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Voltage Drop

Discussion in 'Security Alarms' started by Rich, Aug 12, 2006.

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  1. Rich

    Rich Guest

    Who's good at drawing a circuit? I have a 24 V DC that I want a zener and a
    yellow LED that comes when the voltage drops to a low of 15 Volts.
  2. Petem

    Petem Guest

    one way to do this is to use a opamp circuit

    feed the negative input with the reference voltage you want as a threshold
    (15 volt)and feed the positive input with the voltage you want to monitor
    when the positive input will be lower then the negative input the output
    will switch to ground,so place the led in series of a resistor connected
    from the positive side of the power supply that feed the opamp (must be
    higher then 15 volt by 3 volt at least and not be the monitored source...)
    and the other side of the resistor to the output of the opamp,I didn't put
    any histerisist in the circuit so it could flicker when near the 15 volt
    level,and don't forget to have a common ground with the monitored

    if you have no idea what I am talking about let me know what will draw you a

    one other way would be to play with voltage drop and such thing when using a
    zener,but that need experimentation on a lab bench to be sure of what will
    be the reaction and it need to be tweaked for the zener and led used....
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