> I like Mr Doug's Idea as its the cheapest and would save quite some space
> required by the transformer.

I like it too as long as the PIC does not need to be isolated from the AC
line.

> I could just rectify the AC Voltage and then
> use a
> resistive divider to scale the voltage down to say 3 volts. But i'll have
to
> add a
> couple of Mica Capacitors of say 0.47mfd/300 Volts to flatten out the DC.
> And after
> the Voltage Divider, I might also put up a small LC network based Low Pass
> Filter.

I don't see any need for LC.  RC should be fine unless you're right on the
edge of the tradeoff between ripple rejection and response time.

> And finally, a Kamikaze Zener Diode of say 5.2 Volts to Commit Suicide and
> Protect
> the PIC if one of the Divider resistors is to fail.
>
> So, the voltage I'll be getting will be the peak voltage. How do I get the
> RMS Voltage ?

For a sinusoid, RMS = peak / SQRT(2).  If the waveshape is not known, then
you have to take lots of samples, square them, average them, and take the
square root of the average.  RMS = "root mean square".

Please fix your reply address.  The default reply goes to you instead of the
list.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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