If I use a 4 pin molex from one PSU to trigger a Second PSU will they still be isolated from each other? Or will they both share a ground 0v?
as far as i remember relays should me mechanically isolated, e it's magnets thats using magnetic for to turn it on or off. so they are a 99% chance they don't share ground wiring.
They will not share ground wiring on the output side, BUT because both will be connected to the mains earth the grounds will be connected. In addition, all the metal of the case of the power supply and the whole computer will also be connected to the same earth. If youre planning to get a 24v supply like this it wont work, you have to isolate one of the supplies from its own case and from mains earth ( I think ) there are guides around for doing this. Moriquendi
You got it right, either float one supply from its case, or just isolate the case, and lift the mains earth.
or use an opto isolator on the power led circuit and conect the other side to the green and ground wires of the atx connector on the second power supply. that should work.
Thanks for the replies... Nothing exciting, like wanting 24v. I need (I think?) them to share the ground so I can split the mobo/gfx/hard drives and other devices between the two PSU's. Need approx 900W for a rig I'm putting together...
Why the 10A relay? If you're switching the second PSU on by connecting its green wire to ground, the current is negligible; a sub-min relay is enough. http://www.directron.com/2powersupplies.html#atxauto
Because it's already fitted to the board with molex and PSU sockets soldered to it. Not my choice personnally. Is it correct they need to share a ground, and using the relay method is adequate?
Everything needs the same ground, but any single component (such as graphics card) should only take power from one supply, so graphics card aux connector and motherboard main connector will both need to be from the same psu.
Yep... So using the relay... I was going to set it up like this PSU 1 Mobo GFX Fans etc PSU 2 Hard drives
