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I.R
Headphone System (Transmitter) |
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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. |
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The value of R depends
on the number of transmitter diodes used; for two diodes,
as shown in the diagram, try R = 82W.
If a higher transmitted power is needed, try the
arrangement shown below: |
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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) |
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Transistor: 2N3819 (f.e.t.)
Integrated circuits: 4046 phase-locked loop used as an f.m.
demodulator; 4069UB hex inverter. |
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Vero diagram |
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© David Hoult 2009
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Open Door Web Site