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Mains electricity to circuit board

Discussion in 'General Electronics Discussion' started by screwball, Apr 12, 2013.

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  1. screwball


    Jan 9, 2012

    I've been looking for a circuit that i can use to check if there is power through the mains electricity but dont have a clue where to start,

    Basically, I want to use a microchip (programmable IC) which will detect when the mains electricity is on/off but dont have a clue where to start in terms of making a circuit and then designing it so that it doesn't blow my microchip to pieces. Preferably without any special components of any sort

    Any help would be great
  2. GreenGiant


    Feb 9, 2012
    I would say spend a few bucks and get something like this look under shopping they range from around a dollar to over 50, the main difference is sensitivity

    I paid 10 for a craftsman from Sears that does what I need it to do, youll spend more than that on parts for a circuit without a micro, plus you dont have to fool around with the mains voltage
  3. BobK


    Jan 5, 2010
    Use an optoisolator with a capacitor to drop the voltage to the LED side of it. Be sure to also bypass the LED with a diode pointing in the opposite direction. You should see a 50/60 Hz square wave out when the lines voltage is on.

  4. BobK


    Jan 5, 2010
    Like this:


    The LED is the input of the optoisolator.

    The capacitor is sized for 120V 60Hz and a 20ma LED, if different you need to resize it.

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