Open Energy Monitor promotes a simple way of measuring AC voltage using an AC adapter (9V transformer). Here is an example on a breadboard with an Arduino:
https://openenergymonitor.org/emon/buildingblocks/how-to-build-an-arduino-energy-monitor
If you use their schematic and the microcontroller is NOT powered but the AC adapter IS, the microcontroller would surely end up with an AC current being fed into the Analog input. Schematic shown here:
https://openenergymonitor.org/emon/buildingblocks/measuring-voltage-with-an-acac-power-adapter
Could this harm the microcontroller? If so, how can you protect the analog input in the case the microcontoller isn't powered but the AC adapter is?
Any comments?
David
https://openenergymonitor.org/emon/buildingblocks/how-to-build-an-arduino-energy-monitor
If you use their schematic and the microcontroller is NOT powered but the AC adapter IS, the microcontroller would surely end up with an AC current being fed into the Analog input. Schematic shown here:
https://openenergymonitor.org/emon/buildingblocks/measuring-voltage-with-an-acac-power-adapter
Could this harm the microcontroller? If so, how can you protect the analog input in the case the microcontoller isn't powered but the AC adapter is?
Any comments?
David