home-assistant.io/source/_components/sensor.mqtt.markdown

layout	title	description	date	sidebar	comments	sharing	footer	logo	ha_category	ha_release	ha_iot_class
page	MQTT Sensor	Instructions how to integrate MQTT sensors within Home Assistant.	2015-05-30 23:21	true	false	true	true	mqtt.png	Sensor	0.7	depends

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"

{% configuration %} state_topic: description: The MQTT topic subscribed to receive sensor values. required: true type: string name: description: Name of the MQTT sensor. required: false type: string default: MQTT Sensor qos: description: The maximum QoS level of the state topic. required: false type: int default: 0 unit_of_measurement: description: Defines the units of measurement of the sensor, if any. required: false type: string expire_after: description: Defines the number of seconds after the value expires if it's not updated. required: false type: int default: 0 value_template: description: "Defines a template to extract the value." required: false type: template force_update: description: Sends update events even if the value hasn't changed. Useful if you want to have meaningful value graphs in history. reqired: false type: boolean default: False availability_topic: description: The MQTT topic subscribed to receive availability (online/offline) updates. required: false type: string payload_available: description: The payload that represents the available state. required: false type: string default: online payload_not_available: description: The payload that represents the unavailable state. required: false type: string default: offline json_attributes: description: A list of keys to extract values from a JSON dictionary payload and then set as sensor attributes. reqired: false type: list, string {% endconfiguration %}

{% linkable_title Examples %}

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

{% linkable_title 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.

{% raw %}

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

{% endraw %}

{% linkable_title 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:

{% raw %}

# 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 }}'

{% endraw %}

{% linkable_title 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:

{% raw %}

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

{% endraw %}