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Can I connect 220V AC supply to node MCU pin D1 and D3 while node MCDU is power off?

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    Are you trying to kill yourself? 220V can be fatal. Go and talk to a qualified electrician before you do anything more. – Dougie Apr 28 at 9:50
  • Short answer: HELL no. You should not connect AC supply lines to any low voltage pins, under any circumstances. The insulation on the wires is not sufficient for that voltage, and it would pose a serious risk of fatal injury. Oh by the way, it would fry your Arduino, but that is not important compared to killing anybody who touched anything connected to the Arudino. – Duncan C Apr 28 at 14:57
4

No, never! 220V is way way way too much for a microcontroller. The Uno runs on 5V, the ESP8266 on 3.3V. You should never connect any more voltage than that to the microcontroller. Also you must not connect a negative voltage to the microcontroller pins.

Besides the voltage difference: You should also not connect a voltage to the pins of a microcontroller, while the microcontroller itself is turned off (meaning that it does not have the necessary supply voltage). In that case a parasite current would run through the clamping diodes, which powers the microncontroller, until the diodes get blown.


As an important side note: Don't do anything with mains power (like 220V AC), until you really know, what you are doing!!! One error and it can kill you !!!

| improve this answer | |
  • Thanks a ton... – Hoshang S Apr 28 at 10:29

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