light-to-voltage chip for sensing bright daylight and dark night

Discussion in 'The Projects Forum' started by rousku, Jan 31, 2009.

  1. rousku

    Thread Starter New Member

    Jan 31, 2009
    I'm building a circuit to control brightness of few leds. The brightness should be proportional to ambient light, which can vary from dark night to bright day.

    Could someone point me a sensor (outputs voltage), which can feed me a voltage linearly proportional to ambient light.

    I have found many chips like this -> , but if I have understood right, that chip can't make a difference in irradiance when the day is very bright. Am I right?

  2. beenthere

    Retired Moderator

    Apr 20, 2004
    You may need a photodiode circuit with a logarithmic response. The TAOS light to voltage converters are linear in response.

    Of course, it's all of $1.27 to get one and experiment with it....
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Just now connected a 680Ω resistor, CdS photo-cell [ #G15177 ] ,bright white LED [#G16402 ], & 16V power supply in a loop. In dark LED was out, full light LED was bright. Both LED & photo cell are verry non linear so they compliment ea. other verry well. First detectable light from LED was with one μA, and limited to 18 mA at full illumination by cell & 680Ω. Cell's range about 1 meg to 50Ω. Part nos from The Electronic Goldmine.