detecting zero cross

C

computer

New Member
hi,

what is the best way of detecting the zero cross on 240v 50Hz AC or 36v AC? I need to detect it for a PIC chip.

also, will it work if I send DC instead? I'm making a christmas light controller with 4 pic controlled triacs for dimming, etc. I will be making a few of the units if sucessful and would like 1 common design I can use for some 36v AC sets, and some 12v DC sets with the possibility of some 240v AC ones as well...

Thanks,
computer
 
pot it down with a resistor divider and use a comparator
 

If you search on these forums there was a thread a little while ago, try .

As DC doesn't have a zero crossing point it's not relevent to DC control, you should use PWM instead.
 
I know DC doesn't have a zero crossing point, but if I connected DC upto the zero crossing circuit its not going to short or anything? It just won't detect it and the code for that particular pic will just use a DC option with PWM...
 
Is the output correct? During the -ve part of the input cycle the first transistor will be off, forcing the 2nd on and the output low not high? Output will be a square wave unless the input is taken from a full wave rectifier that have only +ve cycles
 
Absolutely right, the quick draw not always good...
Correction
 

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