Hi Indeed looking at the AC line is a Time Nut sort of thing to do. It was one of the first things I did with an old Beckman counter back in the 1960’s. Yes I realize that the AC line is a very noisy signal and that this may not be needed:
The same limiter / noise shaper stuff that works for a DMTD is equally at home processing a 60 Hz sine wave. The rise time, bandwidth, and progressive stage gain issues are the same. The Collins paper on hard limiters does indeed apply here. You *could* make a 60 Hz chain that got down into << 1 us sort of resolution. Again, just because you can does not mean you should. Bob > On Dec 16, 2014, at 8:58 PM, Dave M <[email protected]> wrote: > > Charles Steinmetz wrote: >> Every so often, the subject of logging the zero-crossings of the AC >> mains comes up. There are any number of ways to couple the AC mains >> to logic circuitry (coupling with very high value resistors, >> capacitor coupling, and optical isolation have been mentioned). A >> simple AC mains ZCD that is transformer isolated and gives excellent >> results, is posted at ko4bb.com: >> >> <http://www.ko4bb.com/manuals/download.php?file=05_GPS_Timing/Simple_AC_Mains_Zero_Crossing_Detector.pdf> >> >> The ZCD uses a small, dual-primary power transformer, two >> transistors, and a few diodes, resistors, and capacitors. It >> produces a ~100uS logic-level pulse at every positive zero-cross, the >> leading edge of which is predictably and stably related to the AC >> mains zero-cross. >> >> Best regards, >> >> Charles >> >> > > I'm not trying to downplay the circuit in the link above, but I want to offer > another possible solution to Zero-Crossing needs. > > Here's an Idea For Design from EDN magazine that I've used a couple times in > non-time-nut circuits, and I must say that it works beautifully. I have no > measurements that would satisfy a time-nut's curiosity, so if someone wants > to Spice it or otherwise tear it apart, please do.. > My use for the circuit was in a spot welder control; the output was used to > sync and cycle a counter-driven trigger for an alternistor, all of which > controlled the number of power line cycles that the welder transformer > received for the weld. It worked well for me until I sold the whole > contraption. Don't know whatever happened to it after the guy moved away > from the area; never heard from him again. I hope it's still working. > > http://electronicdesign.com/analog/differential-line-receivers-function-analog-zero-crossing-detectors > > Dave M > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
