Question How to use an atx 24pin dual PSU switch to power a graphics card with 2 power supplies

[Astrogirl]

Hi I bought one of these but not sure how to use it, if someone can explain please. https://www.ebay.com.au/itm/PC-Desktop-ATX-24Pin-Dual-PSU-PowerSupply-Sync-Starter-Extender-Cable-Connector/371729336120
It has a ground socket so do I connect a cable from main or 2ndary PSU to this socket or where? Also a sata/molex connector - does this go to main PSU? Then 24 pin mainboard cable on 2nd psu connect to adaptor 24-pin socket? Is this right? Aim is to use extra PSU to power an external graphics card while it connects via a usb3 pciex1 slot card to the main pc mainboard like in a mining rig setup. So it gets upto 75W from main PSU and rest from 2ndary PSU as main is much lower power unit. Also plan use the on/off switch on card to have 2nd PSU turn on/off/hibernate etc with main PC when it does - will this work this way?

 

[BFG-9000]

You just plug the SATA power or a 4-pin molex into it from the main PSU. If the switch is set to on, then whenever the device gets power from the main PSU it will switch on any secondary PSU plugged into the device's ATX connector. Honestly the same could be done just by jumping the green wires in each ATX harness together--even an inline switch could be inserted in the jumper wire. Note in both cases, the switch is only for when you don't want the secondary PSU to turn on with the primary. If you always want it to do so then the switch is optional

You could then use the molex, SATA and PCIe connectors from the secondary PSU to power extra stuff.

 

[Astrogirl]

You just plug the SATA power or a 4-pin molex into it from the main PSU. If the switch is set to on, then whenever the device gets power from the main PSU it will switch on any secondary PSU plugged into the device's ATX connector. Honestly the same could be done just by jumping the green wires in each ATX harness together--even an inline switch could be inserted in the jumper wire. Note in both cases, the switch is only for when you don't want the secondary PSU to turn on with the primary. If you always want it to do so then the switch is optional

You could then use the molex, SATA and PCIe connectors from the secondary PSU to power extra stuff.

Thanks help. Just to clarify - so no need to connect 24-pin 2ndary PSU mainboard/motherboard connector to adaptor or a wire to/from ground port from adaptor? Did not come with any cable for ground port. I thought the 2nd psu 24-pin mainboard cable/molex needs to be connected for 2ndary PSU to turn on (or a paperclip short) - or is that not needed as it detects Primary PSU motherboard through the SATA connector to Main PSU via adaptor?
Is it safe to run over a long time/hibernating with nothing connected to grnd from adaptor?

 

[BFG-9000]

I would just make sure both PSUs touch the same metal case, to ensure a common ground.

The paperclip trick shorts the green wire to ground to turn on the PSU. This device does the same, but only when the first PSU is running--provided you have plugged in the 24-pin so it can ground the green wire on it. As the motherboard itself already grounds the green wire when switched on, connecting both green wires together means the motherboard can turn on both PSUs at the same time.

This means with either the device or jumper wire, the secondary PSU will go to sleep and turn off with the first PSU without having to touch any switch. Again, the switch is only to shut off the secondary PSU while leaving the primary PSU running. With a paperclip, the PSU will stay running forever until you remove the paperclip, regardless of whether primary PSU is running or not.

 

[Astrogirl]

Thanks. Just re grounding - The first PSU is already grounded by being attached to pc case - screwed in and via it's cable attached to power strip - is this right? 2nd PSU will also connect to same power strip or wall socket. Do I need to then also use a specific grounding cable/wire (for GRND socket has 4 pins on this adapter) that is then attached on other end to metal case of PC ?) If so can you suggest where can get this online eg on Ebay?

 

[BFG-9000]

That is not a ground socket on the adapter but a molex for ground, +5v and +12v that you can use instead of the SATA power lead which provides the same and +3.3v too. The adapter appears to only use +5v.

You want both PSUs attached to the same case metal, even if you have to drill a single hole and bolt one of them to the top of the case. Or at least use ring terminals and a heavy wire to attach the two PSUs together with a screw on each. Do not rely on just a molex ground because if the ground potentials of the two PSUs differ even a little, a lot of current is going to flow through the ground traces of your PCIe card and motherboard. Theoretically the PSU cases will already be connected via the safety ground on the power leads and the power strip, but you always want a ground connection between two PSUs to be as short and solid as possible, if you are going to be powering a single device from both PSUs. It would be less critical if you were only using the secondary PSU to power HDDs and such.