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Raspberry Pi

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  • Your 50V AC should be OK to light the LED in an optocoupler (on half of the AC cycle if you don't rectify it to DC). An optocoupler can be used to switch a GPIO. Commented Jun 23, 2021 at 20:32
  • That's exactly what I needed, thanks @Dougie. Works like a charm. For future reference, I used the following guides: instructables.com/LED-on-AC-Mains peppe8o.com/… Commented Jun 23, 2021 at 22:18
  • As you suggest this is not a Pi problem but an EE question. I am an EE but given the sparsity of details I would be reluctant to suggest a solution, although I would likely use an opto isolator but running from AC is not straight forward. Commented Jun 23, 2021 at 23:00
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    Incidentally just out of curiosity I looked at the instructables link you followed. I am appalled! DO NOT do this! This violates so many electrical principles and safety rules. Commented Jun 24, 2021 at 0:35
  • Ah, the popular toy for EE newbies are ninjas alike is ACS712: (1) ACS712: Fully Integrated, Hall-Effect-Based Linear Current Sensor IC with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor - Allegro: allegromicro.com/-/media/files/datasheets/acs712-datasheet.ashx, (2) Rpi Current Sensing Using ACS712 and INA219 - Rpi SE, Asked 2019feb20, Viewed 7k times: raspberrypi.stackexchange.com/questions/94403/…. Cheers. Commented Jun 24, 2021 at 5:11