> Somewhere there I think I confused averaging
> this sense voltage (which is really current)
> with actually averaging a voltage. It's been
> too long since I did AC Machines theory... :o)

Well, as long as the circuit is driven by mains AC (which is a sine wave)
and you do not mangle the waveform too badly (triac pwm chopping is
mangling it badly) you can rely on Vef ~= 0.707 Vpeak and Ief ~= 0.707
Ipeak. It is better to use the average rectified voltage (and a different
coefficient) to reduce influence from peaks and glitches. The easiest way
is to load a peak detector with a resistor and add a small resistor in
series with the rectifier diode. By choosing the resistors 'right' the
reduction coefficient will be 'built in'. There will also be some ripple
on the output (larger cap required). This method is often used in cheap
audio VU-meters (VU units are Vef of audio signals expressed on a log
scale).

Peter

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body