doorbell-gateway

Introduction

This is a DIY ESP8266-based doorbell detector and gateway.

The idea is that a microphone and a small pre-conditioning circuit prepares an analogue signal to be sampled and converted to digits by the controller (by its integrated analog-digital converter, ADC). The digital voltage signal is then subtracted by a user-defined offset and a simple algorithm is used to detect the ring of the doorbell by setting an amplitude threshold.

On every ring the software posts a configurable MQTT message which can then be used to switch on a buzzer, blink some LEDs, send you an email or a notification on your smartphone, ... - ideas are endless.

The code has been written in the Arduino IDE as it provides simple, ready-to-use libraries.

Hardware setup

I've been using an ESP-12E (NodeMCU 1.0) which uses an ESP8266. Other boards might be compatible as well.

The additional signal conditioning circuit is based on the Claplight MKII 2017 (PCB and parts in a kit) made by kitbuilding.org. The kit can be bought for ~4 € from their web-shop (they sell other great soldering kits, too!).

This part of the schematic is based on an 2N3906 PNP bipolar transistor:

The kit is originally powered by a 9V battery. Instead of using an additional battery, the supply voltage can be connected to the 3V3 pin of the NodeMCU board directly, too - also thanks to the voltage divider R5/R6 where you can lift the mid-supply to an arbitrary value. The GND signal also needs to be connected to the NodeMCU board. The NodeMCU board itself can be powered by a USB power supply or power bank.

The analog trigger signal is connected to the analog input signal pin AD0 of the NodeMCU board.

Software setup

Sensor software setup

Please change the settings in the file config.h according to your local setup:

• WiFi settings
  • SSID
  • Password
• MQTT settings (the sensor acts as an MQTT publishing client only)
  • Server (IP or hostname)
  • Port
  • Topic
  • Message to be sent on connect event
  • Message to be sent on doorbell detection event
• Hardware-specific settings
  • Pin number of analog input pin
  • Sensor loop delay/ query interval
  • Sensor offset voltage
  • Sensor threshold voltage
  • Sensor detection threshold

Then open the .ino file in the Arduino IDE, re-compile and upload it to your target uC.

Subscriber software setup

As the sensor publishes MQTT messages there needs to be an MQTT client that subscribes these messages.

There's a list of MQTT libraries on github: https://github.com/mqtt/mqtt.github.io/wiki/libraries

For my local Linux PC I've used the mosquitto-clients package as test setup. The commands mosquitto_sub and mosquitto_pub can be used to play around.

Pipe it through ts in order to prepend every line with a timestamp:

$ mosquitto_sub -h localhost -p 1883 -t Test | ts
Apr 01 23:23:11 Connected
Apr 01 23:42:22 Ding-dong

Or why not play a sound file remotely?

$ mosquitto_sub -h localhost -p 1883 -t Test | xargs -i play -q /usr/share/sounds/doorbell.wav

There are better and cooler ways to do things? Let me know! Twitter: @maehw