I am currently doing my project in national certificate in engineering. I am designing a PID that will turn on a computer from standby. My original idea was to put a relay across the on/off button power leads that would connect to the PID.
But i have been told it is possible to connect the PID to the computer using an ethernet cable, and i would need to change the setup in BIOS, but this could be used to turn the computer on from standby.
If anyone has information or site that might help me i would be very grateful.
The relay across the on/off button sounds as though it would work OK.
However, you may want to put some logic to give a defined closure time to the relay contact to ensure that the PC starts OK.
Also, you may want to add some logic to prevent a second pulse from the PIR shutting the PC down again when you want it to remain running.