Yes, for powering the ATX power supply you have to connect the PS_ON to the ground. But when you connect the power supply to a motherboard, the switch will short the pins on the motherboard for a moment. You can’t use the rocker switch if you're planning to use the power supply to power the motherboard.

Yes I want to power up an AT motherboard with the PSU. The PSU is actually a pico PSU, and the ATX connector is going through a ATX2AT adapter, which has two lines coming out of it for manual power up (green and black). I'm hoping to find a power switch with LED in it integrated. Fallback plan of course is to have a dedicated power LED.

wbahnassi wrote on 2023-09-30, 22:45:

The PSU is actually a pico PSU, and the ATX connector is going through a ATX2AT adapter, which has two lines coming out of it for manual power up (green and black). I'm hoping to find a power switch with LED in it integrated.

Details of ATX2AT adapter? (there's a few different designs)

Like this one:

M'kay, can't use that switch for purpose intended ~ PS_ON is active low (switched to ground), so there's no current/voltage present to drive the LED.

You can use a SPST switch with isolated LED (4pin switch) ...

Looks like E-Switch R1966A series is a suitable switch (two terminals for switching purposes and two terminals for LED purposes, that you could hook up to Power LED on your motherboard) but they are rectangular. There should be a circular switch with similar circuitry I guess.

jakethompson1 wrote on 2023-10-01, 01:33:

Looks like E-Switch R1966A series is a suitable switch (two terminals for switching purposes and two terminals for LED purposes, that you could hook up to Power LED on your motherboard) but they are rectangular. There should be a circular switch with similar circuitry I guess.

Yeah, something like that ~ I do note on the datasheet there's no dropper resistor for the led, so one would need to include it (likely left out so different LED supply voltages are catered for)

If you powered the LED from the "power LED" aka keylock header from your motherboard, since the ATX power switch pins don't provide a +5V anyway, doesn't that circuit already incorporate a resistor?

jakethompson1 wrote on 2023-10-01, 01:43:

If you powered the LED from the "power LED" aka keylock header from your motherboard, since the ATX power switch pins don't provide a +5V anyway, doesn't that circuit already incorporate a resistor?

Most do, yes... but I tend to assume nothing =)

Thanks guys that makes sense. I'm not attached to a circular switch. A rectangular one can work too. I'll need to take a ride to my electronics shop and see if has something with 4 pins and an LED.

Cheers!