I'm needing to monitor voltage and the like for some sites with three 
phase 120/208V (and perhaps whatever the 240V/???? version is - if 
someone would like to enlighten me, that would be great).

I was thinking of doing a  PIC essentially directly-on-the-mains to do 
the measurement and then serial the data out via an optocoupler - that 
is, connect the pic 'dangerously' to the line , but I'm not particularly 
eager to have to deal with all of the connect-a-pic-to-the-line issues - 
still an option but want to explore others first.

The simplest thing I can come up with is to stick 3 120V transformers on 
a circuit board connected such that you have 3 'line' and 1 'neutral' 
inputs, and each of 3 transformers have their primary attached to a line 
input and  the netural, and then read the (lower) secondary voltages.  
I've been told on here that this works, but I'm a bit skeptical of the 
linearity and/or other issues.  I would guess this varies based on the 
type of transformers.

Has anyone actually done this?   Or does anyone else have an idea on how 
to measure AC line voltage safely in a way that can be read by a PIC?

-forrest

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist