Manual

Project 108 Reverse Photo
Control
Build the circuit and turn on the switch (S1). The
color LED (D8) and horn (W1) will be on unless
there is bright light on the phototransistor (Q4);
cover the phototransistor if the LED and horn are
on, or shine brighter light on it if they are off.
Projects 108-110 are the inverse
of projects 103-105.
If you remove the phototransistor
from the circuit then the LED and
horn will always be on, because
then the circuit is controlled by the
5.1kW resistor, and it does not
change.
Project 111 Infrared-Controlled
Light
You need an infrared remote control
for this project, such as any
TV/stereo/DVD remote control in
your home.
Build the circuit and turn on the
switch (S1). Place the Q4
attachment on the phototransistor
(Q4). Position the circuit away from
lights in the room so that the white
LED (D6) is off. Point your remote
control directly into the Q4
attachment, and press any button
to turn on the white LED. The LED
may not get very bright.
The phototransistor can
detect light, and infrared
light is light.
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Replace the white LED (D6)
with the color LED (D8).
Project 112
Infrared-
Controlled
Color Light
Use the preceding circuit, but
replace the color LED (D8) with
the white LED (D6).
Project 109
Reverse Photo
Control (II)
Use the preceding circuit, but
replace the horn (W1) with the
color LED (D8).
Project 110
Reverse Photo
Control (III)