MQTT-Connected DHT Temperature and Humidity Sensors Using ESP8266 Modules

This project gives a simple way to deploy temperature and humidity sensors around your house using cheap components and the MQTT protocol. I use it with Home Assistant, an amazing, extensible, open-source home automation system, but this project could be used standalone or with any platform.

The sensor publishes to 2 MQTT topics:

• Temperature topic (example: home/livingroom/temperature): The sensor publishes the temperature in Fahrenheit (example: 67.10).
• Humidity topic (example: home/livingroom/humidity): The sensor publishes the relative humidity in percent (example: 37.40).

In the sample configuration, the values are published every 30 seconds, but that is configurable.

Installation/Configuration

I'll explain how to set the sensor up as an MQTT sensor in Home Assistant. This guide assumes that you already have Home Assistant set up and running. If not, see the installation guides here.

The Home Assistant Side

1. In your configuration.yaml, add the following:

   sensor:
     - platform: mqtt
       name: "Living Room Temperature"
       state_topic: "home/livingroom/temperature"
       qos: 0
       unit_of_measurement: "°F"
   
     - platform: mqtt
       name: "Living Room Humidity"
       state_topic: "home/livingroom/humidity"
       qos: 0
       unit_of_measurement: "%"

2. Set the name and state_topic to values that make sense for you.

3. Restart Home Assistant. Depending on how you installed it, the process differs. For a Raspberry Pi All-in-One install, use sudo systemctl restart home-assistant.service (or just restart the Pi).

The ESP/Sensor

I'm using ESP8266-01 microcontrollers for my sensors because they are so cheap and small. The downside of the size and price is that programming them can be a bit of a hassle. There are many sites that go into detail, so I won't do it here. You'll need an ESP set up to work with the Arduino IDE. See the readme here for instructions.

1. Using the Library Manager in the Arduino IDE, install the Adafruit Unified Sensor Library and the DHT Sensor Library. You can find the Library Manager in the "Sketch" menu under "Include Library" -> "Manage Libraries..."
2. In the mqtt-esp8266_dht22 folder, update the config-sample.h file with your WiFi, MQTT, and DHT settings.
3. Ensure that the CONFIG_MQTT_CLIENT_ID setting is a unique value for your network.
4. Set CONFIG_MQTT_TOPIC_TEMP and CONFIG_MQTT_TOPIC_HUMID to match the values you put in your configuration.yaml.
5. Save the configuration file as config.h.
6. Open the .ino file in the Arduino IDE and upload to an ESP with the correct connections.

Wiring

For my sensors, I've soldered a simple proto-board. They aren't very pretty, but here is the basic wiring.