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boot on power-up

S

Skeleton Man

Jan 1, 1970
0
Hi,

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).

Regards,
Chris
 
P

peterken

Jan 1, 1970
0
Skeleton Man said:
Hi,

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).

Regards,
Chris

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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