Subject: Re: More newbie questions about the PC164
To: Ty Sarna <>
From: Dave Huang <>
List: port-alpha
Date: 04/16/1999 16:55:20
On Fri, 16 Apr 1999, Ty Sarna wrote:
> The simple hack is to connect GND to PS_ON#. I tsested this with a power
> supply and it works for me. YMMV.

I was thinking that that would keep the power supply "permanently on,"
but after looking at the URL Calvin Vette sent, I see that some supplies
have a hard switch too. If I can find one of those, the simple hack'll
be good enough :)

> if you like, you can use +5VSB to power a circuit to do something
> fancier, like use the momentary power button from the case to control
> power. +5VSB is alwways on when the power supply is receiving AC power,
> even if it is "off".

This would be really neat though :) Drawing from my almost nonexistant
electronics knowledge, I think something like a 74LS74 flipflop would
work, with Q' tied to D and the PWR_ON# line, CP with a pulldown
resistor to ground and a connection to +5VSB through the momentary power
button. Would some debouncing on the switch be needed? I dunno how to do
that :) And I also don't know how to make sure the flipflop powers up in
the "off" state. It's got a reset pin, but I don't know how to pulse it
when the power first comes on...