Isolating DC inputs

Discussion in 'General Electronics Chat' started by FlyBD5, Jul 15, 2013.

  1. FlyBD5

    Thread Starter New Member

    Jul 15, 2013
    2
    0
    Hi folks, newbie here. Some electronics/avionics experience, but not very good at design, working on it. I have a project where I want to provide the ability to power the device (12vdc) from more than one source. The power goes to a 78L05 which is then used to power a couple other devices. Everything works perfectly at the moment.

    My question is this: I know I have to isolate the 12vdc inputs just in case some fool decides to plug them both in at the same time... but how? Is as simple as putting a diode on each of the inputs? The device itself will draw maybe 100-150ma and even that is generous.

    Juan
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,123
    3,048
    Yup, that'll work. It can sometimes be a problem because the diodes introduce a small voltage drop but that will actually help your circuit. It's a bit of power that the regulator won't have to dissipate.
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,014
    3,234
    If the diode drop of a standard silicon diode is too high, you can use a large Schottky type which will have a few tenths of a volt lower drop.
     
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,770
    970
    typically called "Diode ORing" or just "ORing"
    Can also be done with mosfets/ORing controllers to reduce dissipation vs diodes when dealing with higher current levels.
     
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