Pro/Forums - View Single Post - What type of relay is needed to connect AT ps to ATX ps?

ck42 · 05-30-2001, 03:12 PM

So can I assume that the relay must have at least 6 terminals, 2 for the ATX 12v and 4 for the wires from the AT switch? Do I get a 12vdc (coil voltage?) SPST, DPST,DPDT or 4DPT relay? What ratings should the coil resistance, contact volatge, contact current be?

CQ:

No, the relay does NOT have to have 6 terminals.

If you're wanting the 1 switch to power up both supplies by controlling the 120V AC, you'll need to modify your ATX supply. ATX supplies always have 120V going to them...it's a signal from the m/b that tells them to actually supply power...if that sounded like it didn't make sense.....just trust me.

Best way to do it is to have a SPST relay control 1 leg of the 120V AC power going to the AT PSU. The relay would be energized by either the 5V or 12V power from the ATX PSU.

Rememeber, you DON'T need to switch both sides of the 120V signal...only one of them needs to go through the relay. The other one can just be hardwired. Without the two completing the circuit, it won't work...so when the relay kicks on and passes the second leg of the AC, then it will work.

Hope this makes sense.

05-30-2001, 03:12 PM	#4
ck42 Cooling Savant Join Date: Dec 2000 Location: Atlanta Posts: 154	So can I assume that the relay must have at least 6 terminals, 2 for the ATX 12v and 4 for the wires from the AT switch? Do I get a 12vdc (coil voltage?) SPST, DPST,DPDT or 4DPT relay? What ratings should the coil resistance, contact volatge, contact current be? CQ: No, the relay does NOT have to have 6 terminals. If you're wanting the 1 switch to power up both supplies by controlling the 120V AC, you'll need to modify your ATX supply. ATX supplies always have 120V going to them...it's a signal from the m/b that tells them to actually supply power...if that sounded like it didn't make sense.....just trust me. Best way to do it is to have a SPST relay control 1 leg of the 120V AC power going to the AT PSU. The relay would be energized by either the 5V or 12V power from the ATX PSU. Rememeber, you DON'T need to switch both sides of the 120V signal...only one of them needs to go through the relay. The other one can just be hardwired. Without the two completing the circuit, it won't work...so when the relay kicks on and passes the second leg of the AC, then it will work. Hope this makes sense.