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MQTT Binary Sensor

The mqtt binary sensor platform uses an MQTT message payload to set the binary sensor to one of two states: on or off.

The binary sensor state will be updated only after a new message is published on state_topic matching payload_on or payload_off. If these messages are published with the retain flag set, the binary sensor will receive an instant state update after subscription and Home Assistant will display the correct state on startup. Otherwise, the initial state displayed in Home Assistant will be unknown.

The mqtt binary sensor platform optionally supports an availability_topic to receive online and offline messages (birth and LWT messages) from the MQTT device. During normal operation, if the MQTT cover device goes offline (i.e. publishes payload_not_available to availability_topic), Home Assistant will display the binary sensor as unavailable. If these messages are published with the retain flag set, the binary sensor will receive an instant update after subscription and Home Assistant will display the correct availability state of the binary sensor when Home Assistant starts up. If the retain flag is not set, Home Assistant will display the binary sensor as unavailable when Home Assistant starts up. If no availability_topic is defined, Home Assistant will consider the MQTT device to be available.

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

# Example configuration.yaml entry
binary_sensor:
  - platform: mqtt
    state_topic: "home-assistant/window/contact"

Configuration variables:

  • name (Optional): The name of the binary sensor. Default is MQTT Binary Sensor.
  • state_topic (Required): The MQTT topic subscribed to receive sensor values.
  • payload_on (Optional): The payload that represents the on state. Default is ON.
  • payload_off (Optional): The payload that represents the off state. Default is OFF.
  • availability_topic (Optional): The MQTT topic subscribed to receive birth and LWT messages from the MQTT device. If availability_topic is not defined, the binary sensor availability state will always be available. If availability_topic is defined, the binary sensor availability state will be unavailable by default.
  • payload_available (Optional): The payload that represents the online state. Default is online.
  • payload_not_available (Optional): The payload that represents the offline state. Default is offline.
  • qos (Optional): The maximum QoS level to be used when receiving messages. Default is 0.
  • device_class (Optional): The type/class of the sensor to set the icon in the frontend.
  • value_template (Optional): Defines a template to extract a value from the payload.

To test, you can use the command line tool mosquitto_pub shipped with mosquitto or the mosquitto-clients package to send MQTT messages. To set the state of the binary sensor manually:

$  mosquitto_pub -h 127.0.0.1 -t home-assistant/window/contact -m "OFF"

The example below shows a full configuration for a binary sensor:

# Example configuration.yaml entry
binary_sensor:
  - platform: mqtt
    name: "Window Contact Sensor"
    state_topic: "home-assistant/window/contact"
    payload_on: "ON"
    payload_off: "OFF"
    availability_topic: "home-assistant/window/availability"
    payload_available: "online"
    payload_not_available: "offline"
    qos: 0
    device_class: opening
    value_template: '{{ value.x }}'