boot on power-up


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

  1. 0.47 uF greencap - does nothing

  2. 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).

Regards, Chris

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Skeleton Man
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power is



drain it


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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