Manual

You need an infrared remote control for this project, such as any
TV/stereo/DVD remote control in your home.
Turn on the slide switch (S1) and 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.
Note that when the phototransistor (Q4) is activated by room lights the
white LED is on continuously, and when the phototransistor is activated
by your infrared remote control LED will be blinking.
The phototransistor can detect light,
and infrared light is light. The white LED
is blinking even if you are pressing your
remote control continuously, because
the signal from your remote control is
not constant, but rather a stream of
infrared light bursts.
Use the preceding circuit, but replace the white LED (D6) with the color
LED (D8). The circuit works the same way, but note that when the
phototransistor (Q4) is activated by room lights the color LED will execute
a blinking pattern, and when the phototransistor is activated by your
infrared remote control the color LED will be on but its normal pattern will
be blurred.
Project 114
Color IR Control
Use the preceding circuit, but replace the color LED (D8) with the horn
(W1). The circuit works the same way, but note that when the
phototransistor (Q4) is activated by room lights the horn makes a loud
continuous sound, and when the phototransistor is activated by your
infrared remote control the horn will be on but only make a low buzzing
sound.
Project 115
Audio IR Control
The color LED needs a constant voltage
to operate its color-changing pattern
properly. The infrared control signal is a
stream of infrared light bursts, which
disrupt the LED’s color-changing circuitry.
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Project 113 IR Control
Similarly, the horn needs a constant
voltage to operate properly, and the
buzzing sound you hear is because the
infrared control signal is not stable enough
to operate the horn properly.