Doorbell Notification for Hearing Impaired Via Home Automation (ESP-now, MQTT, Openhab)

In this Instructable I show you how I integrated my normal doorbell in my home automation. This solution is well suited for hearing impaired people.

In my case I use it to get notified if the room is busy and noisy at a birthday party of the kids.

I can also see when the doorbell was rang for the last time.

This automation uses my ESP-now, Node-Red and MQTT infrastructure, as described in my Instructable.

Supplies

You can find all these common electronic components on Aliexpress or eBay

ESP-01S
4x 1N4001 Diodes
AMS1117 3.3V voltage regulator
10uF and 1000uF capacitors
7.5 or 10k Resistor
Connectors, wires and PCB

The First Try

My doorbell transformer generates 8V. So, I designed a simple circuit, soldered it on a perf board and tried it.

The Arduino code is in my Github. The ESP-01S is flashed according step 3 of this Instructable.

I found out that when the doorbell was rung, the ESP-01S did not start (blue indicator LED did not light). When I measured the voltage across the doorbell when it was rung, I hardly measured any voltage. Why?

Then the bell in my mind rang: It is a AC doorbell. Indeed, when I measured the AC voltage, I measured the 8V AC. So I switched to plan B.

Add a Bridge Rectifier

I found this Instructable which described a bridge rectifier circuit. I hade some room on my perf board and added the four 1N4001 diodes and added a 1000uF capacitor.

For a real product, the voltage regulator should be placed better, but for this small experiment it is sufficiant.

Add the Home Automation

Now the ringing of the doorbell is transformed to a MQTT message, the sky is the limit for the automations you want to start:

Flash lights
Ring other WiFi connected bells or alarms
Close or open windows blinds or shutters.

In my home automation (Openhab) I included the following actions when message "RING" is published on the "sensor/doorbell" topic:

Activate a scene of my LEDstrip (blink red) - when the automation is switched on.
Register the time the doorbell was pressed.
Reset the state of the doorbell item.

My openhab files are in my Github.