120/240Vac LED power indicator circuit

Discussion in 'The Projects Forum' started by bhavlo, Oct 21, 2010.

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  1. bhavlo

    Thread Starter New Member

    Aug 3, 2010
    I need help making my Vac LED indicator circuit more reliable.
    I have been using a design based on the description "Special-purpose diodes" http://www.allaboutcircuits.com/vol_3/chpt_3/12.html for my AC power indicator.

    I have a design that I am using for both 120 & 240Vac. It consists of a series network of a 0.22uf Cap, a 1.2k ohm resistor and a Blue LED. I have also placed a 1n4002 100v 1 amp rectifier diode in parallel but in opposite polarity to the LED to protect it from a reverse over voltage situation.

    I am using this circuit on a power strip to just give me a visual indication that power is on. I am having trouble with the LED burning out when I plug appliances into the power strip. It doesn't happen every time but I can cause it to happen by plugging and unplugging an appliance multiple time rapidly. There must be a peak surge that occurs and kills the LED. I have tried increasing the series resistor all the way up to 2.7k ohms but it still will fail. It also fails allot easier on the 240Vac application.

    I would like to know if anyone has any ideas on how I can make this design more reliable?
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    The method you are trying to use is very dangerous. LEDs are not suited for such applications. LEDs are DC devices, not at all suited to line voltage. The use of a capacitor does not provide galvanic isolation from the line, and therefore presents a lethal shock hazard inherent in that circuit.

    If you must have a visual indicator, look into neon pilot lamps that are made for 120 & 240 VAC operation. Such indicators are readily available.
    bhavlo likes this.
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