Protection

Discussion in 'General Electronics Chat' started by garyp, Mar 20, 2006.

  1. garyp

    Thread Starter Member

    Feb 17, 2006
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    does anyone know of a good over current/over voltage protection circuit i can add to a power supply.
     
  2. windoze killa

    AAC Fanatic!

    Feb 23, 2006
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    What range of current and voltage are you talking about.
     
  3. garyp

    Thread Starter Member

    Feb 17, 2006
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    i've got a 14v and about 0.25 - 1A
     
  4. Gadget

    Distinguished Member

    Jan 10, 2006
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    A fuse followed by a 2 watt zener, say.... 16 volts.
    If the current exceeds the fuse rating , the fuse blows. If the voltage exceeds the zener voltage, the zener "crowbars", and blows the fuse.

    Thats the simple way.

    Another way would be to build a voltage and current regulator for your Power supply. A little more complicated, but well worth it for a versitile hobby power supply.
     
  5. windoze killa

    AAC Fanatic!

    Feb 23, 2006
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    Do a search for crowbar protection.
     
  6. garyp

    Thread Starter Member

    Feb 17, 2006
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    i have just added a crowbar to my circuit but i am having a problem. when i turn the power on the initial surge is tripping the protection circuit. i think i need some kind of soft start circuit as i have proved that if i apply the voltage gradually it doesn't trip.
     
  7. windoze killa

    AAC Fanatic!

    Feb 23, 2006
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    You could try an inductor in series with the O/P line and capacitor to ground prior to the crowbar. This should remove any spikes or sudden changes.
     
  8. Gadget

    Distinguished Member

    Jan 10, 2006
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    If it were me, I think I would be rebuilding the Power supply, using a transformer with a few extra volts, and feeding the rectified output into a basic series regulator..(say an LM317) set up for 13.8 volts (or what ever voltage is required). They have built in current limit (1.5 amp) built in Thermal protection, and of course the voltage remains constant.
    NB, I must admit I've never trusted the Current limit on these, so I'd probably fuse protect the output (just in case)....
     
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