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Bots / The Ultimate Palm Robot/ Mukhar & Johnson / 222880-6 / Chapter 9

242 The Ultimate Palm Robot

The Hamamatsu Photoreflector

The photoreflector from Hamamatsu is similar to the infrared rangers that
we’ve already used. It has an IR light emitting diode (LED) that emits an infra-
red signal. When this signal is reflected by some object, another component
detects the signal. Unlike the ranger, however, this sensor signals only
whether or not it receives the IR pulse, but it does not calculate anything else
from the received signal.

This sensor comes in two varieties. If we assume that we have a black line on
a white surface, one sensor sets the output to a high state (close to 5 volts) when
it detects a reflected IR signal; otherwise, it sends out a low. That is, when the
sensor is over a white or reflective surface (not over the line), its output state
will be 5 volts. This sensor has the model number P5588. The other sensor is just
the opposite. It sets the output to a high state when it does not detect a reflective
IR signal; otherwise, it sends out a low. That is, when the sensor is over the line,
a black surface, its output state is 5 volts. This is the P5587 photoreflector sensor.
These values are illustrated in the following table.

Sensor Output
Over Black Over White
P5587 5V 0V
P5588 0V 5V
This sensor is easily connected to either the SV203 or the BrainStem controller.
The sensor has five pins, but we care about only three of those pins. As with
the IR rangers, we need the power input (also known as Vcc), the ground pin
(GND), and the output pin (Vo).

P:\010Comp\Bots\880-6\ch09.vp
Monday, May 12, 2003 4:33:41 PM