Twin Tweaks ...
FIGURE 4. PROTOBOT.
FIGURE 5. PROTOBOT ELECTRONICS.
surgically removed the entire drive
train to plunk it right down into the
new Protobot.
The stock frame we used for
Protobot was simple — just a long
rectangle with two extra frame
members running lengthwise. After
installing the CIM motors and
associated gears, we added four more
caster wheels that we set slightly
higher than the Colson wheels driven
by the motors. We thought this design
would be effective at tackling uneven
terrain and it had a bit more cool
factor than a level drivetrain.
Building a frame and transplanting
a drive train were easy enough, but
the most daunting task was the
installation of the electronics. Simple
mechanical principles like how to build
a strong frame and how to calculate
gear ratios are accessible to even
budding roboticists, but electronics
can be another story. With
hieroglyphic-like schematics and a
host of enigmatic parts like speed
controllers, breakers, and terminal
blocks, hooking up the electronics
for a robot can be downright
intimidating.
Electronics have their own
vocabulary and their own set of rules,
and the learning curve can sometimes
be prohibitive (especially in the six
week time crunch of a FIRST build,
some team members might be
content to leave the circuitry to the
experts). Thankfully, the folks at FIRST
have provided ample documentation
on the electronic components, and
with two FIRST seasons under the
belts of the Team 1079 veterans, we
were ready to help the new guys
unlock the mysteries of electronics.
The electronics in Modos were
handily confined to a few mounting
shelves, and transplanting the shelves
onto the Protobot frame was relatively
painless. The transfer was expedited
by the fact that the stock frame came
pre-drilled with a plethora of possible
mounting points. The problem,
however, was that Modos was
markedly more complicated than
the new bot we were trying to build.
The drivetrain was simply controlled
by two Victor 884 ESCs, but the other
mechanisms on Modos (the lifting
arm, the grabbing fingers, etc.) were
all controlled by Spike relays that were
not necessary for Protobot.
Instead of completely eviscerating
our electronics boards, we unhooked
the wires to the newly unnecessary
components. After excising the
unnecessary wires, the overall goal of
building Protobot was realized — new
Team 1079 members got the chance
to see that robots do not have to be
that complicated to build.
The electronics in Protobot are
fairly straightforward. The CIM motors
connect to the Victors, which then run
through some 40 amp breakers, a
terminal block, and then onto the
master switch that comes before the
12 volt Exide battery. The Victors also
connect to the IFI controller, which
connects to the radio. Taken as a
whole, the Protobot circuit did not
include a lot of components and the
wiring consists of keeping track of
the power and ground wires (with a
few PWM cables thrown in there for
good measure).
We built Protobot in literally a
couple of days, and the low profile six
wheeler was a great way to practice
driving and to build confidence.
Despite these positive qualities,
Protobot has been neglected in Robot
Central for years. One reason for that
may have been the control system for
Protobot.
There was nothing inherently
wrong with the controls for Modos
that were inherited by Protobot. The
two joysticks gave the bot a truly
high tech feel, the controls were
FIGURE 6. PROTOBOT CONTROLS.
FIGURE 7. PROTOBOT WHEELS.
68 SERVO 05.2009