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.

Configuration

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

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

Examples

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

JSON attributes topic configuration

The example sensor below shows a configuration example which uses a JSON dict: {"ClientName": <string>, "IP": <string>, "MAC": <string>, "RSSI": <string>, "HostName": <string>, "ConnectedSSID": <string>} in a separate topic home/sensor1/attributes to add extra attributes. It also makes use of the availability topic.

Extra attributes will be displayed in the frontend and can also be extracted in Templates. For example, to extract the ClientName attribute from the sensor below, use a template similar to: {{ state_attr('sensor.bs_rssi', 'ClientName') }}.

# Example configuration.yaml entry
mqtt:
  - sensor:
      name: "RSSI"
      state_topic: "home/sensor1/infojson"
      unit_of_measurement: "dBm"
      value_template: "{{ value_json.RSSI }}"
      availability:
        - topic: "home/sensor1/status"
      payload_available: "online"
      payload_not_available: "offline"
      json_attributes_topic: "home/sensor1/attributes"

JSON attributes template configuration

The example sensor below shows a configuration example which uses a JSON dict: {"Timer1":{"Arm": <status>, "Time": <time>}, "Timer2":{"Arm": <status>, "Time": <time>}} on topic tele/sonoff/sensor with a template to add Timer1.Arm and Timer1.Time as extra attributes. To instead only add Timer1.Armas an extra attribute, change json_attributes_template to: "{{ {'Arm': value_json.Timer1} | tojson }}".

Extra attributes will be displayed in the frontend and can also be extracted in Templates. For example, to extract the Arm attribute from the sensor below, use a template similar to: {{ state_attr('sensor.timer1', 'Arm') }}.

# Example configuration.yaml entry
mqtt:
  - sensor:
      name: "Timer 1"
      state_topic: "tele/sonoff/sensor"
      value_template: "{{ value_json.Timer1.Arm }}"
      json_attributes_topic: "tele/sonoff/sensor"
      json_attributes_template: "{{ value_json.Timer1 | tojson }}"
  - sensor:
      name: "Timer 2"
      state_topic: "tele/sonoff/sensor"
      value_template: "{{ value_json.Timer2.Arm }}"
      json_attributes_topic: "tele/sonoff/sensor"
      json_attributes_template: "{{ value_json.Timer2 | tojson }}"

The state and the attributes of the sensor by design do not update in a synchronous manner if they share the same MQTT topic. Temporal mismatches between the state and the attribute data may occur if both the state and the attributes are changed simultaneously by the same MQTT message. An automation that triggers on any state change of the sensor will also trigger both on the change of the state or a change of the attributes. Such automations will be triggered twice if both the state and the attributes change. Please use a MQTT trigger and process the JSON in the automation directly via the {{ trigger.payload_json }} trigger data for automations that must synchronously handle multiple JSON values within the same MQTT message.

Usage of entity_id in the template

The example below shows how a simple filter, that calculates the value by adding 90% of the new value and 10% of the previous value, can be implemented in a template.

# Example configuration.yaml entry
mqtt:
  - sensor:
      name: "Temp 1"
      state_topic: "sensor/temperature"
      value_template: |-
        {% if states(entity_id) == None %}
          {{ value | round(2) }}
        {% else %}
          {{ value | round(2) * 0.9 + states(entity_id) * 0.1 }}
        {% endif %}

Owntracks battery level sensor

If you are using the OwnTracks and enable the reporting of the battery level then you can use an 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.yaml entry
mqtt:
  - sensor:
      name: "Battery Tablet"
      state_topic: "owntracks/tablet/tablet"
      unit_of_measurement: "%"
      value_template: "{{ value_json.batt }}"

Temperature and humidity sensors

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.yaml entry
mqtt:
  - sensor:
      name: "Temperature"
      state_topic: "office/sensor1"
      suggested_display_precision: 1
      unit_of_measurement: "°C"
      value_template: "{{ value_json.temperature }}"
  - sensor:
      name: "Humidity"
      state_topic: "office/sensor1"
      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”. Please keep in mind that the ESPEasy default topics start with a / and only contain the name when writing your entry for the configuration.yaml file.

• Controller Subscribe: home/%sysname%/# (instead of /%sysname%/#)
• Controller Publish: home/%sysname%/%tskname%/%valname% (instead of /%sysname%/%tskname%/%valname%)

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.yaml entry
mqtt:
  - sensor:
      name: "Brightness"
      state_topic: "home/bathroom/analog/brightness"