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166 CONSTRUCTING HIGH- TECH ROBOTS FROM TOYS

from the arm to a computer interface (with relays, for example) and operate the arm via soft-
ware control.
Most of the OWIKIT/MOVITS robots come with preassembled circuit boards; you are
expected to assemble the mechanical parts. Some of the robots use extremely small parts and
require a keen eye and steady hand. The kits are available in three skill levels: beginner, inter-
mediate, and advanced. If you’re just starting out, try a beginner- level kit.
Once (properly) constructed, the OWIKIT and MOVITS robots last a long, long time. I have
several models— no longer available— I built in the mid- 1980s, and, with just the occasional
nut tightening here and a dab of grease there, they have continued to operate flawlessly.

Making Robots from Converted Toy Vehicles

Toy cars, trucks, tractors, and tanks can make ideal robot platforms. With some motorized
vehicles, you can directly convert them to robot service by hacking into their motor connec-
tions. Quick and simple! With others, you may need to do a bit of disassembly and rebuilding,
especially those toys that have only one drive motor— it’s best when they have two.
And let’s not forget that you can rob parts from nonmotorized toy vehicles. I’ve gotten
some of the best stuff off of cheapo “dollar store” toys! Push- around toys with rubber tank
treads are an especially nice find. Rob the treads and put ’em on your own robot base.

MOTORIZED VEHICLES
Let’s start with inexpensive radio- controlled cars. These have a single drive motor and a sepa-
rate steering servo or mechanism; the setup doesn’t lend itself well to robot conversion. In
many cases, the steering mechanism is not separately controlled; you “steer” the car by mak-
ing it go in reverse. The car drives forward in a straight line but turns in long arcs when
reversed. These are impractical for use as a robot base and you should spend your attention
elsewhere (they’re okay for stripping off parts).
On the other hand, most radio- and wire- controlled tractor (farm, military tank, construc-
tion) vehicles are perfectly suited for conversion into a robot. Remove the extra tractor stuff
to leave the basic chassis, drive motors, and tracks.
You can keep the remote control system as is or remove the remote receiver (or wires, if
it’s a wired remote) and replace it with new control circuitry. In the case of a wired remote,
you can substitute relays or an electronic circuit for the switches in the remote. Of course,
each toy is a little different, so you’ll need to adapt this wiring diagram to suit the construction
of the vehicle you are using.

The most common electronic circuit used as a substitute for switches is the transistorized
H- bridge, discussed more fully in Chapter 22, “Using DC Motors.” When replacing manual
switches with an H- bridge, be sure the motors don’t draw more current than the H- bridge can
FYI handle, or damage to the electronics could occur.
Chapter 21 details the method of testing the amount of current consumed by a motor. You’ll
need a digital multimeter to complete the test.

Another option is to use two small motorized vehicles (mini “4- wheel- drive” trucks are
perfect), remove the wheels on opposite sides, and mount them on a robot platform. Your
robot uses the remaining wheels for traction. Each of the vehicles is driven by a single motor,

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