Project: Battery-operated 1 amp current source

Discussion in 'The Completed Projects Collection' started by someonesdad, May 26, 2011.

  1. someonesdad

    Thread Starter Senior Member

    Jul 7, 2009
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    Here's a handy little current source I built a few months ago. It's quite useful, as it lets me measure DC resistances to 0.1 mΩ with my DMM and 1 μΩ with my bench multimeter. The batteries should last for thousands of measurements.
     
    nepdeep and lukasoft like this.
  2. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    Interesting application. I have more need for portable stable voltage sources, than current ones.

    I take it the casing is custom made, right? Neat job!
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,535
    So you solved the stability issue. What did the trick?
     
  4. someonesdad

    Thread Starter Senior Member

    Jul 7, 2009
    1,585
    141
    I first built one using an LM317, but it dissipates lots of power when run at 12 volts and is a bit unstable even with the heat sink I put on it (but it still works fine for a 1 A current for a few seconds). The voltage ref/op amp/MOSFET design is a better one, I think, and the original stability problems with the prototypes were a) the prototype board, b) longer wires, and c) crappy Radio Shack sand resistors.

    The part I like best is not needing a heat sink for the MOSFET.
     
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