ATX Power Supply Question

Discussion in 'Community Discussion' started by designgeek, Jan 19, 2014.

  1. designgeek macrumors 65816

    designgeek

    Joined:
    Jan 30, 2009
    Location:
    "Town"
    #1
    I have a weird question.

    I'm modifying an ATX power supply to use as a bench power supply for my various projects (it's amazing how often one needs 3, 5, or 12 volts) and I was wondering about one of the rails, specifically the -12v. What is it for? It can't handle much current, all the other rails can handle 15 or so amps but -12v on every power supply I've seen can't handle more than a few hundred milliamps. I would imagine it would be coupled with the +12v rail for a total of 24v in a few rare instances but even those I can't find. All the fans I've seen run 12v.

    I'm asking you because you are all brilliant plus it's damn near ungoogleable. Even advanced search options seem to disregard -12. :rolleyes:
     
  2. localoid macrumors 68020

    localoid

    Joined:
    Feb 20, 2007
    Location:
    America's Third World
    #2
    The book, PC Hardware in a Nutshell, published by O'Reilly, might give some insight. (The first link shown goes to the Google Book preview of said book.)
     
  3. chown33 macrumors 604

    Joined:
    Aug 9, 2009
    #3
    It's usually for the negative supply of an RS-232 interface.

    It could also be used to produce -5VDC with an onboard regulator. That's sometimes useful in analog, as is -12VDC.
     

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