George wrote:

> How do you detect zero crossings?  I have had problems in=20
> that area with
> pics connected to the mains. Make sure that there is no input=20
> that can go
> below Vss or above Vdd as current into the protection diodes spells
> problems.

The Neutral terminal of the Mains is connected to a PIC input through a =
4.7M
resistor for detecting zero crossings. (Some may consider this =
dangerous, but
since the power supply itself makes the whole circuit "live", this =
doesn't
make any big difference.) The software checks for 0 to 1 and 1 to 0
transitions. I didn't have any problems with detection of zero crossings =
and
as I had mentioned earlier, everything worked perfectly on the =
breadboard.

Regards,
Bala=20

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