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(Topic ID: 274361)

Ground Connections on Power Supplies


By oldschoolbob

84 days ago



Topic Stats

  • 6 posts
  • 5 Pinsiders participating
  • Latest reply 83 days ago by oldschoolbob
  • Topic is favorited by 1 Pinsider

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    #1 84 days ago

    Sometime back we (me and several Pinside members) built a power supply for testing MPUs.

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    Inside the box are two separate power supplies – one for 12 and 5 volts and one for 24 volts.

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    Each section has its own transformer, wiring, fuse, and on/off switch. I only use the 24 volt section for checking zero crossing and seldom use it. Normally when I use the power supply I connect ground to TP4, 5 volts to TP5, and 12 volts to TP2. When I use the 24 volt section I also connect ground to TP4, and 24 volts to TP3. Therefore I have two test leads connected to TP4.

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    What would happen if I connect both ground wires together at the power supply?

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    Would the ground wire have any effect when using only the 5 & 12 volt section?

    I may win the dumbest question award but I don’t want to harm my power supply.

    Thanks
    Bob

    #2 84 days ago

    You can leave the grounds permanently connected at the power supply even if the 24V is not on. No harm done.

    #3 84 days ago

    Non EE speaking:
    Standard electrical practice is to tie all the grounds from different supplies together at a single point as close to the supplies as possible. Google stuff like "star ground".

    In this case it doesn't really matter where you connect them since you're not really doing any current with the 24v though.

    I can't think of any reason you wouldn't want the grounds tied, but it'd me sorta cool to have a switch on the power supply to control it...

    #4 84 days ago
    Quoted from zacaj:

    I can't think of any reason you wouldn't want the grounds tied, but it'd me sorta cool to have a switch on the power supply to control it...

    I like this idea. I would use a switch to control the ground connection as well.
    -Mike

    #5 84 days ago

    I would just plug them manually, so you can also create a negative voltage which is a nice thing to have when testing some soundboards.

    #6 83 days ago

    Thank you all for your input.

    I read a few articles about tying grounds together but nothing pertaining to my situation. I didn't want to put the switch in because I didn't want to open the case.

    This is what I came up with. It seems to work fine. I booted without the 24 volts - then with the 24 volts. Works just like before.

    Again, thank you all.

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