Dennis Woodworth asks:
Is the power switch on a desktop (front panel) a momentary or constant switch (pulse/constant)?
3 Answers -
Ryan Dube
July 10, 2012It’s a momentary pushbutton switch – in most modern systems the handling of the momentary pushbutton contact and all of the timing is handled by the PSU/motherboard.
Alan Wade
July 10, 2012Your PSU outputs +5 on a specific pin (+5VSB) when ever it’s plugged in and turned on.
This voltage is used to power your motherboards power control circuitry so that i can turn on when the BIOS tells it to, or when you press the button.
The power button is nothing more then a momentary SPST push button switch.
When you press it, your motherboard’s power control circuitry connects the PS_ON lead to ground, then the PSU turns on fully up and provides power to all pins. Then it sends a Ready signal to the motherboard once it is fully powered up, so that the system only starts after the PSU is ready
Oron
July 13, 2012On ATX systems (introduced 1995) it’s a momentary connection. On earlier systems it was constant, but I doubt you are using such an ancient system…