PIC16F877A-based controller using built-in C compiler
RS-232 communications functions. To support the IR
functionality of the Robotics Development Kit, a full-blown
Philips N9085UD IR remote control (like the one you see
in Photo 2) is packed in the black box.
As one would expect, the robotics are battery
powered and a custom nine-volt/AA power harness
is provided. The battery combination is designed to
power the robot electronics, as well as the pair of
hobby servos are also in the black box. The actual CCS
compiler is not part of the kit and if you don’t already
have a version of it, you’ll need to purchase that separately.
The CCS robot senses the proximity of objects it
encounters using the services of a Sharp GP2D120X,
which can be seen in Photo 3. The GP2D120X is designed
to measure short distances ( 10 to 80 cm) using a pulsed
infrared beam/detector scheme. If you want to measure
precise distances using the GP2D120X, there are a number
of application notes available on the Internet that explain
the math behind the IR echoes. In the case of our robot,
we simply want to know if something gets close and needs
to be avoided.
A similar IR emitter/detector operation is performed to
keep the robot glued to a line on the floor. Three Fairchild
QRB1134 reflective object sensors are mounted in such a
way as to keep the robot on the straight and narrow.
The QRB1134 you see in Photo 4
consists of an infrared emitting diode and an NPN
phototransistor mounted side by side. The IR diode and
phototransistor are arranged in a way as to force the IR
light from the emitter to bounce off of a reflective object
into the detector. Unlike the GP2D120X, the QRB1134
sensors are not modulated.
Thus, the QRB1134’s NPN
phototransistor operates in a light-dependent linear mode
and — with the help of a resistor — produces an analog
voltage which is used to determine if the sensor
is over a reflective or dark surface.
If there aren’t any robot control lines on your living
room floor, our little roving mass of sheet metal and silicon
is equipped with an onboard compass. Two axes of a
PNI-11096 three-axis magneto-inductive sensor driver and
controller are used to implement the “compass.”
The physical robot that is spawned from the CCS
Robotics Development Kit has no problem communicating
with humans (or anything that emits IR light, chirps, or
beeps). A software-supported Winbond WTS701EW
single-chip text-to-speech processor is mounted on the
PIC16F877A-based controller printed circuit board (PCB).
We’ve already seen how the CCS robot uses infrared to
its advantage. The Philips N9085UD IR remote control
extends the CCS robot’s IR capabilities. An onboard Sharp
GP1UW IR detector is employed to pick up the Manchester-encoded signal emitted by the N9085UD. Thus, our little
big-mouth-compass-carrying-line-following Boy Scout droid
Photo 2. The CCS C compiler
supports this remote control with
a dedicated source code driver
module. An onboard GP1UW IR
detector mounted on the robot
controller printed circuit board lies
at the other end of the IR link.
Photo 3. This is a very popular
sensor and you can find lots of
information as to how to apply it
on the Internet. By not applying
any serious math, you can use the
GP2D120X in coarse mode. In
coarse mode, the proximity sensor
is a simple object detector.
Photo 4. The minimum focal length for this sensor is
nominally 0.150 inches. I found the sensors to sense
accurately up to about four inches out.
SERVO 09.2009 39