REVIVING A SHOWBOT
with an odd spacing. I didn’t want to
hack off the end of the cable and
install new ends in case the original
transmitter for ARTI was ever found.
Instead, I purchased a set of five 12”
servo extension cables. On each one, I
just cut off the male end, crimped on
new female pins, and inserted the pins
into a 10-pin housing that was just like
the original harness. I made sure the
ground, 5V, and signal lines matched
those of the Futaba receiver.
The channels were named on the
Futaba receiver instead of numbered
like the newer receivers. It had (AILE,
58 SERVO 01.2008
This shows the
and the old one.
ELEV, THRO, and RUDD) which then
had to be converted to the channel
numbers. The only difference was the
location of two channels on the early
Futaba receiver. When plugging in
channels 1 and 2 (Elevator and
Aileron), the two plugs just had to
be swapped on the new Airtronics
receiver to compensate.
Before attempting to power it up,
everything was double/triple checked
to avoid a mistake that could damage
any of the electronics. Doing it right is
much more important than doing it
fast (in my opinion, anyway!).
Getting ARTI to Move
the Way We Want
The first adjustments performed
on the transmitter were to the end
point adjustments for each channel.
This can set a limit on the signal that
would normally drive the servos
which, in turn, limit their travel. On an
electronic speed controller, this can
also act like a governor to prevent the
robot from reaching top speed. I
learned this lesson the hard way.
The first R/C electronic speed
controller I used was a Vantec unit on
my Battlebot ‘Crash Test Dummy.’ The
robot seemed really fast but hadn’t
been going full speed when it was
competing. I was unaware that just
turning those little end point adjustments could make a huge difference.
(Arggh!!) When I figured that out
afterwards, the robot seemed to go
twice as fast! Since then, I check and
recheck every adjustment I can make
when using radio gear like this.
With the new radio gear connect-
ed, it was time to see if and how ARTI
would work. (Again, I want to note
that the wheels were propped up so
they wouldn’t touch the ground!) It is a
convention that the transmitter is the
first thing on and the last thing
off. This prevents the receiver from
potentially picking up a stray signal.
The radio was powered on first, then
the robot. ARTI immediately started
making a loud siren sound and the
wheels started to move. If I moved the
joysticks on the transmitter, I could get
the siren to silence and change
the speed of the motors. The controls
didn’t respond as you would expect,
but I anticipated there would be some
issues to deal with.
Adjusting the trim tabs on the
radio helped. The siren sound finally
subsided and was quiet, and the
wheels almost stopped with the
joysticks centered. Next was to determine if ARTI was meant to drive with
conventional tank style steering (dual
sticks) or if the controller would handle
the mixing of the drive and steering
channels for single stick operation.
Since the drive motors only
seemed to respond to the right stick, it
appeared that the controller did handle
the channel mixing for driving with a
single stick. I suppose that made sense
so that an operator could drive with
one hand on the controller, if needed.
With the motors moving, the next
step was to get them calibrated and
When moving the stick up and
down, the direction the wheels were
turning appeared to be reversed. This
part was easily corrected by flipping the
channel reverse switch on the front of
the transmitter. Some radios have these
reversing switches on the back or hidden under a cover. The steering control
acted a bit differently than I was used
to as it only worked with the stick at the
extreme range of the joystick. Had I not
changed the end point adjustment on
the transmitter, I may not have been
able to steer the robot at all.
When the joystick was full right,
the left motor was off and only the
right motor would go forward and
back. With the joystick at the full left
position, the right motor would be off