A few threads here recently about analogue input recently and it looks a minefield.
I am also interested in implementing a battery level recorder to email me when the battery starts to get low. Reading about the internal analogue input I thought I would be better off using an external ADC but if my supply voltage gets to low it could damage the external ADC.
I suppose some of the confusion may come as some posts are talking about the Nodemcu data and others the ESP8266?
Reading a lot of threads gives lots of different answers:
The Analogue input can be 1V on older boards and 3.3V on newer boards.
The Nodemcu has an internal voltage divider
The impedance of the voltage divider is not practical
The A0 impedance varies on one site to another from 100K to 2M
The input is 10bit but is actually equal to 7bit
I was told to have quite high value resistors for the voltage divider as it should have less current loss and if the R2 value was to close to the internal impedance the voltage divider would not be working properly.
Does anyone have any useful insights?
I think it would be useful to have the bits of knowledge in one thread.