Publish to specific MQTT topic when entity state changes

Configuration
1

I have two sensors for my BMW. The battery soc and the range. I need the values to specific mqtt topics, when their state changes.

sensor.i3_120_verbleibende_batterie_in_prozent needs to be published to openWB/set/vehicle/1/get/soc

sensor.i3_120_verbleibende_reichweite_insgesamt needs to be published to openWB/set/vehicle/1/get/range

Whats the easiest way to achieve that? I already saw there’s an integration MQTT statestream, but thats not what I need as I cannot specify the topic where to publish the new state.

Thanks in advance for your help

2 
alias: Publish Battery Data
triggers:
  - id: 'soc'
    trigger: state
    entity_id: sensor.i3_120_verbleibende_batterie_in_prozent
    not_to: unavailable
  - id: 'range'
    trigger: state
    entity_id: sensor.i3_120_verbleibende_reichweite_insgesamt
    not_to: unavailable
conditions: []
actions:
  - action: mqtt.publish
    data:
      topic: openWB/set/vehicle/1/get/{{ trigger.id }}
      payload: "{{ trigger.to_state.state }}"
mode: queued
3

I’m pretty new to Home Assistant. Where exactly do I put that? Is this a mqtt configuration and I have to put it into mqtt.yaml?

4

That’s an automation.

Start Home Assistant’s Automation Editor like this:

  • Settings → Automation & scenes → Create Automation → Create new automation

  • Click the overflow menu in the upper right corner (three vertical dots) and select Edit in YAML.

  • Delete the existing YAML code displayed in the editing window.

  • Copy the example I provided above and paste it into the Automation Editor’s editing window then click Save.

Do you already have MQTT installed and configured? Because that’s a prerequisite for any MQTT-related project. This automation will fail to publish anything unless you have the MQTT integration installed as well as an MQTT Broker.

5

Cool, the automation itself works. My only problem ist that the value isn’t transmitted via MQTT correctly.

I have the following configuration: I have MQTT installed on Home Assistant as an addon.

There is another MQTT on my OpenWB-Wallbox.

I have configured the HA Broker to establish a bridge to the OpenWB-MQTT.

#
# bridge to openWB Wallbox
#
connection openwb2
local_clientid openwb2.mosquitto
address 10.0.0.8:1883

#Sensors Controller
topic openWB/system/ip_address in
topic openWB/system/version in
topic openWB/system/lastlivevaluesJson in

#Sensors per Chargepoint
topic openWB/chargepoint/3/get/# in
topic openWB/chargepoint/3/config in
topic openWB/vehicle/# in
topic openWB/bat/6/get/# in
topic openWB/counter/4/get/# in
topic openWB/pv/5/get/# in
topic openWB/set# out

topic openWB/# in

When a MQTT state on the OpenWB changes, I get the update in Homeassistant immediately, so getting values from the other MQTT works properly.

Only when I send values to the other OpenWB MQTT, the value isn’t transported. I validated this behaviour by testing with MQTT Explorer. When I publish the topic openWB/set/vehicle/1/get/soc on the remote MQTT (10.0.0.8), the value gets updated. If I do the same on the Home Assistant MQTT, there is no effect.

So this seems like a configuration problem to me?

6

OK, I found the problem

needs to be changed to

topic openWB/set/# out

So there was only the / missing between set and #

Thanks a lot four your help with the automation. This is realy easy!

1 Like
7

One bonus question: In another scenario I have to entities. Both are numbers. Every time, when one of both entities changes it’s state, they need to be summed up and published to a MQTT topic. Can I do the sum operation also within the automation or do I need to create a helper?

Can you give me an example?

The entities names are:
solax_today_s_yield
solaxslave_today_s_yield

The topic is
openWB/set/pv/5/get/exported

8

If I understood your requirements correctly, the automation would look something like this:

alias: Publish Solax Sum
triggers:
  - trigger: state
    entity_id:
      - sensor.solax_today_s_yield
      - sensor.solaxslave_today_s_yield
    not_to: unavailable
conditions: []
actions:
  - action: mqtt.publish
    data:
      topic: openWB/set/pv/5/get/exported
      payload: >
        {{ (states('sensor.solax_today_s_yield') | float(0) +
          states('sensor.solaxslave_today_s_yield') | float(0))
          | round(2) }}
mode: queued