ZCD Circuit

[tiwari.sachin]

Can anyone provide me the circuit for Zero Cross Detector. I need to interface it to PIC16F877.

I dont intend to use a amplifier, rather a stepdown transformer, a fullwave bridge and the zener and transistor would be fine. I do know the concept and i think i am getting the circuit right too but i am not able to get the calculation for exact values.

Kindly Help me out with the design for a ZCD


Regards
Sachin Tiwari

 

[Brevor]

Google "zero crossing detector" there are lots of them.

 

[Sceadwian]

This topic has been covered in the forums on several occasions, no step down transformer is required, all that is needed is a single large value (1meg or more) resistor to limit the current and to chose an I/O line on the PIC that has clamp diodes. The resistor limit the current to the clamp diodes, the I/O line only ever sees the clamping voltage, an isolation transformer can be used if you need electrical isolation.