holes at the bottom of the PCB (printed circuit board)
large enough for #24 AWG insulated wire to pass
through (1.5 mm is fine for this). They create the
strain relief for the wires to the battery holders and
sub-mini toggle switches. The remaining holes are
drilled with a #67 drill bit. After completing your
CheapBot-08 PCB, gather the following components:
Small bottle tops (from a bottle of cranberry juice) are big wheels for this robot. Between the decks, the robot controller is visible on
its stand-offs. You can see it’s a little crowded between the decks.
motors plug into the two male headers (labeled Motor 0/4
and Motor 0/1) near the bottom of the robot controller
(the numbers indicate which I/O pins control that motor
port). There are two pairs of I/O ports to plug sensor
boards into the controller. One port provides + 5 volts and
connection to the -08M’s Input 3, while the other port
provides ground and a connection to the -08M’s Input/
Output 2. Since power and ground are not provided on
a single expansion port, expansion boards must have
connectors for both expansion ports to operate (the
benefit is that the two connections to the controller give
an expansion board better support and stability).
Eight-pin IC socket
Two 1K resistors 1/4 W
10K resistor 1/4 W
22K resistor 1/4 W
LM2950 five volt regulator (TO-92 case)
Two T-1 LEDs (different colors are preferred)
Two Toshiba TA8080K motor controllers**
Two 1 x 2 straight pin headers
One 1 x 3 straight pin header
Two 1 x 2 right angle headers
Two 2 x 2 receptacles***
22 µF electrolytic capacitors****
20 µF tantalum electrolytic capacitor****
Two sub-mini toggle switches
Four-cell “AAA” battery holder
Three-cell “AAA” battery holder
Stranded wire, #24 AWG
Heat shrink for the #24 wire
*Don’t use the PICAXE-08; it only has 128 bytes of memory.
**Purchase from Surplus Gizmos; www.surplusgizmos.com
***You’ll have to cut pieces off a double row receptacle.
****Use physically small capacitors; their voltage ratings
can be as little as six volts.
Order of Assembly
After making your copy of the controller, drill the eight
The CheapBot-08 is a little bit crowded, so space gets
tight in places. Assemble the controller by installing the
lowest lying components first. This means starting with the
six jumper wires (resistor leads make perfect jumper
wires). Next, add the wires for the switches (but wait
to attach the switches to the ends of the wires).
Then, solder the following components in this order:
Right angle headers
These are the parts on the underside of the CheapBot-08 robot
and their placement. To give a scale to this robot, the servo motors are 7/8 inches tall.
50 SERVO 11.2009
Note: The 20 µF capacitor located between the
H-bridges solders to the PCB before the H-bridges so
all three items will fit well. Soldering the H-bridges
first may not leave enough space to fit the capacitor.
Strip the ends of the switch wires and solder
toggle switches to them. Be sure to slide heat shrink
over the wires first so you can insulate the soldered