Madeusa Robot Base, Full Kit: $879
Eddie Robot Platform: $1,249
assembling the inner tube onto the hub and rim, be
sure none of the rubber is pinched or else it could
cause a leak when you add air to the tire.
And, speaking of adding air ... best use a hand
pump. It’s hard to control the amount of air that
goes into the tire when using a powered air
compressor. Even a short blast of air might over-pressurize the tire.
The motors and pillow blocks can be constructed
next. The completed drive assembly with pneumatic
wheel is shown in Figure 6. Before attaching the
motors to the base, however, read up on the jumper
settings for the position encoders. A jumper is
provided to select one of several Device ID addresses,
should you wish to daisy-chain the two encoders off
one serial port. They’re shipped from the factory to
both use Device ID 1; if you’d like to use one serial port for
both encoders, set one of them to Device ID 2.
Caution: When mounting the plastic codewheel onto
the wheel shaft, be sure to apply equal pressure to just the
hub — don’t press on the outer flange of the codewheel.
You don’t want to break off any of the “vanes” of the
codewheel. Once seated on the shaft, turn the assembly
sideways and sight down the center of the optical switches.
Ensure that the codewheel rotates within the middle of the
two infrared slot switches (see Figure 7). You’ll hear a
scraping or tapping sound if the codewheel is rubbing
I found it easier to install all the wiring for the wheel
encoders and motors at this point, before mounting the
motors to the robot. Once the wheels are mounted, the
headers on the wheel encoders can be hard to reach.
The MadeUSA uses two double-wheel casters for
front and back balance. These casters are constructed
from commercial rubber wheels (see Figure 8) and
custom machined parts to create a very sturdy and well
made mechanism. The caster swivels on a center axle;
the whole thing is kept in place with a collar and
setscrew. The caster parts are shown in Figure 9.
The only real trouble I had in assembling my
MadeUSA was getting the setscrew for the axle in place.
Mine used a slotted setscrew (as opposed to a hex
socket setscrew), and the screwdriver wouldn’t keep
the screw captive long enough to thread it. In the end,
I solved the problem by putting a bit of 3M tacky
putty over the head of the screw. That kept the screw
on the screwdriver long enough to thread it into the
FIGURE 8. One of two casters on the MadeUSA. These swivel freely
and give the robot support in both the front and back.
Completing the MadeUSA
batteries, power wiring, and switches. Your choice of
microcontroller and other electronics is up to you. So far,
I’ve built the MadeUSA in two versions; the first (shown in
Figure 10) used an Arduino Mega 2560, along with a
combination MP3/MIDI shield from SparkFun.
My current build uses a Parallax Board of Education
(PropBOE) which has the same footprint as the BASIC
Stamp BOE, used on the Parallax BOE-Bot. Instead of a
BASIC Stamp, the PropBOE uses a Propeller microcontroller.
One of my favorite features of the PropBOE is that it comes
with a socket for an XBee radio transceiver. Just plug in the
XBee, and you’re ready to talk to other devices — no
additional wiring necessary. The PropBOE
also has connections for six R/C servos
and has its own micro-SD card
reader, audio amplifier, video
generator, and analog-to-digital
Both versions I’ve built use
a separate deck constructed
with 6 mm expanded PVC
plastic; the basic idea is shown
in Figure 11. This allows me to
easily swap electronics, without
having to do a major mechanical
overhaul. On the main deck is
the microcontroller plus
area. It’s for
before I commit
any electronics to
The MadeUSA is a starter base; it isn’t a complete
robot, ready to roll right out of the box. What’s not
included: At a minimum, you need a microcontroller,
FIGURE 9. Caster parts before assembly. After some cussing
(and some sticky putty), I finally conquered the small
setscrew shown in the foreground!
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