hi, i have question about how to make zero crossing detector to detect zero crossing for sin wave 220 V RMS without using transformer

 

this is the circuit i will use

 

Your circuit will not work and it would be foolish to attempt it.

 

this is the circuit i will use

If that's what you propose for a zero-crossing detector circuit, I suggest you make sure you have a fire extinguisher close at hand the first time you plug it in. I guarantee you: there won't be a second time.

 

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Good luck.

 

Hello,

As said, ALWAYS use isolation.

Have a look at the following page for some zero crossing detector circuits:
http://sound.westhost.com/appnotes/an005.htm

Bertus