Common Ground

Discussion in 'General Electronics Chat' started by jstrood, Mar 21, 2012.

  1. jstrood

    Thread Starter New Member

    Mar 21, 2012
    Common ground (voltage reference) when using 2 separate power supplies. I have a 12 VDC panel that interfaces with a 24VDC reader. The reader talks about a common ground with the panel. I get errors reading the output of the panel when this is not correct, and have managed to get it working each time, but with different solutions, and still not sure what the correct answer is.

    1 the reader has the connections below
    VDC +
    Shield ground
    Data +1
    Data -0

    The cable is shielded with a drain wire.

    I have had success with below.

    Connecting drain wire to shield ground and nothing on the other side.
    connecting drain wire to negative of power supply for reader
    connecting drain wire to negative of power supply on panel.

    Again I can get it to work, but not sure what the REAL answer is.
  2. #12


    Nov 30, 2010
    and the 12 volt board has what connections?