andrew coughed up some electrons that declared:

PCPaul wrote:

Sounds like a 5V/12V relay plugged into a parallel port line (or even a
serial port handshake line) which then switches a 24V supply to drive the
main relay would be simpler - that way you don't need to drive USB
directly.

I was hoping to use a low power PC which has no serial output but I could
use a usb to serial converter.

AJH

It's probably the simplest and cheapest way.

Your low power PC doesn't have any GPIO (digital IO) lines does it (some
embedded style low power MOBOs do)?

Cheers

Tim