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Dual PSU's and wiring

Discussion in 'General Hardware' started by LeperousDust, 6 Feb 2006.

  1. LeperousDust

    Soldato

    Joined: 4 Nov 2003

    Posts: 5,729

    Location: Edinburgh

    I've just slapped together a PC for backing up, and acting as central storage space. But i've got a cheap power supply running it and it doesn't have enough molex connectors to plug all my 5 hard drives and DVDrom in nor is it probably capable of powering them all if i could plug them in. Rather than buy an expensive power supply. I have another cheapish 300watt thing lying around here. Can i wire this up to run just the hard drives?

    I know if i short the earth and -ve out i kick start the power supply, but am i ok doing this while have the hard drives plugged in (im scared because theyre expensive - 400GB seagates).

    Is it also possible to wire it in such a way that when i press the power button on the computer it starts both power supplies?
     
  2. MarkLP

    Mobster

    Joined: 28 Sep 2004

    Posts: 3,133

    Location: Devon, UK

    I would buy a good psu then, i did the same as you, thinking a cheap psu would be fine, I only lost a 80gb drive.
     
  3. LeperousDust

    Soldato

    Joined: 4 Nov 2003

    Posts: 5,729

    Location: Edinburgh

    You have a decent point, and i will do in time, i just want this to tide me over. I'll be running the power supplies at less than half capactiy so chances of them failing it low to zero. Surely 5 hard drives isn't going to overload a power supply on it own :p?

    I couldn't care if the rest of the PC went, its all cheap stuff thrown together.
     
  4. Bobbler

    Mobster

    Joined: 18 Oct 2002

    Posts: 4,210

    Location: Bath, UK

    Hard drives are roughly 20 - 25 watts each draw on the PSU...depends what else you have in there.

    OCUK used to sell a device for coupling two PSUs together, but due to the diabolical search on the shop site I cant find it.
     
  5. LeperousDust

    Soldato

    Joined: 4 Nov 2003

    Posts: 5,729

    Location: Edinburgh

    I just had a look in all the places i think it could be in cant find anything either =/

    Searching around though i've found this, and it looks as simply as i thought it would be :). Just a matter of connected the earths and -ves in parallel. But i didnt realise i had to short two other cables on the "piggy backing" PSU.

    http://www.bp6.com/images/psu2.gif

    Gonna do a little bit more research before i start wiring stuff together though.
     
  6. Phemo

    Soldato

    Joined: 6 May 2004

    Posts: 5,460

    Location: Portsmouth

    I got a simple adapter with my Coolermaster Stacker case. The secondary PSU simply plugs into an ATX socket, which then has two wires coming out - one from the green wire and one from a ground. This then goes to an ATX pass-through connector which then sits between the mobo and the PSU ATX connectors and joins the green/black from the 2nd power supply onto it.

    That way, both power supplies come on at the same time.
     
  7. LeperousDust

    Soldato

    Joined: 4 Nov 2003

    Posts: 5,729

    Location: Edinburgh

    Excellent, thats what i thought i had to do, i was just worried electricity might start going where i dont want it to, or where its not meant to and blow something! :p.
     
  8. LeperousDust

    Soldato

    Joined: 4 Nov 2003

    Posts: 5,729

    Location: Edinburgh

    Just to update, i've got it all working and its been completely stable over the last 24 hours. I doubt i'll be buying a better PSU as both of these are probably only half loaded.

    old seemingly pretty reliable 300w running:
    1 x 40gb old HDD
    1 x Rarely used optical drive
    3 x 80mm fans

    new 300w running:
    The actually PC, motherboard, CPU etc...
    and 4 x 400GB hard drives.

    I can't see either of them really maxing out 200w if im honest, although my processor is a 2.8Ghz P4c and that could theoretically peak at about 80ishw. Still that leaves 120w for 4 hard drives and nout all else really.

    If something dies and everything goes **** up suddenly, i will update and make you all aware :D.