help !! photo cell sensor

Discussion in 'The Projects Forum' started by feesoo, Mar 3, 2007.

  1. feesoo

    Thread Starter New Member

    Mar 3, 2007
    4
    0
    i have photo cell sensor that contains transmitter (IR LED) and receiver (transistor) i want full design for the signal conditioning unit ,,i have buit many forms but still cannot work .
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    If you are lucky, the emitter and detector sides are marked E & D, and should also have polarity marks. Otherwise, you wil need the spec sheet from the manufacturer.

    The emitter will need between 20 and 50 milliamps current. Chooes a resistor based on the voltage applied. The detector always runs common-emitter, so put the - to ground. IR photons don't carry much energy, so make the collector resistor fairly large. You can adjust for sensitivity by observing the transistor switching - when the collector resistor is too small, the output can no longer go to ground with full illumination.

    The signal out is not capable of driving anything without amplification or buffering. Use a FET like a 2N7000 or a high input resistance op amp like an OP27.
     
  3. feesoo

    Thread Starter New Member

    Mar 3, 2007
    4
    0
    can you provid me with some drawings so i can imagin the circuit more.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    I have no idea what specific device you are trying to use. But, the manufacturer will provide a data sheet which will almost certainly illustrate a typical circuit using that device.
     
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