Twin Tweaks ...
CAN YOU HEAR ME NOW?
we were first getting started in the world of competitive
robotics, we obtained some awesome Maxon motors to
use for our combat robots. The motors came with fancy
mil spec connectors that featured numerous interlocking
pins and sockets. The sockets can be crimped around
individual wires to easily connect them to pins on any
board. Removing the sockets can be a bit of a chore, so
instead we cannibalized the sockets off of some switches
that we had used on another snake themed project — the
Viper from Microbric (see the September ‘06 issue for
more fun with that modular kit).
With the sensor wired up, we were ready to see if the
Cobra chassis could expand its horizons beyond the
ascetic minimalism of the mini Sumo ring.
Hear No Evil
Sometimes when robotics kits are meant to be
experimental platforms, they will dedicate specific parts of
FEATS OF STRENGTH!
72 SERVO 09.2012
their physical frame to support additions of sensors and
mechanisms (see the RobotShop Rover in the March ‘ 11
issue for an example). The Cobra has a few such places
for sensors. Specifically, there are cutouts in the steel base
and holes in the Garolite to accommodate QRD1114 IR
sensors. Other than that, however, there are no super
obvious places to mount a sensor or additional
One could conceivably drill additional mounting holes
in the base, but that would require keeping the holes in
the steel and Garolite aligned. Plus, Swiss-cheesing the
baseplate risks jeopardizing the low center of gravity so
helpful for a mini Sumo bot. Fortunately, such extreme
measures would not need to be taken.
When we first mounted our Mark III brain to the
Cobra, we were a bit dismayed to see that the mounting
holes on the board did not match up with the standoffs
protruding from the base. We were able to rig up an
adaptive frame with the VEX pieces that used two
diagonally situated standoffs. The others could be used to
attach brackets capable of holding sensors. We could also
use the standoffs more directly. It made sense for the
ultrasonic sensor to face forward, and it turned out that
the spacing of the standoffs provided the perfect back
support for the sensor. We covered the back of the sensor
PCB with electrical tape to avoid shorting anything, and
with a few tie wraps we had a set of ears firmly mounted
to the front of the bot.
Now that we knew where the sensor felt at home, we
could make our final adjustments to the wiring. The
mismatch of the standoffs and brain mounting holes
ended up being quite serendipitous — the wires for the
SRF-05 routed through one of the holes in the brain board
perfectly. We also discovered that our initial
apprehensions about disparately placed pins were
unfounded. All of the pins lined up nicely. We were able
to make use of the other standoffs, as well; one
supported a bracket that held the TinyESCs and the other
held the LiPoly pack in place under the brain. With the bot
put together, all we needed to do was program it.
C No Evil
When you’re dealing with sensors, wiring them up
and mounting them is only half the battle. We still had to
program them. Especially when dealing with a new
sensor, our tendency is to find example code to build off
of. There were plenty of sample codes available on the
Internet, but it seemed like almost all of them were in
BASIC syntax. We were programming our bot in C.