B4R Question d1 mini 8266 help - question

[user_an]

Hi all,
I need help with a connection for my d1 mini. Please forgive my ignorance as I am very new to this.

So, the doorbell in the house is video doorbell. It has 2 wires that expose 27.3 volt in idle mode (black screen etc) and when someone ring the bell ti goes to 26.5 - 26.7.
Ideally I need to know when someone is ringing the bell. So I thought to use a transformer to step down to 3.3 volts or something less and attach it to d1 mini.
I saw some videos and I suppose to connect the ground of transformer to the ground of d1 mini, and the other wire to A0 of d1 mini.

My first question is, if it is ok to proceed as above.
I am not sure if 1 of my 2 wires of my video door bell can be considered as a ground?

My next question is if with the above set up is a way to power the also the d1 mini. This is ideally. I don't have a plug near to connect it with 5v phone charger which is my favorite choice.

** One key problem I saw is that if I connect these 2 wires the camera reboots so I am not sure at all that how and if this can work or what else alternatives I have

Again, I know that I'm asking very basic and probably stupid questions, but I'd appreciate if you could help.

Thanks

 

[derez]

1. Is it DC or AC ? a transformer works on AC, if it is DC you need something like this "LM2596 DC-DC Buck Converter Adjustable Step Down Voltage Regulator 3-40V to 1.5-35V High Efficiency Power Supply Volt Reducer"
2. The difference between 27.3 and 26.7 , after downconverting, is null so you will not be able to tell when the ring button is pressed...
3. Check again the voltage on the wire that comes out from the ring button, it does not make sense. I guess it is 0v when not pressed and above 0 when pressed, or vice versa.