Mains electricity to circuit board

[screwball]

Hey,

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

 

[GreenGiant]

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

 

[BobK]

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.

Bob

 

[BobK]

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.

Bob