the robot or
the people around it should drive its
interaction. SV
Lewis, the Robot Photographerwww.cs.wustl.edu/MediaAnd
Machines/Lewis
The Media and Machines Labhttp://mm.cse.wustl.edu/about/
index.html
Washington University in St. Louiswww.engineering.wustl.edu
RESOURCES
Full frontal view of Lewis.
Here, Nik Melchior (left), a fifth year B.S./M.S.student in computer science and engineering, helps create the programming framework that
allows others to command Lewis. Shannon Lieberg(center) of the Engineering class of ‘04, works Lewis’
controls with Assistant Professor Bill Smart.
GEERHEAD
Geerhead.qxd 5/30/2008 10:51 AM Page 14
SERVO 07.2008 15
New breed of robots could soon wander Antarctica
By GREG BLUESTEIN, Associated Press Writer
Robotic rovers have patrolled deep space and the deepest seas,but scientists are still struggling to create drones that can
overcome the multiple challenges of exploring Antarctica.Georgia Tech researchers think the SnoMote — a small robotdesigned like a snowmobile — will be able to deal with the nastyweather and with slippery terrain that constantly cracks andshifts. They envision dozens of SnoMotes roving Antarctica's vast expanses to add to data already collected by satellites and a handful of weather stations and sensors. Ayanna Howard, an associate professor at Georgia Tech in Atlanta, has worked for two years under a NASA grant to perfect thetwo-foot-long robots.
Her initial designs with spider-like legs proved too cumbersome to navigate snowbanks. So, she and her colleaguesleaned on others' designs, outfitting a snowmobile designed forkids with sensors, gauges, and cameras, and then programming it.
She developed a program that lets the SnoMotes negotiatewith each other and “bid” on which site to investigate, allowingthem to decide for themselves how to dole out their assignments.
The next challenge, though, was to come up with navigation for the rovers. Other probes tend to use distinguishingcharacteristics like rocks to chart their paths. But such featurescan be hard to come by in vast icy expanses.
On a field trip to a Colorado glacier, Howard's team discovered they could use microscopic fissures in the ice andsnowbanks to guide their way.
“If you can come up with a way to classify these uniquely,you can come up with a way to navigate,” she said.
Simulations so far have proved her team's formula effective,but plenty of challenges await when the robot is put to the teston the glaciers of Alaska.
With Penn State University researcher Derrick Lampkin,Howard has designed a shell that weighs 60 to 70 pounds, canwithstand harsh winters, and eventually could include heaters tokeep computers and wiring running in the cold.
Lampkin said his goal is to develop a "scale-adaptable,autonomous, mobile climate-monitoring network."
The researchers hope the robots will ultimately cost around$10,000, relatively cheap for governments, researchers, and others seeking to document changing conditions in the world'smost remote places.
The more the better: Howard said in order for scientists tosay with certainty how climate change is affecting the ice, theyneed plenty of accurate data points to create climate models.
She envisions a field of 40 to 50 of the SnoMotes wanderingicy plains, a small army gathering data to shed light on globalwarming and other quandaries without breaking the bank.
“The whole concept is: How do you do this in the mostaffordable way?” she said.
The Mechanicrawl • Saturday, July 12, 2008Spend a summer day exploring the mechanical marvels along
San Francisco's North Shore! See giant running steam engines, turnof the century automata, mechanical computers, an eight foot highmechanical planetarium, and more. You'll be able to map your own
route for the event and spend as much time at each location as you'dlike. You can walk, bicycle, or use public transport for Mechanicrawl;maps, routes, and additional info are listed under Map Your Crawl onthe website. For all the details, go to www.mchanicrawl.com.
Page 15.qxd 6/4/2008 3:26 PM Page 15
16 SERVO 07.2008
Q. Every once in a while there is a question floated
around in my local robotics group that (I think) is
such an epiphany (read: slap forehead) that I think
it deserves a wider audience. This first question is one of
this nature:
Does anyone have any recommendations for an
inexpensive DC-DC converter that has 11-14 VDC in, 5 VDC
out (up to 3-5 amps)? I need a heftier supply for the low-
level control system on my robot. Currently, I’ve got a 12V,
12 Ah lead-acid battery with a 5V-1A converter, and I’m
reaching the limit of the converter when I add my sonars
and IRs ... later, I would prefer an off-the-shelf solution.
— Daniel Herrington
A. My first thought was the TI PT78ST105, which is a
1.5 amp 5V switching regulator that works with up to
38V. This nifty part has the same pin-out as the
venerable 7805 regulator and is way more efficient.
Another suggestion was the TI PTN78020 which has similar
input voltage maximums and a 6 amp output with high
efficiency since it too is a switching DC/DC converter.
However, this part has lots more pins; it still needs no
external components. These parts are easily found at places
like Mouser, pricing depends upon various options. As good
though, as these solutions are, they are not “off-the-shelf”
and would need a circuit board to use. Don Clay put
forward the solution of using a BEC that the R/C airplane
hobby crowd commonly uses on electric aircraft that use
large battery voltages. This is a very cool idea because it
can be connected to the robot’s main battery and will
efficiently give the needed 5V in a small, self-contained
unit, and it already has easily usable cabling. The one that
Daniel selected was the Castle Creations CC BEC which sells
for about $22 at good ol’ HobbyTown USA (www.hobby
town.com); see Figure 1. This device is very useful because
it can be set to output voltages from 4.8V to 9V by using
the Castle USB link adapter (not included). In case you were
wondering, BEC stands for Battery Eliminator Circuit. In the
“old days,” electric R/C cars had a battery for the motor and
another for the R/C electronics. The BEC “eliminated” one
of those batteries.
Q. I want to send commands to my robot using an
IR remote. I don’t want to build another IR remote;
I want to use one of the bazillions that I have lying
around the house. How do I use these? How can I decode
their output?
— George S.
A. Oh boy, I feel a marathon answer
coming up! I’m not going to go into
huge detail about every kind of IR
remote out there — there are a ton of web
pages that you can Google and find those
kinds of details. I’ll provide a selection of
them at the end of this answer for those
curious though. I did not find a lot of pages
that connected the dots between the various
formats and how to write a program to read
them, either. So, in this answer I’ll provide the
nitty gritty details of how the most popular IR
codes are created and provide some PIC code
that allows you to decode them. First, the
ugly details ...there are many, MANY different
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 youwhere you are — and what more would you expect from a complex service droid?
byDennis Clark
Our resident expert on all things robotic is merely an email away.
Figure 1. CC BEC.
NEW
∧
MrRoboto.qxd 5/30/2008 11:21 AM Page 16
IR encoding schemes out there. Wikipedia tells us that there
are literally hundreds of IR protocols! Fortunately for us, there
are three that are by far the most common: SONY SIRC,
NEC, and Phillips RC-5. If you pick up any odd remote at
your house, it will most likely be using the SONY or NEC
formats. Let’s discuss each of the “big three.”
SONY SIRC Format
First off, here are a couple of links that discuss this
format. There is a lot of useful information in these; I
disagree with a few things that they say (more on that later),
but since some of the data that I used to write my code
came from these links, most of what they say is accurate:
www.hifi-remote.com/infrared/IR-PWM.shtml
This site gives a lot of information on how to read the
universal IR remote entries that you use to program your
universal remotes. The author calls this “PWM,” or pulse
width modulation. It is more accurately called “PPM,” or pulse
position modulation, rather like R/C radio communications and
what we deal with when controlling hobby servos.
www.edcheung.com/automa/sircs.htm
This site gives some hints on how to write code to send
IR signals. Not what I was looking for, but you might be
interested in this if you wanted to have a robot wander into
your TV room and take over control of the TV set!
The SONY format has three timing values that we are
interested in, shown in Table 1. The Lead In is the header
before the data that tells us that the code is coming.
Everyone says this is to set up the AGC (automatic gain
control) in the receiver, but quite frankly, if it didn’t look
different from the rest of the transmission how could we
tell that a new command was coming? The rest of the data
is an asynchronous data stream of 1s and 0s like the serial
data in RS-232, but coming in over modulated IR radiation
instead of a pair of wires. When I say “On,” I mean that the
IR carrier is detected. An “Off” means that there is no IR
detected by the sensor.
The actual SONY IR command can come in three
variations: 12 bits, 15 bits, and 20 bits. In every variation,
we first have the Lead In header, then we have a seven-bit
command. Next, in the 12-bit protocol we have a five-bit
Device ID. The Device ID tells us what is being controlled,
for instance, a TV or a DVD. In the 15-bit format, the
Device Code is eight bits; in the
20-bit code, we have a five-bit
Device ID and then an eight-bit
Extended Command byte. All
of my remotes were either
12-bit or 15-bit. All of the
codes come in LSB first. This
means that the Least
Significant Bit is first and the Most Significant Bit (MSB) is
last. The packet format includes some kind of a Lead Out as
well, but it is really just a guarantee of some time spacing
before the next packet is sent. Don’t bother to look for it
since its length depends upon the data just sent; it doesn’t
seem to be consistent (see Packet 1).
When you code for this protocol, you need to
remember to assemble the bytes by putting the bits in
reverse order! Remember, they are LSB first.
When you press a button on a SONY remote, it will
simply repeat the command packet every 45 ms for as long
as you hold the button. Some buttons on my remotes
would only send a command once when you let up off of
the button, but the rest just kept repeating endlessly.
NEC Format
I found useful information on the NEC format here:
www.hifi-remote.com/infrared/IR-PWM.shtml
and here:
www.mcselec.com/index.php?option=com_content&
task=view&id=223&Itemid=57
The NEC format is a bit different. It includes some error
checking and has a different way of dealing with repeating
packets. The NEC protocol sends a Lead In, 32 bits of data,
and a Lead Out. Since we can count on the Lead In and 32
bits of data, don’t bother to look for the Lead Out here
either. The NEC format sends its data LSB first like SONY,
SERVO 07.2008 17
[Lead In] [0 | 1 | 2 | 3 | 4 | 5 | 6| 7] [0 | 1 | 2 | 3 | 4 | 5 | 6| 7] [0 | 1 | 2 | 3 | 4 | 5 | 6| 7] [0 | 1 | 2 | 3 | 4 | 5 | 6| 7] [Lead Out]Device ID ~Device ID Command ~Command
12 Bit Code [Lead In] [0 | 1 | 2 | 3 | 4 | 5 | 6] [0 | 1 | 2 | 3 | 4]Command Device ID
15 Bit Code [Lead In] [ 0 | 1 | 2 | 3 | 4 | 5 | 6] [0 | 1 | 2 | 3 | 4 | 5 | 6 | 7]Command Device ID
20 Bit Code [Lead In] [0 | 1 | 2 | 3 | 4 | 5 | 6] [0 | 1 | 2 | 3 | 4] [0 | 1 | 2 | 3 | 4 | 5 | 6 | 7]Command Device ID Extended Command
Description ON Time OFF Time
Lead In 2.4 ms 0.6 ms
Logic 1 1.2 ms 0.6 ms
Logic 0 0.6 ms 0.6 ms
Table 1. SONY timing values.
Description ON Time OFF Time
Lead In 9 ms 4.5 ms
Logic 1 0.56 ms 1.68 ms
Logic 0 0.56 ms 0.56 ms
Repeat 9 ms 2.25 ms
Table 2. NEC timing values.
PACKET 1
PACKET 2
MrRoboto.qxd 5/30/2008 11:24 AM Page 17
but there the similarity ends. The packet format looks like
that in Packet 2. By ~Device ID and ~Command, I mean
that it is inverted, or 1’s complement of its respective
Device ID and Command. To check for a proper reception,
all you need to do is AND the byte with its respective
complement; if it comes up all zeros, then you have a good
reception. When you hold down a button on the NEC
remote, it does not send out the same command over and
over; it sends out a special signal called the Repeat Code.
The NEC protocol has four timing values that we care
about, and one we don’t (the Lead Out). Table 2 shows the
ones that we pay attention to.
Phillips RC-5 Format
Some useful information on the Phillips RC-5 format
can be found here:
www.hifi-remote.com/infrared/IR-bi-phase.shtml
and here:
http://home1.stofanet.dk/hvaba/fprc5rx/index.html
The last of the big three formats that I’m going to talk
about is the Phillips RC-5 protocol. Rather than using PPM
encoding like SONY and NEC, the RC-5 format uses Bi-Phase
encoding. This means that the transition from a logic ‘1’ to
a logic ‘0’ and vice-versa is shown by a change in the bit
phase. If you are like most of us, your eyes just glazed over
at that description. This is one time that a picture is pretty
much needed to explain what I mean (see Figure 2).
Note that it isn’t the timing that shows what the bit is,
but rather the phase of the timing. But how — you ask — do
you know what a ‘1’ is and what a ‘0’ is? You know because
the bit stream of RC-5 starts out with two 1 bits and then a
toggle bit, which on the first press of the button is a 0. Figure
3 shows how a transmission is formatted. An RC-5 packet
consists of the preamble of 1 1 0, then a five-bit address and
then a six-bit control. RC-5 packets are encoded with the MSB
(Most Significant Bit) first. Because you know that the first
bit is a 1, then any bit transition from that point onward
you can track to know what the current bit is — a 1 or a 0.
Figure 3 may look a little odd because I put both same
and switch phases in every bit cell except for the start bits.
Just to make it more confusing though, I’ve read that the
start bits can be either 1 1 or 1 0. I hope not; it’d make it
hard to figure out the 1 startup. The RC-5 protocol will
repeat the button press every 113.8 ms, but every packet
after the first one will have the Toggle bit toggled
differently than the last start bit.
How to Decode IR Transmissions
Okay, now that the explanations are over with, how
18 SERVO 07.2008
Figure 2. Bi-Phase encoding.
Figure 3. RC-5 packet.
Figure 4. IR detector schematic.
Part Description
C1 110 μF 25V capacitor
C2-C4 .1 μF 25V capacitor
R1 10K 1/4W 5%
R2 2.2K 1/4W 5%
R3 1K 1/4W 5%
D1 Green LED
S1 N.O. button
U1 PIC16F688 DIP
U2 7805 regulator
U3 PNA4602 IR demodulator
J1 Power connector
J2 Four-pin male .1” connector
J3 RJ-11 six-pin connector
Table 3. IR detector parts list.
MrRoboto.qxd 5/30/2008 11:24 AM Page 18
can we use the IR transmissions from our remotes in our
robots? To see what is going on, I built a special IR
decoder board that has a Panasonic PNA4602 (38 kHz) IR
demodulator, a PIC16F688, a power plug, regulator,
programming header (Microchip ICD2 six-pin type) and a
plug for the Acroname RS-232 converter board. Figure 4
shows the schematic and Figure 5 is a photo of the finished
board with everything plugged in. This board was wired
together with a bunch of wire that I had lying around, so it
isn’t very sensitive to how you put it together. I just wanted
an experimenter board that would show me the IR
codes and allow me to experiment with decoding the IR
transmissions. Different remotes use different modulation
frequencies, but the Sharp PNA4602 will work with
frequencies between 36 kHz and 40 kHz just fine. I chose
the PIC16F688 because it had an interrupt line, a hardware
USART, two timers, and an internal RC oscillator that runs
at 8 MHz, all in a 14-pin package. These were all of the
hardware interfaces that I needed. Unfortunately, for some
reason Microchip requires some kind of dongle to debug
this chip which I didn’t have, so I debugged using “printf”
statements in the code.
The board isn’t particularly sensitive to the components
that you can use. My previous list just came from my parts
bins. The power connector was a barrel socket that fit the
various wall warts that I had lying around. I chose the pin
out of the RS-232 connector to match the Acroname Serial
Interface Connector that you can get from www.
junun.org/MarkIII for about $10. Finally, the
programming connector is chosen to fit the cable on
my Microchip ICD2 so that I can just plug in and program
the board without constantly taking the part out of a
programmer board and plugging it back into my test board.
If your programmer allows In Circuit Serial Programming
(ICSP), then get a connector that matches its cable.
Figure 5 shows what my board looks like. I put little
rubber feet on the bottom to make it extra spiffy looking. I
put a small three-pin socket on my board so that I could
swap around IR demodulators that have the same pin-out
as the Panasonic units, should I so desire.
Now that we understand the formats and we have a
board to look at the signals, how can we decode them?
The answer is software, of course. I like to use C as my
programming language, but the logic that I use here can be
ported to any compiler language that you feel comfortable
with. I should qualify that statement — any compiler that
allows interrupts to be used is required. In this case, my
compiler of choice is the CCS C compiler for the Microchip
14-bit cores (the PIC16Fnnn series.) I am not going to go
into the gory details about how to program a PIC; whole
books have been written on that subject and that isn’t my
intent with this column. However, you can benefit from my
line of reasoning for doing things how I did them and move
these procedures to your compiler or even your other
microcontroller if you wish. I’m only going to show SONY
and NEC decoding in my code. This is because I don’t have
any RC-5 remotes; all of mine were SONY and NEC formats.
My test code has two sections in it. The first is the
set-up of the interrupt routine that will capture the times
between pulses by measuring between falling edges on
the INT line. When the IR transmitter is On, this will be
detected by the PNA4602 and it will drop its output low.
This is why I chose falling edges; the output of the device
is normally high, or Off. Before I go into my logic for
detecting pulses and parsing them out, let’s get an idea of
how I set the PIC up to look for these transmissions. To do
that, let’s look at how to initialize this PIC. The code snippet
below shows how I set up the timers:
//Turn off comparatorsetup_comparator(NC_NC_NC_NC);
//We will be doing interruptssetup_timer_0(RTCC_INTERNAL | RTCC_DIV_128);//16ms timersetup_timer_1(T1_INTERNAL | T1_DIV_BY_4);//Gives 131ms max timeoutext_int_edge(H_TO_L);//IR IRQ on falling edge
CCS does a good job of hiding the ugly details of the
hardware from you, but you still need to read your data
sheets to understand what they are hiding! Here we turn
off the comparators because these pesky things default to
on in the PIC and will get in the way of those I/O lines.
We’re going to use TMR0 to time our pulses because it
is an eight-bit timer and we don’t want all that much
resolution in our times. This “slop” allows us to quickly
check a bit time and save it away; the coarseness of the
measurement allows us to read remotes that are close, but
not perfect to the specified times. We know that the pulses
in SONY and NEC are between 1.2 ms and 13.5 ms (see
Tables 1 and 2 again) so we want this timer to have a
maximum time before it rolls over that is near that
maximum time. Since our PIC is running on its internal
8 MHz clock (which is divided by four internally), we know
that if we use the prescaler on TMR0 at divide by 128, we
will have a maximum time of:
(1/(2MHz/128))*256 = 16.384 ms
SERVO 07.2008 19
Figure 5. IR detector board and Acroname serial connector.
MrRoboto.qxd 5/30/2008 11:24 AM Page 19
That is pretty close to 13.5 ms. Why are we using
TMR1? When we start saving times to measure for our
data bits, we need some way to stop looking if the signal is
interrupted, otherwise we’ll just appear to “hang” and do
nothing. TMR1 will be set to values that are just a little
larger than the inter-packet repeat rate. For NEC, this is
108 ms; for SONY, it is 45 ms. TMR1 is a 16-bit timer and it
only has four prescales to choose from, so I took the one
that got me close to 108 ms. Finally, I set the INT interrupt
to trigger on a high-to-low transition for my measurements.
Here is the code for the actual interrupt service routine:
#int_globalvoid isr(void)/** Lets handle all ISR save/recovery functions, the
default isn’t lean enough for * an ISR that is highly time critical.*/
{#asm//store current state of processorMOVWF save_wSWAPF status,WMOVWF save_statusSWAPF FSR,WMOVWF save_FSRBCF status,5 //Set to page 0 for SFR’sBCF status,6#endasm
//We only have two interrupts, so if it isn’tthis one, it’s the other.
if (bit_test(PIR1,0)) //Timer1 overflow IRQ{
bits[wBits++] = 255; //timed outbit_clear(PIR1,0); //Clear TMR1 int flagbit_clear(T1CON,0); //Turn TMR1 off until...
}
if (bit_test(INTCON,1)) //CCP1 capture IRQ{
bits[wBits++] = TMR0; //save the pulse timebit_clear(INTCON,1); //clear external
//interrupt flagTMR1H = t1h; //reset the timeoutTMR1L = t1l;bit_set(T1CON,0); //turn TMR1 back on so
//we can time outTMR0 = 0; //clear out the timer
}
if (wBits == MAXBIT) //rollover the bit //buffer
wBits=0;
#asm// restore processor and return from interruptSWAPF save_FSR,WMOVWF FSRSWAPF save_status,WMOVWF statusSWAPF save_w,FSWAPF save_w,W#endasm
}
I can hear the groaning now! I’ve used PIC assembly
language! In CCS C, the compiler flag “#int_global” means
that CCS will not handle the saving of registers that need
to be saved during an ISR call. This means that we need to
do it. Really, the only reasonable way to do this is with
some simple assembly code. This function needs to be
FAST and we do that by keeping it lean. I combine this
lean ISR with the definitions at the top of the program that
looks like this:
unsigned char save_w; //These next 3 bytes //are saved on interrupt
#locate save_w=0x7funsigned char save_status;#locate save_status=0x7eunsigned char save_FSR;#locate save_FSR=0x7dunsigned char wBits=0; //To make access to
//these variables fast#locate wBits = 0x7c //Keep them in common
//memory for ISR useunsigned char t1h;#locate t1h = 0x7bunsigned char t1l;#locate t1l = 0x7a/** Give me direct access to several SFR’s that CCS
doesn’t handle the way I want.*/
#byte TXREG = 0x15#byte T1CON = 0x10#byte INTCON = 0x0B#byte FSR = 0x04#byte status = 0x0#byte TMR1L = 0x0E#byte TMR1H = 0x0F#byte PIR1 = 0x0C#byte TMR0 = 0x01
Those confusing compiler directives tell the compiler to
put certain variables into “access RAM” that is available in
all data banks. This means that I don’t have to waste time
switching banks to save our timing measurements or our
saved registers. Make sure you look this up in the CCS
manual. You don’t have to do this in other micros that
don’t use banked data memory.
Now look at the ISR from above. When we get an
interrupt from INT, we record the value in the TMR0 register
in the next available data slot in our ring buffer (called ring
because it rolls over to 0 when it reaches the end of the
“ring”). If we time out on TMR1, then we stuff a 255 into
the buffer telling the decoding routine that we timed out
and we should ditch the entire set of numbers and wait for
the next start to be detected.
The second part of the program will decode the times
saved in the buffer and turn them into 1s and 0s. It uses its
own pointer into the ring buffer and knows when to look
for a value when the read pointer is different from the
write pointer. I’ve put lots of comments into this code, so
I’m not going to go over it line-by-line. Here is what the bit
decoding routine looks like:
20 SERVO 07.2008
MrRoboto.qxd 5/30/2008 11:24 AM Page 20
unsigned char DecodeBit(unsigned char time)/** This will determine if the bit is a 0 or a 1,* by whichever standard is in being used. * Returns a 1 if a logic 1 bit, 0 otherwise.*/
{unsigned char ret = 0;unsigned char val = 0;
val = time; //Can be used to “fuzzy” //the time for rounding
if (whichOne == NEC){if ((val <= NEC_ONE+FUZZY) &&
(val >= NEC_ONE-FUZZY))ret = 1;
else if ((val <= NEC_ZERO+FUZZY) && (val >= NEC_ZERO-FUZZY))ret = 0;
}else if (whichOne == SONY){if ((val <= SONY_ONE+FUZZY) &&
(val >= SONY_ONE-FUZZY))ret = 1;
else if ((val <= SONY_ZERO+FUZZY) &&(val >= SONY_ZERO-FUZZY))
ret = 0;}return ret;
}
There is more magic in DecodeCode() that shows how
to recognize the start of a transmission and how to end
one. This little routine above simply shows the decoding of
a single data bit. Notice the + and – FUZZY settings. IR
specs allow for about a 10% slop in the standard times.
This FUZZY setting gives us that. You can experiment with
how large you want that FUZZY to be since it is a #define
at the top of the program. I’ve found that a setting of 2
works well.
My code will “auto” detect NEC
code if you hold the button down.
This is because NEC uses the repeat
code frame that is distinct from any
other transmission. You don’t have to
do that if you don’t want to, and
you’ll need to reset the PIC to get it to
pay attention to SONY codes again
regardless. I have two modes of
operation that can be selected by the
setting of the TEST define. If this is set
to 1, then the program will only print
out the times. This is useful for when
you are trying to understand a new
format. If TEST is set to anything else,
then the program will decode either
SONY or NEC, and print out the
device and control codes when they
are received. The entire program
source can be found on the SERVO
website www.servomagazine.com).
It is called IRdecoder.c.
Conclusion
Figure 6 shows my collection of IR remotes that I used
to test my program. I found interesting departures from the
established standards in some of them; no doubt you will, too.
I’ve given you a powerful tool that you can use to
discover IR codes and a basic template that you can use
to embed the ability to control your robot using a common
household device: the IR remote. Have fun and be creative.
If you have any questions about this program or how I
“figured it all out,” send your questions to roboto@servo
magazine.com — I’m happy to answer! SV
NEWS FLASH! At the last possible moment I discoveredthis site. It is an excellent compendium of various IRremote formats: www.rhoads.nu/bjorn/hp48/remote.
SERVO 07.2008 21
Figure 6. A selection of IR remotes.
MrRoboto.qxd 6/4/2008 4:58 PM Page 21
Know of any robot competitions I’ve missed? Is your
local school or robot group planning a contest? Send an
email to [email protected] 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
JJuu llyy
7-11 Africa Championship Robotics Competition
Pretoria, South Africa
Students from various countries and continents
will compete in several robot challenge
events.
www.nydt.org/home.asp?pid=963
8-10 European Micro Air Vehicle Competition
Research Airport, Braunschweig, Germany
Tiny, autonomous flying robots compete for
prizes. Every year, these things get smaller
and smaller.
www.mav08.org
8-11 Botball National Tournament
Norman, OK
Educational robot contest for middle and
high school students designed to use science,
technology, engineering, and math to solve
real world problems.
www.botball.org
13-17 AAAI Mobile Robot Competition
Chicago, IL
This year’s competition will take the form of
exhibits that demonstrate either robot creativity
or mobility and manipulation. Expect to see
robots that dance, paint, play musical instruments,
and much more.
www.aaai.org/Conferences/conferences.
php
14-18 K’NEX K*bot World Championships
Las Vegas, NV
This competition includes events for two-wheel
drive autonomous K*bots, four-wheel drive
autonomous K*bots, and the remote control
Cyber K*bot Division.
www.livingjungle.com
22-25 FIRA Robot World Cup
Shinan Software Park, Qingdao, China
This competition has events for every kind of
robot soccer imaginable, ranging from the
humanoid robot league down to the tiny
Khepera robot league.
www.fira.net
26 RoboBombeiro
Polytechnic Institute of Guarda, Guarda, Portugal
Autonomous fire-fighting robot contest.
http://robobombeiro.ipg.pt
28 AUVS International Aerial Robotics
Competition
Fort Benning, GA
Autonomous flying robots complete missions
that include dropping sub-vehicles and gathering
information. This event runs through August 1st.
http://avdil.gtri.gatech.edu/AUVS/IARC
LaunchPoint.html
29 AUVS International Underwater Robotics
Competition
Space and Naval Warfare System Center,
San Diego, CA
In this competition, autonomous underwater
robots built by university students must complete
an underwater course. This event runs through
August 3rd.
www.auvsi.org/competitions/water.cfm
TBA RoboCup Robot Soccer World Cup
Suzhou, China
Soccer Simulation — teams demo and test their
robots; Small-size Robot Soccer — F180 robots
play soccer; Mid-size Robot Soccer — larger robots
play soccer; Sony Legged Robot Soccer — legged
Send updates, new listings, corrections, complaints, and suggestions to: [email protected] or FAX 972-404-0269
22 SERVO 07.2008
Events.qxd 6/4/2008 9:37 AM Page 22
robots play soccer; RoboCup Junior — small robots
play soccer; Humanoid Soccer — humanoid robots
play soccer; Rescue Robots — NIST Standard
Rescue Robot Test Field; RoboCup@Home — real
world robot event.
http://www.robocup.org
TBA War-Bots Xtreme
Saskatoon Saskatchewan, Canada
“Robots” (RC vehicles) attempt to destroy each
other.
http://www.warbotsxtreme.com
AAuugguusstt
23-24 Motodrone AFO Competition
Finowfurt, German
Autonomous Flying Objects (AFOs) compete in
several areas including the ability to hover in
changing wind conditions, stable flight between
points, capturing photos of targets, recovering
from free fall, and automated take off and
landing.
www.motodrone.de
29 DragonCon Robot Battles
Atlanta, GA
Remote-controlled and autonomous robots fight it
out at the DragonCon science fiction convention.
www.dragoncon.org
TBA DPRG Robot Talent Show
The Science Place, Dallas, TX
Autonomous robots demonstrate their talents.
www.dprg.org/competitions
TBA Robot Fighting League National
Minneapolis, MN
“Robots” (RC vehicles) attempt to destroy each
other.
www.botleague.com
TBA Robots at Play
City Square, Odense, Denmark
Robots compete to demonstrate playfulness and
interactivity.
SERVO 07.2008 23
Events.qxd 6/4/2008 3:06 PM Page 23
24 SERVO 07.2008
DEVELOPERS IN ROBOTICS TECHNOLOGYFOR USE IN SPACEEXPLORATION RECEIVE2008 IEEE ROBOTICSAND AUTOMATIONAWARDContributions to AutonomousRobotic Operations Result inSignificant Data Collectionfrom Mars
IEEE (Institute of Electrical andElectronics Engineers) has named
Paul Backes, Eric T. Baumgartner, andLarry Matthies recipients of its 2008Robotics and Automation Award. Thethree are being recognized for theircontributions to different roboticstechnologies used in space flightsystems including the successful MarsExploration Rover (MER) missionrovers Spirit and Opportunity, whichto this day are still functioning onthe surface of Mars. The IEEE is the
world’s leading professionalassociation for the advancement oftechnology.
The award, sponsored by theIEEE Robotics and AutomationSociety, recognizes Backes,Baumgartner, and Matthies forcontributions to robotics enablingeffective autonomous operations ofscience investigations under extremeconditions on the planet Mars. Theaward was presented to the threeon May 23, 2008 at the IEEEInternational Conference on Roboticsand Automation (ICRA) inPasadena, CA.
The works of Backes (distributedand remote operations),Baumgartner (manipulator control),and Matthies (navigation systems)have advanced robotic technology,particularly rover operations, andmade possible the scientific exploration of Mars. MER is the firstlong-term mobile autonomous robotic exploration in an unknownspace environment.
An IEEE member, Backes is thetechnical group supervisor of theMobility and Manipulation group inthe Mobility and Robotic Systemssection at the Jet PropulsionLaboratory of the California Institute
of Technology in Pasadena. Heconceived and led the developmentof an interface system to allowscientists and engineers tocollaborate in generating activitysequences, which was used as theprimary science planning tool in the2003 MER mission. The interface alsoenables the public to view missiondata and simulate their own activitysequences. Backes holds sevenpatents, has won several awards,and has published numerous bookchapters, articles, and papers. Hewas associate editor of the IEEERobotics and Automation SocietyMagazine from 1993 to 1998.
Baumgartner contributed tothe MER project as the lead systems,test, and operations engineer forthe MER Instrument PositioningSystem. This system was responsiblefor the robotic deployment andplacement of four in-situ — meaning“in place” — instruments onto theMartian surface through the useof a five degree-of-freedom roboticarm. Presently, Baumgartner is thedean of the T. J. Smull College ofEngineering at Ohio NorthernUniversity in Ada. He has publishednumerous papers in the area ofmobile robotics and vision-guidedmanipulation and has receivedseveral awards for his efforts on theMER project.
Matthies’ work on autonomousnavigation of robotic ground andair vehicles led to the developmentof algorithms for descent motionestimation, visual odometry, andreal-time 3D perception with stereovision. These capabilities wereincorporated into the MER mission,providing landers with the ability toestimate horizontal velocity androvers with the ability to detectobstacles and measure slip. Hiswork can be found in terrestrialapplications including off-roadautonomous navigation and roboticvision systems. An associate memberof the IEEE, Matthies is an adjunctprofessor at the University ofSouthern California and a memberof the editorial boards of theAutonomous Robots Journal and theJournal of Field Robotics. He hasreceived several awards, holds twopatents, and is widely published.
BloBlow Outw Out
SpecialSpecial
$9.95!$9.95!
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Showcase Jul08.qxd 6/4/2008 2:08 PM Page 24
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VISIT OUR ONLINE STORE ATwww.allelectronics.comWALL TRANSFORMERS, ALARMS,FUSES, CABLE TIES, RELAYS, OPTOELECTRONICS, KNOBS, VIDEOACCESSORIES, SIRENS, SOLDERACCESSORIES, MOTORS, DIODES,HEAT SINKS, CAPACITORS, CHOKES,TOOLS, FASTENERS, TERMINALSTRIPS, CRIMP CONNECTORS,L.E.D.S., DISPLAYS, FANS, BREAD-BOARDS, RESISTORS, SOLAR CELLS,BUZZERS, BATTERIES, MAGNETS,CAMERAS, DC-DC CONVERTERS,HEADPHONES, LAMPS, PANELMETERS, SWITCHES, SPEAKERS,PELTIER DEVICES, and much more....
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SERVO 07.2008 25
Showcase Jul08.qxd 6/4/2008 2:11 PM Page 25
Baby Orangutan B-168Robot Controller
Pololu announces the release of
the Baby Orangutan B-168 robot
controller, the latest addition to Pololu’s line of
Orangutan robot controllers. The compact module
has dimensions of 1.2” x 0.7”, and it can be configured
to fit in a solderless breadboard or a 24-pin dual in-line
package (DIP) socket. For applications with low I/O usage,
the Baby Orangutan B-168 board can also be configured
with pins on just one side of the module for use as a single
in-line package (SIP). The diminutive size of the Baby
Orangutan B-168 makes it well suited for primary control of
miniature robots or for auxiliary control on larger robots.
The Baby Orangutan B-168 is based on an Atmel
ATmega168 microcontroller running at 20 MHz with 16
KB of Flash program memory and 1 KB data memory.
The use of the ATmega168 microcontroller makes the
Baby Orangutan B-168 compatible with the popular
Arduino development platform. Free C and C++
development tools and libraries are also available.
Integrated motor control sets the Orangutan family
of controllers apart from other small microcontroller
boards, and the Baby Orangutan B-168 features dual
high-performance, MOSFET-based H-bridges to deliver up
to 1A per channel over the 5-13.5V operating range.
With hardware-based ultrasonic PWM generation, two
independent, bidirectional DC motors can be controlled
symmetrically and without any processor overhead.
The unit price is $29.95.
For further information, please contact:
PC Windows USB Interface forOWI-535 Robotic Arm
The robotic arm interface kit available from Images
connects OWI’s 535 Robotic Arm Edge™ to a personal
computer (IBM PC or compatible). The interface connects
to the PC’s USB port. The software for the interface
permits real time control and contains a built-in
interactive script writer. A user may write a script that
contains up to 99 individual robotic arm functions
(including pauses) into a single script file. Script files
may be replayed automatically for demonstrating
computer controlled automation and animatronics.
The Robotic Arm PC Interface creates a fun way of
learning and experimenting with computer automation
and animatronics.
The USB OWI-535 Interface (assembled and tested)
costs $99.95; the USB OWI-535 Interface Kit (requires
soldering and assembly) is $84.95.
The Interface Kit Includes:
• Windows 2000/XP/Vista program
• Printed circuit board for easy construction
• All components
For further information, please contact:
Motor Mount and Wheel Kit
It’s time to give your robot the mobility and style it
deserves with the new Motor Mount and Wheel Kit
with Position Controller from Parallax. Powerful 12 VDC,
150 RPM motors are combined with precision machined
6061 aluminum hardware to provide enough power,
strength, and beauty to make other robots jealous.
New Products
CONTROLLERS & PROCESSORS
INTERFACE
MECHANICS
NNEEWW PPRROODDUUCCTTSS
26 SERVO 07.2008
Website: www.imagesco.comImages ScientificInstruments6000 S. Eastern Ave. Suite 12-D
Las Vegas, NV 89119Tel: 877•7•POLOLU or 702•262•6648
Fax: 702•262•6894Email: [email protected]
Website: www.pololu.com
PololuCorporation
JUL08NewProd.qxd 6/4/2008 4:41 PM Page 26
Conveniently positioned
screw holes in the bearing
block make mounting this
kit a breeze, and the
included six inch
pneumatic rubber tires
perform well on a variety of
smooth or rugged terrains. The
kit includes two position controllers which
use a quadrature encoder system to reliably
track the speed and position of each wheel with
36 positions/rotation resolution and report the data
on command via a 19.2 kbps serial bus. The position
controllers can also be interfaced with HB-25 motor
controllers (sold separately) to automatically provide user-
definable smooth speed ramping and accurate position
control, which frees up the main processor to handle
more important tasks.
The entire Motor Mount and Wheel Kit (#27971) is
a value at $279.95.
For further information, please contact:
Flowcode for ARMMicrocontrollers
Matrix has recently
launched a new
version of their popular
graphical programming
language for micro-
controllers — ‘Flowcode
for ARM micro-
controllers.’ Now, 32-bit
ARM microcontrollers
are available for the
same price as eight
bit micros but offer
massive advantages to
developers: low power,
more I/O lines, several
times more ROM and
RAM than a typical eight bit micro, full floating point
and maths libraries, and a massive increase in processing
speed and power.
This new version of Flowcode provides
engineers and developers access to all of these features
of the ARM based on Atmel’s popular range of AT91
microcontrollers. Flowcode for ARM is also backwards
compatible with Flowcode for PICmicro®
microcontrollers and AVR® microcontrollers which
provides an easy migration route to 32 bit power.
ARM hardware development tools, based on the
Matrix’s E-blocks range, are also available. A fully
functional demonstration version is available on the
Matrix website.
For further information, please contact:
Four-Channel Digital BatteryTest System
The Cadex C8000 is an advanced battery test system
capable of performing complex lifecycle tests. These
tests may include discharging a battery with GSM,
CDMA, or other pulses of choice. Replicate battery
runtime of a power tool, digital camera, or computing
device by first capturing the current profile and then
applying the load on the test battery for verification. The
C8000 can also test the function of a Li-ion charger,
verify battery safety circuits, and read SMBus registers.
Automated programs assure safe charging and correct
discharge terminations; custom programs provide for
user-defined settings. Each of four independent channels
delivers up to 10A and 36V, with 0.1% FSR. Total power
is 400W on charge and 320W on discharge. The Cadex
C8000 runs as a stand-alone unit or with PC-BatteryLab™
software.
For further information, please contact:
SOFTWARE
TOOLS & TEST EQUIPMENT
Is your product innovative, less expensive, more functional,or just plain cool? If you have a new product that youwould like us to run in our New Products section, pleaseemail a short description (300-500 words) and a photo ofyour product to:
Show Us What You’ve Got!
Website: www.parallax.comParallax, Inc.
Website: www.matrixmultimedia.co.ukMatrixMultimedia
Website: www.cadex.com/c8CadexElectronics
SERVO 07.2008 27
JUL08NewProd.qxd 6/4/2008 4:42 PM Page 27
Featured This Month:
Features28 BUILD REPORT:
Apollyonby Mike Jeffries
30 MANUFACTURING:High-Performance DrillMotor Modificationby Bryan Ruddy
32 PARTS IS PARTS:Mag Motor Upgradesand Repairsby Nick Martin
Events33 Apri/May 2008 Results and
Jul/Aug 2008 UpcomingEvents
ROBOT PROFILE – TopRanked Robot This Month:31 Billy Bob by Kevin Berry
28 SERVO 07.2008
Idesigned this 12 pound,
Hobbyweight, robot with the
purpose of cramming as much
power as I could into the smallest
box possible. It’s low, it’s fast,
and it’ll just keep slamming its
face into your spinning weapon
until something breaks. The horns
on top allow it to
take its opponents
into the wall of
the arena while
wearing them like a
polished metal hat.
Apollyon won its
debut tournament
this past December
with a 3-1 record.
● by Mike Jeffries
Apollyon
BUILD REP RT
FIGURE 2
FIGURE 1
CombatZone.qxd 5/29/2008 2:26 PM Page 28
SERVO 07.2008 29
Figure 1 is a CAD model of
Apollyon drawn in SolidWorks. Some
minor changes were made, but most
of the parts are almost identical to
the ones in the drawing, for example,
the side and internal frame rails, as
well as the horns that are used to
catch other robots. The horns are
steel and the rest of the frame is
6061 aluminum (see Figure 2).
The sides of the frame are
lined up to show the profile of the
chassis, shown in Figure 3. The
holes in the top, front, and bottom
of the plate are tapped to allow
armor to be bolted directly to them.
Figure 4 shows the chassis with
the baseplate, drive motors, and inter-
nal portion of the front armor installed.
Figure 5 shows a mostly
assembled Apollyon sitting inside
the chassis of my 60 lb robot Ruiner.
In Figure 6, Apollyon has been
painted, the front steel wedge has
been mounted, and the robot is
almost ready for competition.
Take a look at Figure 7.
You’ll see an internal shot of
Apollyon the night before the
“Wreck the Halls” event in
Greensboro, NC. This shows
the layout of the electrical
components and the battery
mount. The piece of PVC pipe
in the back left of the robot
serves as a power distribution
block and battery mount.
Figure 8 shows Apollyon at
Wreck the Halls being prepared for
the first match of the competition.
Apollyon won the 12 lb class
with a 3-1 record (see Figure 9).
The damage was all cosmetic
and easily repaired. The shaft collar
on the visible axel was torn off in
combat. A new front wedge is
being designed to reduce
impacts on the chassis. SV
FIGURE 3
FIGURE 4 FIGURE 5
FIGURE 6
FIGURE 7
FIGURE 8
FIGURE 9
Parts ListITEM QTY PRICE• Victor 883 speed controller 2 $139.99• GB42 gearbox 2 $85.99 (no longer available)• Mini-EV motor 2 $8.99• 18V 1,650 mAh NiMH battery pack $62.50• Spektrum DX6 with BR6000 receiver 1 $199.99• 3” Colson wheel with hub 2 $25.00 (no longer available)
(www.cncbotparts.com)• GWS elevator/aileron mixer $14.99• S-BEC Super BEC 5V $46.99 (being replaced
with receiver battery packfor future events)
• MS-05 power switch 1 $48.00• 45A powerpole connectors $1.39/set• #8 ring terminals $1.99/25• Deans Wet Noodle Wire — 12 awg $1.25/ft• Raw metal, nuts, and bolts (www.mcmaster.com and www.onlinemetals.com)• Wood and plumbing pieces for battery mount — local hardware store• Machining (www.teamwhyachi.com)
NOTE: All items are from www.robotmarketplace.com unless noted otherwise.
CombatZone.qxd 5/29/2008 2:28 PM Page 29
30 SERVO 07.2008
MANUFACTURINGHigh-Performance Drill Motor Modification
● by Bryan Ruddy
Cordless drills are among the
richest sources of affordable
gearmotors for the robotics hobbyist;
from inexpensive, low-power imports
(such as the drills offered by Harbor
Freight) to high-performance, name-
brand drills (particularly DeWalt).
Unfortunately, drill gearmotors lack
convenient mounting features, often
have minimal bearings, and generally
contain slip clutches, making them
unsuitable for use in robotic drive
and mobility applications without
modifications. While there are
commercially-available modification
kits for some drill gearmotors, most
motors must be modified by the
hobbyist. The photos here document
my modifications to
DeWalt’s newest and
most powerful drill
motor. SV
PHOTO 1. The 36-volt DeWalt DC900KLcontains a gearmotor rated for 750 watts ofpower and is capable of a bone-crushing 200foot-pounds of stall torque in low gear. Onpaper, this gearmotor should be capable ofmoving a 200 pound robot at about five milesper hour in a 4WD configuration.
PHOTO 3. The original motor mount is shown on the left, withits twist-lock interface to the gearbox. An alternative mount— machined from a block of magnesium — is shown on theright. Long bolts will be used to assemble the motor mountto the new gearcase.
PHOTO 2. The gearbox (part #629059-00) and motor (part#639521-00) are shown without the drill casing. They aremounted to the casing by the small plastic tabs where themotor and gearbox meet. To mount the gearmotor securelyto a robot, we will make a metal replacement for the stockplastic gearcase.
PHOTO 4. As shown on the left, the first-stagering gear (part #628002-00) is free to rotate aspart of the clutch mechanism. To lock this gearin place, we can machine it down to a square,as shown on the right. The modified gearpresses into the motor mount.
PHOTO 5. The DC900KL uses a three-speedgearbox — for robotics use, the gears must be secured for a single speed. The stockgearcase (top) uses a set of molded-in teethto keep the ring gears (bottom) from turningwhen engaged; these have been duplicated inthe magnesium gearcase (right).
PHOTO 8. The completed gearcase, withmotor and gearbox parts installed, isshown here. The parts were made on CNCequipment, but could be made manuallywith slight simplifications. The motor,gearbox, and spare ring gears areavailable from www.dewaltservicenet.com, at a total cost of $110 permotor-gearbox assembly.
PHOTO 7. The gearbox output (left)uses a simple double-D shaftgeometry, duplicated in the hardened,high-strength shaft on the right. Thestep in shaft diameter allows the newgearbox to be protected from impactsby a bronze thrust bearing.
PHOTO 6. The stock gearboxoutput has an overrunningclutch to prevent back-driving.Since this can cause the output tolock up under some conditions,it must be disabled by removingthe five pins and outer ring.
CombatZone.qxd 5/29/2008 2:30 PM Page 30
SERVO 07.2008 31
ROBOT PR FILETOP RANKED ROBOT THIS MONTH
Billy Bob has competed in House
of NERC 2006, Motorama 2007,
RoboGames 2007, Franklin Institute
2007, and Motorama 2008.
Details are:
● Configuration — Vertical Spinner
● Frame — 2024 milled aluminum
frame
● Drive — Two AstroFlight 940s
with Team Whyachi gearboxes
● Wheels — Two 3.5” Colsons
● Configuration — Two wheel drive
in the rear
● Drive ESC — Two IFI Victor 883s
● Drive batteries — 21.6 volt A123
battery pack
● Weapon — Custom S7 tool
steel single tooth blade at 8,000
RPM
● Weapon power — 24 volt NiCd
2,400 mAh battery pack
● Weapon motor — Axi 5330 at
24 volts
● Weapon ESC — Castle Creations
Phoenix HV85
● Armor — Rubber shock mounted
steel and a rear titanium wedge,
along with various attachments for
other types of bots
● Radio system — Spectrum DX6
● Future plans — Four-wheel drive
version
● Design philosophy — Balance the
drive, weapon, and armor with
smart engineering, and make it
cool!
● Builders bragging opportunity —
Billy Bob went undefeated at its first
event. SV
All fight statistics are courtesy of BotRank(www.botrank.com) as of May 10,2008. Event attendance data is courtesyof BotRank and The Builder’s Database(www.buildersdb.com) as of May 10,2008.
● by Kevin Berry
Weight Class Bot Win/Loss Weight
Class Bot Win/Loss
150 grams VD 26/7 150 grams Micro Drive 7/1
1 pound Dark Pounder 44/5 1 pound Dark Pounder 23/3
1 kg Roadbug 27/10 1 kg Roadbug 11/4
3 pounds 3pd 48/21 3 pounds Limblifter 12/1
6 pounds G.I.R. 17/2 6 pounds G.I.R. 11/2
12 pounds Solaris 42/12 12 pounds Surgical Strike 17/7
15 pounds Humdinger 26/4 15 pounds Humdinger 26/4
30 pounds Totally Offensive 43/13 30 pounds Billy Bob 12/4
30 (sport) Bounty Hunter 9/1 30 (sport) Bounty Hunter 9/1
60 pounds Wedge of Doom 43/5 60 pounds Texas Heat 11/4
120 pounds Devil's Plunger 53/15 120 pounds Touro 10/0
220 pounds Sewer Snake 43/12 220 pounds Sewer Snake 11/5
340 pounds SHOVELHEAD 39/15 340 pounds Ziggy 3/0
390 pounds MidEvil 28/9 390 pounds MidEvil 3/0
Top Ranked Combat Bots
Rankings as of May 10, 2008
History Score is calculated byperfomance perfomance at all
events known to BotRank
Current Ranking is calculated byperformance at all known events,
using data from the last 18 months
History Score Ranking
Billy Bob – Currently Ranked #1
Historical Ranking: #9Weight Class: 30 lb FeatherweightTeam: Benson LabsBuilder: Brian BensonLocation: Winchendon, Massachusetts
BotRank Data Total Fights Wins LossesLifetime History 16 12 4Current Record 16 12 4Events 5
CombatZone.qxd 5/29/2008 2:31 PM Page 31
32 SERVO 07.2008
If you rely on the Satcom Mag
motor to deliver a deadly blow or
a punishing push to your robotic
opponent, you will want to follow
these simple tips for improved
reliability and performance.
Tape the Brush Covers
The quickest tip is to place elec-
trical tape over the four brush covers
(see Figure 1). They don’t often come
loose, but losing a brush cap during
an event can be a disaster. If your
motors get particularly hot, you
might need high temperature Kapton
tape, however I have never had a
problem with the cheap stuff.
Replace the CaseScrews (beginner)
The long case screws supplied
by Satcom are 10-32 by 3” stainless
steel with Phillips
drive heads. These
are not up to heavy
combat duty and
should be replaced.
I use hex socket
cap screws,
McMaster-Carr part
#91251A360, for
this; they can be
tightened more
than the original
screws and the
threads are better
formed (Figure 2).
The heads of these
screws are
sometimes
too tall for the counterbores in the
front of the motor, so start by
grinding the heads down by about
.016” (0.4 mm).
Grinding the heads down also
puts a small burr around the 5/32”
hex socket, making it a tight fit on
your hex driver. Use the driver to
wiggle the screw about until it
starts to thread into a hole; after
the first screw, this becomes very
easy. I like to apply a slathering of
Loctite 243 to make sure the screws
stay put. NOTE: If you have a newer
four screw motor, one screw is only
2-3/4” long; you will need to cut
one of the replacement screws
down to fit.
Replace the MountingScrews
The tiny 8-32 face mounting
screws always look inadequate to
me; if you are mounting the motor
with these screws, I recommend
up-sizing them to around 12-24 or
M6. Start by removing the front
plate of the Mag motor, leaving the
armature and case in place.
● by Nick Martin
PARTS IS PARTS:Mag Mot r Upgrades
and Repairs
FIGURE 1. Tapedbrush covers andthe timing marks.
FIGURE 2. Replacementcase screws. (Insert:
The replacements havefar stronger heads.)
FIGURE 3. Aligning themounting holes with a taperedpin. (Insert: Which screw sizewould YOU trust?)
CombatZone.qxd 5/29/2008 2:32 PM Page 32
SERVO 07.2008 33
Position the front plate
accurately on your drill press using
a tapered pin made from the shank
of an old drill (see Figure 3). This
will keep the new mounting points
accurately in position; important if
you have a pre-made gearbox to fit.
Drill each of the mounting holes
out to fit your preferred screw size;
5 mm for M6 and #17 for 12-24
sized screws.
Tap the new holes and take
extra care to remove all the swarf
from the inside of the plate; you
don’t want conductive chips falling
into the armature! Re-assemble the
motor as detailed in previous tips; if
you combine this tip with the
stronger case screw tip, you will
have one tough motor.
Neutral Timing
Mag motors can be timed
slightly advanced or retarded,
although I find that advanced timing
makes hardly any difference so I
leave them neutrally timed. If you
want to experiment or need to
adjust the timing after repairs, here
is the quick way to do it. Mark a line
along the case so it meets the rear
end bell, as shown in Figure 1. With
the case screws loosened enough to
just turn the case, rotate the
case left until the screws touch a
magnet. Mark the position of your
line on the rim of the endbell. Now
rotate the case left until the screws
stop on the opposite magnets.
Mark this position on the endbell
rim. The marks on the rim represent
the extremes of forward and
reverse timing; draw a line midway
between your two extremes
and this is your neutral timing
position — too easy! SV
You can contact Nick via his build thread atwww.robowars.org/forum/viewtopic.php?t=74&start=0.
Results Apr 14 –May 12, 2008
HORD
Spring
2008 was held
in Brecksville,
OH on April
19th. Twenty-
five bots were registered.
Rotunda Rumble was held at the
Mall Of America in Minneapolis,
MN on April 25th. Twenty-seven
bots were registered.
Smackdown in Sactown IV
was held on April 27th in
Sacramento, CA. Eight bots were
registered.
BotsIQ: The Competition 2008
was held April 30th–May 4th in
Miami Beach, FL. One hundred
thirty-five bots were entered.
Roaming Robots presented
Fenton Manor 2008 on May 4th
in Stoke On Trent, England.
Upcoming Events forJuly-August 2008
D. W. Robots will
present
Pennsylvania Bot
Blast 2008 in Bloomsburg, PA on
July 12th. Seventeen bots were
registered at press time. For more
details, go to www.dwrobots.
com/tournament.html.
War-Bots
Xtreme
will present
WBX-V
“Taking the
Fifth” on July
26th in
Saskatoon,
Saskatchewan, Canada. Nineteen
bots were registered at press time.
For more details, go to www.war
botsxtreme.com.
The North East Robotics Club will
present House of Benson –
Barnyard Brawl in Winchendon, MA,
on July 26th. Thirty-six bots were
registered at press time. For more
details, go to www.nerc.us.
Roaming
Robots
will present
Guildford
2008 in
Guildford, England on June 15th,
and UK Champs 08/RAF Fairford in
Gloucestershire, England on July
12th and 13th. For more details, go
to www.roamingrobots.co.uk.
RoboCore will present Winter
Challenge 4th Edition in
Amparo, Sao Paulo, Brazil on
July 26th–27th. SV
EVENTSResults and Upcoming Events
CombatZone.qxd 5/29/2008 2:33 PM Page 33
... including car audio, home audio, cell
phones, DVD players, laptops, digital
photo and video recorders, and of
course, massive plasma TVs. There was
a 150 inch TV at the Panasonic booth
that was the talk of the show. Imagine
a TV as big as a queen-sized bed
hanging on your wall? Seems like one
would have to reinforce the wall just to
keep it from falling down.
Most of the booths that are
technology specific are organized into
Tech Zones, such as USB, ZigBee,
Blu-ray Disc, HDMI, Mobile Internet and
WiMAX, IPv6, Sustainable Technologies,
CES 2008Robot RoundupCES 2008
As usual, in the second week of January,over 100,000 technology lovers convergedon Las Vegas for the 41st annual
Consumer Electronics Show (CES). The showwent on from 8 AM to 5 PM for four days, andeven then, it was almost impossible to seeeverything. CES took up 1.8 million squarefeet of trade show space, spanning all of themajor convention centers in Las Vegas. So muchwalking is involved for the attendees, you caneasily blow out your feet unless you are wearingrunning shoes.
Just about every electronicconsumer device is
represented at CES ...
by Ted Larson
34 SERVO 07.2008
Photo 1
Larson.qxd 5/30/2008 12:08 PM Page 34
and finally, Robotics. With just a few exceptions, most of
the robots and robot companies were on display in the
Robotics Tech Zone or in nearby booths.
The biggest exhibitor in the Robotics Tech Zone this
year was WowWee (www.wowwee.com). Every year they
seem to have many innovative, new designs and this year
was no exception. The most noteworthy items they brought
out were the Femisapien, Tribot, and Rovio. Femisapien is a
female counterpart for the popular Robosapien. She
dances, poses, and with her 9x degrees of freedom is
capable of 56 interactive functions. They had a nice demo
with three of them line-dancing together (Photo 1). She has
a learning mode where you can pose her and learn
sequences for playback, which seems like endless fun. I
thought the best feature of all was that when brought in
proximity to a Robosapien, she is the boss and tells him
what to do (sounds a bit like my wife). With an MSRP of
$99, I can see her ending up on the desks of many geeks
for fun and show.
Tribot (Photo 2) certainly received the most attention
out of the WowWee group, with the TV crews swarming
around him to get some footage of him doing his demo. I
was really surprised at how much personality he had when
they switched him on. He has animated ears and a pop-top
head, and goes on and on about how great it is that you
rescued him from his packaging when you turn him on for
the first time. He has an omni-wheel, holonomic drive
system which seems to be a new theme for WowWee
robots. Several of their newer products are now sporting
omni-wheels, including Rovio. Rovio is a WiFi capable,
omni-wheeled robot with a camera and navigation
capabilities. It can be tele-operated over the Internet,
with live streaming video of what it sees. The notable and
unique technology item here is that it is using the Evolution
Robotics (www.evolution.com) Northstar 2.0 system
for navigation.
Northstar is like “micro-GPS” for a robot. It uses
constellations of infrared energy beamed onto the ceiling
from a fixed point to determine its location within a room.
Rovio is the first use of this technology in a low-cost,
consumer package and it is quite impressive. One can set
waypoints for Rovio within the room and it easily find its
way back to them, even if the robot is picked up and
moved. At a retail price of $299, it is quite amazing that all
this technology can be packed into such a cool little robot.
Since I am on the topic of indoor positioning, it is a
good time to mention the booth of Hagisonic. Hagisonic
(www.hagisonic.com) is a Korean sensor manufacturer
which makes an indoor positioning system for robots called
StarGazer. StarGazer analyzes the image of an infrared ray
which is reflected from a passive landmark with a unique
ID, mounted on the ceiling. From this landmark, it is able to
determine its repetitive position down to 2 cm of accuracy.
The technology is similar to that of Evolution Robotics
Northstar system, although Evolution does not need to stick
anything to the ceiling. StarGazer is currently manufactured
as a module you can simply mount in a robot, place the IR
projectors in the room with the passive landmarks, and you
are ready to go. They had a nice demonstration of two little
robots navigating around on the floor, avoiding obstacles,
and mapping their positions (Photo 3).
Meccano showed their new additions to the Spykee
(www.spykeeworld.com) robot line-up. All the Meccano
robots are being sold under the ERECTOR brand as a robot
CES 2008 Robot Roundup
SERVO 07.2008 35
“The biggest exhibitor in the RoboticsTech Zone this year was WowWee ...”
Photo 2
Photo 3
Larson.qxd 5/30/2008 12:08 PM Page 35
Erector set. The four new robots in the line are Spykee Cell,
Spykee Miss, Spykee Vox, and Spykee Micro, three of which
are designed to cradle your iPod, and allow it to be voice
controlled and give it some personality (Photo 4). Spykee
Cell can be controlled from your cell phone via Bluetooth
and is targeted at both boys and girls. Spykee Miss is an
emotional electronic friend targeted at girls that gives you
advice when you ask her a question. Spykee Vox is also
voice controlled, an interactive friend, and can be either a
hero or a villain. It is targeted primarily at boys. Spykee
Micro is a small, little remote controlled robot that looks
similar to its larger counterparts, but is primarily just for
driving around and making noise. Again, all the robots are
kits — in the spirit of the ERECTOR brand — and some are
easier to assemble than others. When we were packing up
at the end of the show, the Meccano people were looking
to lighten their load for their trip home, so they gave us
several Spykee Micro kits. I brought two assembled units
home, and had great fun with my four-year-old daughter
having robot races in the hallway with them.
About 50 feet from the Robotics Tech Zone was the
iRobot booth. Among all the consumer robots they showed,
the two that were the standouts were the iRobot Looj
Gutter Cleaning Robot (Photo 5) and the new iRobot
Roomba 500. The Looj has piqued my interest ever since it
was announced, although I had never seen one in person
before. I have heard many rumors about what it can and
cannot do, so I thought I would ask the tough questions,
and see if I could clear some things up. In a nutshell, the
Looj is a remote controlled robot that is designed to be put
in a gutter and run up and down to dislodge any debris,
using a rotating rubber agitator. The idea is you climb up
the ladder to the corner of your house, put the Looj in the
gutter, and run it up each gutter section, thus minimizing
CES 2008 Robot Roundup
36 SERVO 07.2008
Photo 4
Photo 5
Photo 6
Larson.qxd 5/30/2008 12:09 PM Page 36
the number of times you have to go up and down the
ladder. They had a nice little demo with a piece of roof, a
gutter mounted to it that was filled with plastic leaves, and
they would drive the Looj down it and it would throw the
leaves all over the aisle in front of their booth (Photo 6). It
was great fun to see it go.
After asking many questions, I came up with all the
things it cannot do, to dispel any myth making. It cannot
climb the downspout, you cannot just throw it up on the
roof and let it do the rest, it cannot go around the corners
in your gutters, it is not compatible with ancient gutters,
with weird dimensions, and it won’t do the job all by itself
while you sit down on your lawn with a glass of lemonade.
What it can do, it does very well, and is quite amazing. Its
paddle is capable of blasting through all kinds of gunk in
your gutters, like pine needles, twigs, and sludge. If your
gutters are a standard 2-1/4” size, it is capable of driving
underneath the straps that hold the gutter to the house,
so you can clean long sections. If your house was perfectly
square, you would only need to ascend and descend the
ladder four times, thus minimizing your risk of life and limb
by falling off the ladder. It is certainly better than the old
method of climbing up there with gloves and a plastic
scoop, and at only $99 for the base unit, it is cheaper than
most lawn and garden appliances.
The iRobot Roomba 500 Series (Photo 7) was there,
driving around a little test carpet that anyone could scatter
all kinds of debris on, and it would happily slurp it up. Every
time I see a new version of the Roomba I think, okay, what
now, seen this before, ho-hum. However, this one has some
great new features that would make me upgrade. It has
anti-tangle technology, that detects if it sucked up a carpet
fringe or an electrical cord, and automatically backs it out
of the beater-brush before continuing along and restarting
to clean. It has upgraded bump switches which give it a
lighter touch to keep it from scuffing the baseboard or
furniture. Also, it has a new Virtual Wall, called a
Lighthouse, that the robot interacts
with to allow it to be contained to one
room until the room is clean, which
then allows it to move onto the next
room and so on, and so on. So, one
robot can clean multiple rooms, and
know when it has completed them all.
At $349, it is in line with the pricing
of previous Roomba robots, and offers
significant improvements without a
significant increase in price.
Roboware (www.roboware.
com.hk) had a booth in the Tech
Zone, where they were showing off an
impressive looking, three wheeled,
holonomic drive humanoid named E3
(Photo 8). I guess 2008 is the year for
holonomic drive humanoids?!?!
Roboware was founded by Mike Kim,
who previously was one of the
researches on the Canadarm space
robot on ISS, was part of the Hubble Telescope rescue
project, and has contributed to some WowWee projects
such as RSMedia, Elvis, and RSG products. According to
Mike, E3 stands for Education, Entertainment, and Emotion,
which makes it a platform much like a video game. E3 can
express its emotion through motions (head, arms, body,
wheel), light, and multi-media with customized content.
It has five login modes: Baby, Teen, House-Keeper, Single,
and Silver. Each mode has its own unique and updatable
personality according to the user’s age. E3 has WiFi built in
so it can be controlled remotely via the Internet and
through its ad-hoc networking capabilities can be voice
controlled, or stream or playback live video. It is even
capable of doing Sykpe teleconferencing. E3 has a big 5”
LCD mounted in his chest and runs Windows Mobile
edition, so he can do many PDA-type functions, as well.
The retail price range of E3 will be between $1,500-$2,000
and he will be available in the US around November of
this year.
Robotis (www.robotis.com) returned to CES again this
Photo 7
Photo 8 Photo 9
CES 2008 Robot Roundup
SERVO 07.2008 37
Larson.qxd 5/30/2008 12:10 PM Page 37
year with yet more new
things to show, such as
an updated version of
their Bioloid (www.
bioloid.com) educational
robot kit, their Dynamixel
high-performance servo
line, as well as their new
URIA Robot (Photo 9).
The Dynamixel servos
are designed specifically
for robotic actuator
applications, and are
networked together using
a communications bus
such as RS-485 or TTL
signaling. They are
powerful, metal geared
servos with torque up to
64 kg-cm. The Bioloid kits
(as well as URIA) are
constructed from these
servos. URIA stands for
Ubiquitous Robotic
Information Assistant, and
is designed as a research
platform for working
with humanoids. It has
a fully embedded PC onboard, running Windows XP, with
peripherals such as USB, LAN, Camera, VGA, WiFi, and a
microphone. He has a nice big LCD in his chest so you can
see what is going on with the PC.
Other interesting peripherals include a Passive
Infrared Sensor (PIR) and a six-axis gyro for measuring
motion. The robot stands 22 inches tall and weighs about
12 pounds. In comparison to most of the Robo-One type
humanoids, he is really, really big. They didn’t give exact
pricing on this monster humanoid, but they were quite
specific that it is designed for researchers and not the
hobbyist. With all the servos and PC onboard, I don’t
imagine he is going to be inexpensive.
OLogic was there with plenty of interesting robots to
show (www.ologicinc.com). OLogic is an outsourced
research and development company with a focus on
robotics, that I co-founded with Bob Allen. Of course, we
brought out some balancing robots to demonstrate our
capabilities to design difficult control systems. On the first
day of the show, we realized we could place one on top of
another and do a Las Vegas acrobatic act, in true Vegas
style (Photo 10). Needless to say, it always attracted a
crowd and the TV people whenever we stacked them up.
Dean Kamen, the inventor of many things including the
Segway, came by and we were able to snap some photos
of us with Dean and the balancing robots (Photo 11).
NPC Robotics (www.npcrobotics.com) commissioned
OLogic to build a robot to demonstrate a device they have
been reselling, called a Ribbon Lift (Photo 12). A Ribbon Lift
is a device that takes three stainless steel ribbons rolled up
on a spool like a tape measure, uses a motor to unwind
them, and stitchs them together into a self-assembling,
triangular shaped pole. Since we just finished the robot
before CES, we brought it out to show off. The robot is
appropriately named “Giraffe” due to its long neck it can
extend. The lift mounted in the robot is capable of raising a
50 pound load to 15 feet, and can collapse down into a
spool eight inches high by 20 inches in diameter. It is quite
amazing to see it unfurl, and some people commented that
it seemed like magic, like Ali-Babba’s magic rope trick. We
mounted a WiFi camera on the top and had it feeding a
big plasma display to demonstrate its use for surveillance
applications. We are looking forward to building some
robots using the larger version of the Ribbon Lift that can
lift a 500 pound load 25 feet in the air.
Two robots I missed at CES this year, but heard about,
were robots that showed up for just one day to make a
cameo appearance in the Robotics Trends booth (www.
roboticstrends.com). They were Pleo (www.pleoworld.
com) the Camarasaurus, made by UGOBE, and Zeno the
Revolutionary Robotic Friend by Hanson Robotics (www.
zenosworld.com). It was a bummer I missed them both,
but there was so much
to see, and certainly
one couldn’t see it all.
Hopefully, I will be able
to catch up with them
both next year. SV
Ted Larson is the CEO ofOLogic, Inc., and an activemember in the Home BrewRobotics Club of Silicon Valley.OLogic is an embeddedsystems research anddevelopment company witha focus on robotics. OLogicis currently working withclients across a wide spectrumof application domains suchas consumer electronics,toys, medical products, andeducation (www.ologicinc.com).
CES 2008 Robot Roundup
38 SERVO 07.2008
Photo 10
Photo 11 Photo 12
Larson.qxd 5/30/2008 12:12 PM Page 38
Getting a valid lower resolution reading of the encoder
is certainly better than high resolution unreliable data.
I needed to know how far the motors really moved but
didn’t necessarily need to know with as high of a resolution
as the encoders were providing. So, the task at hand was
a way to lower the resolution enough so that I could
always count on the readings and help keep track of the
movements. A bit of encoder resolution may be lost but it
should still be close enough for this particular project.
Symptoms oof tthe PProblem
I was watching the
encoder counts while running
some robot drive motors.
During the initial bench
testing, the motors weren’t
running at full speed and the
results I saw were just as
expected. However, things
got interesting when I started
ramping up the speed. A very
peculiar thing started happen-
ing. The encoder counts
started to rise as expected
but as the motors sped up,
the counts started going backwards! As it sped up some
more, it counted forward again. This cycle continued back
and forth a bit and then the counts were completely erratic.
It appears that the encoder was exceeding the polling time
used by the controller and would start missing pulses at
higher speeds. Obviously, the encoders were not matched
up well with the controller. I’ve seen this happen with my
robot drive base and also when I was using some salvaged
encoders from HP scanners and DeskJet printers. Whenever
you see symptoms like this, it should throw up a red flag and
make you take a look to see if this may be the problem.
Encoder processor board (component side). Encoder processor board (solder side).
One of the joys of the robotics hobby is mastering the art of interfacing. A lot of the parts arealready in front of us and we just need to make them work together. Recently, I ran into aproblem with a pair of quadrature encoders for the drive train on one of my robots. Theencoders themselves worked fine and were generating perfect quadrature outputs. However,they were sending out data faster than the controller could handle at higher speeds. As aresult, the encoder readings were worthless and could not be trusted.
SERVO 07.2008 39
by Robert Doerr
Doerr.qxd 6/3/2008 1:08 PM Page 39
40 SERVO 07.2008
Methods oof CCorrecting ttheProblem
There are a few different methods of fixing this
problem. In a nutshell, we just need to reduce the number
of transitions of the encoder per revolution. Obviously, the
encoder itself could be swapped out with a lower resolution
one. If feasible, it may be possible to replace just the
encoder disk with one that has a fewer number of holes.
Another option is to change the physical placement of the
encoder within the drive train. When it is directly attached
to the armature of the motor, it may send out too many
pulses. If it was moved downstream to the wheels
themselves or at some point in the gear train, it would slow
down the speed of the encoder. It will still be sending the
same number of pulses per revolution of the encoder but it
will be rotating slower so we get the effect we’re after.
Instead of altering the mechanics of the encoder — which
isn’t always an option — we can look into electronic means
of scaling the values. At first, I considered making something
up with standard logic ICs but an easier and more flexible
option was to use a small microcontroller to help match up
the readings. Whatever method is selected, we would like
the encoder to supply as high as possible a resolution
without sending them too fast for the controller to handle.
Microcontroller tto tthe RRescue
I’ve run into this problem with other encoders and
controllers. I wanted a flexible solution so I decided to use a
small microcontroller to scale the encoder readings. This
ended up being an excellent solution that can be used for
other projects, as well. I selected an SX28 processor and
wrote all the code in SX/B. This development went really
fast. I started building the encoder scaling board one
evening and had a working prototype with the core
functionality the next day. Everything is handled by the
single SX28 chip which costs under $3. A few more
features were then added and the code cleaned up to
make it more presentable.
One of the extra features is the ability to allow a host
controller to change the scaling factor on the fly. Since it
will accept commands via serial connection, I also added a
resonator for the clock timing to ensure the serial communi-
cations would be reliable. This microcontroller will be
installed in between the existing encoder and the controller.
This way, it can monitor the encoder, condition the signal,
and output a virtual encoder signal to the host controller.
Quadrature EEncoders 1101
Many of you already know how tachometers and
quadrature encoders work, but for those who don’t, here is
a quick review. A tachometer signal only has one signal and
therefore only provides speed information and not any
directional information. It will only tell how fast something
moved but not any details about the direction of travel. It
can be used to get an estimate on distance traveled as long
as the direction is known ahead of time. However, a problem
can come up if the tachometer stops at a transition (edge).
If there are any vibrations, it can toggle state back and forth
and mistakenly give the impression that it is moving. It is
more suited to regulate the speed of a motor where distance
/direction are not important; just the speed is critical.
Adding a second channel makes all the difference! A
quadrature sensor will have two signals 90 degrees out of
phase. These two signals are commonly referred to as
Channel A and Channel B. With these, both position and
direction can be determined. The direction is determined by
comparing if Channel A is leading Channel B or if Channel
B leads Channel A. The distance can be computed by
keeping track of the counts and factoring in the direction
of movement. Velocity can be calculated by counting the
number of pulses per second. I’ve seen some references to
encoders that state: “If A leads B, for example, the disk is
rotating in a clockwise direction. If B leads A, then the disk
is rotating in a counter-clockwise direction.”
That may be true for some encoders, but needs to be
verified for the particular encoder being used. I prefer to
just think of them as two channels of information and look
at which one is leading, then match that to the actual
direction of how it is installed in the robot. The clockwise/
counter-clockwise description isn’t something that lends
itself well to straight quadrature encoders, so keeping it
generic works out well. After all, it shouldn’t matter if it is
clockwise/counter-clockwise, right/left, up/down,
forward/back, etc. The important part is that two distinct
directions can be determined; the rest is relative.
Look at the examples of output from quadrature
encoder, through a few cycles.
Chan A 0 1 1 0 0 1 1 0 0 1 1 0
Chan B 0 0 1 1 0 0 1 1 0 0 1 1
Encoder assembly on robot base.
Doerr.qxd 6/3/2008 1:10 PM Page 40
Notice that if you follow the chart from left to right
and then from right to left you’ll see that one channel will
lead the other and that is what can be used to determine
direction.
How tthe EEncoder SScalingProgram WWorks
Using a microcontroller really makes this solution
flexible. As a starting point for this program, I used the
example in the SX/B help file for reading an encoder and
displaying it on a set of seven-segment displays. Since no
display is involved, all code relating to the display was
removed. The remaining code to watch an encoder became
the basis to build upon. Instead of just incrementing and
decrementing a counter for the encoder, we just need to
keep track of a small count which ends up being the
number we’re scaling the encoder value by. This will then
be used to walk up and down the virtual Channel A and
Channel B of our scaled encoder output. Whenever we
rollover our count of the scale factor, we then update
(either up or down) the count of our virtual encoder on
the output.
Upon start-up, the program does a bit of housekeep-
ing. It will check the status of four DIP switches to get the
initial scaling factor. If the scaling factor is 0, then no
encoder processing occurs and nothing gets passed to the
host. It made sense because micros don’t like dividing by
zero. This can be useful, more for troubleshooting, though.
If the scaling factor is 1, then we end up just passing the
values from the encoder to host as they are. After all, any
number divided by 1 is the same number. For any other
value (2-15), the encoder reading will be scaled by that
amount. In other words, if we have a DIP switch setting of
3, then it takes three transitions of the real encoder to
make one transition of our virtual one on the output of the
SX28. A setting of 15 means it would require 15 transitions
of the real encoder to make one transition of our virtual
one. The scaling factor goes like this:
DIP Switch Description
0 Encoders off
1 Encoders passed as-is to host
2-15 Encoder scaled down by number specified
There are also two DIP switches used to specify the
direction of the encoders. This is useful if the encoder is
going in the wrong direction. Instead of swapping any of
the wiring for Channels A and B, the DIP switch for that
encoder can be flipped to correct the direction. This feature
was easy to implement and makes this an even more
flexible gadget.
All of the heavy lifting is done in the ISR (interrupt
service routine). The main program looks for commands
coming in from the serial port to either change the scaling
factor or reset it to the ones specified by the DIP switches.
When looking at the source code in the ISR, we can
focus on half of it since the code for the second encoder is
exactly the same with the exception of the pins used to
watch the encoder and the output pins of the virtual one.
Schematic of encoder processor board.
SERVO 07.2008 41
Doerr.qxd 6/3/2008 1:11 PM Page 41
42 SERVO 07.2008
A LLook IInto tthe IISR
The initial ISR code deals with receiving serial data in the
background and buffering it. After that code is done, the
first thing that is checked is the scaling factor. If the scaling
factor is 0, then nothing needs to be done and we just exit
the ISR. Otherwise, we call the code to check and process
the encoders. There are a couple of important points here.
First, whenever you put code within an ISR routine you
must make sure there is enough time to execute the code.
It must all run within the ISR interval allocated to the ISR
routine. If you have too many instructions in there, you’ll
have to find ways to optimize your code or make the interval
longer so that you can execute more instructions in the ISR.
In the program presented here, it may seem odd to see
a GOSUB within the ISR. The code that is called still
executes within the ISR but needs to be moved to another
bank of memory due to the way SX/B structures the
compiled program. By moving things around, it resolved an
SX/B error on Pass 2. “Address xxx is not within lower half
of memory page.” I’ve had good results with SX/B so far,
and when errors like this crop up they can often be resolved
by re-organizing some of your program.
The code to process the encoder starts out by reading the
current value of the encoder port and masking off the bits so
that the current states of Channel A and Channel B on the
first encoder are used. Then, this value is XOR’d with the
previous encoder state. If there is no change in state, then the
value will be zero and we end up dropping down to check
the next encoder. If there was a change of state, then we
need to figure out what the direction of the change was.
This is again accomplished with our friendly XOR instruction.
In this case, we shift over the old state by one bit before
performing the XOR. We just need to compare bit 0 of one
channel to bit 1 of the other. It doesn’t matter which one you
use as the base, as long as you understand that using the
opposite set of bits will switch the direction of the encoder.
In the original program, it would see if the result from the
XOR operation was 1 which would specify to decrement
the counter. A 0 would then mean the counter should be
incremented. Instead of using a hard coded value, it compares
the XOR’d value with a DIP switch. This way, if the encoder
is going the wrong way, a flip of a switch will correct it! No
wiring changes or coding changes will be required.
Awh, YYou CCount FFunny
Whenever we decrement our counter so it rolls over or
increment it past our scaling factor, we need to update our
virtual encoder values on the output. When I did this, it was
late and I just updated a simple counter from 0-3 and sent
that value out as the scaled value. When I tested it, the
encoder output would only change by one up or down but
that was it. Upon looking at the code, I realized what I had
done. I forgot about counting funny. At least that is what my
kids would say. Instead of counting 0, 1, 2, 3, the proper
count was more like 0, 1, 3, 2, etc. This was due to the
gray encoding where only one bit can change status at a
time. This was easily fixed by using my counter as the index
for a LOOKUP command. This would then take the value that
was looked up and present that at the output. This results in
the correct gray code as the output for our virtual encoder.
The processing of the second encoder is identical. It
starts out slightly different, however, because the second
encoder is on a different set of pins. To accommodate that,
it has a slightly different mask of %00001100 to isolate the
two bits we need. Those two bits are then shifted right two
bits which will put them in the proper position so all the
calculations are the same as for the first encoder. The result
is then presented to the host controller on a separate set of
pins for the second virtual encoder.
The EExtras
Whenever I have leftover pins available on a microcon-
troller, I always seem to find a use for them. One of the
features I wanted to add is the ability to alter the scaling
factor on the fly. To accommodate this, one pin is used to
receive serial data from the host controller. The command
structure follows the AppMod style for compatibility with
other modules. The header is “!ES” for Encoder Scaler
followed by an address 0-3 and then the command. The
address must match those selected
by a pair of jumpers connected to
RC6 and RC7. If the address
doesn’t match, it will ignore the
command and wait until something
is directed toward it. The exception
is an address of 255 which would
broadcast out to all the modules of
this type, regardless of their config-
ured address. At the moment, there
are only two commands supported.
The command “S” is a scale value
followed by a binary number 0-63.
Anything higher than this gets
limited to the highest scaling factor
HP encoder assembly.High resolution encoder disk.
Doerr.qxd 6/3/2008 1:12 PM Page 42
of 63. This new scale value
overrides whatever value was
used at start-up from the DIP
switches. This is useful if a
higher scaling factor is needed
than what’s available on the
DIP switch or for changing the
scaling factor on the fly. The
“R” command will reset scale
value to the one specified by
the DIP switch setting. In a
future version, a couple more
commands may be added to
return a version number to
the host and also one for
returning the current scaling factor.
Conclusion
Adding an extra microcontroller to offload tasks can help
make the overall programming of the robot easier by letting
the main controller focus on higher level tasks. They are also
useful to handle odd interfacing and protocol issues that
come up. One example is the speech translation device
covered in the December ‘07 issue of SERVO. Another is
this encoder processor to help address a problem with the
data from a set of encoders. With the addition of this
encoder scaling processor, some encoders can now be used
for controlled closed loop movements at any speed. This
allows the encoders and host controller to work well
together. There are multiple ways of accomplishing the
same goals and using a microcontroller made sense for this
particular project. Keep those robots alive! SV
Robert Doerr can be reached via email at [email protected].
Dual I/R sensor withlinear encoder.
RobotWorkshop (Author’s website)www.robotworkshop.com
SX28 series processorsOffers free software development tools like SX/B
www.parallax.com
Online user forum for the SX series of microcontrollershttp://forums.parallax.com/forums/
Wikipedia article on encodershttp://en.wikipedia.org/wiki/Rotary_encoder
National Instruments article on encodershttp://zone.ni.com/devzone/cda/tut/p/id/4763
WEB RREFERENCES
SERVO 07.2008 43
Doerr.qxd 6/4/2008 5:24 PM Page 43
44 SERVO 07.2008
This month, we’ll pull together what it takes to design,
build, and code a heavy duty DC motor driver module.
First, we’ll look at the electrical theory behind the DC motor
driver electronics. Then, we’ll build up the DC motor driver
module’s “intelligence” and meld it with the DC motor
driver’s “brawn.” If all of that passes the smoke test, we’ll
code a simple RS-232 interface, which will allow you to
control the big DC motor with simple serial commands.
The DC motor driver IC of choice for this project is the
Allegro MicroSystems A3959. The A3959 is a DMOS Full-
Bridge PWM Motor Driver IC. Before we begin our DC motor
driver IC walk-thru, let’s take a look at the problem at hand.
Big Mama Gearmotor
The behemoth you see in Photo 1 is an Anaheim
Automation BDPG-60-110-24V-
3000-R326 DC brush planetary
gearmotor. This motor is really
not a “problem.” It’s actually our
project design point. The BDPG-
60-110 weighs in at four pounds,
10 ounces. From shaft to tail, the
BDPG-60-110-24V-3000-R326
measures in at 8.08 inches. The
planetary gear section is 2.65
inches in length while the shaft
adds 1.10 inches to the overall
length. The actual motor cylinder
comes in at 4.33 inches in length.
The BDPG-60-110’s maximum diameter at the motor cylinder
is 2.36 inches.
The BDPG-60-110’s name tells much of its story. All of
the planetary gear motors in the BDPG-60-110-24V-3000-
R326’s class share the same part number including the “R.”
The numbers that follow the R provide us with more
information about the planetary gearmotor. The R326 is
the most powerful gearmotor in the bunch as it can provide
4,166 ounce-inches of continuous torque. The BDPG-60-110
can peak at twice the amount of continuous torque. The
326 also tells us what the gear ratio is. In our case, the
BDPG-60-110-24V-3000-R326 has a gear ratio of 326:1. At
326:1, the BDPG-60-110 rotates its shaft at a brisk 9.2 RPM
unloaded. If you work the gearmotor, the shaft rotation will
fall to a loaded value of 7.7 RPM. Those RPM figures may
seem too low to perform any real work. However, when
you add external gearing to the
BDPG-60-110, I can assure you
that heavy loads will move about
relatively quickly. The 3000
number in the BDPG-60-110’s
part number is the speed of the
motor before the gearbox.
I initially gave you the
BDPG-60-110-24V-3000-R326’s
dimensions in terms of inches.
However, in reality the BDPG-60-
110 likes to be described
metrically. The body diameter is
called out in the part number as
There are times when a standard hobby servo just won’t do the job.The same goes for small DC motors. Sometimes parts of aluminumhumans require a bit more torque than servos and low-load DCmotors can provide. In these cases, a hefty DC motor fills the bill.However, a meaty DC motor needs a beefy DC motor driver.
Fortunately, there is inexpensive and easyto use DC motor driver technology that isavailable to us that will drive heavy iron.
PHOTO 1. This is one heavyduty motor all packed up ina relatively tiny package.
by Fred Eady
Eady.qxd 6/4/2008 9:51 AM Page 44
60 mm. The motor cylinder length
is also part of the part number
and is specified as 110 mm.
The 24V in the part number
calls out a 24 VDC gearmotor
operating voltage. By the way,
BDPG = Brushed DC Planetary
Gearmotor. Now that we know
all about what our “problem” is,
let’s move to the next step and
learn about our “problem solver.”
The AllegroMicroSystemsA3959
I’m experimenting with the
BDPG-60-110-24V-3000-R326 and
likewise with the A3959. So,
instead of building up a
professional printed circuit board
(PCB) in the dark, I decided to base the initial tests on
official Allegro MicroSystems A3959 electronics. We will be
working with the hardware you see in Photo 2. Before I
describe the Photo 2 basic circuitry to you, let’s take a close
look at the A3959 itself.
The A3959 in many ways is a pumped-up A3979. Recall
that the A3979 output current is limited to ±2.5 amperes with
a maximum motor voltage of +35 VDC. The A3959 doesn’t
contain all of the A3979’s internal logic as the A3979 is
designed to drive stepper motors. However, the A3959’s
power grid is much heftier than the A3979’s. The A3959 is
designed to drive DC brush motors at voltages up to +50 VDC.
The maximum current capability of the A3959 is ±3.0 amperes.
Like the A3979, the A3959 is capable of controlling its
attached DC brush motor using pulse width modulation
(PWM). And again, like the A3979, the A3959 can be com-
manded to operate in slow, fast, and mixed
current-decay modes. The current-decay modes all
work in conjunction with the A3959 internal fixed
off-time PWM current-control timing circuitry.
I’ve used a bunch of motor control ICs. I’ve
also released my share of motor control IC magic
smoke. To help avoid the release of the A3959’s
magic smoke, its designers have outfitted the
A3959 with internal circuit protection. If the
A3959 gets a bit too hot under the collar (165°
C), it will shut itself down. To avoid hiccupping
on and off as it cools off, a bit of hysteresis is
built into the thermal shutdown protection.
In the course of building custom motor drivers,
one also has to build a suitable power supply
for the motor and the motor driver electronics.
I have also freed the magic smoke
of many a power supply compo-
nent in my years of working with
electronics. The A3959 relies on a
charge pump to help keep its
internal H-bridge conducting and
the motor shaft turning. To
provide a measure of safety when
it comes to the power source,
the A3959 monitors the supply
voltage and the charge pump
voltage for undervoltage condi-
tions. When a problem occurs,
the A3959 goes into shutdown
and disables the H-bridge drivers.
Okay, we’ve read the sticker
on the A3959 window. Now, let’s
kick the tires and open the trunk and look under the hood.
I’ll add some important detail to Figure 1 as we walk around
the A3959. Since the A3959 is in a DIP configuration on our
A3959 demonstration board, all of our references to its pin
locations will be based on the DIP package from here on out.
The A3959 SLEEP function is controlled by pin 22. Just
because the A3959 handles monstrous motor winding
currents doesn’t mean it can’t be included in a low-power
application. By driving the A3959 SLEEP pin logically low,
we command it to enter SLEEP mode. The majority of the
A3959’s internal circuitry including the regulator and charge
pump will be disabled while it sleeps. If we choose not to
employ SLEEP mode in our application, we must drive the
A3959’s SLEEP pin logically high using a 4.7K pullup resistor.
To understand the functionality offered by the EXT
MODE pin — which happens to be pin 15 of our A3959 —
SERVO 07.2008 45
PHOTO 2. This is a shot of the “brawn”of our DC motor driver. Beforewe’re done, we’ll add homebrewedintelligence to this picture.
FIGURE 1. Once you understand what the A3959is and what it can do for us, this figure doesn’t
seem that busy anymore.
Eady.qxd 6/4/2008 9:52 AM Page 45
46 SERVO 07.2008
we must first have a firm grasp on the ENABLE pin. If we
wanted to control the speed of a motor, we would feed the
PWM speed control signal into pin 10 (ENABLE) of the A3959.
When the incoming ENABLE PWM signal swings logically
high, the A3959’s selected H-bridge sink and source pair are
activated. The H-bridge sink and source pair is selected with
the logic level present on the PHASE pin. The A3959 PHASE
input is located on pin 3. By driving the PHASE pin logically
high or logically low, we select alternate sink and source
H-bridge DMOS pairs and dictate the rotational direction of
the motor shaft. Driving the ENABLE input logically low will
switch off the source driver or both the source and sink
driver depending on the logic present at the EXT MODE pin.
When the ENABLE pin is at a logically low level, this is
called the chopped cycle. The EXT MODE input logic
determines the current path during the chopped cycle.
For instance, when EXT MODE is driven logically low, the
opposite pair of selected drivers will be enabled during the
chopped cycle. This is called External Fast Decay Mode.
Conversely, when the EXT MODE pin is driven logically high,
External Slow Decay Mode is invoked and both of the sink
drivers are activated during the chopped cycle.
All of the switching of the H-bridge source and sink
drivers generates current spikes. The A3959 contains
circuitry to synchronize the activation of the source and
sink drivers versus the current drawn through the motor
winding. A current spike could erroneously reset the source-
enable latch. To filter out the current spikes, the A3959
simply ignores its motor winding current sensing circuitry
for a period of time when the spikes are known to occur.
Driving the BLANK pin logically high provides twice the
blanking (ignoring) time of driving the BLANK pin logically
low. The BLANK timing is set via the A3959’s pin 12.
How much BLANK time is twice as much? Well, that all
depends on what we hang off of the A3959’s ROSC pin.
The datasheet recommends an internal oscillator frequency
of 4 MHz. To utilize the services of ROSC, we simply hang a
resistor from pin 4 to VDD. Here’s how we come up with
the 51K ROSC resistor value you see in Schematic 1 that
provides the basis for the 4 MHz clock:
NOTES:1. LED1 AND LED2 - MOUSER 606-4302F5-5V2. SP233ACP 20-PIN DIP
+5VDC
+5VDC
VBB
+5VDC
+5VDC
+5VDC
C1.1uF
C13
.1uF
C3
.1uF
C14.1uF
C10
.22uF
C2.1uF
C9
.1uF
U1
PIC18F4620
123456789
1011121314151617181920 21
22232425262728293031323334353637383940*MCLR
RA0RA1RA2RA3RA4RA5RE0RE1RE2VDDVSSOSC1OSC2RC0RC1RC2RC3RD0RD1 RD2
RD3RC4RC5RC6RC7RD4RD5RD6RD7VSSVDDRB0RB1RB2RB3RB4RB5RB6RB7
U2
A3959SB
765
17
3
4
14
15
8
9
16
1311
20
18
12
10
23
24 2 1
21
19
22
GN
DG
ND
GN
D
SENSE
PHASE
ROSC
REF
MODE
GN
D
VDD
OUTA
PFD1PFD2
VBB
GN
D
BLANK
ENABLE
VREGVCP
CP1
CP2
OUTB
GN
D
SLEEP
C4.1uF
LED1
R310K
C5.1uF
LED2
R413K
R55.6K
MT1MOTOR DC
P1
DB9 FEMALE
594837261
ICSP CONNECTOR
123
456
123
456
R1100
U3
SP233ACP
12
320
11151610
1217
518419
6
7
9
T2INT1IN
R1OUTR2OUT
C2+C2+C2-C2-
V-V-
T1OUTT2OUT
R1INR2IN
GND
VCC
GND
+
C6 10uF
+
C8 47uF
C12 .22uF
R2 1K
C11 .22uF
C7
.22uF
R74.7K
R8
.1
R651K
SCHEMATIC 1. The PIC18F4620 isunderutilized here and that’s a
good thing. That leaves you withlots of I/O and memory resources
for your motor application.
Eady.qxd 6/4/2008 9:53 AM Page 46
fOSC = 204 x 109 / ROSC
4 MHz = 204 x 109 / ROSC
ROSC = 204 x 109 / 4 MHz
ROSC = 51K
Applying our clock frequency to the BLANK pin logic
level results in the following:
When BLANK = 0 tblank = 6/fOSC
When BLANK = 1 tblank = 12/fOSC
I’ll let you do the BLANK math. Recall that I mentioned
earlier that the A3959 used internal fixed off-time PWM
current-control timing circuitry. Well, now that we know
what the internal oscillator is doing, we can compute the
fixed off-time interval. The A3959 is factory set for a fixed
off-time of 96 cycles of the internal oscillator. That comes to:
Fixed off-time = 96 x (1 / 4 MHz) = 24 μs
The PFDx pins control the function of the A3959’s
Internal Current-Control Mode. Those switching spikes we
just discussed are detected at the SENSE pin. The SENSE
input is responsible for monitoring the motor winding current
and feeding that information into the A3959’s internal current
sensing/control circuitry. When an overcurrent event is
detected at the A3959’s SENSE pin (pin 17), the selected
internal current-decay method is invoked. The internal current-
decay method is determined by the logic levels of pins 13 and
11, which are PFD1 and PFD2, respectively. We already know
what the internal current-decay modes are. So, applying
logical low levels to both of the PFDx pins selects slow decay
mode. Conversely, when both PFDx pins are driven logically
high, we have selected fast decay mode. In slow decay mode,
both of the A3959 H-bridge sink drivers are turned on for
the entire fixed off-time, which we computed as 24 μs.
A combination of logic inputs on the PFDx pins provides
us with two mixed decay mode selections. Driving PFD1
logically high and PFD2 logically low will invoke fast decay
mode for 15% of the fixed off-time with slow decay taking
up the rest of the fixed off-time interval. Driving PFD1
logically low while driving PFD2 logically high will produce
fast decay mode for 48% of the fixed off-time and slow
decay mode for the remaining 52% of the fixed off-time
interval.
If this all seems a bit too much on the theory side, don’t
worry. We’ll have total program control over all of the A3959’s
inputs. That way, we can experiment with the logic levels
until we find a combination that suits the BDPG-60-110.
If you had the opportunity to check out my SERVO A3979
article, you already know about the A3959’s VREG pin and the
A3959’s charge pump as their functionality across devices is
identical. We need only hang a 0.22 μF capacitor from the
VREG pin (pin 23) to ground. The voltage associated with VREG
is generated internally and is used to operate the A3959’s
H-bridge sink drivers. The charge pump pins, CP1 and CP2,
also require a 0.22 μF capacitor connected between them
to assist in the charge pump operation. The charge pump
generates a gate supply voltage that is greater than the VBB
motor winding supply voltage. The gate supply voltage
drives the A3959’s H-bridge source drivers. Another 0.22 μF
capacitor is tied from the CP pin to ground to act as a
reservoir for the H-bridge source drivers. CP1 and CP2 are
represented as pins 2 and 1, respectively, on the A3959 DIP
package. CP functionality can be found at pin 24. Access to
the motor winding voltage input (VBB) is at pin 20.
A3959 load current regulation is a function of the internal
fixed off-time PWM control circuit working in conjunction
with the external sense resistor, which hangs from the SENSE
pin. When the OUTA and OUTB outputs (pins 16 and 21,
respectively) are activated, current flows through the motor
winding. The motor winding current increases until it reaches
a predetermined trip value. The current trip value is a direct
product of the value of the external sense resistor and the
voltage applied to the VREF pin. The A3959’s sense comparator
resets the source-enable latch when the current trip point is
reached. As a result, the H-bridge source driver is deactivated.
Recall that we use blanking to prevent the source-enable latch
from being reset at the wrong time by a current spike. Once
the source driver is turned off, the motor winding current
recirculates for a time equal to the fixed off-time interval.
During the recirculation time, the logic levels at the PFDx pins
determine which internal current-decay mode (slow, fast, mixed)
is invoked. The current trip value is calculated as follows:
ITRIP = VREF / 10RSENSE
Let’s calculate the ITRIP value from the values you see in
Schematic 1:
Using good old Ohm’s Law against the VREF pin:
Where VDD = +5 VDC
I = E / R
I = 5 / 18.6K
I = 268.8 μA
Voltage at VREF = 268.8 μA x 5.6K = 1.505 Volts
ITRIP = 1.505 x (10 x 0.1) = 1.505 amperes
We can crank up ITRIP if we want to as our BDPG-60-
110 can eat 2.2 amperes of current. What we have is fine
for now. In the process of computing ITRIP, we covered the
only pin of the A3959 we have not yet addressed: VDD. Pin
9 needs to be sourced with +5 VDC.
The A3959 DIP package is 24 pins deep. So, that leaves
a total of six pins we haven’t covered thus far. We can end
our A3959 walk-around right here as the remaining six pins
are all GROUND pins. Any internal heat that is generated is
dissipated through pins 6,7,18, and 19, which should be
directly attached to a heatsink pad.
The circuit for the A3959 motor driver is already laid
SERVO 07.2008 47
Eady.qxd 6/4/2008 9:53 AM Page 47
48 SERVO 07.2008
down for us on the demonstration board. So, let’s build up
our A3959 controller.
PICing an A3959 Motor DriverController
I’ve chosen the PIC18F4620 to perform the A3959
controller duty. If you’ve ever designed with a PIC micro-
controller, there’s nothing new for you here. In fact, the PIC
controller hardware is so easy, I could simply tell you to look
the circuit over in Schematic 1 and be done with it. As you
can see in Photo 3, the PIC hardware is so simple, I
hand-wired the PIC A3959 controller circuit on a perfboard.
I elected to leave the SLEEP pin alone and tie it to an
inactive state. I also chose to use the lesser PWM Blank
time (6 / fOSC ) by tying the BLANK pin to ground.
There are plenty of I/O pins to spare. So, if you want to
experiment with the control lines I’ve chosen to logically tie
to a static state, don’t be afraid to hook up the SLEEP and
BLANK control lines to the PIC. If you use my existing
control line code as an example, you won’t have any
problems coding in the extra control lines.
The real work involved with building up an A3959
motor driver controller is in the firmware. With that, let’s
begin our firmware build by associating the A3959 control
pins with their PIC18F4620 counterparts:
//*******************************************************//* A3959 PIN DEFINITIONS//*******************************************************#define PFD1 LATB0#define PFD2 LATB1#define ENABLE LATB2#define PHASE LATB3#define MODE LATB4
The names I’ve assigned to the PIC18F4620 PORTB I/O
pins should be very familiar to you. It would be nice if we
reduced the complexity of the PFDx selections, as well:
#define decay_slow PFD1 = 0; \PFD2 = 0;
#define decay_mixed_15 PFD1 = 1; \PFD2 = 0;
#define decay_mixed_48 PFD1 = 0; \PFD2 = 1;
#define decay_fast PFD1 = 1; \PFD2 = 1;
Using C macros to put human-readable names on the
PFDx selections will make life a bit easier if you want to
experiment with the PDFx settings. The same holds true for
the EXT MODE selections as well:
#define ext_mode_fast MODE = 0#define ext_mode_slow MODE = 1
The reason we are here is to turn the BDPG-60-110
motor shaft. So, it would be fitting to put together some
motion macros:
#define CW 1#define CCW 0
#define motion_CW ENABLE = 1; \PHASE = CW;
#define motion_CCW ENABLE = 1; \PHASE = CCW;
#define motion_HALT ENABLE = 0;
Note the use of the A3959 ENABLE pin to start and stop
the BDPG-60-110-24V-3000-R326. When you run your motor,
remember that clockwise and counter-clockwise rotation is
determined depending on how you attached the motor leads
to the A3959 OUTx pins. These CW and CCW settings worked
for me. The PHASE logic swaps the polarity of the OUTx pins.
If your CW and CCW directions are opposite of mine
here, it’s much easier to simply swap the motor leads than
recompile and reload the PIC18F4620.
With all of our A3959-to-PIC18F4620 definitions and
associations complete, we can add this bit of code at the
end of our initialization routine:
//*******************************************************//* INITIALIZE A3959 MOTOR DRIVER HARDWARE//*******************************************************
decay_mixed_15; // PFD1 = 1 - PFD2 = 0ext_mode_fast; // MODE = 0motion_HALT; // ENABLE = 0
I promised that we would also write some PIC firmware
that would allow us to control the BDPG-60-110 through
the A3959 controller’s serial port. I have coded up all of the
necessary EUSART firmware for the PIC18F4620. You can
see what I’ve done with the PIC18F4620’s EUSART by
downloading the A3959 driver firmware from the SERVO
PHOTO 3. It doesn’t getmuch better than this.I’ve taken to poweringsmall PIC projects like
this from a PC USB port.
Eady.qxd 6/4/2008 9:54 AM Page 48
website at www.servomagazine.com. Here’s the code
that will put the menu up in a terminal emulator window:
void show_menu(void){
cls();cls();printf(“%c[2;4H SERVO A3959 MOTOR CONTROL
MENU”,esc);printf(“%c[5;7H F - ROTATE CW”,esc);printf(“%c[6;7H R - ROTATE CCW”,esc);printf(“%c[7;7H S - STOP”,esc);
}
Entering an F, an R, or an S invokes the main routine code,
which is looping continuously:
//*******************************************************//* MAIN SERVICE LOOP//*******************************************************
show_menu();do{if(CharInQueue())
{bytein = recvchar();switch(toupper(bytein))
{case ‘F’:
motion_HALT;mdelay1(100);motion_CW;
break;case ‘R’:
motion_HALT;mdelay1(100);motion_CCW;
break;case ‘S’:
motion_HALT;break;
}}
}while(1);
The CharInQueue() function informs the main routine
that a character is waiting in the EUSART’s external buffer.
When a character arrives from the personal computer, we
retrieve it from the external buffer and parse it. If the
character is an F, we stop the BDPG-60-110-24V-3000-R326,
wait for 100 ms and rotate the BDPG-60-110’s shaft in the
clockwise direction. An incoming “R” stops the motor, waits
for 100 ms, and forces the BDPG-60-110’s motor shaft to
rotate in the counterclockwise direction. To stop the motor
shaft, we simply drop the ENABLE line to a logical low.
That’s all there is to it!
Spinning OutMy version of the A3959 motor controller is shown
attached to its demonstration board in Photo 4. When
you’re ready to put the A3959 to work in a real-world
motor driver application, be sure to solder the A3959 directly
to the PCB. The A3959 tabs need to be soldered to a
copper heatsink area provided on the PCB. Give the
heatsink area as much of the PCB’s copper as you can.
The download package firmware was written using the
HI-TECH PICC-18 C compiler and contains lots of goodies
you can use in other projects, such as timer manipulation
routines, timer interrupt handlers, serial communication
routines, and serial communications interrupt handlers. The
A3959 is a really robust and easy to use part. I have no
doubt you’ll have your aluminum human doing some heavy
lifting in no time flat. See you next time! SV
Fred Eady can be reached via email at [email protected].
Allegro MicroSystems — www.allegromicro.comA3959
A3959 Demonstration Board
Microchip — www.microchip.comPIC18F4620
HI-TECH Software — www.htsoft.comHI-TECH PICC-18 C Compiler
Anaheim Automation — www.anaheimautomation.comBDPG-60-110-24V-3000-R326
SOURCES
PHOTO 4. You’ll want to build up an A3959 motor driver boardwithout the socket if you plan to run a motor for an extended
length of time. It is important to make sure that the A3959heatsink tabs are soldered to the copper heatsink area.
SERVO 07.2008 49
Eady.qxd 6/4/2008 9:55 AM Page 49
In Part 1, we studied Loki’s mechanical construction from
PCB (printed circuit board) material. The controller board
mounts on top of the body.
Part 1 also mentioned that I was inspired to build Loki
because of his antics in walking and posturing. Another
reason I had for building Loki was to investigate subsumption
and behaviors. Simply put, behaviors are the actions taken
by a bot with given inputs. Loki will avoid an obstacle in its
path. Another behavior would be to follow (or avoid) a light
source. Subsumption is the inhibiting of one behavior by
another. However, more in-depth discussions of behaviors
and subsumption are beyond the scope of this article. I do
intend to port these ideas as ‘C’ functions into my hexapod
(Shelob), as well.
Controller BoardAlmost any controller board and processor can be
used on a robot this size. I had several bare QwikFlash
boards on hand I had purchased from the PICbook website.
This website (www.picbook.com) supports the book
Embedded Design with the PIC18F452 Microcontroller
written by John Peatman. I’m currently using the 18F4620
PIC, although the 18F452 discussed in John’s book can be
used, and possibly even an old 16F877, as well (untested
and limited). See the CA1.PDF document on the PICbook
website for construction, bill of materials, block diagram,
and a schematic of this fine board. Note that no hex file or
code is planned for the ‘877 chip at present. A hex file is
currently available for the ‘4620 PIC implementation.
The BookJohn’s book on the ‘452 is an excellent tutorial for
learning the workings of the 18F452, as well as the
18F4620 I used. And having a board to try out code on is
very helpful. Although John’s book uses assembly language
to test out the inner workings of the PIC, It is still quite useful
for C language developers and experimenters. Microchip
thought enough of the book to give out copies of it as
prizes for their seminar classes at the recent Embedded
Systems Conference. Other prizes were the ICD2 in-circuit
debugger and PIC start boards. (Now I have an additional
copy to pass along to my oldest son, who is also a
hardware engineer and is interested in the PIC.)
The QwikFlash board with a ‘4620 PIC runs at 40 MHz,
has 64K of Flash, 3986 bytes of RAM, and 1,024 bytes of
EEPROM. Plenty of I/O bits, counters, and timers too for
our use! To control Loki — or any other small bot — I added
connectors for four R/C servos, two Sharp GP2D12 IR
In this second part of the Loki project, theQwikFlash controller board and its controlsoftwaRE will be examined. This is a very usefulboard for all kinds of robotic projects. I have two runningbots at this time and another one in the works!
Loki Crosses thePond — Part 2Loki Crosses thePond — Part 2
50 SERVO 07.2008
by Alan Marconett
QwikFlash board populated with LCD (on Shelob).
Marconett2.qxd 5/30/2008 2:14 PM Page 50
rangefinders, and a Devantech
SRF08 ultrasonic rangefinder in the
“prototype” area of this board.
The QwikFlash controller board has
an RS-232 level converter and a built-in
DB-9 connector for communications,
although I currently use just the TTL
lines for telemetry (via Bluetooth). With
it, I run a terminal interface program
called T2 on my PC to access Loki’s
small monitor program. I used the
monitor program to develop Loki’s
gaits and postures.
There is even an 8x2 character
LCD that can be added to the board,
although only the board on Shelob has
this part. The LCD is not currently used
on Loki. The Bluetooth (Blue SMiRF)
setup I’m using is from SparkFun, and
is great for freeing Loki from wires
(it doesn’t take much weight to off-
balance a small robot such as this).
Otherwise, a lightweight, three-
conductor cable can be used for
normal RS-232 communications.
The QwikFlash board requires 7 to
9 VDC, which I get from a 1,300 mAh
7.2V battery pack I salvaged. A 6V
battery pack would be sufficient if
you’d like to use a 9V battery for the
controller instead. I added three
1N4001 power diodes in
series to drop the voltage
from the battery pack closer
to 6V for the R/C servos I
used (servos don’t like too
much voltage). A modular
RJ11 connector to match
the Microchip MPLAB ICD2
in-circuit debugger cable is
also on the board. I used the
ICD2 to download and
develop the code for Loki.
MPLAB IDE v7.4 runs the
ICD2 and invokes the HI-TECH
Software compiler that I used.
Controller BoardConstruction
To build the QwikFlash
controller board, you can
follow the instructions in the
CA1.PDF document found on
the previously mentioned
PICbook web page. Some
comments are in order. If
you use a Bluetooth module,
SERVO 07.2008 51
Schematic 1. Drawingof Loki sensor, servo,and battery wiring.
Loki Crosses the Pond — Part 2
• Cheap walking robot, low cost parts, can be made at home• Loki is inspired by the efforts of David Buckley
http://davidbuckley.net/DB/Loki.htm.• Original construction was wood (I later found out)• My Loki is constructed of PCB material to a similar size• Currently using four Futaba S3004 R/C servos, need bigger knee servos• Battery is a salvaged six-cell Ni-MH 7.2V 1,300 mAh pack• Controller board is a $15 (bare) QwikFlash 18F4620 PIC board available from
www.picbook.com• 50 MHz, 64K Flash, 3K RAM, plus EEPROM• Bluetooth wireless for telemetry and monitor control• EEPROM gaits editable over wireless link• PIC programming via ICD2• Control program written in HI-TECH C, used to develop gaits• Two modes, autonomous and control via a small monitor program• Parser used to decode commands received by monitor• EEPROM commands save, view, and execute steps in sequences• Autonomous control currently consists of simple obstacle avoidance while doing
a simple walk• Sensors include two Sharp GP2D12 IR range finders and a SRF08 ultrasonic
rangefinder• Body and feet PCB material CAD designed and cut on my CNC’d Sherline mill• Loki’s gait is exaggerated due to the need to clear the toes of the overlapping feet• R/C servos are driven by two timers and interrupts in the PIC• Servo commands set new angle for servo and time to get to new position• Gaits are stored by strings of servo move commands, similar to those of the
Lynxmotion SSC32 servo controller• To walk, a simple array of six strings is repeated in an endless loop• More strings allow Loki to make turns• An FSM selects the strings to be used, and changes the string selection upon
recognition of an object by a sensor
LOKI Four-Servo Biped Robot Summary
Marconett2.qxd 5/30/2008 2:14 PM Page 51
you will not install the U1 MAX232 level converter IC.
Also not installed is U2, the MAX522 DAC, as we will be
using the I2C interface for our ultrasonic sensor. We don’t
need the connector on the bottom of the board, unless
you just want it.
Add Parts to the Prototype AreaTo interface to our four servos and two IR sensors, we
need to add some three-pin, single row, straight solder tail
headers. I used the same header stock used elsewhere on
the board. A six-position header is used for the Bluetooth
connections and a five-position header is used for the
ultrasonic rangefinder. These sensors are for the
autonomous operation, but you can run Loki without
them in the terminal mode.
Six resistors are needed. Four of the resistors are
in-line to the data pins of the servo connectors, while the
remaining two resistors are pull-ups for the I2C lines.
I used a three-position terminal block (optional) to
experiment with different batteries. You’ll want to provide
a direct path from the battery to the servos to minimize
52 SERVO 07.2008
Loki Crosses the Pond — Part 2
VDD
VDD
VDD
VDD
VDDPOT15 k�
potentiometerAlive LED
VDD
VDD
VDD
VDD
VDD
VDD
VDD
VDD
GND31
32
12
11
14
1
13
GND
OSC2
OSC1
MCLR
2526
1413
7
16
15
8
INT2INT1
(RB7)
(RB6)
(RC7)(RC6)
(RC5)
(RC3)
RC4
RC2
RC1
RC0
(RA5)
RA4
RA3
RA2
RA1
(RA0)
Unused
RB5RB4RB3
Unused
RB2RB1
RC1RC0
VDD
VDD
VDD
RE2RC3
GND 1
H2Expansion header
(See Appendix A2)
3579111315
246810121416
RC2RD2
RB0RB1RB2RB3RB4RB5
RC5RC4
B1/INT1GNDB0/INT0GND
GNDDACA
24
23
18 2
85
61
4 7 3
17
16
15
7
6
5
4
3
2
10
98
30292827
ERS 8 � 2 LCD
display
LCD1
"Nibble"interface
B7B6B5B4
SW3Pushbutton switch
Unused
RPG1Rotary pulse
generator(24 inc./rev.)
64
14131211
2
3
15
22
21
20
19
D8
D4
D5
D6
D7
GND
GNDC2/CCP1
GNDC1/CCP2
QwikFlashinstrument input
(bottom of board)
Protection circuitry
DACB
GNDE2/AN7
DIN
U2Dual 8-bit DAC
OutA
OutBSCLKCS
H3
H1Terminal
strip at topof board
RB0INT0
SDO
SDI
SPI
CC
PA
DC
SCK
CCP1
CCP2
AN4
AN0
AN7
Inte
rrup
ts
910
RTS*
CTS*
1112
3837363534
33
RD0
C1222 pF
C1322 pF
Yl10 MHz
SW1
D3
D1R2 � 1 k�
R447 k�
R3470 �
SW2RESET
*RTS & CTS can beconnected to unused
PIC18F452 pinsto support hardwareflow control of serial
data transfers.
R12 � 1 k�
Right LED
Center LED
Left LED
C8
C7
R11 � 47 k�
R1 � 470 �
R13 � 10 k�
R9 � 10 k�
R10 � 10 k�
R15470 �
R143.3 k�
R5 � 1 k�
R6 � 1 k�
R7 � 1 k�
R8 � 1 k�D2
CON3Power
connector
PowerLED
REG1
9 V in, 5 V out
� �
RD1
PO
RT
DP
OR
TC
PO
RT
BP
OR
TA
PO
RT
E
RD2
RD3
RD4RD5RD6RD7
RE2
RE1RE0
VDD
VDD
GND1
U3PIC18F452
40
39
J1Jumper forQwikBug
Forin-circuitdebugger
ForQwikBug
Deb
ugha
rdw
are
CON1Modular
connector
CON2DB9F
connector
U1MAX232A
UARTRXTX
C170.1 F�
C1 � 0.1 F�
C533 F�
C150.1 F�
C160.1 F�
C1433 F�
2
1
3C4 � 0.1 F�
C11 � 0.1 F�
C10 � 0.1 F�
4
5C2 � 0.1 F�
6
C3 � 0.1 F�
C6 � 0.1 F�
VDD
132456
32785
�
C9 0.1
F
MCLR
MCLR
VDDTMP1
Temperaturesensor
Schematic 2
Marconett2.qxd 5/30/2008 2:15 PM Page 52
noise. Install two or three 1N4001 diodes in series with the
battery if you intend to use the 7.2V higher voltage battery
pack. A bypass cap is sometimes needed on the servo
battery line. Another possible addition is a seven-pin,
double row, straight solder tail header for
the optional LCD display (follow
instructions in CA1). An external 16x2
LCD display could also be used. In
this case, you might want to put the
connector on the top of the PCB.
Current software does not utilize the
LCD display; and the RE0 and RE1
pins were usurped for use by the IR
sensors. These PIC pins will need to be
re-assigned if the LCD is used.
The above parts are all added to
the prototype area of the QwikFlash
board. Wire these per the “Servos and
Sensors” diagram in Schematic 1.
There are hole positions for four
miniature toggle switches on Loki’s
body. I’m currently using only one for
servo power. There is already a toggle
switch on the QwikFlash board for 5V
power, but it is wired after the 5V
regulator chip. Builders might want to
add a switch in the power line to the
QwikFlash board, or for a board that
does not have its own power switch.
CablesI used four 4” pre-made “jumper”
wires for the ultrasonic rangefinder
(cut two blue 8” lengths in half) and
six 6” yellow wires for the Bluetooth
transceiver. These are available from
SchmartBoard (the colors designate
the length) and have female pins for
.025” posts on either end. (These are
great for working on proto boards.)
The ultrasonic rangefinder cable will
need a CST-100 six-position connector
receptacle stuffed with six Crimp
CST-100s. A tool is available to crimp
the pins, or use a pair of needle-nose
pliers to crimp the pin on the wire
before inserting them into the
connector receptacles. You’ll also want
to solder in a five-position, single row,
straight solder tail header into the
backside of the ultrasonic rangefinder.
One of the other standard length
jumpers (red) would probably work for
the SMiRF, but I wanted a connector
body here. As an afterthought, I’d
have put one on the ultrasonic sensor
cable, as well.
ElectricalThe electrical system on Loki is simple. It consists of a
battery, switch, battery connector, and wiring. The free
ends of this wiring are to be terminated in the power
SERVO 07.2008 53
Loki Crosses the Pond — Part 2
ITEM/DESCRIPTION QTY SUPPLIER/PNQwikFlash board options• Blank PC board only 1 Micro Designs Inc./QF-QFPCB3.1• Parts kit for 452 demo board 1 Digi-Key/18F452-KIT-ND-OR-• Unassembled PC board and parts kit 1 Micro Designs Inc./QF-PARTS2• IC MCU Flash 32KX16 40 DIP 1 Digi-Key/PIC18F4620-I/P-ND
Available as programmed part from the author. (un-programmed)
Additional parts for prototype area of QwikFlash board• Rectifier GPP 50V 1A DO-41 3 Digi-Key/1N4001DICT• Conn Header .100” SINGL STR 36 POS 1 Digi-Key/S1011-36-ND• RES 2.7K ohm 1/4W 5% carbon film 2 Digi-Key/2.7KQBK-ND• RES 1.0K ohm 1/4W 5% carbon film 4 Digi-Key/1.0KQBK-ND• Qty. 10 5” jumpers and 20 headers 1 SchmartBoard/920-0006-01• Qty. 10 7” jumpers and 20 headers 1 SchmartBoard/920-0007-01• CST-100 six-position connector receptacle 1 Digi-Key/A19494-ND• Crimp CST-100 pins 6 Digi-Key/A19520-ND• Conn 2.1 mm female plug 5.5 mm OUT 1 Digi-Key/CP3-1000-ND
Sensors• Devantech SRF08 ultrasonic rangefinder 1 Super Droid Robots/TS-012-008• Sharp GP2D12 IR sensor 2 Lynxmotion/SIR-01
Servos and batteries• HS-475HB (76 oz in) standard servo 4 Lynxmotion/S475HB• 7.2 volt Ni-MH 1600 mAh battery pack 1 Lynxmotion/BAT-02• Wiring harness — battery connector 1 Lynxmotion/WH-01• 2.4 - 7.2 VDC Ni-CD and Ni-MH universal 1 Lynxmotion/USC-01
smart charger
Bluetooth• Bluetooth modem — BlueSMiRF RP-SMA SKU# 1 SparkFun/WRL-00158• Bluetooth USB module SKU# 1 SparkFun/WRL-00150• 2.4 GHz duck antenna RP-SMA SKU# 1 SparkFun/WRL-00145
Body parts• 0.25” dia. standoff RND 4-40 .625”L alum 8 Digi-Key/1839K-ND• 0.25” dia. standoff RND 4-40 .375”L alum 2 Digi-Key/2026K-ND• 4-40 x 1/4” Philips head screws 8• 4-40 x 5/8” Philips head screws 2• 4-40 nuts 10
• Approximately 150 sq in. 1/16” double-sided Digi-Key or surplusPCB board
• PCB copper clad 4.5” X 7” two-side 3 Digi-Key/PC41-C-ND• PCB copper clad 6 X 9” two-side 1 Digi-Key/PC53-ND
• Approximately 25 sq in 0.0625” 5052 (H32) Onlinemetals or surplusaluminum plate
• Servo angle brackets bend up from 2aluminum plate
• IR sensor mount 1/2” x 1/2” x 6” long 1aluminum angle bend up from aluminum plate
-OR-• IR sensor mount 1/2” x 1/2” x 6” long 1
aluminum angle
Parts List
Marconett2.qxd 6/4/2008 8:55 AM Page 53
connector. The red +V wire goes to the center connector;
the black -V wire goes to the shell. This connector allows
easy disconnect from the controller board. The battery
connector can be disconnected to allow connection of the
battery charger.
SoftwareNow down to the software issues. I’m an old hand at
the C language, and I naturally grabbed my trusty HI-TECH
compiler for the job. (Note that any one of several different
languages would work.) Although I’m not using one, a
boot loader would be a good choice for a ‘bot like this.
As mentioned, I use an ICD2 for programming, and have
to plug in a modular cable for this. Obviously with a boot
loader and wireless connection, no cables would be
needed! But don’t dismiss this simple umbilical cord; it is an
easy way to get started. In fact, I initially ran my Loki with a
battery pack lying on my desk. Having the weight of the
battery pack off-loaded allowed me to use some old Futaba
S3004 R/C servos I had laying around until I could
determine what size servos I needed. The S3004 servos at
the knees are too weak to lift up the body of Loki. You
could also use the Hitec RCD servos listed here:
Hitec HS-645MG 107 oz-in @ 4.8V, 133 oz-in @ 6.0V
Hitec HS-475HB 61 oz-in @ 4.8V, 76 oz-in @ 6.0V
Note: Futaba 3004 servos rotate the opposite direction
to Hitec HS-475HB servos! Be sure you account for this
if you change between the servo brands. I’m currently
making modifications to the code to accommodate both
rotations.
RTOSLoki’s controller program is basically a “baby RTOS”
(real time operating system), which means that there are
several tasks that run at the same time, managed by an ISR
(interrupt service routine).
The ISR is called at a regular
interval by a timer interrupt.
The ISR generates “system
ticks” that initiate various
background tasks. Also,
several peripherals are
supported by an ISR in the
background. The USART
and A/D converter are
examples of this, as are the
updates for the R/C servo
positions. The I2C FSM for
the ultrasonic rangefinder
relies on multiple calls from
the scheduler to avoid
“blocking” while waiting for I2C events. This RTOS is not
pre-emptive and only supports a fixed list of tasks; hence,
the baby moniker.
The current controller program (RTOS) is a bit eclectic
in that it has a monitor that accepts commands from a
console and also supervises an autonomous mode for
when the robot is on its own. I’ve mentioned the monitor
command to move the servos; there are also commands to
save/view/execute the servo positions stored in EEPROM,
and to read the sensors. The current autonomous mode
is in its infancy; it’s merely a simple obstacle avoidance
behavior for now. More is planned for it in the future.
ParserThe heart of the monitor is a simple hacked-together
parser to decode commands for Loki. Perhaps the most
important command is the R/C servo command which takes
position parameters for up to four servos (although I’ve
planned to allow up to eight servos) at a time. A servo
command is a simple string of ASCII characters (like
“#0P1200 #1P1500”) ending in a CR (carriage return) in a
format similar to that used by SSC (Serial Servo Controllers)
such as the Lynxmotion SSC32 servo controller. This is
convenient for me, as Shelob — my main hexapod — uses it.
Add to the command a parameter for the required time of
the move (“T1000”), and we have a means of commanding
1-4 servos to move in what’s called in CNC parlance a
“coordinated motion” (all axis motion starts and ends at the
same time). This is very convenient for moving the legs of
Loki, or any robot, for that matter.
Loki currently recognizes the following commands or
parameters:
• REV Loki revision # sign-on
• ESC Clear error
• #n Servo #
• + - Offset of servo position
• Tnn Time
• Pnn Servo position
54 SERVO 07.2008
Loki Crosses the Pond — Part 2
Top view of Loki (new legs). Sonar and IR sensors.
Front view of Loki (new legs).Sonar and IR sensors.
Marconett2.qxd 5/30/2008 2:16 PM Page 54
• POnn Servo offset
• Cnn Canned sequence #
• Knn Continuous canned sequence #
• R Reset (stop) sequence
• U Range request (sonar)
• Z.. Pot update of a servo
• I Range request (IR)
• X Execute step of stored EEPROM sequence
• Y Execute (back) step of EEPROM sequence
• V View stored EEPROM steps
• E Save current position into EEPROM step
• A Set address of execution step
Loki can execute either one of the canned sequences,
or the EEPROM sequence that’s been saved. I developed
the simple six-step gait and turn sequences used by the
autonomous mode (and the canned sequences) with the
EEPROM commands.
Either the ‘Z’ or ‘+/-’ offset commands can be used
to position a servo, and then store all servos with the ‘E’
save command.
Sequences and Autonomous ModeThe SW3 pushbutton is pressed to start up the
autonomous mode of Loki. Loki starts by walking forward,
and will take random turns at random intervals. Loki turns
away if the IR sensors encounter an obstacle. The forward
walk is accomplished by continuously looping through
canned sequence #1.
A full left turn is really three #3 sequences, and a full
right turn is three #5 sequences. Although not very efficient
on space, the sequences are “man readable,” and easily cut
and pasted into a program or manually sent via a terminal.
Wondering what sequences #2, #4, and #6 are? They
are backwards gaits of #1, #3, and #5, respectively.
Sequence #7 reads the pot to determine position (more on
that later), and #8 is a waving posture.
To control the transitions between the sequences, a
FSM (finite state machine) is used. This FSM is scheduled to
run periodically by the main ISR. The FSM can be called the
first “behavior” for Loki. I intend to add additional behaviors
such as following a light source. These too are implemented
as FSMs. All FSMs run in parallel and all are scheduled
from the main ISR via the system ticks. This parallel FSM
operation allows a new behavior to be easily programmed
(that’s the theory). The multiple FSMs will be controlled
by subsumption. Loki doesn’t have all that implemented
yet, however.
SensorsLoki has three sensors currently. The two IR distance
sensors (also called proximity sensors or rangefinders)
have analog outputs. The processor reads the IR sensors
with the A/D and is controlled by interrupts. The IR data is
conditioned and results in left and right range values in
inches. The ultrasonic sensor is interfaced by I2C and
controlled by another FSM. The ultrasonic sensor data read
is in inch range readings. The behavior FSM checks these
ranges for use in deciding when to make turns and when to
stop. If a terminal is connected (either by a direct RS-232
connection or by Bluetooth), the telemetry (actually, just a
lot of printf statements) will be available, and the ranges
seen by the sensors will be displayed, along with some
sequence information.
LEDsThe controller board has five LEDs. D1 is the power
on LED. D2 is the “heart beat” LED which flashes at a one
second rate to indicate that the program is still running. D4
is the message LED that indicates when a command is
being received. D5 is the ERROR LED, which gets set when
a received command is in error. D6 is the move LED that
indicates when a servo move is in progress.
SwitchesThere are three switches on the controller board.
SW1 is a miniature toggle switch for +5V. SW2 (small
pushbutton) is the reset switch and resets the processor.
SW3 (small pushbutton) is the data switch used to initiate
autonomous activity. There is also the miniature servo
power switch on the body.
Servo OperationThe main timer already generates interrupts for the
main ISR at the frame rate of the servos (2,500 μs). This
rate is also divided down to generate system ticks at a 1/10
second rate for other background tasks. A second timer
times the pulse width for each of the four (or eight) servos
sequentially. We don’t just suddenly “jump” from one servo
position to the next. What we do is “sweep” the servo(s) to
SERVO 07.2008 55
Loki Crosses the Pond — Part 2
Close-up front view of Loki (new legs). Sonar and IR sensors.
Marconett2.qxd 5/30/2008 2:16 PM Page 55
the new position over the time period allocated for the
move. An increment in position for each servo frame is
calculated for each servo to be moved. Each frame we
increment each servo position as required. The result is a
smooth transition of position for the servos. And it all runs
in the background! The new positions, of course, come
from the servo commands parsed. The code also reads and
parses the canned sequences. The action of turning on a
servo output line for the time determined by the second
timer results in a PWM (pulse width modulated) signal
suitable for controlling R/C servos.
CheckoutBefore powering up Loki, make sure his legs are
positioned left foot first and he is standing up. This is the
starting position, and all of the canned move sequences
both start and stop here.
Initially, both the servo and the controller board power
switches should be off and the battery disconnected.
Remove the PIC chip U3 if installed. It is recommended that
the servos and sensors be unplugged at this time.
You may now connect the battery and turn on the
controller power switch, and observe the LED power
indicator come on. Measure +5V on the output terminal
of the 5V regulator REG1.
Turn the power off and insert the PIC (the end with pin
1 and the little notch faces the three LEDs). When you turn
the power back on, you should again observe the LED power
indicator come on and still read +5V on the output of the
regulator. The “heart beat” LED D2 should be flashing once
a second, which indicates that the program is running.
Terminal TestsPower down again and connect either a checked-out
Bluetooth module (TTL) with a viable wireless link to the PC
or install a MAX232 level converter chip into U1 (any
Bluetooth module should be disconnected) and a 1:1 three-
wire DB9 cable to the PC. Run a suitable terminal emulator
program such as T2 or Docklight (even HyperTerminal). Loki
expects a 115K baud rate, no parity, and no handshake. Set
your terminal software (and Bluetooth if used) accordingly.
(Because of the variety of Bluetooth modules available, no
detailed description of using the Bluetooth or SmiRF will be
given here).
Assuming the terminal program is configured properly
and the Bluetooth (if used) is operational, then you should
observe the sign-on message “Loki 1.0 here!” when the
board power is turned on. Insure that you are familiar with
Bluetooth before attempting to use it! I suggest you try
RS-232 first (I did).
Loopback TestsIn case no sign-on message is seen, and assuming you
have the proper voltages and the chip(s) in right, you
should first check out communications. It is normally easier
to start off with a simple RS-232 serial cable known to
work. If no message is seen upon power-up of the board,
disconnect the RS-232 cable and plug in a loopback plug
into the end of the cable instead. You should see your
keystrokes echoed through the loopback plug. In the case
of Bluetooth, the Tx and Rx jumper leads (blue) can be
unplugged from the controller board and connected
together with a small piece of .025” header pin. This
“loops” the Rx out of the Bluetooth module and right back
in. This is a typical way of checking out a terminal program
and cabling, and also the Bluetooth. After verifying the
communications, standard troubleshooting techniques
apply. Check for shorts, grounds, damaged traces, and the
like. Pins are easy to bend over on the IC chips. Mind the
polarity of the electrolytic caps, LEDs, and diodes.
Loki Here!On your terminal, send the string REV<CR>. <CR> is a
RETURN keystroke. It is often represented as ‘\r,’ as well.
Loki should reply with “Loki 1.0 here!” This is the message
also seen on power-up, but it is a good fast test of a valid
two-way connection to the terminal. And with Bluetooth,
it’s nice to have a quick way to verify that you’ve still got
a connection.
You are now ready to send some initial servo
commands to Loki to test him out. Insure Loki’s legs are
positioned with the left foot first. (Loki always puts his left
foot forward!)
WARNING! Servos can rapidly jump when first turned
on. Positioning the feet as mentioned will minimize any
undesired jerking motion of the feet upon application of
servo power.
KEEP YOUR FINGERS CLEAR of Loki’s feet when
starting up!
I recommend connecting and testing one servo at a
Loki Crosses the Pond — Part 2
Loki in a posture.
56 SERVO 07.2008
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time. Driving servos into their mechanical stops can damage
them. Proceed cautiously. Also be aware that if the battery
discharges too far, erratic servo operation can occur. Turn
off the power immediately!
Okay, we’ll now power-up Loki’s controller with ONLY
servo #0 connected. Next, turn on the servo power, being
careful to hold up Loki by the body, and WATCH YOUR
FINGERS!
Issue the command #0P1600<CR> from the terminal.
Servo #0 is the right knee; it should move a little. This is the
basic servo command. You should experiment with the
servo command to familiarize yourself with it and to check
out the other servos, as well. Try some other positions, such
as 1800 and 700. Add T1000 to the servo command, or
issue it by itself to set the move time at 1,000 ms (default).
Try other move times.
You’ll find out that the servos have limits assigned to
their travel. For example, 700 and 1779 are the limits for
servo #0. There are similar limits for the other servos. These
limits prevent Loki from kicking himself.
Servo CalibrationAs mentioned earlier, with the servo horns only
allowing rough squaring, we save a calibration value for
each centered servo position. The servos can be finely
adjusted from a terminal program by setting up your
terminal program to send the strings #nP+25<CR> and
#nP-25<CR> when buttons are pressed. These buttons can
then be used to jog the joint up or down to the required
position; ‘n’ is the servo number and the ‘25’ is the amount
to move. Change the amount to suit your taste. The goal
is to have the feet flat on the table, parallel, and about
1/2” apart. Record the location of all four servos (offsets
are 0 at this point).
After getting the servos where you want them, the
calibration values are sent to Loki’s controller via the
command #n PO nn <CR>. The servo number is n, and the
centered position is nn. All four servo offsets can be sent
in one command, if desired. The offset values will be
calculated and stored in EEPROM. The centered or “left foot
forward” position of Loki’s legs will be normalized to 1500
with the offsets. A position of 0 results in the servo going
to sleep (PWM pulses cease).
Loki’s First StepsNow that we’ve got the servos moving, we can take a
little walk! A C1<CR> command will command a single gait
cycle, and K1 will initiate a continuous walk. The walk can
be stopped by a R<CR> command. Note that Loki always
finishes out his gait cycle to the left foot forward posture.
This is to ensure that the feet are in a known position,
which minimizes the possibility of Loki getting his feet
tangled up.
A C3<CR> Partial Right Turn or C5<CR> Partial Left Turn
can also be executed. Three will be needed to complete a
full 90 degree turn.
Sensor TestsWith a terminal connected, the U (ultrasonic sensor)
and I (IR sensor) commands can be issued from a terminal
to conveniently test Loki’s sensors. Note that distances less
than about 4” are invalid for the IR sensors.
Issuing walk commands with the servo power turned
off can also be used to view the range values and various
walk sequence states on a continuous basis.
After Loki is successful in taking a few walks, the
autonomous mode can be tried. Press SW3 to start Loki.
Objects should cause Loki to turn. An object too close will
cause Loki to shut down.
Other Board UsesI found the QuikFlash board a very useful and
convenient board to use. It is also inexpensive and perfect
for other small robots. I’m already looking at it for another
robotic project.
Up to eight servos could easily be accommodated with
additional connectors. Although Loki is a legged bot, one
could also drive R/C servos modified for continuous rotation
and use them to build a small wheeled robot (I’m a leg
man, personally.). The navigation portion of the software
would be a little different, but the section of the code
driving the servos would probably be the same. And don’t
forget robotic arms! Just add software.
Loki’s FutureThis is only the beginning for the controller board and
Loki! A custom control board for Loki is envisioned, which
would eliminate the need for hand-wiring servo and sensor
connectors in the prototype area.
On the software side, it is anticipated that more
behaviors will be added, and improvements made over the
rudimentary “rules” that currently suffice for subsumption.
Sequence entry to the EEPROM is at its infancy, to say the
least, and currently no fast download of sequences from a
terminal is available. SV
Loki Crosses the Pond — Part 2
Loki and author Alan, KM6VV.
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58 SERVO 07.2008
Humanoid shaped servo robots are
some of the coolest robot kits
around. They are generally simple
to build, and the finished product is
agile and undeniably entertaining.
Robots this cool, however, often come
with a hefty price tag. We’ve been
lucky enough to review two such kits
for SERVO so far. The surprising
nimble Robonova-1 from Hitec will run
you over $1,000, and the versatile
Bioloid kit from Robotis comes with a
price tag of about $900. These prices
likely put these bots out of the reach
of many casual hobbyists, which is a
shame because they have so much
to offer. The construction of these
robots is an excellent lesson in shrewd
engineering design, and there are
numerous competitions that cater to
this unique type of bot at events like
RoboGames.
This month, we have the pleasure
of introducing the Robophilo from
Robot Brothers, Inc. The Robophilo is
pitched as the most
affordable of the
humanoid servomotor
bots, and it certainly
makes good on that
claim with its scant
$400 price tag when
compared to its
competitors. But does
affordability sacrifice
quality, or is the
Robophilo agile enough
to hold its own in a
dance off, kung-fu, or soccer against
the Robonova and Bioloid? That’s
what we aim to discover.
Like The Six MillionDollar Man With a99.995% Discount
The second half of Robophilo’s
cryptic name stands for Programmable
Humanoid In Lifelike Operation. If the
other servo module humanoids that
we’ve gotten our hands on are any
indication, this moniker is certainly not
an exaggeration of its abilities. But for
us to check on that, we first need to
build the thing.
The Robophilo can be acquired as
the pre-built Ready-To-Walk form or in
kit form, and we were fortunate
enough to get the Robophilo in
pieces. The Robophilo kit comes with
a CD that contains all of the necessary
software and an electronic instruction
manual in pdf form. The kit also
comes with a rechargeable battery
pack and charger.
And, in case there was any doubt
about whether or not the Robophilo
was meant to be treated as a high
tech plaything, the instruction manual
THIS MONTH:There’s a New Humanoid
on the Block
ROBOPHILO KIT.
ROBOPHILO TEAM.
TwinTweaks.qxd 6/4/2008 4:16 PM Page 58
declares on its very first page that
“Robophilo is not a toy.” It just goes
to prove that intellectually intensive
and brain stimulating robot projects
can be so fun that there might be
some confusion, so we’re glad that
the distinction has been made.
The Robophilo instruction manual
gives the directions on how to build
the bot with clear text and helpful
3D illustrations of the step-by-step
assembly. The pictures are very nice,
but the detail on the page, the
background watermark, and the
length of the manual (78 pages!)
discouraged us from printing it out.
Following along on the computer,
however, proved to be easy enough.
The brackets for the arms and
legs of the Robophilo are certainly
reminiscent of those used on the
Robonova and Bioloid, and this tried
and true design works just as well on
the Robophilo. These parts are made
out of lightweight plastic instead of
metal as one of the money saving
measures on the kit, but the quality of
the parts do not appear to suffer for
the sake of economy.
One thing that the Robophilo has
that its competitors do not is its own
set of tools. This simply consists of a
crosshead and a hex head screwdriver,
but one hugely helpful detail about
the crosshead screwdriver is that it
is magnetized. This proves to be
invaluable when dealing with so
many tiny screws.
Other aspects of the Robophilo kit
that set it apart from it contemporaries
are the inclusions of silicone grease
and rubber o-rings — the robot’s
substitute for synovial fluid, if you will.
The Robophilo also uses some smaller
servomotors in conjunction with
some small metal push bars for the
movement of the head and waist. An
unfortunate distinction is that a very
small number of steps demand the
judicious use of some super glue,
which is not included in the kit. But by
planning ahead and having some super
glue at the ready, this minor detail
shouldn’t mess up your building flow.
One problem that we encoun-
tered with the Robophilo construction
was with the actual casings of the
servomotors. The casings, like most
others for various servos, have little
tabs on the side with holes for
mounting. We figured that the
Robophilo made use of these
tabs, but we were mistaken. The
illustrations in the instruction manual
and the pictures of completed
Robophilos on the box show servo
casings sans tabs, so we had to chop
them off. Perhaps this was a manufac-
turing oversight that will be corrected
for future kits, but the tabbed casings
are only a minor setback that we
easily corrected after some quick
surgery with a hacksaw.
Other than that, the Robophilo
went together relatively easily. All of
the plastic parts have part numbers
directly on them for reference, and all
screws and other bits are stored in
conveniently labeled bags (except for
the fact that some of our bags were
labeled in Chinese, the parts were
very easy to keep organized). At the
end of most steps, rough tuning is
PHILOMOTION CREATOR.
ROBOPHILO FINE TUNING.
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60 SERVO 07.2008
Twin TTweaks ....
done for the servomotors by hooking
them into the PCB (printed circuit
board). The kit does include a battery
pack, and the tuning is a nice way to
become familiar with the PCB before
the more daunting task of wiring up
the entire robot.
Final Touches andFine Tuning
Once the Robophilo is given all of
its limbs, there are only a few fine
touches before it is finished. One of
them is to
wire it up,
which is made
very straight-
forward by helpful diagrams in the
instruction manual. The mess of wires
can be cleaned up with some wire
sleeves included in the kit.
The penultimate step of building
the Robophilo is to do the fine tuning
for all of the servos, which is a
laborious and time-consuming process.
The major money-saving measure
employed in the design of the
Robophilo is in the servos, and the
tradeoff for achieving a low cost
becomes clear during the fine tuning
process. The Robophilo servos are
cheap analog servos that lack the
torque of the servos in the Robonova
and Bioloid, and are also more
difficult to tune. Thankfully, the tuning
process is more tedious than difficult
and the quality of your experience will
most likely depend on how perfect
you insist the tuning to be.
Tuning basically consists of
entering various positions for the
servos and then adjusting the offset
and range of motion in the
Robophilo’s fine tuning editor. With
20 servos to tune, this can turn into a
time-consuming affair. During the
tuning process is also when the
instructions recommend to connect
the pushbars for the left and right leg
movement and head turning into the
servos. The pushbar is easy to insert
into the large servo horn for the waist
movement, but the other servo horns
have holes that are simply too small
for the pushbars. After vigorously
pressing the pushbars into place, we
were able to attach everything, but
nonetheless it was a vexing setback.
During our fine tuning of the
Robophilo we witnessed something
disturbing and tragic. We were editing
the range of motion on the right leg,
and then the Robophilo’s arm began
to quiver. We checked to see that
nothing was blocking it, but the
quivering only got worse. Then, the
entire robot started to convulse as its
LED started to dim. It was a tragic
thing, watching the Robophilo run out
of batteries before our eyes. The good
news is that the battery pack is
rechargeable, and the kit comes with
a charger. A few hours later, we were
ready to press on.
Philo Goes West
After what seemed like hours of
fine tuning, we were finally ready to
finish the robot. The last steps include
cleaning up the wires and attaching
the final body panels. Unfortunately,
halfway through putting on the
Robophilo’s ill fitting shoes we ran out
of screws! Most robot kits like the
Robophilo come with ample numbers
of spare screws, and running out was
a disappointing surprise. We suppose
we could have seen it coming,
because several other sizes of screws
came in only the exact amount
necessary, with no extras left over.
Thankfully, we had enough screws to
keep the shoes on and the main body
panels on.
Unfortunately, the body casing for
the Robophilo was a big engineering
disappointment in that it seemed to
sorely underestimate the amount of
space needed for the wires to escape.
Also, the front panel doesn’t even
seem to consider that extra room is
required on one side for the small
servo that turns the head. The thin
plastic is easy to modify, but it is a bit
annoying that it has to come to that.
Putting the final pieces onto the robot
should be a triumphant experience,
not the most frustrating of the entire
build.
Despite the final frustrations, we
had finished the bot and there was no
denying that it scored high marks in
cool factor. As a final touch, the
ROBOPHILO MANUAL.
ROBOPHILO REMOTE.
ROBOPHILO PCB.
TwinTweaks.qxd 6/4/2008 4:17 PM Page 60
There’s a New Humanoid on the Block
Robophilo includes a
variety of decals to give
the bot some pizzazz,
and also as a way to tell
one Robophilo apart from
the other.
The Robophilo can be
controlled by an infrared
remote that bears a
stunning resemblance to
a TV remote. The rascally
robot was even seemingly
designed with team
sports in mind, because
the receiver can be adjusted in such a
way so as to operate four Robophilos
with four separate remotes and
without interference. The Robophilo
also has motion and pose editors so
users can create their own unique
actions. There is even an option to
assign the user created motions to
buttons on the remote.
The Robophilo also has an option
for a software upgrade that would
allow users to program their own
motions in C. We always like to see
this kind of versatility in robot kits, but
for our purposes we stuck with the
easy to use GUI.
After all of the frustration and
tedium, seeing the Robophilo move
around is a well deserved reward. The
weaker servos don’t give it quite the
agility of the Robonova or the Bioloid,
but it still gets around just fine. In a
dance-off between the Robophilo and
the Robonova the Robonova
would be more like the Korean
pop star and the Robophilo the
late night comedic pundit, but the
Robophilo certainly puts up a
valiant effort.
Rock’em Sock’emHuros
By now, we had accumulated
three different “androids” as they
seem to be referred to in the
competitive robotics community,
and three seems to be the magic
number for a number of events.
The classic team sport of
competitive robotics is soccer, and
a quick online search of humanoid
soccer will return numerous
pictures of servomotor androids
decked out in makeshift jerseys
kicking around tiny soccer balls.
Sometimes these events are referred
to as “Huro” events (RoboGames even
features a HuroCup), which we can
only guess is a playful portmanteau of
the words human and robot.
By the time of this printing,
RoboGames will have already taken
place in June, but it always seems like
a great way to analyze the versatility
and effectiveness of a robot is in the
context of a competition.
The Robophilo, Robonova, and
Bioloid all easily pass the height and
weight requirements for three-on-
three soccer and for the variety of
events that make up the HuroCup.
The main constraints on these events
are height, weight, and footprint
dimensions. The wide open HuroCup
allows robots that are up to 150 cm
tall and 30 kg, so our three androids
easily make the cut. Another three-on-
three soccer event, however, seems to
only cater to the smaller and lighter
Robonova with a height limit of a
mere 30 cm and a weight restriction
of 600 g.
The HuroCup still offers a
plethora of events for intrepid
roboticists. The mission of the
HuroCup is actually quite high
minded. According to the Laws of the
HuroCup, “The goal of the HuroCup
league is to encourage research in
practical, autonomous, highly mobile,
flexible, and versatile robotic
platforms.” That may sound like a lot
of work and a daunting task, but
the thrill of competition and exciting
variety of events are sure to make it
as much a pursuit of fun as one of
progress.
Track and field style events like
ROBOPHILO SERVO. ROBOPHILO TORSO (APART).
ROBOPHILO TORSO (TOGETHER). ROBOPHILO WORK.
SERVO 07.2008 61
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62 SERVO 07.2008
the Forward-Backward Dash and the
Marathon test the limits of bipedal
mobility, and events like Weight Lifting
and the Lift and Carry stress balance
and strength. The Robonova seems
like a popular choice for these events,
but we think the hefty Bioloid could
also be a strong competitor. Without
modification, the Robophilo would
face an uphill climb (Stair Climbing is
actually another android event held at
RoboGames). The catch about all of
these events is that the Huros have to
be autonomous. In that case, the
Bioloid might look like a better option
because of the sophisticated sensors
that each and every Dynamixel servo
module is equipped with. But
one shouldn’t count out the
Robophilo either — its PCB has
numerous open ports for
additional servos and sensors,
and with the C upgrade it
proves to be a formidable
autonomous competitor.
The epic RoboGames also
include a number of remote
controlled humanoid robot
events. The remote control
events include Kung-Fu, Golf,
and even Taiko Drumming.
Our three humanoids fit the
bill as far as height and weight
restrictions for these events,
and at first glance the
Robophilo might seem like a better
contender for these events than the
Bioloid. The reason for this is that the
Bioloid is the only one of the three
that does not come with a remote
control, but an extra receiver module
can be added to make it controllable
by radio frequency. The impressive
sensor arrays on each of the
Dynamixel modules give it more than
enough autonomous capabilities to
compensate for this inconvenience,
but such upgrades would likely be a
burden on a lot of hobbyists that have
already grappled with the steep price
tag. The Robophilo, on the other
hand, comes with a remote and is
ready to go — it even comes with some
preprogrammed karate chops, and the
motion editor would be a great way to
add some more Kung-Fu moves.
Such physically demanding events
like Kung-Fu and Taiko Drumming
would necessitate robust robots, and
once again we think the Robophilo
would be up to scratch. The
Robophilo miraculously seems to be
free of one of the major concerns
we’ve had about the Bioloid and
especially the Robonova — loose
screws. Perhaps it’s due to the pitfalls
of mass production or loose
tolerances, but the screws that hold
the Robophilo together certainly seem
determined to stay put from our own
clumsy cross threads or some other
mystical mechanism. The fine metal
threads of the Robonova’s sleek metal
frame may have made the initial
construction a breeze, but the screws
seem to come out as easily as they go
in. It’s nothing a little Lock-Tite would-
n’t fix, but it’s also nice to know that
the Robophilo probably wouldn’t lose
an arm in the middle of a golf swing.
The Price of aLow Price
Overall, the Robophilo is a bit of a
Curate’s Egg — good in some parts
and bad in others. The troublesome
servo casings, the ill fitting servo
horns and body panels, the weak and
unruly servos, and the shortage of
screws are all quite irksome. Even the
seemingly neat addition of a hanger is
a mixed bag. Unlike our other two
androids, the Robophilo comes with
its own hanger for storage or display.
The hanger is a nice idea and
refreshingly simple to put together,
but it is not very stable and we had to
add our own extra base to it so it
wouldn’t topple over. The hanger
looks like a gallows, where an unruly
Robophilo could be justly put to death
for criminal frustration.
Actually, that would be hyperbolic,
because the Robophilo is not
significantly more tedious to build
than any other servomotor humanoid,
but these numerous small details
worked together to somewhat tarnish
our opinion of the robot. To make
sure we weren’t crazy, we searched
for other reviews of the Robophilo to
see if our sentiment was widespread
or a fluke. Searching for other
commentary on the Robophilo online
returned a number of glowing reviews
that seemed somewhat incongruent
with our experience. Then we noticed
that most of these reviews were for
the Ready-To-Walk version of the
Robophilo, which clocks in at $100
more than the kit version for a grand
total of $499. This is still significantly
less than other humanoid robot kits,
and for tinkerers that are short on
time or money it might be a decent
option. Even so, other reviewers also
noted the weak analog servos that
were the big money saving item.
They did, however, also tout the
expandability of the kit as a way to
ROBOPHILO FINISHED.
ROBOPHILO HANGER.
Twin TTweaks ....
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overcome these problems. We couldn’t
agree more, and the Robophilo folks
are also hard at work at improving
their product.
We think that getting a humanoid
robot out there at such a low price is
an admirable accomplishment that
shouldn’t be overshadowed by a few
missing screws. The Robophilo still has
a number of great plusses in addition
to its affordability. The nice tools,
handy hanger (once stabilized), intu-
itive motion editor, stylish remote with
numerous channels, and expandability
all make for an impressive robot.
The HuroCup Laws even mention
how there is a drive to get more
competitors involved in Huro events,
and we think that the Robophilo will
certainly help in that department. It
may not be as stylish as the Robonova
or as versatile as the Bioloid, but the
Robophilo is accessible. The tradeoffs
made for affordability can easily be
overcome with later upgrades and
some ingenuity, but the Robophilo
and Robot Brothers should be
applauded for their sincere effort to
democratize humanoid robotics. SV
ROBOPHILO SOCCER.
Recommended WWebsitesFor more information, go to:
www.robophilo.comwww.robogames.net
SERVO 07.2008 63
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64 SERVO 07.2008
Just because one person doesn’t
want it doesn’t mean it isn’t
valuable. That’s the case with surplus.
Simply put, surplus is excess stock
for resale. Sometimes it’s used,
sometimes it’s new. Occasionally, it’s
worthless junk, but very often, surplus
has a beneficial use to someone,
somewhere. And just as importantly,
surplus means the item isn’t being
thrown away in the trash, so it’s not
clogging up a land fill.
Why bother with surplus? For
starters, it usually costs less, often a
lot less — there are exceptions, such
as rare or antique items, but we’re
not talking about that kind of stuff
here. The downside to surplus is
limited selection and quantity. You
may not find exactly what you’re
looking for, so you have to be
prepared to improvise. And don’t
expect unlimited supplies of an item.
Surplus is often one-of-a-kind, or at
least restricted quantity.
You can find just about anything
at surplus — cars, jet engines, elevator
parts, you name it. But the kind we’re
most interested in this time around is
surplus electronics and related gear —
ICs, resistors, capacitors, small motors,
jacks and plugs, and just about
everything else you might need for
the average robot.
Where to Go forSurplus
The Internet — and by extension,
mail order–is an ideal playground for
surplus shopping. We’ll get to mail
order buying in a moment, but before
logging into your PC, consider any
local surplus stores in your area. Don’t
have any? You’d be surprised at
what’s out there. Look in the Yellow
Pages under the heading of
Electronics. Sometimes you’ll find
what you’re looking for under a
Surplus heading, but these tend to be
military/camping surplus outfitters,
rather than electronics surplus.
Referrals are a great way to find
out-of-the-way businesses. If you
attend a local robotics or other user’s
group, ask members where they like
to shop. And when you find one
store, ask the sales clerks if they know
of others in the area that might be of
interest to you. Most are willing to
point you to the competition, since in
the surplus world, if one store doesn’t
have it, another one might. Customers
are gladly shared among the area
stores.
Local thrift outlets are another
good source for surplus. Many have
sections devoted to old electronics
such as TVs, VCRs, and radios. You’ll
need to do your own dismantling to
get at the parts, but for many, that’s
half the fun! Some thrift stores test
their electronic goods and charge
more if they are working; for
cannibalizing surplus parts you won’t
care if they’re working or not, so just
go for the cheapest you can find.
Odds are, even if your area
supports just a couple of nearby retail
surplus stores, you’ll probably rely
mostly on mail order to get what you
need. Many of the better online
stores are listed in the Sources section
that follows, but don’t forget to use
your favorite Internet search tool to
find more. Google, Yahoo!, MSN, or
other web search engines let you
find items of interest from among the
millions of websites throughout the
world. Add the keyword “surplus” to
the search terms to help narrow the
hits you get.
Keep in mind that the Internet –
and all mail order – is world wide.
You may find some retail stores that
are not located in your country. Many
businesses ship internationally, but not
all do so, and the added shipping
costs can all but negate the cost
savings of surplus. Read the fine print
of the website to determine if the
company will ship to your country,
and note any specific payment
requirements. If a check or money
order is accepted, the denomination
usually must be in the company’s
native currency.
Many surplus electronics outlets
sell a mixed bag of new and surplus
wares. In fact, it’s often difficult to
know what’s new or prime products,
and what is surplus. These stores
sell new products in order to keep
a stable inventory. What this means
is that the store may be able to
re-order some of the product, but
not others.
Remember that most surplus is a
“get it while you can” commodity.
Once it’s sold, it’s sold, and the stores
Stocking Up WithSurplus Electronics
Tune in each month for a heads-up onwhere to get all of your “roboticsresources” for the best prices!
RoboResources.qxd 6/3/2008 11:11 AM Page 64
move on to the next item. Should you
need a larger quantity of a particular
part, inquire to see if additional
quantities are available, and whether
it is a standard stocked item or limited
availability surplus.
What to Stock Up On
Because the availability of surplus
comes and goes, you will want to take
advantage of a product offering while
you still can. But that involves buying
things you may not need at the
moment — which could end up being
not needed ever! It’s prudent to
exercise caution in ordering surplus
merchandise that you have no
immediate plans for. I like to limit non-
essential purchases to a certain dollar
amount per month or per quarter. I
often use surplus to refill depleted
inventory. This includes basic items
such as wire and switches.
For project-specific purchases –
such as motors and gears – I will
refrain from buying these until I need
them. Yes, this does mean sometimes
losing out on a great opportunity, but
if you’re not careful it’s easy to
over-buy, and end up with a garage
full of components you may never
use. This has happened to me, and I
ended up donating several hundred
pounds of unused inventory to some
local robot user groups and schools.
As surplus electronics often
involves small parts, it is advantageous
to organize your inventory so that you
can find what you need quickly.
Plastic divider drawers sold at home
improvement stores are a good
option. For odd-size items, I use heavy
duty self-sealing plastic bags, and
write down the contents using a thick
felt marker. I then put the filled bags
in shoe boxes. It only takes a moment
to sift through the bags to find just
the part I need.
Of course, the real benefit of
shopping the electronics surplus
outlets is the savings on things you
need right now. When you start a
new project, get into the habit of
checking the surplus traders first. That
way, you’ll save money where you
can. Be realistic in your expectations
and be prepared to deviate from
your original project plans to suit the
materials on sale at the time. For
example, if your robot calls for 2-1/2”
diameter wheels, but you’ve found a
great deal on 2-3/4” ones that can
save you money, consider changing
the specifications to accommodate the
different wheel size.
Sources
Following are numerous online
outlets that offer electronics surplus,
either exclusively or as part of a
broader selection. Several have printed
catalogs for offline review, but bear in
mind that because surplus product
comes and goes, you’ll always want to
check the company’s website for the
latest deals.
Bear in mind that many other
types of online resellers such as
robotics specialty stores carry surplus
electronics. These aren’t listed for the
sake of space constraints. The moral:
It pays to study the Web catalogs of
your favorite online retailer to be sure
you’re finding all the best deals.
A-2-Z Solutions, Inc.www.a2z-solutions.com
A-2-Z Solutions carries new and
surplus electronics. Mostly computer
equipment (PCs, monitors, scanners,
and so forth). Online sales with Web
catalog.
AE Associates, Inc.www.ae4electronicparts.com
AE Associates carries new and
used electronics, including switches,
connectors, electronic components
(resistors, capacitors, diodes,
transistors, etc.), and test equipment.
Searchable database. Also sells a small
number of compact black and white
and color video cameras. Local store
in Van Nuys, CA; online sales with
Web catalog.
All Electronics Corp.www.allelectronics.com
All Electronics is one of the
primary sources in the United States
for new and used robotics compo-
nents. Prices and selection are good.
Walk-in stores in the Los Angeles area.
Product line includes motors, switches,
discrete components, semiconductors,
LEDs, infrared and CdS sensors,
batteries, LCDs, kits, and much more.
Specifications sheet for many
products are available on the website.
Online store, Web catalog, and
printed catalog.
Alltronicswww.alltronics.com
New and surplus merchandise.
Among their product line useful in
robotics are DC and stepper motors,
stepper motor controllers, power
MOSFETs, small CCD video cameras,
and tools. Online sales with Web
catalog.
American Science & Surpluswww.sciplus.com
AS&S sells surplus of all types,
including some you’d normally find in
an Army/Navy surplus store. But they
also carry motors, gears, batteries,
switches, and some electronics.
APEX Electronicswww.apexelectronic.com
Military and industrial surplus,
with a major emphasis on wire of all
types and sizes. Huge selection, but
the retail store is not well organized,
in my opinion. Limited online sales
(only some components listed on
the site).
Apex Jr.www.apexjr.com
Surplus electronics and
mechanicals. General electronics,
transformers, and “movie props.”
Online store with Web catalog.
Ax-Man Surpluswww.ax-man.com
Local (St. Paul, Fridley, and St.
Louis Park, MN) electronic and
mechanical surplus.
B.G. Microwww.bgmicro.com
B.G. Micro is a haven for the
SERVO 07.2008 65
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66 SERVO 07.2008
electronics tinkerer and robotics
enthusiast. Much of the stock is
surplus, so it comes and goes, but
while it’s being offered, it has a good
price attached to it.
Online sales through Web
catalog; printed catalog available.
BMI Surpluswww.bmius.com
Electronic surplus, much of it
high-end industrial or scientific;
opticals, laser. Online sales with
Web catalog.
Brigar Electronicsbrigarelectronics.com
Handy selection of electronic
components, including unique
sensors, construction hardware, and
motors, along with the usual
transistors, resistors, etc. Online sales
with Web catalog.
CTR Surpluswww.ctrsurplus.com
Surplus electrical, including
motors, test equipment, and power
supplies. Online sales with Web
catalog.
Electro Mavinwww.mavin.com
Electro Mavin carries electronic
components, motors, batteries, optics,
and test equipment. Online sales with
Web catalog; retail store in Los
Angeles area.
Electronic Dimensionswww.el-dim.com
Electronic Dimensions carries
military and industrial surplus,
electronics, radio receivers,
transmitters and parts, electron tubes,
test equipment, and ham gear. Retail
store in Washington state, and online
sales with Web catalog.
Electronic Goldminewww.goldmine-elec.com
Electronics Goldmine carries new
and used electronic components
(LEDs, potentiometers, resistors,
heatsinks, transistors, etc.), robot
items, electronic project kits, and
more. Online sales with Web catalog.
Electronic Surplus, Inc.www.electronicsurplus.com
Electronic Surplus has a wide
selection of test equipment and
electronics parts.
Electronix Expresswww.elexp.com
New and surplus electronics,
including passive components, motors,
relays, and more. Online sales with
Web catalog.
Excess Solutionswww.excess-solutions.com
Surplus electronics. Local store
and online sales.
Fair Radio Saleswww.fairradio.com
Though specializing in surplus
for ham radio, Fair Radio also offers
plenty of general electronics and
test equipment. Online sales with
Web catalog. A printed catalog is
available.
Gateway Electronics, Inc.www.gatewayelex.com
Gateway Electronics is a general
electronics mail order and retailer.
Among their products are passive
and active components, motors,
electronic kits, gadgets, books, and
tools. Some of their goods are new;
others are surplus.
Hosfelt Electronicswww.hosfelt.com
General electronics. New and
surplus.
HSC Electronic Supplywww.halted.com
Online mail order sales, with
walk-in retail stores in northern CA.
Halted offers a mix of computer and
electronics surplus.
Marlin P. Jones & Assoc., Inc.www.mpja.com
MPJA sells both new and surplus
electronic and mechanical products.
Their assortment of items such as
motors is fairly small, but they make
up for it with a wide selection of
other common (and some not-so-
common) products.
MECI — Mendelson’sLiquidation Outletwww.meci.com
Surplus electronics, motors, and
even a special section for combat
robot parts — large motors, batteries,
that sort of thing. Online sales with
Web catalog.
Quickar Electronicswww.quickar.com
Quickar carries surplus electronics
and tools. Online sales with Web
catalog.
Skycraft Parts & Surplus, Inc.www.skycraftsurplus.com
Skycraft Parts & Surplus, Inc., is
a “surplus mall” offering power
supplies, transistors, relays, ICs, wire,
cable, heat shrink, transformers,
motors, fiber optics, test equipment,
resistors, diodes, and more. Local
store in Florida, plus online sales with
Web catalog.
Timeline, Inc.www.timeline-inc.com
Surplus of all kinds: electronic,
computer peripheral, laser, motors,
LCDs, and more. Online sales with
Web catalog.
Unicorn Electronicswww.unicornelectronics.com
Unicorn Electronics has a large
selection of electronic components,
including passives, transistors, logic
ICs, relays, and more. Online sales
with Web catalog.
Weird Stuff Warehousewww.weirdstuff.com
Weird Stuff Warehouse sells
surplus, including electronics. Retail
store in Sunnyvale, CA. SV
Gordon McComb can be reached viaemail at [email protected]
CONTACT THE AUTHOR
RoboResources.qxd 6/3/2008 11:12 AM Page 66
First, a little history. The concept of chance appears in
most ancient cultures, dating back at least as far as
the ancient Egyptians use of the “talus,” an early
predecessor to the die. Fashioned from the knuckle or heel
bone of a hoofed animal, the talus had four possible
outcomes. It has been found alongside tomb illustrations
and scoreboards in Egyptian sites lending support to the
idea that playing dice and gambling were popular pastimes.
In the words of Ian Hacking, a historian of probability,
“It is hard to find a place where people use no randomizers
yet theories of frequency, betting, randomness, and
probability appear only recently. No one knows why.”
An intriguing mystery! And indeed it is not until 1654
that what we know as probability today began to take
shape. French nobleman Chevalier de Mere had a gambling
problem. He wanted to know if it would be profitable to
bet that double-sixes would appear at least once in a set of
24 dice throws. Luckily for him, he was a friend of one of
the most brilliant mathematicians of his day, Blaise Pascal.
De Mere posed the problem to Pascal and the theory of
probability emerged from the ensuing correspondence
between Pascal and his good friend Pierre de Fermat,
another brilliant mathematician.
What Fermat and Pascal realized is what we all learned
in grammar school — that with each throw of the dice,
each possible outcome is equally likely. The possibility of
throwing a six is therefore 1/6. They further realized that
probabilities could be multiplied, and the probability of
throwing two sixes was 1/6 x 1/6 = 1/36. The probability,
therefore, of throwing two sixes in 24 throws is 1/36 x
1/36 x 1/36 … 24 times or 0.4914. So it was not advisable
for Chevaler de Mere to bet on throwing two sixes within
24 throws after all, and probability theory was born!
So what does any of this probability stuff have to do
with random number generation?
Games of chance are, as Hacking called them
“randomizers.” They are a way of abdicating responsibility
for decision-making to the world of probabilities. In turn,
results returned from such activities are random outcomes.
At any given moment of the game, you cannot predict with
certainty which number will appear next. And a set of ran-
dom outcomes produces a sequence of random numbers
containing no repeating patterns — a sequence which
Algorithmic Information Theory would call uncompressable.
AIT and CompressibilityAs Gregory Chaitin, founder of algorithmic information
theory describes it, compression occurs if data can be repro-
duced by a computer program with a smaller number of bits
than the original data contains. In other words, if I have a
data set of 500 one-byte measurements, the data contains
500 * 8 = 4,000 bits. If I can find a repeating pattern in that
data, I can simplify it by creating a simpler symbol to represent
each repeating subset of the sequence. I can then code an
algorithm to process the input string and replace the
symbols based on a key. In this way, I can shrink the size of
the data itself without losing any of the original information.
by Heather Dewey-Hagborg
Throughout this column, we have relied on the idea of randomness to seed all of our
unconventional computing experiments. In this month’s article, we will take a brief
detour from code and hardware to examine just what the concept of “random”
actually means, how our microcontroller is implementing it, how this differs from a
computer, and some schemes for creating “true” random number generators.
DIFFERENTBITS
DIFFERENTBITSRANDOM BITS
SERVO 07.2008 67
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68 SERVO 07.2008
DIFFERENT BITS
Example:
Original dataset
70, 15, 111, 32, 56, 70, 15, 70, 15, 7, 1, 3, 5, 20, 67, 54,
42, 29, 113, 7, 1, 3, 5
Compressed dataset
a, 111, 32, 56, a, a, b, 20, 67, 54, 42, 29, 113, b
Key
a = 70, 15
b = 7, 1, 3, 5
The more you can compress the data, the more
patterned or predictable it is, the less information it
contains, and the less random the sequence of numbers is.
By contrast, if the data cannot be compressed at all, “if the
smallest program for calculating it is just as large as it is ...
then the data is lawless, unstructured, patternless, not
amenable to scientific study, incomprehensible. In a word,
random, irreducible!” (Chaitin, p. 64)
So randomness is equivalent to information. The more
information a sequence contains, the more difficult it is to
compress, and the closer it is to randomness. In this light,
white noise becomes pure information and a perfect source
— in addition to games of chance — for generating random
sequences. Anywhere noise is present, for example, radio
waves and the atmosphere, we can tap into it to extract
random sets of numbers.
RadioactivitySomething that we thankfully have rare occasion to
contemplate, radiation is an excellent source of random
numbers. Radioactivity can be defined as “The spontaneous
emission of radiation from the nucleus of an unstable atom.
As a result of this emission, the radioactive atom is converted,
or decays, into an atom of a different element that might
or might not be radioactive.” (Defined by the Radiation
Emergency Assistance Center.) For our purposes, this means
that given an unstable atom, there is no way of predicting
when it will lose its extra nucleon resulting in the radioactive
decay. By proxy, if you have multiple radioactive atoms,
there is also no way of predicting the interval between
decays, and it is exactly this combination of random periods
that can be used to generate random strings of binary.
So, we know that randomness comes from dice
throws, card games, coin tosses, noise, and radioactive
decay, and I think we can safely bet that our computers are
not striking up a game of cards each time we request a
random number, so how do they do it?
rand() and srand()Most likely, if you are reading this magazine you
have also done at least a little programming and have
encountered some version of the rand() function or random
class. Almost every contemporary computer language and
platform has had some variant of this, from microcontroller
C to Java to Python. These functions generate what are
known as pseudo-random sequences of numbers. Why
pseudo-random? Well, for one thing, the random number
generator in your computer is actually just an equation.
Most computer languages (including C and Java) contain
a version of the classic algorithm, the linear congruential
generator, as the source behind rand(). A linear congruential
generator works by computing each successive random
number from the previous, starting with a seed, X0. The
seed is generally what you supply to the algorithm by calling
srand(seed_value) before requesting a number from rand().
Here is the formula:
Xn+1 = (aXn + c) mod m
where Xn is the output set of random numbers
m is the modulus value
a is the multiplier value
c is the increment value and X0 is the initial seed value
(ex. supplied by srand)
In Ansi C, for example, m = 232, a = 1103515245, and
c = 12345. The number returned by the rand function is
actually drawn from only bits 30:16 of the output result of
the function.
Similarly, Java uses the linear congruential generator
with an a value of 25,214,903,917 and a c value of 11.
ProblemsOne of the defining characteristics of pseudo-random
number generators is that given the same seed, they will
always produce exactly the same series of numbers as output.
This is very useful when you need a sequence of data that
appears random and is the same each time, for example, in
rendering computer graphics, but it is an annoyance for most
of the applications we have implemented in this column.
The other problem with linear congruential generators
is that they are not terribly random. The longest random
sequence it is possible to generate is the length of the
chosen modulus value (232 in C) before it begins to repeat
from the beginning; a characteristic referred to as the
period of the generator. Additionally, it has a characteristic
called serial correlation which means that there are
predictable patterns in the data. To return to our discussion
of algorithmic information theory above, this means that
the data could be compressed; it is not 100% random.
In comparison, the Python programming language uses
For more details on radioactive decay as a source of randomness, check out Hotbits, a company that supplies random number sequences sourced from radioactive behaviorvia the Internet; www.fourmilab.ch/hotbits/.
FOR YOUR INFO
DifferentBits.qxd 6/4/2008 1:55 PM Page 68
a different random number generating algorithm known as
the Mersenne Twister. This algorithm has been proven to
generate significantly more random data (the period is
219937 – 1), but it requires more memory for implementation
and is therefore not suitable for microcontroller or space
intensive implementations.
What About Microcontrollers?CCS (www.ccsinfo.com) reports their rand function to
be the following:
unsigned int16 rand(void){
_Randseed = _Randseed * 1103515245 + 12345;return ((unsigned int16)(_Randseed >> 16) %
RAND_MAX);}
This is clearly derived from the ANSI C example we looked
at above, as you will recognize the linear congruential
function, simply separated into two steps. Notice also that
the a and c values are identical to the ones above, and the
only difference between the two functions is that in the
CCS version, m is the user defined value RAND_MAX rather
than 232. Note that this makes explicit the relationship
between the maximum period of the random number
generator RAND_MAX and the modulus value m.
(Hitec did not respond to my query about their random
number generation technique, but it is probably safe to
assume it is similar.)
A Better rand()If you have read some of the examples from earlier
installments of this column (neural networks, genetic
algorithms), you have undoubtedly noticed plentiful use of
the rand() function. And if you have actually implemented
any of these examples, you have also noticed that the
methods used to seed the PIC random number generator
are less than satisfactorily random. I will conclude this
month’s column by briefly explaining some possible
methods for generating better random seeds on the PIC
and providing some links to more details.
CCS recommends measuring the time in microseconds
between power up and the first user keypress, and then
using the least significant bits of that measurement. In terms
of code, this involves using a hardware timer to generate
interrupts and counting the number of intervals between
device initialization and the user’s keypress. An example of
this is available on the CCS website at www.ccsinfo.com/
content.php?page=compexamples#seconds.
Their suggested workaround solution for when user
input is not possible is saving an initial seed in EEPROM and
then incrementing it each time the processor is reset, and
saving the new value in place of the old. CCS has read and
write EEPROM functions available for doing exactly this; see
their EX_EXTEE.C example for more details.
Other possible solutions for getting a good random
sequence on a microcontroller involve either developing
hardware specific to this task, or connecting to the Internet
and querying a site like Hotbits (mentioned previously) or
random.org.
If you do want to build your own dedicated random
number generating hardware, there are a few tried and
true methods. The first makes use of the principle that a
reverse-biased PN junction generates completely
unpredictable output known as “avalanche noise.” Lots of
details about making a random number generator using
this technique, as well as interfacing it to the PIC, are
available online from Rob Seward’s art project
‘Consciousness field generator’ at http://robseward.com/
itp/adv_tech/random_generator/.
The basic idea is to sample the weak avalanche noise
signal and amplify it dramatically. This value is then sampled
by a microcontroller either by sampling the time interval
between spikes or simply choosing a constant sampling rate
and accumulating 1s and 0s each iteration. Because
succeeding bits may be more correlated than is desirable,
different unbiasing techniques exist. One popular technique
called the Von Neumann method samples two bits at a
time, discards them if they are equal, and keeps the first
one if they are different. Another method known as the
XOR corrector samples two sets of pairs of bits and then
performs an XOR operation on them and uses the output.
More information on the PN junction technique is
available at www.cryogenius.com/hardware/rng/.
Another method for hardware random number
generation makes use of the radioactivity method described
earlier. The basic premise is to use a Geiger-Müeller tube
to count instances of individual atom’s decay in a given
isotope. Again, the time interval between decays can be
used, or a fixed sampling period can be established and the
number of decays per unit of time can be counted.
A detailed description of this idea is available on Bernd
Ulmann’s blog at www.vaxman.de/projects/rng/
rng.html.
Finally, if you can’t do the user keypress, EEPROM, or
external hardware techniques, you can try sampling a
floating pin on the analog-to-digital converter of your PIC,
and accumulating the least significant bit each sample. To
maximize your randomness on this technique, test out one
• Gregory Chaitin: Meta Math!
• Ian Hacking: The Emergence of Probability: APhilosophical Study of Early Ideas about Probability,Induction, and Statistical Inference
• Peter J. Bentley: The Book of Numbers: The Secret ofNumbers and How they Changed the World
SUGGESTIONS FOR FURTHER READING
SERVO 07.2008 69
DIFFERENT BITS
DifferentBits.qxd 6/4/2008 1:55 PM Page 69
of the unbiasing techniques just mentioned.
To close on a completely random note, I will leave you
with a fun example of a very early musical piece that took
advantage of true random number generation. In 1787,
Mozart composed a set of instructions for a ‘musical dice
game’ — a method of using consecutive dice throws to
generate a minuet! Lots more information about this and a
computer generated version are available online at
http://sunsite.univie.ac.at/Mozart/dice/. SV
Heather Dewey-Hagborg can be contacted via email [email protected]
CONTACT THE AUTHOR
DIFFERENT BITS
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By the time I graduated high
school, I had already met the
love of my life, Vern, and was well on
my way to my career goal. We got
married in our early 20s and, although
I had a “day job,” I embraced my
home life in my free time. Fast-
forward 10 years and enter our first
child, Nic. Finally! The time to stay
home and hone my mothering skills
had arrived. I had picked up some
techie skills through my job, but didn’t
really anticipate ever needing them
again, except for working on our
home network or fixing my sister’s
computer. Then came reality.
A mere two months after our son
was born, Vern and I decided to open
a small ISP and network services
company. My marginal techie skills
took a quick ramp up to being a full-
fledged Novell CNA with a strong A+
skill set. My husband was (and is) an
excellent network engineer. As he
designed and installed networks, I
would assist and then go on to
administer, repair, and upgrade as
needed. Our son became accustomed
to a wide range of environments as
he traveled with me to customer sites
and enchanted everyone there. After
the business settled into more ISP and
less network services, child number
two was on her way and I once again
attempted the stay-at-home thing. But
my quiet Suzy Homemaker world was
not going to stay that way for long.
By then, my husband’s electronics
interests had branched out to include
the Halloween world.
Let me explain: My husband is a
prolific designer of devices. He has
developed the Robo Spin-Art machine,
the Ponginator, Therepings, Ping Pong
Printer, Sonar Station, a talking skull in
a coffin, a 20-foot wide “venomous”
spider, and so much more. The ideas
he has still on the drawing board have
the same potential for eye-catching
Dusting RobotsOne Woman’s View of Life
With an Electronics Hobbyistby Kym Graner
When you were five, 10, or even 15 years old, what did you want to be when you grew up?
I’m betting those career aspirations changed with your interests until you eventually became
whatever you are today. Maybe you wanted to be a fireman-superhero-doctor, or maybe
a veterinarian-cheerleader-cop. I wanted to be a mom. From the time I was about 12,
I knew that was the job for me. Nothing showy, nothing extremely technical or requiring
decades of schooling. I just loved kids, cooking, crafts, and the outdoors. I couldn’t think
of anything better than being a stay-at-home mom.
74 SERVO 07.2008
Nic as a baby (left). Nic now (right).
Appetizer.qxd 6/4/2008 3:46 PM Page 74
fun that the ones already living in the
outside world possess. He’s always
been like this — inventing things since
he was in grade school. He really
can't help it.
Many of these creations came
together in 2005 to make an awe-
some Halloween Haunt that the
neighborhood still talks about.
Unfortunately, it was made at the
expense of my one beautifully deco-
rated room — the dining room. My
vintage cherry Queen Anne dining
set, hutch, and my grandmother's
antique desk had to take shelter in
my bedroom. The stained glass
chandelier was removed, black
plastic sheeting was stapled onto
my gorgeous crimson walls, and
voilá! One scary spider’s lair was
created. Like I said, it was fab —
award-winning, even! But just last
weekend, I found another staple in
the ceiling, holding just a scrap of
spider webbing.
The accoutrement that
currently grace my dining room
include two human-sized robots/
sculptures, the coffin guy, Bob —
who, at roughly six feet in height
— is also human-sized, a Stargate
Defender machine, a trashcan
zombie, and an evil spider-con-
trolled robot. My living room set
includes a former motorized
wheelchair base, turned mobile
platform for an in-process “boogie
bot,” one of the Robo Spin-Art
machines, and a supply of ping
pong balls for the Ping Pong
Printer. Rather than reflecting my
daydreaming interest in a Better
Homes & Gardens living space, our
house now sports a look that was
once described by a friend as
looking like Godzilla swallowed a
RadioShack and then threw up.
There’s a part of me that wishes
my home could revert to the
“normal” decorator dream it started
to become. But then I look at all
the fun we’ve had making and
showing off these things, teaching
our children to design and build,
and getting to meet like-minded
people, and it makes the “clutter”
worth the sacrifice. SV
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SERVO 07.2008 75
Sami as a baby (left). Sami now (right).
Appetizer.qxd 6/4/2008 3:08 PM Page 75
Over the years, I have written
about advances in all types of
robot designs, robot technology, and
various robotic subsystems in this
column. In each article, I have tried to
cover advances in the science of
robotics and have covered the history
of a part of robotics in a specific
way. I have never tried to examine
the way that we humans have
viewed these creations of ours as
they have slowly taken over many
parts of our lives. I have often
wondered just what mindset
developed in people’s thought
processes as the science of robotics
took a certain turn. We, as robot
experimenters and hobbyists, certainly
view robotics in a way different from
the average person. We don’t just sit
back and read about how they weld
and paint our cars in far away
factories. We build our own or buy
ready-built robots or robot kits so we
can see the technology at work, first
hand. As a society, robotics is now
changing our lives in ways we never
imagined.
The ‘20s to the ‘50s —The First Visions ofRobots in Our Society
The idea of a non-human
humanoid in our society has been
around for thousands of years. Most
of these mythical creatures were not
particularly nice to us. A hundred
years ago, the very word robot did
not exist as Czech playwright Karel
Capek had yet to write his 1920 play,
RUR, which stood for Rossum’s
Universal Robots. The Czech word,
robota meant ‘serf,’ ‘drudgery,’ or
‘laborer’ in Czech — a person who
does hard work. Karel attributes his
brother, Josef, as the inventor of the
word robot, though he first suggested
the word roboti. It was changed to
robot for the play. The term robotics
was later derived from a mix of robot
and electronics or mechanics (there
are those who steadfastly stand by
each of the two words that are
attached to robot).
Robots were always thought of
as anthropomorphic or ‘man formed’
in the plays and movies of a century
ago. The earliest robots of man’s
imagination were machines to be
feared. Maria from the film Metropolis
was anything but an agreeable
creature. The many stories of Isaac
Asimov (Figure 1) from the 1940s on
brought a semblance of ‘man-like’ to
these machines. They walked on two
legs as nobody had a clue in those
days just how difficult it was to have a
machine balance while walking.
Asimov had enough technical
knowledge to realize that the
electronics of his day were not
sufficient for a robot’s brain, so he
envisioned the ‘positronic brain’ in his
robot tales as the mystical power
behind his creations. There was no
way he could have imagined the
cheap Flash drives that we use today
that contain billions of transistors as
memory cells. Transistors were still
years in the future so electronics relied
on the lowly vacuum tube.
Asimov’s robots were also a
bit kinder to mankind. In later
years, his ‘Three Laws of Robotics’
have had a great impact on all
levels and types of robots including
the design and manufacturing of
industrial robots — the only robots
Then NOW an
d
ROBOTICS — A HISTORICALPERSPECTIVE
b y T o m C a r r o l l
SERVO 07.2008 77
First Law: A robot may not injure a human, or, through inaction, allow a human being to come to harm.
Second Law: A robot must obey theorders given it by human beingsexcept where such orders wouldconflict with the First Law.
Third Law: A robot must protect its own existence as long as such protection does not conflict with theFirst or Second Law.
THE THREE LAWSOF ROBOTICS
FIGURE 1. The Late Dr. Isaac Asimov.
Then&Now.qxd 6/4/2008 10:02 AM Page 77
78 SERVO 07.2008
of the ‘60s with sufficient power to
injure a human being.
The ‘60s and ‘70s —Robots Arise fromFiction to Reality
When George Devol received his
patent on universal automation for
‘programmable transfer of articles in
a factory’ and later met young Joe
Engelberger in 1954 (Figure 2),
Unimation was born and so was the
first industrial robot — nothing at all
like the walking creatures of film and
literature. This was the first pivotal
point in the history of robotics. Robots
were now real and useful tools to
humanity. These two men were
thinking only of ways to automate
manufacturing processes, not to
replace people in their jobs.
The original Unimate robot had a
single arm extending out of a turret,
much like a military tank gun (Figure
3). However, despite the lack of
human form, the robot was here to
stay as the first Unimate toiled away
in a General Motor’s plant in New
Jersey. ‘Robots’ became the new tools
that made American industry the envy
of the world.
Factory robots started out
handling parts and soon were spot
welding and spray painting cars on
assembly lines. Robots always seem
extremely powerful to the average
person but few realize that a typical
industrial robot can actually only
handle a small payload. What they are
capable of doing is moving this small
payload quickly and precisely and
many times; thus the need for a
massive structure. Humans quickly tire
when asked to
handle items many
times. The media
touted these times
as the ‘Robotics
Age’ and a
magazine was
actually published
in the ‘80s with
that same name.
“The ‘steel collar’
worker has
arrived!” touted the headlines.
Industries welcomed these
machines as workers who never tired,
never asked for a raise, and never got
sick. Human factory workers first
looked at these intruders with a jaded
eye, worried that their jobs were at
stake. Soon, they saw their dirty,
repetitive, and dangerous jobs being
replaced by the machines and their
job status being elevated to robot
operator or robot repairman. Workers
were happy and management even
happier. The robot tide rapidly spread
overseas, primarily to Japan. The
world was now accepting robots
in society.
The presence of ‘the Three Laws’
did not prevent Robert Williams, a
worker in a Ford Motor Company
plant in Flat Rock, MI, from being
killed by a robot in early 1979. He felt
that the robot was operating a bit too
slow and was retrieving a part from a
bin when the robot’s arm struck him
in the head, killing him instantly. A
massive structure moving at high
speed can be very dangerous. No, the
robot wasn’t acting in anger that a
human was taking his job back, but a
jury awarded Williams’ family $10
million from the robot’s manufacturer.
Two years later, a Japanese worker,
Kenji Urada, was killed in a Kawasaki
plant when a robot that he thought
he had turned off, pushed him into a
grinding machine.
Throughout the ‘60s, the vast
majority of the world’s robots were
the industrial variety. Talented
experimenters built some machines
in their garage workshops and
universities allowed a few grad stu-
dents to craft a robot or two for a
thesis project, but the word ‘robot’ to
most people meant the machines in
car factories. Newsreels and
magazines showed images of rows of
mechanical servants snaking their
lanky arms into car frames, sparks or
paint mist spewing onto the floor.
Robot ‘intelligence’ — if that word
applied at all — usually meant an
expensive mini-computer or maybe a
mainframe in another room, linked to
the robot by a bi-directional RF or
wired link. Sensors were almost
non-existent on industrial robots.
Expensive cameras and factory
automation devices served as sensors
for university experimental robots.
Large drum memories held crude
programs for the robots, but, hey,
they worked, and more and more
were being installed in factories
around the US and the world.
You could ask a kid on the street
in those years, “What is a robot?” He
might, at first, say it was Tobor The
Great from the movie of the same
name. You could then ask, “No, what
is a real robot?” He would then
describe the rows of robots in a car
factory, as would any adult of those
times. Others might mention the
unmanned Surveyor or Viking lunar
landers, or the space probes sent
across the solar system to explore our
planetary system. Some might even
recall the ‘hot cell’ teleoperators
at Oak Ridge, TN that handled
radioactive materials by remote
control. All will agree that robots are
now real creations of man.
The ‘80s — JapanBecomes the Leaderin Robotics
The US can take pride in many
innovations in robotics but it is Japan
that has taken the lead in implementa-
tion of robotic technology. In the
beginning, virtually all of the robot
manufacturers were based in the US
but today’s list of the top companies
are all Japanese based. There are still
a few innovative US, Canadian, and
European robot companies but most
of the original US companies were
either bought out by their Asian
competition or went out of business.
Japan also has the greatest
FIGURE 2. JoeEngelberger. Photo
courtesy of Industry Week.
FIGURE 3. Unimate Robot.
Then&Now.qxd 6/4/2008 10:03 AM Page 78
number of industrial robots installed in
their factories; a good reason they are
one of the world’s top manufacturing
powers. By the end of 2005, Japan
had over 373,000 industrial robots in
place in factories, with the US in a
distant second place with 131,000.
Sweden, Germany, Korea, Canada,
and other countries were soon
installing robots and even manufactur-
ing their own. The UP400RN robot in
Figure 4 is made by Motoman, the
North American name for the
Japanese parent company, Yaskawa.
This company has a line of over 250
different robots for all types of indus-
tries, not at all untypical for modern
robot manufacturers. The proverbial
‘yanking the rug from under North
American robot manufacturers’ was
the second pivotal point in the history
of robotics. Actually, the rug wasn’t
yanked; it was handed over.
The ‘RobotRevolution’ Beginsin the ‘80s
Applications soon spread from
just material handling, spot welding,
and painting to more sophisticated
operations such as vision-aided pick
and place systems. The SCARA
(selective compliance assembly robot
arm) soon became the most popular
robot configuration when it was first
used in 1978 in small assembly
operations such as electronic circuit
board ‘parts insertion.’ Gantry x-y-z
axis robots were developed to handle
large and small parts. AGVs (automat-
ed guided vehicle) took a departure
from fixed base robots and moved
about factory floors carrying parts,
guided by invisible paths on the floor
or by other means. Surveillance and
security robots silently guarded factory
and office floors.
Robot applications were
spreading outside of the typical
factory floor to many new uses. The
Robotic Industries Association (RIA)
and the Robotics International of the
Society of Manufacturing Engineers
(RI/SME) were in their heyday in
the mid-1980s with thousands of
members attending the many industry
shows around the country. The
world’s industries touted all these new
applications for robotic technology as
the Robot Revolution.
Service Robot — aNew Category
A new tide of interest in robotics
began to develop. With varieties of
robots spilling over into all aspects of
life in the early ‘80s, it was natural
for the large electronic kit maker,
Heath, to design a robot kit for the
experimenter and hobbyist (Figure 5).
The Hero 1 was an instant hit, and
a later Hero Jr. and the more
sophisticated Hero 2000 rounded out
the line. With Heath long since out of
business, for those who are interested,
Robert Doerr at www.robots
wanted.com has many Hero parts
and whole robots to sell. Bob also
handles the equally famous RB5X
robot that cost a whopping $2,295 in
1984 (Figure 6).
Nolan Bushnell of Atari fame
started a company called Androbot
and began selling his ready-built TOPO
and BOB robots in early 1983, or as
he stated — “the year 1 AB,” for the
first year of AndroBot, or After Bob,
as others have said. Universities and
community colleges began to offer
courses in robotics for the budding
roboticist — a new buzz word that
began to make the rounds in the late
‘80s. I’m assuming that the word was
derived from robotic and scientist. As
the science of robotics comprises so
many diverse technologies, robotics
students found their special interests
within mechanical engineering,
electrical engineering, computer
science, physics, computer
engineering, and other technical
fields such as chemistry and optics.
Once the dominate force in
robotics, industrial installations took
a back seat to newer applications.
Robot technology had now spread out
from the factory floor to teleoperators
for remote manipulation, mobile
military robots, and remotely-operated
vehicles for under the sea, on the
ground, and in the air. Medical
applications were replacing the
surgeon, floors were being cleaned by
robots, and medicines delivered by
robot couriers in hospitals. Robots
snaked their way through pipes for
inspection, crawled up the sides of
buildings to clean windows, delivered
food to tables in restaurants, and
entertained us in our homes.
SERVO 07.2008 79
FIGURE 6. RB5X.
FIGURE 5. Hero Robot.
FIGURE 4. MotomanUP400RN by Yaskawa.
Then&Now.qxd 6/4/2008 10:03 AM Page 79
Entrepreneurs searched for different
ways to use this new technology.
Interest in Roboticsfrom the ‘90s to thePresent is Phenomenal
Robot experimenters have long
been interested in robotics as a means
of using a machine to do something
physical, in that it either investigated
its environment by roving about or it
actually made changes to the environ-
ment. With the advent of affordable
microprocessors and microcontrollers,
robots can now operate on their own.
These autonomous robots do not
need “man” in the loop to
accomplish something intelligently.
It is this seemingly intelligent
appearance of robots that
appeals to a new breed of robot
enthusiasts — those with strictly
computer science or AI
backgrounds. Once called gear
heads for their mechanical bent,
the new generation of robot
experimenter now has at his
or her disposal all types of
sophisticated microcontrollers,
sensors, vision systems, and
navigation methods to create
some ‘killer’ robots.
SophisticatedRobots BecomeAvailable to Everyone
Gone are the old robot kit
companies as new hobby robot
manufacturers step up to the plate.
LEGO — the maker of the plastic block
sets for kids — develops some
amazingly unique and powerful robot
kits with their Mindstorms series.
Robot Sumo moves from Japan and
becomes popular in the US and the
world. Dean Kamen, inventor of the
Segway Personal Transporter of 2001,
had interests in robotics back in
1989 when he founded FIRST (For
Inspiration and Recognition of
Science and Technology), a robotics
competition that in 2008 had
over 37,000 high school students
in robotics teams across the
nation. A recent article in Electronic
Design magazine indicated that
students in the FIRST competition
were more likely to attend college
and were likely to be interested in
engineering fields, were more
community oriented, and aspired to
post-graduate studies. Does this
mean students who entered the
competitions were then inspired to
go into robotics and engineering, or
that FIRST naturally attracted the
type of student who would have
gone this route, anyway?
Robots have always appealed
to children, and the child in all of
us. Tiger Toys brought forth the
extremely popular Furby in 1998 — a
small, furry robot animal reminiscent
of the characters in the Gremlins
movie (Figure 7). This talking and
somewhat moving creature sold over
40 million units. Sony, the huge
electronics manufacturer first
produced its robot dog (and cat)
named Aibo in 1999. Many people
wondered just who would shell out
$1,500 to $2,000 for a plastic dog but
almost 200,000 did until Sony ceased
production in early 2006. It is
rumored that they will bring out a
new model this year called the Aibo
PS to be controlled by their latest
PlayStation (Figure 8).
History will show that these
introductions of sophisticated robot
toys were an important turning point
in robotics and its acceptance with
non-technical people. CrustCrawler,
Lynxmotion, Parallax, and many other
companies advertising in SERVO
now supply or make some amazing
robots or robot components for robot
experimenters.
The average person has no clue
how these creations of ours work,
so our various clubs have arranged
exhibitions for the public. Robothon
was one of the larger robotics
expositions developed and presented
by the Seattle Robotics Society at
the Seattle Center — home of the
Space Needle. For years, Robothon
introduced thousands to the exciting
science and hobby of robot building
and robot competition. This year, it
will not be held, not because there
is not interest for such events but
because leadership of the Robothon
has kept it alive for so many years that
burnout has occurred.
The same applies to the Portland
Robotics Society’s popular PDXBot and
other group’s events around the
country. However, others such as the
big San Francisco RoboGames and
the Dallas group’s contests are still
packing ‘em in. The leadership of
these events has seen a gradual
lessening in the attendance of these
exhibitions, unfortunately. Possibly the
downturn in our economy is making
money a bit tight for expensive
hobbies. Maybe the rest of society has
become so used to robots vacuuming
our floors and entertaining us that a
80 SERVO 07.2008
FIGURE 7. Furby.
FIGURE 8. Aibo.
Then&Now.qxd 6/4/2008 10:04 AM Page 80
demonstration of a championship
Robo-Magellan or a 20-servo
humanoid walker brings a bored “ho
hum” from the average bystander. Do
they really want a full-size Honda
Asimo as a servant in their homes?
Does this hiccup in interest signify
another turn in the history of robotics?
Possibly. Have we failed as robotics
enthusiasts? No way! The history of
any technology has always gone
through these cycles of interest and
acceptance. The steam engine was a
marvel until it drove trains, ships, and
factories everywhere. The common
light bulb that lit the world as the
marvel of a century ago, is so
commonplace that it is ignored today,
soon to be replaced by LED lamps.
The amazing $2,000 cell phone of
two decades ago is now given away
and is in the hands of most school
children.
The Robot Revolution
The recent April 21st edition of
U.S. News and World Report had an
article entitled ‘The Robot Revolution
May Finally be Here.’ I’m thinking,
“They’re saying this again, after 20
years?” The article went on to
mention that iRobot has sold almost
three million Roombas — the vast
majority of the new helper robot
category. “Personal robots emerged as
a mainstream product last Christmas,
with Sharper Image’s catalog
featuring a “Shop for Bots” section,
says Philip Solis of market tracker ABI
Research,” as written in U.S. News.
Yet, the March 27th edition of
Electronic Design had a picture of
Star Wars’ C-3PO on the cover with
the article title under it stating: “The
Droid War: Cost, Lack of Industry
Focus Clouds Robotics Future.” The
article actually paints a rosier picture
of the state of robotics in the actual
essay, with an emphasis of LEGO’s
Mindstorms NXT robotics kit and
National Instrument’s LabVIEW
software package.
So, you see, there are always
multiple sides to any historical subject,
whether a part of the Civil War or
the subject at hand we all love so
much. It just depends on your point
of view and what particular facet of
robotics interests you most. Outside
of the usual timelines, every “history
of robotics/robots” that I Google
always seems to have a different
slant on the subject. I would very
much appreciate some of you readers
of SERVO to email me with your
feelings about the future trends of
robotics, for it is you who will
ultimately change the directions of
experimental robotics with your
purchases, designs, exhibition
attendance, and comments at
meetings and on the web. SV
Tom Carroll can be reached via emailat [email protected].
SERVO 07.2008 81
All Electronics Corp. .........................25, 70
AP Circuits/e-pcb.com ............................10
AWIT ..........................................................70
Boca Bearings ....................................23, 70
CipherLinx Technologies .........................70
CrustCrawler .............................................82
Electronics123 ..........................................25
Endurance Robotics ................................70
Hitec ..........................................................15
Images Co. ................................................70
Jameco ......................................................75
Lorax Works ........................................25, 70
Lynxmotion, Inc. .......................................11
Maxbotix ...................................................70
Mini Robotics .....................................63, 70
Net Media .................................................83
Parallax, Inc. ...............................Back Cover
PCB Pool ..............................................21, 70
Pololu Robotics & Electronics ..........43, 70
Rabbit, A Digi International Brand ............3
RoadNarrows Robotics ...........................24
Robot Craft ...............................................70
Robot Power ............................................23
RobotShop, Inc. .................................70, 76
Skycraft Surplus ........................................25
Solarbotics/HVW .....................................14
solderbynumbers.com ............................25
Sparkfun Electronics ..................................2
Technological Arts ...................................70
Vantec .......................................................10
Weird Stuff Warehouse ...........................25
Advertiser Index
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