Detecting Zero Crossing in AC220V using resistor

[skmdmasud]

Hi..
i was wondering can i use a 2Mega or 3Mega Ohms resistor in the interrupt pin of my uC to detect AC220V zero crossing. I understand my uC will not be mains isolated which is ok for my application.

Regards.

 

[ericgibbs]

Hi..
i was wondering can i use a 2Mega or 3Mega Ohms resistor in the interrupt pin of my uC to detect AC220V zero crossing. I understand my uC will not be mains isolated which is ok for my application.

Regards.

hi,
This is a microchip pdf for mains interrupt.
E

 

[skmdmasud]

hi,
This is a microchip pdf for mains interrupt.
E

I also found AVR's version of main interrupt detection, hope this will help others.
http://www.atmel.com/Images/doc2508.pdf

 

[ronsimpson]

When you connect to the power line look at the resistor voltage ratings.
It is likely that your resistor can not with stand line voltage for long periods of time. You might need to use two or more resistors in series.

 

[skmdmasud]

When you connect to the power line look at the resistor voltage ratings.
It is likely that your resistor can not with stand line voltage for long periods of time. You might need to use two or more resistors in series.

Hi
yes i read in the note section where it said to have 2 or more resistors in series for safety cuz if one blows and becomes closed circuit then other one will protect the uC.

Although i did not find any suggestions on voltage rating. I think most resistors available in my location are most probably 350V. Is 1/4 watts resistor ok for this job.