boot on power-up

[Skeleton Man]

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

 

[peterken]

"Skeleton Man" <invalid@guestwho.com> wrote in message
news:rGIJd.135139$K7.2484@news-server.bigpond.net.au...

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)