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63 lines
2.1 KiB
Markdown
63 lines
2.1 KiB
Markdown
---
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layout: page
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title: "MQTT Sensor"
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description: "Instructions how to integrate MQTT sensors within Home Assistant."
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date: 2015-05-30 23:21
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sidebar: true
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comments: false
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sharing: true
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footer: true
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logo: mqtt.png
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ha_category: Sensor
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ha_release: 0.7
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---
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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.
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To use your MQTT sensor in your installation, add the following to your `configuration.yaml` file:
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```yaml
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# Example configuration.yml entry
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sensor:
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platform: mqtt
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state_topic: "home/bedroom/temperature"
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name: "MQTT Sensor"
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qos: 0
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unit_of_measurement: "°C"
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value_template: '{% raw %}{{ value.x }}{% endraw %}'
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```
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Configuration variables:
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- **state_topic** (*Required*): The MQTT topic subscribed to receive sensor values.
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- **name** (*Optional*): The name of the sensor. Default is 'MQTT Sensor'.
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- **qos** (*Optional*): The maximum QoS level of the state topic. Default is 0.
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- **unit_of_measurement** (*Optional*): Defines the units of measurement of the sensor, if any.
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- **value_template** (*Optional*): Defines a [template](/topics/templating/) to extract a value from the payload.
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## {% linkable_title Examples %}
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In this section you find some real life examples of how to use this sensor.
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### {% linkable_title Get battery level %}
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If you are using the [Owntracks](/components/device_tracker.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:
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```bash
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owntracks/tablet/tablet {"_type":"location","lon":7.21,"t":"u","batt":92,"tst":144995643,"tid":"ta","acc":27,"lat":46.12}
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```
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Thus the trick is extract the battery level from the payload.
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```yaml
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# Example configuration.yml entry
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sensor:
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platform: mqtt
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state_topic: "owntracks/tablet/tablet"
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name: "Battery Tablet"
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unit_of_measurement: "%"
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value_template: {% raw %}'{{ value_json.batt }}'{% endraw %}
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```
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