I'm currently trying to automate my intercom system. My overall aim is to have it so that I can both detect when the buzzer has been pressed and then also to have it so I can open the door. I am using a NodeMCU as the main controller. I'm fairly familiar with DC but have had virtually no experience with AC. Therefore, it has been easy for me to simply wire a relay triggered by the NodeMCU to open the door when requested.
However, I have been stuck trying to work out a method of detecting the buzzer press with the NodeMCU. This is due to the fact that the intercom system runs off 12V AC. After some searching around, my options were narrowed to either a Current Sensor or a Relay. The Current Sensor seems to be too much detail for what my purposes are; leaving me to fall once again on Relays. This time, however, due to the fact that the thing triggering the relay (the buzzer in this case) is using 12V AC rather than DC it has left me in a slightly awkward position as I am unsure exactly what I am looking for.
I have found myself upon this relay which seems to be what I am looking for. I would really appreciate it if someone could:
A) Let me know if this is the right sort of relay for my use case. And if not then what is (and costs little)?
B) Point me in the right direction of exactly how to wire this sort of relay.
This is because, unlike DC relays, I expect that AC relays only take 2 inputs (compared to 3); i.e. the relay gets triggered when electricity flows into the module. Is this correct?
Thank you in advance for any help.