MQTT Sensor

This mqtt sensor platform uses the MQTT message payload as the sensor value. If messages in this state_topic are published with RETAIN flag, the sensor will receive an instant update with last known value. Otherwise, the initial state will be undefined.

To use your MQTT sensor in your installation, add the following to your configuration.yaml file:

# Example configuration.yml entry
sensor:
  - platform: mqtt
    state_topic: "home/bedroom/temperature"

Examples

In this section you find some real life examples of how to use this sensor.

JSON attributes configuration

The example sensor below shows a configuration example which uses JSON in the state topic to add extra attributes. It also makes use of the availability topic. Attributes can then be extracted in Templates; Example to extract data from the sensor below ‘{{ states.sensor.bs_client_name.attributes.ClientName }}’.

# Example configuration.yml entry
sensor:
  - platform: mqtt
    state_topic: "HUISHS/BunnyShed/NodeHealthJSON"
    name: "BS RSSI"
    unit_of_measurement: "dBm"
    value_template: '{{ value_json.RSSI }}'
    availability_topic: "HUISHS/BunnyShed/status"
    payload_available: "online"
    payload_not_available: "offline"
    json_attributes:
      - ClientName
      - IP
      - MAC
      - RSSI
      - HostName
      - ConnectedSSID  

Get battery level

If you are using the Owntracks and enable the reporting of the battery level then you can use a MQTT sensor to keep track of your battery. A regular MQTT message from Owntracks looks like this:

owntracks/tablet/tablet {"_type":"location","lon":7.21,"t":"u","batt":92,"tst":144995643,"tid":"ta","acc":27,"lat":46.12}

Thus the trick is extracting the battery level from the payload.

# Example configuration.yml entry
sensor:
  - platform: mqtt
    state_topic: "owntracks/tablet/tablet"
    name: "Battery Tablet"
    unit_of_measurement: "%"
    value_template: '{{ value_json.batt }}'

Get temperature and humidity

If you are using a DHT sensor and a NodeMCU board (esp8266), you can retrieve temperature and humidity with a MQTT sensor. A code example can be found here. A regular MQTT message from this example looks like this:

office/sensor1
  {
    "temperature": 23.20,
    "humidity": 43.70
  }

Then use this configuration example to extract the data from the payload:

# Example configuration.yml entry
sensor:
  - platform: mqtt
    state_topic: 'office/sensor1'
    name: 'Temperature'
    unit_of_measurement: '°C'
    value_template: '{{ value_json.temperature }}'
  - platform: mqtt
    state_topic: 'office/sensor1'
    name: 'Humidity'
    unit_of_measurement: '%'
    value_template: '{{ value_json.humidity }}'

Get sensor value from a device with ESPEasy

Assuming that you have flashed your ESP8266 unit with ESPEasy. Under “Config” set a name (“Unit Name:”) for your device (here it’s “bathroom”). A “Controller” for MQTT with the protocol “OpenHAB MQTT” is present and the entries (“Controller Subscribe:” and “Controller Publish:”) are adjusted to match your needs. In this example the topics are prefixed with “home”. Also, add a sensor in the “Devices” tap with the name “analog” and “brightness” as value.

As soon as the unit is online, you will get the state of the sensor.

home/bathroom/status Connected
...
home/bathroom/analog/brightness 290.00

The configuration will look like the example below:

# Example configuration.yml entry
sensor:
  - platform: mqtt
    state_topic: 'home/bathroom/analog/brightness'
    name: Brightness