FIGURE 2. These are the tools I highly recommend for rapid
prototyping of electronic circuits with the VEX microcontroller.
They include wire cutters, long nose pliers, a RadioShack
wire-wrap tool, and wire-wrap wire.
combined total from all the pins. Although these
I/O pins are internally protected with resistors
and diodes, they can still be damaged or
shorted. Care should be taken when connecting
the wires so as not to create direct shorts to
ground unless specifically directed to do so. We
must not short these pins or connect them to
the power supply using the wrong polarity. The
schematic in Figure 1 shows you how to wire a
simple LED circuit to the microcontroller’s digital
output pins. VEX motors are connected to the
motor port. Everything’s assembled on a
RadioShack breadboard.
More Safety Stuff
FIGURE 3. The “brain” of the robot. The microcontroller
contains the robot’s programs and processes all signals
received from both human operators and onboard sensor
systems. It also manages power allocation on board the
robot, and directly controls the motors.
50 SERVO 03.2010
Safety should always be first on the mind of any builder
when working with electronics. Always wear safety eye
glasses or goggles with side shields. As an alternative to
soldering, (to avoid spatters) I highly recommend using
wire-wrap and a low-cost tool. If you need to solder, only
use unleaded ROHS solder and components when possible.
Most of the experiments that will be presented here can be
carried out without soldering. The tools I highly recommend
for rapid prototyping are shown in Figure 2. The wire-wrap
tool in particular is very useful for making the connections
between pin headers inserted into the microcontroller’s I/O
ports and external circuits.
Another precaution to take is to make sure the
workspace is static free in order to prevent Electrostatic
Discharge (ESD) damage to the microcontroller and any
circuits. Purchasing a low-cost ground strap is also a good
idea.
Getting Better Aquainted
The VEX microcontroller shown in Figure 3 is more
than just a motor controller since it provides access for up
to 16 digital or analog input or output pins, eight motor
outputs, and six interrupts. It uses its silicon brain to process
algorithms with its internal processors and memory. It will
provide a convenient platform to carry out our electronic
experiments and will allow us to extend the controller’s
input and output capabilities to read new kinds of sensors,
switches, keypads, LED displays, and LCD displays.
Powering The VEX Controller
The recommended power supply to attach to the
power connector (on the back of the microcontroller) is a
7. 6 volt battery pack; although you can also connect a 9. 6
volt battery pack since it shares the same connector and
does not seem to harm the controller. Connecting the 9. 6
volt battery pack does make motors and servos run faster,
which could wear them out sooner. (For this reason, IFI
does not recommend using the higher voltage battery pack.
It also is not allowed in most VEX VRC contests.)
