I've been tinkering on-and-off over the past couple of years with measuring mains frequency. One problem I found is that inexpensive and homebrew timestampers and counters can often only measure positive signals, not bipolar signals. There are various messy solutions to this problem that have always seemed a little janky or unsafe to me, so I decided to make a clean solution and built a small zero-crossing detector. In case other people might find it useful, I made it available for sale for $25 ( https://www.amazon.com/dp/B0DK2GTKS4). The board is simple: it takes 5-12VAC input on a barrel connector from an AC wall wart. It gives you a 3.3V square wave output on an SMA connector, suitable for plugging into a variety of measurement devices. The AC input both powers the device and serves as the source of the signal being measured. The square wave indicates high or low depending on the polarity of the input. The board is small (about 30mm x 55mm) and includes 4 mounting holes. More information, photos, and some graphs showing data I've collected with it, are available here: https://www.lectrobox.com/projects/zero-crossing-detector/ -Jeremy N3UUO

And for those who want to compare their measurements with the rest of the country/world, there’s this link to the University of Tennessee at Knoxville: https://fnetpublic.utk.edu/ “Operated by the Power Information Technology Laboratory at the *University* *of* *Tennessee*, FNET/GridEye is a low-cost, quickly deployable GPS-synchronized wide-area *frequency *measurement network.” They have measurement devices all over (mine is #853 in the Western Interconnection). In the screen brought up by the link, select “Table Display” and scroll down to Western Interconnection. Jeremy N6WFO On Sat, Jan 25, 2025 at 5:21 AM Jeremy Elson via time-nuts < time-nuts@lists.febo.com> wrote: > I've been tinkering on-and-off over the past couple of years with measuring > mains frequency. One problem I found is that inexpensive and homebrew > timestampers and counters can often only measure positive signals, not > bipolar signals. There are various messy solutions to this problem that > have always seemed a little janky or unsafe to me, so I decided to make a > clean solution and built a small zero-crossing detector. In case other > people might find it useful, I made it available for sale for $25 ( > https://www.amazon.com/dp/B0DK2GTKS4). > > The board is simple: it takes 5-12VAC input on a barrel connector from an > AC wall wart. It gives you a 3.3V square wave output on an SMA connector, > suitable for plugging into a variety of measurement devices. The AC input > both powers the device and serves as the source of the signal being > measured. The square wave indicates high or low depending on the polarity > of the input. The board is small (about 30mm x 55mm) and includes 4 > mounting holes. > > More information, photos, and some graphs showing data I've collected with > it, are available here: > https://www.lectrobox.com/projects/zero-crossing-detector/ > > -Jeremy > N3UUO > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com >