Starting PC from PIC

[Charles Linquis]

I have an ECS motherboard that doesn't automatically restart upon power fail. The machine is in my attic, and provides (MP3) music 24/7 to my bathroom. I got tired of going up to the attic to restart it after every power flicker.

I use a 12F675 powered from the 5V standby of the power supply. One PIC output pin is tied to one of the "PowerButton" pins. After power up, I wait for 3 seconds (for the power supply voltage to stabilize) and then write a 1 to an output pin and set it as an output for 300ms, then I set it back as an input. This simulates an open-collector driver (so that the ordinary power button still works). The entire circuit consists of the PIC and a 10uF cap across the power leads.

Works great.

My motherboard needed a logic "high" on the pin to start it. Check your motherboard. It may need a logic "low". In that case, just write a "0" to the PIC pin before you set it as an output.

[Squibcakes]

Yeah I've done this.. very neat program too!

Two things I found, to get you started.

1. Use the pic and relay in parallel with the soft Soft -Off wire. I used an omron G5V-1 SPDT type, but you could use a reed relay instead. I know you dont want to use a relay.. but for a couple of bucks... you'll get total isoltation!

2. Depending on your ap, you may need feed back from the pc (floppy power cable example) so the pic doesn't turn the pc off, when it's actually turning it on. Opto isolator for this is a must!

Good luck
J

[Luciano]

Hi,

Automatically restart upon power fail

Go into the PC BIOS and under the menu POWER see if you can find
the option "Restore on AC Power Loss".

Best regards,

Luciano