Download I.R Headphone System (Transmitter)

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I.R Headphone System (Transmitter)
The 555 forms on oscillator generating pulses at a frequency of about
100kHz. Pin 5 on the 555 is the “control voltage” pin. A voltage applied to this
pin will vary the frequency of the oscillations. If the input is an audio
frequency alternating voltage, it will modulate the frequency of the oscillator.
We therefore have a frequency modulated (f.m.) infra-red beam.
R
+12v
4
7
3
555
0·47µ
4k7
5
10k
25k
8
6
1
2
330pF
-
The value of R depends on the number of transmitter diodes used; for two
diodes, as shown in the diagram, try R = 82Ω. If a higher transmitted power is
needed, try the arrangement shown below:
10Ω
+12v
pin 3 of 555
10Ω
The vero for the transmitter can be almost the same as the vero for the
transmitter for the “I.R. switch”.
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I.R Headphone System (Receiver)
Transistor: 2N3819 (f.e.t.) Integrated circuits: 4046 phase-locked loop used
as an f.m. demodulator; 4069UB hex inverter.
+9v
BP104
or
BPW34
200pF
4k7
1M
3 4 6
100n
d
13
1
2
2k7
12
14
180pF 4046
5
8
s
g
100µ
11
7
10
2
12
1M
220µ
11
330k
3
9
100n
1n
100n
4
10
output
100n
47
-
82pF 15mH
47k 270k 27k 470pF
© David Hoult 2001
2