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Photocell Light Level Controls Bar Graph

Discussion in 'LEDs and Optoelectronics' started by DenisNH, Dec 3, 2006.

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  1. DenisNH

    DenisNH

    1
    0
    Dec 3, 2006
    Hi All. I'm new here and have been searching around for more information on this subject without much luck. If this has already been discussed, I apologize. I've always worked on a systems level and have done very little component level work, so my theory in that area is pretty rough.

    What I would like to do is make a basic light meter using cadmium-sulfide photocells available at Radio Shack. (Part# 276-1657) I would like to use the LM3914 bar graph driver with a 10 LED bar graph. The greater the light intensity, the more LED segments would glow.

    These photocells vary resistance rather than supply a micro-voltage, and this is messing me up a bit. The greater the light intensity, the LESS the resistance. The photocells are very sensitive, though, and I think they would do a great job if I can work them into the circuit.

    I've only spent a few hours on the circuit so far, but at this point feel that I'm spinning my wheels. Having just printed off a bunch of data sheets and application notes, I'm ready to go back to studying the available information before jumping back into the project.

    If anyone has pointers to web sites that explain this, or have any advice to offer, I will be very grateful. The LM391 seems like an awesome chip with a lot of potential!

    Thanks!
     
  2. gravesend

    gravesend

    2
    0
    Jan 5, 2010
    intriguing question
     
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