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The Machine Man Band
John Rigg, RobotHut
As for the Machine Man band, I have it programmed
with over 140 songs right now. I use Cake Walk 9 to do
the MIDI programming for the robots. There are 100
electro-mechanical devices all under computer MIDI
control, and I plan to add more some day.
It took me about seven months to learn how to make
the 48 organ pipes and the electric valves to control them.
I used PVC pipe, aluminum, and resin parts that I designed
to make them from scratch. The second robot with the
xylophone, ride cymbal, and sleigh bells took about four
months to design and build.
Carl Kalkhof, Mentor, OH
The hexapod has six legs with three degrees of freedom per leg for a total of
18 motors that need to be driven by the control system. The “brain” is a Parallax
BS-2e microcontroller because it has enough memory for this application. The
servo driver I used was the PicoPic because it could drive 20 servos — and was inexpensive. The PicoPic interfaces to the BS-2e through a serial line and is very easy to
use. For the human interface, I found a small LCD on eBay that also interfaces to
the BS-2e easily. This LCD and some push buttons allow me to access different
modes of operation that have been pre-programmed in the Hexapod.
The hardest part of the whole project was finding suitable servos. I had a certain “look” in mind for this robot and wanted
long, thin legs. I found that retract servos fit the dimensions, but only came in “limit to limit” operation — without proportional
control. My solution was an expensive one: I used the retract servos, but substituted the non-proportional controls with
micro servo controls (the only controls that would fit in the retract servo casing). This meant that I had to buy a retract servo,
a potentiometer, and a micro servo for each degree of freedom.
The end result was a neat configuration that has good torque at the joints. The legs
may have been the hardest consideration, but the most important one was the battery
selection; I used a 7. 4 V LiPoly (lithium polymer) to cut down the weight. These batteries
have just recently become popular with the R/C guys and, without them, I doubt that my
robot would be able to stand up! A low dropout 5 V regulator was used for the Stamp
and PicoPic electronics, while three diodes in series (to drop around 2.5 V) — connected
to the batteries directly — supplied the 6 V for the servos.
SERVO 07.2004 35