REVIVING A SHOWBOT
easily removable and can
be changed, if needed. An
example is an extra head
(McGruff, the crime dog) that
came with the robot. I’ll just
need to pick up a trench coat
if we use that extra head.
One of the first things to
do after taking an inventory
of the major components
used is to get an idea of how
everything was connected.
RX and harness.
This entails making a sketch of the
connectors on the controller board and
tracing out where the wires go.
The controller board had a 10-pin
connector for the radio receiver, a large
3 x 5 connector near the top, and
another large 3 x 4 connector near the
bottom. A rough schematic was made
of the charging and power sections
since that was one of the first sections
to deal with. Then, the rest of the
connections were mapped out.
tell that the battery shipped with it was
the wrong one. It was a 12V battery
with some handmade extensions to
connect it. The battery was much smaller than the compartment and as a
result, it would slide around. (It is not a
good thing to have a battery freely
moving around and banging into stuff!)
If you can’t follow the wires directly
or they are hard to see, an ohmmeter is
your friend and can help verify you have
the correct wire. It helps if you can
unplug any connectors so that you’ll just
be mapping out the wiring itself and not
have to worry about any feedback from
a board or device it may be plugged into.
After measuring the battery compartment, I found that it was perfectly
sized to accommodate a 12V 17AH
battery. I ordered a new one and it fit
perfectly! When the original one died,
I’m sure that someone just picked up a
12V battery and didn’t really care if it
was the correct one or not. This larger
battery has the extra capacity needed
for longer performances.
The 3 x 5 connector provided the
power to the OHRA communicator, the
charge LEDs, cassette power, cassette
audio, headset out, and a couple
unused pins. The 3 x 4 connector has
the main power, charger, left and right
drive motors, and the body lights.
Having at least the basic wiring of
the robot documented helps before
getting into the project.
The power switch has three
positions. If the switch is in the right
position, the robot will be on. When
the switch is in the left position, the
battery will be connected to the
charging circuit. The center is everything off, which keeps the main
battery completely isolated. This center
position would normally be used if
ARTI was going to be stored for a while
or being transported to a show.
After installing new ring terminals
on the wiring and bolting them to the
battery, that portion was now all set.
An important note of caution here!
Before attempting to power up a
strange robot for the first time, make
sure that the wheels are lifted off the
ground! This way, it won’t run over you
or wreak other havoc in your workshop
if it decides to do something unexpected. Be safe and be smart when
working with mechanical and
electrical gadgets! With the new
battery, the robot would power up, the
eyes and mouth would light, but that
was about it.
Getting ARTI to Move
We Need More Power
When examining the robot, I could
The original remote was probably
a standard dual stick Futaba four channel remote. It may have been a hacked
version customized to fit in a bag or
otherwise concealed for the operator.
That way, no one would notice it if the
operator was hanging out with the
crowd around the robot. At first, I was
ARTI 1 robot.
going to find an old Futaba transmitter
on the surface 75 MHz band and then
swap crystals (if needed) for the correct channel/frequency. However, after
looking into it a bit more, I discovered
that the original R/C gear was an older
wide band AM unit which probably
shouldn’t be used these days, anyway.
Instead, I decided to use an extra
Airtronics VG600 75 MHz FM six
channel radio set that was leftover
from my old Battlebot. This new R/C
gear should prove to be more reliable
and more immune to interference than
the original gear. My radio set also has
two extra channels that could be put to
use later to control other features.
However, it ended up requiring
more than just plugging in the new
receiver into the robot. (Things are
never that easy!) The connectors were
different on the early Futaba receiver
than on the current crop of radio
receivers. Each had male connectors
Close-up of connector
on new RX cable.
SERVO 01.2008 57