I’ve built a system which detects if someone presses the intercom and sends me a push notification.
I’m using an ADS1115 ADC in differential mode to measure the analog voltage across the buzzer and negative terminal of the intercom. It works but I end up getting some noise and maybe some kind of feedback loop which causes buzzing to come through the speaker.
The speaker is connected to both the buzzer and voice terminals of the intercom. See diagram.
Does anyone have any ideas for how I can detect when the buzzer rings without introducing noise into the intercom circuit?
Thanks in advance!