Detect and Prevent Revere Polarity Circuit?

Discussion in 'General Electronics Chat' started by cjdelphi, Feb 14, 2011.

  1. cjdelphi

    Thread Starter New Member

    Mar 26, 2009
    I'm not talking about preventing a circuit by using a diode, I have an ultrafire charger (for flashlights, well did have, hence this thread) i've had it for 2 years been very careful up to now, I wired up a cable works great and one day i was using the 12v out for something else so i used a couple of crocodile clips and connected up the positive / negative manually so i could charge it..

    Almost instantly the thing died, I got a feeling the regulator had a fit and died because of it, the caps were not too happy either but they are fine, so anyway to prevent this from ever happening again on anything..

    how about a circuit that sits between the device and the 12vdc (most of my stuff is 12vdc, so im not worried about about anything less than 5v) so what about some kind of circuit which detects the short and almost instantly cuts off supply to protect the circuit?.. this possible?
  2. Wendy


    Mar 24, 2008
    It is called current foldback, and it is an old protection scheme for power supplies. Try Googling it.
  3. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    You could also Google "electronic fuse" .....
  4. tom66

    Senior Member

    May 9, 2009
    How about a fuse?

    A good regulator should not fail if shorted out. Most have short circuit protection.

    I'm not sure if you want reverse polarity protection, or overcurrent protection... you appear to be talking of two different things.
  5. cjdelphi

    Thread Starter New Member

    Mar 26, 2009
    well hmm umm, nothing more fancy? lol seriously you just spoilt the fun...

    'reverse' not revere typo, benifit of a circuit is that it could be reused, how about a circuit where it could reverse the polarity on the fly and invert the output if the current > recommended, maybe a small capacitor to fine tune it to say anything over 500ma within a couple of ms..

    yes, the fuse idea even fast blowing ones would not help because by then it's too late no?... but fuse? seriously too easy lol
  6. cjdelphi

    Thread Starter New Member

    Mar 26, 2009
    Not entirely sure what happened, I took apart nothing looked burnt out and took a guess and soldered a couple of surface mounted caps and resistors they all checked out fine, what can i say, cheap Chinese crap can't even add a single diode for protection, but following the path from the 12v in, everything looked ok for basic components leaving just a few IC's anyway i'm not interested in repairing it i have a spare and a new one is easy to get..

    electronic fuse though ill look it up now thanks..