measuring current from a photo diode


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  1. #1
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    Default measuring current from a photo diode

    hello all

    i would like to read in the brightness of light. i have a sun-wind-sensor with a build in photo diode (i think) in direction of barricade.
    if i unterstod it right, the diode generate current in reference to the light. how can i measure this current (the light at the end) with my pic. i work with a 18f876a at port ra.0
    in the attachment a jpg of my test, but this doesn't work allright. must i change this current to a voltage, how?

    thanks for a hint
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    Last edited by mischl; - 12th November 2005 at 13:31.

  2. #2
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    Wink Precision, Precision ???

    Hi, mischl

    depends on how precisely you want to measure ...

    in your drawing, invert res. and diode, may be adjust a little the resistor value ... and you will have an rough idea ( linearity of photdiodes ... LOL ).

    Note amorphous photo-voltaic cells, used as current generators, are pretty linear devices ...

    the other way is a classical current to voltage converter around an OPA ... will be probably necessary.

    Alain
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  3. #3
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    Default

    A good explanation can be found at:



    http://www.national.com/onlinesemina...hotodiode.html

  4. #4
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    Default works

    hi alain and charles

    thanks a lot for the inputs.
    i replaced the resistor in the schematic with a 10k and it works fine now.

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