ATX to Lab Supply Case Grounding

Discussion in 'General Electronics Chat' started by blah2222, Mar 9, 2013.

  1. blah2222

    Thread Starter Well-Known Member

    May 3, 2010
    554
    33
    Hi all,

    I know that this topic has been beaten to death but I had a question regarding earth grounding a custom case.

    I already converted an ATX to Lab supply and it works fine but I wanted to go down another route by having my own unit that connects to the ATX motherboard connector rather than opening up the ATX supply.

    Like this:

    [​IMG]

    The designer of this one used a wooden case but I was thinking of using a metal container as wood is combustable and when dealing with mains I don't want to take any chances.

    The only thing that I am not sure about is how to earth my stand-alone metal container.

    The earthing is connected to the ATX case, so should I just get a wire and connect a piece of the ATX case to my container?

    Any suggestions would be much appreciated.

    Thanks,
    JP
     
  2. mkbutan

    Senior Member

    Sep 30, 2008
    270
    16
    hi
    I think the EARTH is not required even if you plan to use the METAL CASE for your O/P Cabinet (YELLOW ONE)
    Because it's all DC no AC (3.3v/±5v/±12v and one Power Good Signal(+5v))
    The EARTH is required only in AC Ckt's.
     
  3. blah2222

    Thread Starter Well-Known Member

    May 3, 2010
    554
    33
    My concern with that is that the +5V and +12V lines on these supplies are capable of pulling an excessive amount of current. If they happen to touch the metal case while I am holding it wouldn't that be an issue?

    Regardless if it's AC or DC, current through your body is never a good thing.
     
  4. takao21203

    Distinguished Member

    Apr 28, 2012
    3,577
    463
    If you worry about 5V then use batteries. Or apply discipline and never work on powered circuits. Sometimes you have to, at least take measurements or adjustments.

    ATX suppliies make poor experimentation supplies. They easily will become destroyed from SMPS circuits, motors, and even short circuit. The protection they have is only marginally.

    Better get an electronic transformer for the voltage you need. They cost only $6 to $20.
     
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,073
    3,846
    If you are concerned, run a jumper wire from theATX case to your secondary metal case. Drill a new hole and use a sheet metal screw to hole a wire loop to the case. Sand off the coating for a good connection.

    I have beat an ATX supply running a RepRap 3D printer with four stepper motors, plus two resistive heaters (25 watt and a 150 watt). More than a year and all is well.

    Be careful, you might want to put a reasonable inline fuse (1 to 5 amps) on each output. You are right, they can draw a lot of current so keep safety in mind.
     
    Last edited: Mar 9, 2013
    blah2222 likes this.
  6. blah2222

    Thread Starter Well-Known Member

    May 3, 2010
    554
    33
    Yeah, I have 1A fuses for all voltage lines. I think I might run a jumper connecting the cases.

    Thanks for input.
     
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