20-04-2012, 12:43 PM
IR MUSIC TRANSMITTER AND RECEIVER
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Using this circuit, audio musical
notes can be generated
and heard up to a distance of
The circuit can be divided into
two parts: IR music transmitter and
receiver. The IR music transmitter
works off a 9V battery, while the
IR music receiver
works off
regulated 9V to
12V.
Fig. 1 shows
the circuit of
the IR music
transmitter. It
uses popular
melody generator
IC UM66
(IC1) that can
continuously
generate musical
tones. The
output of IC1 is
fed to the IR
driver stage (built across the transistors
T1 and T2) to get the maximum
range.
Here the red LED (LED1) flickers
according to the musical tones generated
by UM66 IC, indicating modulation.
IR LED2 and LED3 are infrared
transmitting LEDs. For maximum
sound transmission these should be
oriented towards IR phototransistor
L14F1 (T3).
The IR music receiver uses popular
op-amp IC μA741 and audio-frequency
amplifier IC LM386 along with
phototransistor L14F1 and some discrete
components (Fig. 2).
The melody generated by IC UM66
is transmitted through IR LEDs, received
by phototransistor
T3 and fed to pin 2 of
IC μA741 (IC2). Its gain
can be varied using
potmeter VR1. The output
of IC μA741 is fed to IC
LM386 (IC3) via capacitor
C5 and potmeter VR2.
The melody produced
is heard through the
receiver’s loudspeaker.
Potmeter VR2 is used to
control the volume of
loudspeaker LS1 (8-ohm,
1W).
Switching off the
power supply stops
melody generation.