Dual Powersuppy mod...

S

seniorpaul

Limp Gawd
Joined
Aug 8, 2005
Messages
412
i'm in the process of planning out a fairly extensive project. It's basically going to be an external box to house watercooling equipment that is going to sit on top of my case. Since i'm going to be modding this myself, i figured that i would have the unit serve a couple of other purposes. I'm planning on having a docking station for my Ipod built into the top, the audio controls for my speakers built in somewhere, and i'm toying with the idea of an LCD screen on the front that would display system information (temps, etc....).

I currently have a OCZ PowerStream 520, and it powers my system fine (the one in the sig below along with a couple of optical drives), but i plan on adding a second 7800GTX and a few more HD's in the next few months. Add to that my water pump, around ten 120mm fans, and a couple of things that are going to require power for my mod (lcd, etc..), and i'm not sure my OCZ is going to be able to hold up.

Sooooo...I could go get a PC P&C 850W SLI PS, but what fun would that be (and i can't don't want to drop the money). Instead i think i'm going to throw a second PS in there (probably another OCZ 520 that i could get for cheap from a friend). I've found a couple of places that show how to connect a couple of power supplies with 20 pin MOBO connectors so that both units power up when the computer is started, but i'm wondering if anyone has done it with 24pin connectors. I've found the diagrams showing what each pin is for, so i'm fairly confident i could figure it out, but wanted to see if anyone had done it already.
 
You will need to splice two or three black wires on the 2nd PSU to two or three black wires on the PSU that powers your MOBO. This will give the two PSUs a common ground.

Then splice the green wire on the 2nd PSU to the green wire on the PSU that powers your MOBO. Make sure you have a power cord plugged into each. Your PC power switch should turn both PSUs on and off at the same time.

There are a couple of rules you need to follow:

Don't connect any other wires together between the two PSUs (except black ones). Doing so will cause huge amounts of current to flow between the two PSUs.

Make sure all MOBO power and video card power is from only one PSU. You do not want to use one PSU to power the MOBO, and the other PSU to power your video card. If you have two video cards, power them both from the same PSU.

If you use 3.3 volts from the 2nd PSU, connect the brown wire to an orange wire (on that PSU) so the 3.3 output regulates properly.

You need to have a fairly large load on the 5 volt output of the 2nd PSU for it to regulate properly. A couple of drives should do.

Fans, hard drives, optical drives, and your other stuff should not care which PSU you use.
 
you need to connect the grey wire too. this is the PW_OK lead and it is nessesary for proper voltage regulation between the two supplies.
 
Darkala said:
you need to connect the grey wire too. this is the PW_OK lead and it is nessesary for proper voltage regulation between the two supplies.
Click to expand...

No... not a good idea... PW_OK is a TTL driver, and as such it is never a good idea to connect two TTL drivers directly together. It is a status output from the PSU that is used to tell the MOBO that power is ok (from the PSU that is powering it) and that it is OK to boot... doesn't have anything to do with PSU regulation.
 
correction for my previous... PW_OK needs to be shorted to ground on the ATX cable not connected to a mobo.
 
I think you are confusing PW_OK with PS_ON*. PW_OK is a status discrete to the MOBO and grounding it has no effect on PSU operation (except that you might damage the PSU by grounding it). Grounding PS_ON* (green wire) turns the supply on which is covered above. ATX PSU spec here >-- Link
 
Frank4d said:
You will need to splice two or three black wires on the 2nd PSU to two or three black wires on the PSU that powers your MOBO. This will give the two PSUs a common ground.

Then splice the green wire on the 2nd PSU to the green wire on the PSU that powers your MOBO. Make sure you have a power cord plugged into each. Your PC power switch should turn both PSUs on and off at the same time.
Click to expand...

The green wire would be the PS_ON correct?

Also, i was looking at the wiring diagram that someone else followed to use multiple power supplys, and they seemed to be connecting the PWR_OK pin to a ground pin on the second powersupply(the one NOT attached to the MOBO). This was in addition to connecting ground wires between the two, as well as the green (what i beleive to be the PS_ON) wire. Would the grounding of the PWR_OK be needed?

thanks for the help.
 
Correct, PS_ON is the green wire.

PWR_OK is an output that tells the MOBO that the power supply voltages are OK. Since the MOBO and video cards are not powered by the second power supply, the MOBO doesn't care whether the second power supply voltages are ok anyway. It is never a good idea to ground outputs so leave it disconnected.
 
I would always use a relay or an optocoupler to make sure the two PSU's are seperated.

With the relay it should be like this

schema.jpg


The left is the first PSU and on the right is the second PSU. You see you will also have to use a diode.
 
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