> How's this for zero detection ...
>
>                                  o Vdd
>                                  |
>                                  / 4k7
>                                  \
>                                  /
>                                  |-----o Zero Detection
>                                 /n
>    220VAC                     |/
>    o--------/\/\/\-------o----|p   BC547
>              330K        |    |\
>                          |     _\/n
>                          |       |
>                          |--|<---o
>                           1N4001 |
>                                  o Gnd


Good.

The 330k should be rated for greater than main peak voltage. Most single
resistors aren't rated for 230 VAC mains use, regardless of power
dissipated, and using two in series would often be wise.

The 4k7 could be higher if desired - draws less current.



        RM

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