I have a 12V phone entry system for my flat and I want to monitor when someone rings my buzzer.
For the first stage I have connected the buzzer wire into one of the 12-bit ADC inputs on the Automation HAT on my Raspberry Pi. Once I have finished testing I will then add a wire from the input terminal and connect it into the buzzer terminal so my buzzer is functional again.
As soon as I connect my buzzer wire to any of the three 12-bit ADC inputs the three 12-bit ADC input lights start to flash. Assuming this was normal I continued to monitor the analogue input from a python script.
(I also found it odd that when I connected a single wire to one of the analogue inputs the light turned on even when the wire wasn’t connected to anything.)
Even when the buzzer was not being pressed the values went from -2 for a few cycles then up to 30. Since documentation says that the inputs are reduced to a range of 0 to 3.3v I assume that 30 represents 3v and is therefore switching between a high and low voltage.
This made me believe I was dealing with a PWM yet when I tested the buzzer wire with a multimeter there wasn’t any sign of modulating current.
In the off chance, I had misunderstood the readings I decided to see if I could determine if there was a difference in the waves when the buzzer was pressed but no pattern emerged between the two states.
At this point I am starting to think my Automation HAT is broken or I have some misunderstandings that need cleared up.