Re: Looking for two-input comparator with hysteresis

In article <BcIcg.13960$fb2.6644@xxxxxxxxxxxxxxxxxxxxxxxxxx>,
notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx says...
Hello Keith,


Use an optical isolator to connect to the line, even if there is an
isolation transformer inbetween.

Depending on your clock circuit, it may be eaiser to do the
filtering in the digital domain. After the isolator turns on wait
1/119th of a second to look for it to go off, then 1/119th of a
second for it to turn back on...


That only works for a nearly perfect since wave, like if you'd tap into
the output of one of the generators at Hoover dam. It could fail in very
common situations where the since wave is distorted. That is common
these days because of all the switch mode supplies and dimmers in
households. A brief distortion can also be caused by a large AC motor
spooling up (air conditioner, pool pump etc.).

No, it simply works. Once an endge is sensed one ignores any more
for some time. If there are multiple edges, no one cares. If the
waveform is *really* distorted where the sensing is done may shift,
but it'll soon find an "edge", rather like a phase detector.

I'd go with a nice analog filter. Being an analog guy I am, of course, a
bit biased here :-)

If it's a digital problem, stay digital. Unlike analog, digital
transistors are free.

--
Keith
.