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Input: variable voltage; Output: 3 LEDs switching depending on voltage.

Discussion in 'LEDs and Optoelectronics' started by pixelapex, Nov 26, 2012.

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  1. pixelapex


    Nov 26, 2012
    I'm trying to assemble a circuit that will switch between 3 LEDs depending on input voltage. Electronic knowledge is very-very basic, but I'm working on it. I want 3rd LED to blink when circuit switches to it. Looks like I can accomplish with 555 timer.

    So... Let's say input voltage is 0-9v
    0-4v - nothing
    4-6v - 1st LED
    6-8v - 2nd LED
    8-9v - 3rd LED blinking.

    I'd like to be able to adjust points where each LED lights up (couple pots?). I want them to switch without overlap.

    Is there some kind of voltage sensing relay or something like that?... Please, point in the right direction. Thank you.
  2. GreenGiant


    Feb 9, 2012
    the way that I would do this is a few comparator circuits using op-amps, you would need a few different set voltage supplies (4V, 6V, 8V) or just an 8 with voltage dividers.
    or you could use analog to digital converters and do it that way but that would be more complicated with only 3 outputs. Im talking encoders/decoders, probably a multiplexer in there, complicated.

    using the comparator method would grant you a lot of fine tuning if you want/need to using pots
  3. duke37


    Jan 9, 2011
    Look at the LM3914. This has 10 comparators and 10 outputs to measure voltage.
    You could neglect the first three outputs and drive a led from 4 and 5 (use a diode from each output to stop interaction) and so on to the top. The top led could be a flashing type.

    The chip has a voltage reference.
  4. pixelapex


    Nov 26, 2012
    Originally, I looked at LM3914, will research further.

    GreenGiant, thank you for your idea, researching :)
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