ATX power supply safety

Discussion in 'General Electronics Chat' started by zeta_no, May 23, 2011.

  1. zeta_no

    Thread Starter New Member

    Jan 20, 2009

    I finished the conversion of an ATX power supply as a benchtop power supply. It works.

    Now I am concerned about the safety of such a device. Let say I take the 5V rail of my power supply. It is rated 5V, 29.0A.

    If I short this rail what will happen?

    My DMM gives 0.2 Ohm for the wire I would use to short. A quick calculation gives 25A and therefore 125W rushing in. To me, it looks like a good spark!

    Nobody seems to care on internet. Is there a safety mecanism in these ATX power supply that prevents large current rush? If so, what is it? Do all power supply implements it?

    Thank you,

  2. beenthere

    Retired Moderator

    Apr 20, 2004
    One way to avoid allowing the magic smoke out of the supply is to fuse the outputs at a level below the maximum rating. Use 32 volt rated instantaneous fuses.
  3. Jaguarjoe

    Active Member

    Apr 7, 2010
    I used resetable Polyfuses.
  4. muthukumar_ece2004

    New Member

    May 20, 2011
    For Bench top power supply, 29A rating not necessary. Simply limit the output current of the SMPS and use it!
  5. magnet18

    Senior Member

    Dec 22, 2010
    If you short an ATX power supply it will shut itself off, try it and see (be careful in case it doesn't for some reason)
    You might get a brief spark, nothing more.

    And whered you get a 29A supply!
    mines only 12 :(
    (not that I really have any use for 5V 29A...)