Figure 7. Reusing parts for sensor relocation.
The best place to mount the WheelCommander is right
on top of the servos (directly under the SumoBoard). Due to
vibrations in the robot and flexure between the two servos, I
decided that I was going to place a small board between the
WheelCommander and the servos. Figure 9 shows some
double sided foam tape added to the servos for mounting
the intermediate board, and Figure 10 shows a 1/4” thick
piece of scrap Sintra (expanded PVC). You can use different
types and sizes of material here. This was just something I
had lying around. I then used two more pieces of double
sided foam tape to attach the WheelCommander to this
Figure 9. Double sided foam tape for
mounting the WheelCommander to the servos.
Figure 11. WheelCommander mounted
on the servos.
board (see Figure 11).
Figure 12 shows all
the wiring attached to
the WheelCommander. You
should notice that there is a
new battery attached to
the front of the robot. The
a minimum of 6. 2 volts to
operate properly. Since the
regular SumoBot uses
only four AA batteries
( 6.0V), they were insufficient to power the
WheelCommander along with the BASIC Stamp and drive
the servo. So, I added a 9V battery to the front of the Parallax
SumoBot. This battery fitted nicely in front of the servos and
WheelCommander. A rubber band was used to hold the
battery to the screws that hold the servos in position.
Figure 13 shows the completed robot. The servo power
to the WheelCommander is plugged into the B and R pins
used to power the servos on the original SumoBoard. I chose
to do it this way so that I can take advantage of the
three-way power switch on the SumoBoard to make sure
that the servos are not accidentally powered during
rogramming efforts. The rest
of the wiring is pretty much
the same as outlined in the
Ideally, you would add a
power switch to turn the power
on to the WheelCommander. I
chose to use simple connectors.
There are two things you
are going to want to download
from the Nubotics website.
The WC Wizard program
and the example program
( wc116_bs2_demo.bs2) for the
BASIC Stamp. The WC Wizard is
a great utility for testing and
configuring the WheelCommander
for your specific robot’s
geometry. Also with the WC
Wizard, you can tune the PID
(Proportional, Integral and
Derivative) constants for the
closed loop position and velocity
control of your robot.
In addition, you can change
the serial communication baud
rate for the WheelCommander.
The default baud rate is 38400.
Now all of these configuration
parameters can be transmitted
to the WheelCommander via
the BASIC Stamp. The WC
Wizard has some nice visual
Figure 8. New edge/line sensor orientation.
Figure 10. Intermediate board between the
servos and the WheelCommander.
Figure 12. All wiring attached to
22 SERVO 03.2008