Current sink

Discussion in 'The Projects Forum' started by Gregfox, Mar 28, 2013.

  1. Gregfox

    Thread Starter Member

    Jul 23, 2011
    14
    1
    Hello all, I’m working on a project, a Battery powered Current sink with low voltage cutoff. I want to be able to connect a dummy load to a project, or run tests on batteries etc. and be able to set a low voltage cut off point. The Sink will go up to 1.5A.
    In the attached schematic, the current sink works and the low voltage cutoff also works, but not well.
    The problem is that when the low voltage cutoff is set with R5 it does not shut off clean. As it’s shutting off power by grounding T1 there is a lot of rail to rail chatter on IC1C, and the current drops off slowly, and also is not clean.
    I hoped R9 would provide about ½ volt of hysteresis but it does not. The hysteresis is for battery testing, so that when the set point is reached, the circuit will not “chatter”, when the voltage drops to the set point, Q1 turns off, and the battery voltage rises slightly.
    My problem is:
    1. I can’t figure out how to stop the chatter on IC1C.
    2. Add hysteresis when Q1 turns off, so that it doesn’t chatter.
    Any help will be much appreciated.
     
    Last edited: Mar 28, 2013
  2. Gregfox

    Thread Starter Member

    Jul 23, 2011
    14
    1
    I am posting the schematic is some different formats.
     
  3. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
    So post it to that thread!
     
    Gregfox likes this.
  4. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    Threads merged.

    Bertus
     
  5. Gregfox

    Thread Starter Member

    Jul 23, 2011
    14
    1
    how do I post to my thread I already posted??
     
  6. Gregfox

    Thread Starter Member

    Jul 23, 2011
    14
    1
    never mind...
     
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