He reasoned that he could tap into the low-voltage side of the doorbell transformer and watch for the telltale fluctuations that would indicate the bell was doing its thing. The ESP8266 has an ADC ...

In this configuration, your existing doorbell transformer will trickle charge the battery ... This section can be filtered by event type and date, so it’s generally pretty quick to find an event that ...

This means that the old dumb doorbell system will still work even if the Arduino loses power or is disconnected. The system consists of a transformer powering two doorbell chimes, with a button to ...

The device works with compatible doorbell transformers, requiring a 16-24VAC, 10-40VA rated doorbell transformer and chime, which are sold separately. You may need to replace existing hardware.