Wiring two dc inputs with diode or gate

Discussion in 'General Electronics Chat' started by Gilmai, Feb 24, 2011.

  1. Gilmai

    Thread Starter New Member

    Feb 23, 2011
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    0
    I have a battery powered device and I want to add a DC jack. I am using a simple diode or gate to switch between the two. Of course this leaves me with one negative return from the device but two power inputs to return to. Do I simply split the V- return or is it more complicated?

    I know this is really basic, but I am new with a lot to learn (as the last few hours of searching these forums for an answer has proven).
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Wire the returns together.

    Use a couple of Schottky diodes to OR the battery with the alternate power input.

    A 1N5817 through 1N5819 will work OK for <= 1A current. However, if you're above perhaps 500mA current, go for a 1N5820 through 1N5822; they're rated for up to 3A continuous, and you'll have a lower Vf.
     
  3. Gilmai

    Thread Starter New Member

    Feb 23, 2011
    2
    0
    Thanks. I thought it was that simple but wanted to be sure. I am using 1N4001 diodes. The current is only about 20mA so it should be fine.
     
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