+5-5 dual power supply

Discussion in 'The Projects Forum' started by RodneyB, Oct 29, 2013.

  1. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    I am trying to build a bench digital volt meter using the ICL7107 it needs to be powered from a dual power supply.

    I have attached the circuit diagram I tried to follow and build. the 7905 regulator gets hot and I don't know where I am going wrong.

    Thanks

    Rodney
     
    Last edited: Oct 29, 2013
  2. Nykolas

    Member

    Aug 27, 2013
    87
    31
    You did not connect the CT of the transformer to the "common" terminals of the regulators. E
     
  3. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    Sorry I am lost what is the CT (centre tap?)
     
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,061
    3,833
    Yes, center tap. Connect a wire from the connection between C1 and C2 to the grounds of your two voltage regulators.
     
  5. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    Thank you for all the help, I also had made a mistake on my PCB layout assuming that the Pin outs were the same as the positive voltage regulator.

    Best wishes

    Rodney
     
    GopherT likes this.
  6. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    You are not the first:rolleyes: Electronics are attention to details. Never ever assume anything. It will less than 1% chance that you will be correct in my experience
     
    RodneyB likes this.
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