If you rectify the 230VAC first you can use a very non-perfect
rectifier.  The errors will be insignificant vs. the 300VDC result.
Then use a resistive divider to reduce the 300V to 5V for the PIC A/D.

The will give you the average voltage level.  If you are looking for
single cycle dropouts you will have to do something faster, probably
synchronized to the power line frequency.

Do you need to isolate the PIC ground from the AC mains?

Sherpa Doug

> -----Original Message-----
> From: Peter L. Peres [mailto:plp@ACTCOM.CO.IL]
> Sent: Friday, June 22, 2001 1:56 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [PIC]: Reading Mains Voltage From a PIC
>
>
> Jeethu, imho look into a National analog databook and build one of the
> 'perfect rectifier' circuits pictured there. They accept AC (you use a
> resistive divider) and output DC which can be fed to the A/D. They are
> rather good (i.e. precise) even if using cheap parts.
>
> Peter
>
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