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There are multiple hardware solutions to do amp/current monitoring, but I cant seem to find one to do AC Frequency monitoring. Anyone have a pointer to board that can handle line power and return line frequency?

I have devices that are sensitive to Dirty power, and when the frequency of the line strays too much from 60 hertz I want to flip-a-switch…

Stuart Siegler
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    This might be considered off-topic. Consider using a [search engine to get some information on `power line frequency meters` from the Internet](https://duckduckgo.com/?q=power+line+frequency+meter). If you elect a "DIY" approach, keep in mind that accurate frequency measurement will require an accurate time source. Also know that [RPi's timekeeping is not considered particularly accurate](https://raspberrypi.stackexchange.com/questions/1397/how-accurate-is-raspberry-pis-timekeeping). Finally, [more info on RPi timekeeping can be found here](https://raspberrypi.stackexchange.com/a/87921/83790) – Seamus Jan 03 '20 at 22:16
  • Electric power distribution (at least in advanced countries) rigidly controls the power line frequency. While there may be minor variations the average frequency is maintained to a high level of accuracy - at least an order of magnitude better than the Pi clock! – Milliways Jan 03 '20 at 22:38
  • Hi@Stuart Siegler，Welcome and nice to meet you. Ah, let me see. My home 220V 50Hz mains was once very dirty. I used a scope to look at it, but home MCB blew up immediately. I googled and learned that it is the scope grounding problem. So I used a hand held scope and saw how dirty, with ugly glitches, was the AC wave. Later I used a very low power transformer to step down 220V AC to 3/6/12V (AC is now floating, so I can use desktop scope to look at it). Then I rectify AC to DC. Now I have a positive going only sine signal to mess around. / to continue, ... – tlfong01 Jan 04 '20 at 02:23
  • I use a HCT14 Schmitt inverter https://assets.nexperia.com/documents/data-sheet/74HC_HCT14.pdf to convert the sine signal to digital signal to read and count by Rpi GPIO. Now it is all Rpi python's job to data log, do analysis and make an AC frequency deviation statistics report and complain to the power company (Yes, I did that). PS - I also DIYed a frequency counter using 32.768Hz quartz clock module, binary and decimal counter, 7 segment LEDs. But the all 74HC hardware DIY frequency counter is only for human eyes only, /to continue, ... – tlfong01 Jan 04 '20 at 02:24
  • I later found that using minimal hardware (in this case only HC14) and let all the rest for Rpi to do is the most time and space saving effective and efficient, way to do AC power line monitoring. By the way, my city's power company is now introducing home use "smart" electricity meters. I am anxiously waiting to get one and hack inside for AC power frequency and amplitude data etc. Cheers. – tlfong01 Jan 04 '20 at 02:34
  • Actually there are out there various power electronic devices/chips/modules you can make use of, to monitor AC power amplitude and frequency etc. You may like to read the following discussion for more details: Rpi3B+ based AC Power Monitoring using HCPL3700 (A37) and also HC14 - rpi.org forum discussion 2018aug30 https://www.raspberrypi.org/forums/viewtopic.php?f=32&t=219744&p=1359339&hilit=HC14+tlfong01#p1359339. Please feel free to ask me any DIY and hobbyist level questions! :) – tlfong01 Jan 04 '20 at 02:40
  • And I also use the realtime clock module DS3232 https://datasheets.maximintegrated.com/en/ds/DS3232.pdf schedule my AC Mains and other time monitoring. DS3232 has a built in 32kHz clock. All DS3232 clocks are extremely accurate. Using I2C and also MCP23017 with interrupts, you can place you monitoring sub systems far away from Rpi, as discussed in the rpi.org.forums I referred in the above comment.. . – tlfong01 Jan 04 '20 at 05:53
  • BTW, the place I am living is promoting the smart city idea, with smart public utilities home use meters (gas/electricity/water). I heard that my projects start using Rpi, but more using ESP8266/32. I knew some decade ago, 8051 was used everywhere, in every PC keyboard, mouse etc. I won't be surprised not too many years from now more ESP8266/32, and less Rpi will be found in wireless keyboards, WiFi mains switches, aircon, freezers. In other words ESP8266/Rpi IoT everywhere.. – tlfong01 Jan 04 '20 at 06:00
  • I have been working on a similair problem! I use an SCT013 with an AC sensor board. https://www.dfrobot.com/product-1486.html To get around the clock issue I bought a gps module and connected it via USB. GPS gives accurate clock readings. Check out this youtube video https://www.youtube.com/watch?v=Z3YSHhS39Bc. – Tuomas Talvitie Jan 04 '20 at 16:27

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