Connecting DC power supply grounds?

Discussion in 'General Electronics Chat' started by raptorjp, Jul 13, 2010.

  1. raptorjp

    Thread Starter Member

    Nov 24, 2008
    11
    0
    Hello all,

    I know that this may be a stupid question, but I feel that I have to ask this question.

    I am trying to send 3 DC power supply voltages over a cable (5, 12, and 24). I know that I can use the same common for each (4 wires total) if I use a power supply that generates the 3 voltage (ie they come from the same source).

    But what if I have 3 different power supplies? Do I need 3 separate commons?

    Sorry for the stupid question, but I don't want to make a power cable with 6 wires when I could cut it down to 4.

    Thanks in advance!

    raptorjp :)
     
  2. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    If you have three separate power supplies, you can use one common ground, or return wire. This ground wire must be sized to take the total load of all three supplies. IOW, if supply one was capable of putting out 10 amps, supply two was capable of putting out 20 amps and supply three was capable of putting out 30 amps, your common ground wire must be capable of handling 60 amps to be safe and have minimal voltage drop.
     
  3. raptorjp

    Thread Starter Member

    Nov 24, 2008
    11
    0
    Thanks,

    So I can connect the common terminal on 3 ac/dc adaptors without a problem? I was worried that they each could be at different potentials and therefore I could get much higher voltages in my dc power lines.

    raptorjp
     
  4. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    I'm assuming your working on the DC side. You'll be fine making one common for all three adapters, just make sure the wire is big enough to handle the total current.
     
  5. raptorjp

    Thread Starter Member

    Nov 24, 2008
    11
    0
    Yeah, just the DC side :)

    You were a great help! Thanks!!!

    raptorjp
     
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