I'm looking to measure AC voltage (just the voltage, not the phase etc.) and power a raspberry pi 3 with a lora concentrator (so there would be a power draw up to 2A @ 5V) from the same ac-ac adaptor, like in the schematic:
The main reason I don't want to use a separate power supply and sense adapter is installation inconvenience.
Would this work, if I chose a beefed up enough wall wart? I'm thinking that a 12V 24VA should be more than sufficient. And since it's using a transformer, the voltage at the adc divider should be linearly proportional to the mains.
The required resolution is 1V, so using a 10bit should be sufficient. 1V @ 240V translates to 12.5mV @ 3V and the ADC has a resolution of 3.2mV @ 3.3VRef
Edit: The 5V regulator before the raspi would most probably be a switching one