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boot on power-up

Discussion in 'Electronic Basics' started by Skeleton Man, Jan 26, 2005.

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  1. Skeleton Man

    Skeleton Man Guest


    I'm trying to accomplish what I thought was an extremely simple task, of putting
    a capacitor across the atx power switch so it will turn on as soon as power is
    applied (as the bios does not have this feature).

    I do NOT want a 555 circuit or any kind of circuit at all.. just a single
    capacitor and maybe a resistor to drain it..

    I tried 3 different caps as follows:

    1. 0.01 uF ceramic - does nothing

    2. 0.47 uF greencap - does nothing

    3. 10 uF electrolytic - will work the first time power is applied, but nothing
    after that untill I drain it (remove and short the leads for a few seconds).

    What value capacitor should I use ? Do I need a resitor across it to drain it
    quickly when power is lost ?

    I thought it would be a simple thing and the value wasn't important (ie. I could
    use any reasonable value).

  2. peterken

    peterken Guest

    use the resistor option, experiment a bit for the value
    (might be a rather big value so if power drops short it may fail)
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