how do i make a ATX PC power up automatically?

  • Thread starter Thread starter Mogse
  • Start date Start date
M

Mogse

i've got a pc compaq en 6400 that i want to power up when ever i put
power into it instead of having to hit the switch each time?

is it possible

thanks
 
Mogse said:
i've got a pc compaq en 6400 that i want to power up when ever i put
power into it instead of having to hit the switch each time?

is it possible

thanks
Click to expand...

This is usually an option built into the motherboard BIOS.

Roby
 
Can you find something to the effect of RTC (return to current?) in your
mobo bios?

-----Original Message-----
From: Mogse [mailto:[email protected]]
Posted At: Friday, December 03, 2004 7:17 AM
Posted To: alt.comp.hardware
Conversation: how do i make a ATX PC power up automatically?
Subject: how do i make a ATX PC power up automatically?


i've got a pc compaq en 6400 that i want to power up when ever i put
power into it instead of having to hit the switch each time?

is it possible

thanks
 
Mogse said:
i've got a pc compaq en 6400 that i want to power up when ever i put
power into it instead of having to hit the switch each time?
Click to expand...

If your BIOS does not have such a setting, try a small cap (1 uF or so)
across the MB/front panel switch connector.
 
i've got a pc compaq en 6400 that i want to power up when ever i put
If your BIOS does not have such a setting, try a small cap (1 uF or so)
across the MB/front panel switch connector.
Click to expand...

Why the cap instead of a dead short (jumper across the pins) ?

Regards,
Chris
 
Skeleton Man said:
Why the cap instead of a dead short (jumper across the pins) ?
Click to expand...

Hold down the power button on your ATX machine and find out! : )

A cap will open the circuit once it's charged. The cap will make the contact
until it is full at which point it will open. The same as a user momentarily
pressing the ON button.

I've done the same thing across RESET for old flaky AT machines. They needed
a half second of power before they'd boot reliably.
 
Why the cap instead of a dead short (jumper across the pins) ?

Regards,
Chris
Click to expand...

Because a capacitor will store energy, thereby allowing the circuit to
remain energized. Be aware, however, that capacitors will discharge
over time. The time constant is as the demand goes up, the capacitor
will discharge more quickly.
Raymond Sirois
SysOp: The Lost Chord BBS
607-733-5745
telnet://thelostchord.dns2go.com:6000
 
Skeleton said:
Why the cap instead of a dead short (jumper across the pins) ?
Click to expand...

The switch is a momentary switch. The capacitor mimics the operation
of the momentary switch - it is a short upon application of power, and
looks like an open once it is charged.
 
Raymond said:
Because a capacitor will store energy, thereby allowing the circuit to
remain energized. Be aware, however, that capacitors will discharge
over time. The time constant is as the demand goes up, the capacitor
will discharge more quickly.
Click to expand...

It better discharge. It wouldn't turn the unit on upon application
of power if it didn't. Be advised - as long as the ATX PSU remains
connected to AC power, there will be voltage on the cap from the +5vsb.
Once the AC power is removed, the cap discharges and is ready to provide
a "short" upon application of power. If the discharge time is too long,
simply use a smaller cap.
 
ric said:
The switch is a momentary switch. The capacitor mimics the operation
of the momentary switch - it is a short upon application of power, and
looks like an open once it is charged.
Click to expand...

I suggest using a non-electrolytic capacitor, like mylar or some other
plastic type. An electrolytic type is leaky, and over time the leakage
may be enough to cause intermittent problems like unwanted resets.

This reminds me of my TV repairing days. There was a series of similar
Panasonic TV models that had a momentary-contact switch built in with
the main power switch. This m-c switch triggered the digital control
microprocessor when the power switch is pushed on, but had a tendency
to burn out. It was practically impossible to get a replacement part
and many TVs were junked because of this. I solved this by placing a
capacitor across the m-c contacts. (Must be about 20 yrs ago).
 
Skeleton Man said:
Why the cap instead of a dead short (jumper across the pins) ?
Click to expand...

Several years ago, my friend's computer suddenly started to
shut down within seconds after turn-on. CrapUSA diagnosed
this as a bad power supply and hard drive, but because hard
drives were so expensive back then, he seeked a second
opinion from an independent computer shop near his house.
They told him the power button was sticking abd staying
shorted even after being released, and they offered to
replace it for $12. But after they heard CrapUSA's
misdiagnosis, they did it for free.
 
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