SER FAQ: TVFAQ: IR detector circuit

S.E.R. FAQ

NotTaR of Television Sets : IR detector circuit
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IR detector circuit

This IR Detector may be used for testing of IR remote controls, CD player laserdiodes, and other low level near IR emitters.

Component values are not critical. Purchase photodiode sensitive to near IR - 750-900 um or salvage from optocoupler or photosensor. Dead computer mice, not the furry kind, usually contain IR sensitive photodiodes. For convenience, use a 9V battery for power. Even a weak one will work fine. Construct so that LED does not illuminate the photodiode!

The detected signal may be monitored at the collector of the transistor (Q1) with an oscilloscope.


 Vcc (+9 V) >-------+---------+
                   |         |
                   |         \
                   /         /  R3
                   \ R1      \  500
                   / 3.3K    /
                   \       __|__
                   |       _\_/_  LED1 Visible LED
                 __|__       |
       IR ---->  _/_\_ PD1   +--------> Scope monitor point
         Sensor    |         |
       Photodiode  |     B |/ C
                   +-------|    Q1 2N3904
                   |       |\ E
                   \         | 
                   / R2      +--------> GND
                   \ 27K     |
                   /         |
                   |         |
      GND >--------+---------+
                  _|_
                   -

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