Power Supply turn-on

[Spike6]

Hi: I am tired of the “soft shutdown” gimmick on all modern PCs. [If I wanted a Mac I’d buy a Mac!]. I'm now building a new PC and I’d like to get back to a single switch on an AC line outlet box where PC, Printer, VDU, etc. all come-on or go-off together without a need to push more buttons (like the old ATs). Can I accomplish this by simply shorting P/S plug pins 14 and 15 together permanently and ignoring the motherboard connected pushbutton or is there a downside to this seemingly simple solution?

 

[Rik]

Shorting those pins together long term can result in damage to the psu. I wouldnt recommend it.

 

[Spike6]

Tks Rik:
Is there an OK way to accomplish this? I'd like my ATX to behave like an AT -- that is to come up and boot automatically when AC power is applied.

 

[Rik]

The only way i can think of doing it would be to use a 555 timer to deliver a pulse to power up the mobo, but i have no idea how to go about it tho. The 555 timer produces a positive pulse so it would need to be converted into a negative pulse as shorting the green wire to a black pulls it down to ground.

I have been experimenting with trying to get the 3v hdd led output up to 12v to run el string but i have the same problem, its easy to use a transistor to switch 12v using 3v as the trigger, however, the led output from the mobo is negatively switched too.

 

[Spike6]

Ok then how 'bout this? Wire a sizable (maybe 100mfd @25v) capacitor across the PC start push button. When power is applied to the PC and the +5v standby power appears at the pushbutton the capacitor passes a brief pulse on to the mother board to signal it to start the PC. May need to wire a diode across the cap to discharge it when the power is removed if the back circuits don't do it.

 

[Spike6]

It's in the BIOS!

Hey, problem solved. Turns out there is a BIOS setting to accomplish this. It's called various things depending on the BIOS but it's usually something like "restart on power applied."