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Solar Lighting

Discussion in 'Electronic Basics' started by Louis Hom, Aug 17, 2004.

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  1. Louis Hom

    Louis Hom Guest

    I know it would be easier to buy a new one, but I want to learn about
    this. We have a box that charges 2 AAs during the day with a little
    photovoltaic cell, then illuminates our house numbers (yellow LEDs) at
    night. It stopped working, and I found that jumping the wires across the
    light sensor turns on the lights. So I'm guessing that's the flawed
    component. The little circuit board is buried beneath some opaque epoxy
    or silicone-like material.

    So first, what is the name of the component I need to replace? Photocell?
    Photodiode? I'm all mixed up because I read that photocells have low
    resistance in light and high resistance in the dark . . . how do you turn
    on current flow by increasing resistance?

    My neighbor also gave me his failed solar-powered fluorescent light
    (collector is about 6"x8", with a 6V sealed lead acid battery), that I'd
    like to turn into a white LED system. Do I need more than the solar
    panel, battery, LEDs, diode to prevent back current into the panel, and a
    photocell to turn on the LEDs at the appropriate time?
  2. Blake

    Blake Guest

    It sounds like you're describing a cadmium sulphide Light Dependant Resistor
    (LDR). They are usually the problem in failed light sensing switches. Have a
    look at this web site for a sketch of one, and a descripition of how they
    work. There's even a schematic showing how to use one to turn on an LED. It
    should answer all of your questions.

    ----- Original Message -----
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