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Brown out protection

Discussion in 'Electronic Basics' started by ., Aug 28, 2003.

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  1. .

    . Guest

    Hi
    I have a 12V relay that is being fed from the mains by a capacitor power
    supply, through a bridge and a 12Vcrowbar zener.

    If I get a brown out my relay chatters. Is there a simple single component
    that will act like a DS1810 Econo Reset, except at about 10V instead of
    4.5V? That is, hold its output voltage to zero until the supply returns to
    an acceptable level.

    I don't have much room and hope someone can suggest a single component
    solution.

    Any suggestions appreciated

    Kez
     
  2. Guest

    Guest Guest

    Hi Kez

    If my understanding of the circuit is correct; capacitors are being used
    instead of a transformer to drop the voltage for this relay.
    There is no filter capacitor mentioned either.
    If this is so, the voltage across the relay coil will be a pulsed DC.
    This complicates things somewhat.
    If this relay has a spare/isolated set of contacts maybe the following might
    work.
    Install a resistor in series with the relay coil so that the relay only engages
    at or near normal mains voltage.
    When the relay engages use the spare contacts to short out this resistor.
    This will provide some hysterisis and reduce or eliminate the chattering.

    Note: The capacitors do not properly isolate the high voltage mains, do not
    work on this circuit while it's powered up!

    Regards

    Strill


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