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.yamlThe configuration.yaml file is the main configuration file for Home Assistant. It lists the integrations to be loaded and their specific configurations. In some cases, the configuration needs to be edited manually directly in the configuration.yaml file. Most integrations can be configured in the UI. [Learn more] file:

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

Configuration Variables

availability list (Optional)

A list of MQTT topics subscribed to receive availability (online/offline) updates. Must not be used together with availability_topic.

payload_available string (Optional, default: online)

The payload that represents the available state.

payload_not_available string (Optional, default: offline)

The payload that represents the unavailable state.

topic string Required

An MQTT topic subscribed to receive availability (online/offline) updates.

value_template template (Optional)

Defines a template to extract device’s availability from the topic. To determine the devices’s availability result of this template will be compared to payload_available and payload_not_available.

availability_mode string (Optional, default: latest)

When availability is configured, this controls the conditions needed to set the entity to available. Valid entries are all, any, and latest. If set to all, payload_available must be received on all configured availability topics before the entity is marked as online. If set to any, payload_available must be received on at least one configured availability topic before the entity is marked as online. If set to latest, the last payload_available or payload_not_available received on any configured availability topic controls the availability.

availability_template template (Optional)

Defines a template to extract device’s availability from the availability_topic. To determine the devices’s availability result of this template will be compared to payload_available and payload_not_available.

availability_topic string (Optional)

The MQTT topic subscribed to receive availability (online/offline) updates.

device map (Optional)

Information about the device this sensor is a part of to tie it into the device registry. Only works when unique_id is set. At least one of identifiers or connections must be present to identify the device.

configuration_url string (Optional)

A link to the webpage that can manage the configuration of this device. Can be either an http://, https:// or an internal homeassistant:// URL.

connections list (Optional)

A list of connections of the device to the outside world as a list of tuples [connection_type, connection_identifier]. For example the MAC address of a network interface: "connections": [["mac", "02:5b:26:a8:dc:12"]].

hw_version string (Optional)

The hardware version of the device.

identifiers string | list (Optional)

A list of IDs that uniquely identify the device. For example a serial number.

manufacturer string (Optional)

The manufacturer of the device.

model string (Optional)

The model of the device.

model_id string (Optional)

The model identifier of the device.

name string (Optional)

The name of the device.

serial_number string (Optional)

The serial number of the device.

suggested_area string (Optional)

Suggest an area if the device isn’t in one yet.

sw_version string (Optional)

The firmware version of the device.

via_device string (Optional)

Identifier of a device that routes messages between this device and Home Assistant. Examples of such devices are hubs, or parent devices of a sub-device. This is used to show device topology in Home Assistant.

device_class device_class (Optional)

The type/class of the sensor to set the icon in the frontend. The device_class can be null.

enabled_by_default boolean (Optional, default: true)

Flag which defines if the entity should be enabled when first added.

encoding string (Optional, default: utf-8)

The encoding of the payloads received. Set to "" to disable decoding of incoming payload.

entity_category string (Optional)

The category of the entity. When set, the entity category must be diagnostic for sensors.

expire_after integer (Optional, default: 0)

If set, it defines the number of seconds after the sensor’s state expires, if it’s not updated. After expiry, the sensor’s state becomes unavailable. Default the sensors state never expires.

force_update boolean (Optional, default: false)

Sends update events even if the value hasn’t changed. Useful if you want to have meaningful value graphs in history.

icon icon (Optional)

Icon for the entity.

json_attributes_template template (Optional)

Defines a template to extract the JSON dictionary from messages received on the json_attributes_topic.

json_attributes_topic string (Optional)

The MQTT topic subscribed to receive a JSON dictionary payload and then set as sensor attributes. Implies force_update of the current sensor state when a message is received on this topic.

last_reset_value_template template (Optional)

Defines a template to extract the last_reset. When last_reset_value_template is set, the state_class option must be total. Available variables: entity_id. The entity_id can be used to reference the entity’s attributes.

name string (Optional, default: MQTT Sensor)

The name of the MQTT sensor. Can be set to null if only the device name is relevant.

object_id string (Optional)

Used instead of name for automatic generation of entity_id

options list (Optional)

List of allowed sensor state value. An empty list is not allowed. The sensor’s device_class must be set to enum. The options option cannot be used together with state_class or unit_of_measurement.

payload_available string (Optional, default: online)

The payload that represents the available state.

payload_not_available string (Optional, default: offline)

The payload that represents the unavailable state.

suggested_display_precision integer (Optional)

The number of decimals which should be used in the sensor’s state after rounding.

qos integer (Optional, default: 0)

The maximum QoS level to be used when receiving and publishing messages.

state_class string (Optional)

The state_class of the sensor.

state_topic string Required

The MQTT topic subscribed to receive sensor values. If device_class, state_class, unit_of_measurement or suggested_display_precision is set, and a numeric value is expected, an empty value '' will be ignored and will not update the state, a 'null' value will set the sensor to an unknown state. The device_class can be null.

unique_id string (Optional)

An ID that uniquely identifies this sensor. If two sensors have the same unique ID, Home Assistant will raise an exception.

unit_of_measurement string (Optional)

Defines the units of measurement of the sensor, if any. The unit_of_measurement can be null.

value_template template (Optional)

Defines a template to extract the value. If the template throws an error, the current state will be used instead.

Examples

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

Processing Unix EPOCH timestamps

The example below shows how an MQTT sensor can process a Unix EPOCH payload.

Set up via YAML:

# Example configuration.yaml entry
mqtt:
  sensor:
    - name: "turned on"
      state_topic: "pump/timestamp_on"
      device_class: "timestamp"
      value_template: "{{ as_datetime(value) }}"
      unique_id: "hp_1231232_ts_on"
      device:
        name: "Heat pump"
        identifiers:
          - "hp_1231232"

Or set up via MQTT discovery:

Discovery topic: homeassistant/sensor/hp_1231232/config

{
  "name": "turned on",
  "state_topic": "pump/timestamp_on",
  "device_class": "timestamp",
  "value_template": "{{ as_datetime(value) }}",
  "unique_id": "hp_1231232_ts_on",
  "device": {
    "name": "Heat pump",
    "identifiers": [
      "hp_1231232"
    ]
  }
}

To test, you can use the command line tool mosquitto_pub shipped with mosquitto or the mosquitto-clients package to send MQTT messages.

Payload topic: pump/timestamp_on Payload: 1707294116

To set the state of the sensor manually:

mosquitto_pub -h 127.0.0.1 -p 1883 -u username -P some_password -t pump/timestamp_on -m '1707294116'

Make sure the IP address of your MQTT broker is used and that user credentials have been set up correctly.

The value_template will render the Unix EPOCH timestamp to correct format: 2024-02-07 08:21:56+00:00.

JSON attributes topic configuration

The example sensor below shows a configuration example which uses the following separate topic and JSON structure to add extra attributes.

Topic: home/sensor1/attributes

{
   "ClientName": <string>,
   "IP": <string>,
   "MAC": <string>,
   "RSSI": <string>,
   "HostName": <string>,
   "ConnectedSSID": <string>
}

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 the following topic and JSON structure with a template to add Timer1.Arm and Timer1.Time as extra attributes.

Topic: tele/sonoff/sensor

{
    "Timer1": {
        "Arm": <status>,
        "Time": <time>
    },
    "Timer2": {
        "Arm": <status>,
        "Time": <time>
    }
}

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 }}"

    - 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 }}"

Warning

If json_attributes_topic and state_topic share the same topic, a state update will happen only once, unless the state update did not change the state or force_update was set to true.

Setting up MQTT sensor’s with extra state attributes that contain values that change at every update, like timestamps, or enabling the force_update option, is discouraged, as this will trigger state writes for every update. This can have a serious impact on the total system performance. A better option is creating separate sensors instead.

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:

Topic: 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:

Topic: 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 }}"
    - 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.yamlThe configuration.yaml file is the main configuration file for Home Assistant. It lists the integrations to be loaded and their specific configurations. In some cases, the configuration needs to be edited manually directly in the configuration.yaml file. Most integrations can be configured in the UI. [Learn more] 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"