Howto trigger a doorbell?

[Harrdy]

Hello guys,

a want to trigger and notify my phone if the door rings. I already open my intercom and found a 12v ac bell. Now i think its a option to use a diode to transform 12v ac to dc. After that i use a 12v to 3.3v stepdown board and connect this 3.3v line with the arduion interrupt pin.

Can this work the way I imagine? I am not quite as fit for electrical engineering. Or does someone know a finished solution in the form of a board to realize this?

The intercom is a SSS Siedle ht 611-01 w

Thanks :)

[electrik]

@harrdy You don't have to use a stepdown board, you can just use a resistor divider to lower the voltage.
With one diode you will still not have a DC signal yet, better to use two diodes or a bridge rectifier. After the rectifier place a capacitor and the resistor divider.

[freynder]

Hi,

Felix from https://lowpowerlab.com has an interesting blog post on the subject:
https://lowpowerlab.com/2015/04/13/doorbell-moteino/

He uses a zero-crossing detector optocoupler to transform to a 5V DC pulsating signal which he then inverts using a transistor and smooths out to a stable 5V DC using a capacitor.

[sundberg84]

@harrdy - as mentioned above some good tips.
Myself I just used a single diode to rectify the AC and a capacitor to make it smoother. After that Opto-isolator chip with 5v from the Arduino to a inputpin.

[sglue]

Glass reed switch and Fibaro Door/window Sensor (before I stumble on to Mysensors) if you have an electromagnetic door bell.
Battery a bit expensive last more then a year with DS18B20 temperature sensor connected.