ATX power supply power switch

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Hi,
I am planning on using an ATX power supply in a kiosk type
application, and I am trying to figure out what to do with the power
switch.
The ATX power supply has a normal on/off AC switch, which is what I
would
like to use. However, this only puts the supply in standby mode.
The power switch on the front of a PC, pulls the PS_ON line to ground,
which
turns on the rest of the supply.
What I am not sure, is if I can keep the PS_ON line permanently tied
to ground,
or is it just a momentary input? Can it do any damage to the supply if
I keep it hardwired to ground?
Thanks,
Allen

Re: ATX power supply power switch
You can keep it tied to the ground permanently, no problem.


Piotr


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Re: ATX power supply power switch
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Except that it won't necessarilly work.  I had a similar situation and was
appaled to find there was no consistent way to assure an ATX power supply
will turn on without the momentary ON signal.  It is a rather silly
oversight IMHO.



Re: ATX power supply power switch
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Not from the point of view of the intended usage, I'd say.  I don't
think ATX was ever intended to be used in unattended systems.  Nor was
it ever planned to *have* a primary-side power switch in an ATX system
--- it's supposed to be always-on on the primary side.

Anyway, the issue is quite moot since most BIOSes let you configure
the mainboard to do this for you.  "Automatic AC power loss restart"
is what this feature is often called.

--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

Re: ATX power supply power switch
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... Which will work if he is actually planning to use an ATX motherboard of
some kind and his BIOS has that option.

If not, then a simple way to guarantee proper startup is power a small
microcontroller from +5STBY, have it monitor the +5V line or 'Power good'
and pulse the ON/OFF line if power isn't present after a short time.

Rob



Re: ATX power supply power switch

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Or a simple 555 timer circuit or similar.



Re: ATX power supply power switch
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Where does one find this for say Windows XP?

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Interesting:  Bootstrapping the bootstrapping the bootstrapping.

Where is the uC getting the power to operate to ensure
the power supply has started?

Re: ATX power supply power switch
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+5STBY is the "standby voltage", provided at all times while the PSU
is plugged in, specifically for circuits like this (and WOL and other
similar frippery).

Re: ATX power supply power switch
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What makes you think Windows would have anyting to do with that?  I
wrote "BIOS" up there, didn't I?

--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

Re: ATX power supply power switch

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Yes, you did!



Re: ATX power supply power switch
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Let's be nice now.  You are dealing with less than expert
PCers here in this newsgroup.  If we were expert PCers,
we wouldn't have to work for a living.

Substituting "BIOS" for "Windows XP", how does one
find the "Automatic AC power loss restart" feature?

Re: ATX power supply power switch


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[...]

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Am I?  Well, then let me put it in a different way: if you are
building something that isn't a PC, you probably shouldn't be trying
to put an ATX supply into it --- or be prepared to blame all the side
effects on yourself, not the ATX designers.  If you _are_ building a
PC, you really should be enough of a PC expert to recognize the term
"BIOS" without needing further explanations.

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In the Motherboard's internal BIOS setup.

--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

Re: ATX power supply power switch
Now I'm shooting from the hip, but if only a momentary signal is
required, couldn't you just tie the PS_ON to ground through a
capacitor?  This would  pull the signal to ground until the cap
charges, and toggle the power supply on.

-Jim


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Re: ATX power supply power switch
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Sure, no problem - except that it will probably shut the entire unit
down after a couple of seconds of powerup. The switch-on signal has to
be momentary. I suggest a one-shot powered off the +5V standby power
line.

Re: ATX power supply power switch
That is Not the Solution.
Look in the BIOS Settings the is an option about what to do after a power
interruption.
the usual options are:
Stay Off
Turn On
Resume at last state.

Try that.


Re: ATX power supply power switch

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Careful with such blanket statements.  There BIOSes out there that
have been reported to lack this option completely.  Silly, yes, but
they exist.

--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

Re: ATX power supply power switch
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Herr Broeker is not inclined to answer the question, so
I'll try again:

How does one get to the BIOS settings?  I vaguely recall
something about hitting some key during power startup...

Re: ATX power supply power switch
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It varies based on system board manufacturer.  Look it up in the manual
which came with the board or go to their website.



Re: ATX power supply power switch
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While the computer is booting, before the OS starts loading,
the screen normally displays a message, something along the
lines of:"Press Del to enter setup".
At this point press the delete key.
I think where there was some confusion, in that you asked
specifically for Windows XP, whereas the BIOS is completely
independant of any OS.

Thanks everyone for the useful replies, fortunately I have
some custom hardware attached to the PC motherboard. This
has an "always on" microcontroller on it, so I can use that
to pulse the power line.
Regards,
Allen

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