Push sensor values to MQTT

Configuration
1

I want to use Node-RED for automating my home. And I use RFXtrx433XL as 433MHz sensor gateway. The data from the sensors is received just fine, so that works. But when getting those values into Node-RED (for the purpose of e.g. turning a panel oven on/off when evaluating the room temperature), I was adviced to use MQTT. That is, push the values received on 433MHz to MQTT topics, and then read those topics in Node-RED to carry out automations. But how can I have a trigger on the received values on 433MHz that pushes the received value to MQTT?

1 Like
2

How is this related to home assistant?

3

Use an automation with state trigger , with only entity_id, so it will trigger on every change.
Then you can use the Trigger state object to get the value and publish it to a mqtt topic.

4

I’m using Home Assistant (or Hass.io), but I want to use Node-RED for automations.

5

Thanks. I want the automation to trigger on all values, and basically push all values received to MQTT. From the examples I’ve found, it seems I have to set a range (from/to or above/below) when using state or numeric_state. I’ve tried the following:

alias: Kitchen Temperature 
trigger:
  platform: event
  event_type: signal_received
  event_data: {'entity_id': 'sensor.kitchen_temperature'}
action:
  service: mqtt.publish
  data:
    topic: "home/notification"
    payload_template: "{{ states.sensor.kitchen_temperature }}"

This does fire on every temperature received, but in MQTTBox I see that the payload contains all of the information from the sensor, not just the temperature.

<template state sensor.kitchen_temperature=21.5; Temperature=21.5, Humidity=45,
Humidity status=comfort, Humidity status numeric=1, Battery numeric=9, Rssi numeric=6,
unit_of_measurement=°C, friendly_name=Kitchen Temperature @ 2018-11-03T11:44:15.011387+01:00>

So I gather that I either have to limit the payload template in some way, or I shouldn’t trigger on events and rather use a different method.

6

When you omit the state in the state trigger, it triggers on evey change.

alias: Kitchen Temperature 
trigger:
  platform: state
  entity_id: sensor.kitchen_temperature
action:
  service: mqtt.publish
  data:
    topic: "home/notification"
    payload_template: "{{ trigger.to_state.state }}"

With the payload you can play in Dev Tools/Templates.
For example:

{% set value = '<template state sensor.kitchen_temperature=21.5; Temperature=21.5, Humidity=45,
Humidity status=comfort, Humidity status numeric=1, Battery numeric=9, Rssi numeric=6,
unit_of_measurement=°C, friendly_name=Kitchen Temperature @ 2018-11-03T11:44:15.011387+01:00>' %}
{{ value.split(';')[1].split(',')[0].split('=')[1] }}

Returns: 21.5

EDIT: I think you don’t need to split the value.
Just use "{{ states.sensor.kitchen_temperature.state }}" or "{{ trigger.to_state.state }}"

2 Likes
7

Ah, thanks a lot. The final state in the payload template did the trick. :slight_smile:

- alias: Kitchen Temperature 
  trigger:
    platform: event
    event_type: signal_received
    event_data: {'entity_id': 'sensor.kitchen_temperature'}
  action:
    service: mqtt.publish
    data:
      topic: "home/notification"
      payload_template: "{{ states.sensor.kitchen_temperature.state }}"

As for numeric_state, it seems it’s mandatory to set either above or below. The YAML check fails if I don’t set it.

8

I said the ‘state’ trigger, not ‘numeric_state’ !

9

I stand corrected: state worked as well.

Any thoughts on triggering on an event vs triggering on a state change, performance-wise?

10

Sorry, no!

11

Did you investigate using node-red-contrib-home-assistant?

Rather than using automations to publish/push the sensor values, you use a node that already knows how to talk to Home Assistant (via its REST API). The “event-state” node will receive state-changes from the sensors.

If your sensors are publishing a JSON payload, it’s very easy to parse it in Node-Red (no need to filter it in Home Assistant).

There are many video tutorials available. Here’s one from The Hookup.

EDIT
There’s another version of node-red-contrib-home-assistant that communicates with Home Assistant via a websocket (vs HTTP). It’s called node-red-contrib-home-assistant-websocket and its advantages are described in this thread.

12

Yes, I started out with using the Home Assistant nodes directly in Node-RED. But when asking a question about extracting the value/state of the sensors when receiving the events (https://discourse.nodered.org/t/switching-on-off-oven-using-temperature-in-home-assistant/4486), I was advised to use MQTT rather than HA events in Node-RED.

It seemed like a logical choice, given that I eventually want to implement InfluxDB and Grafana into the mix (and who knows what else… :smiley:).

My problem is that I lack the experience to know the best approach.

Option 1:

  1. Receive 433 MHz sensor values in HA.
  2. Read HA events in Node-RED, and somehow extract values/states.
  3. Regulate and drive outputs (wall-plugs in my case) from Node-RED using HA nodes.

Option 2:

  1. Receive 433 MHz sensor values in HA.
  2. Convert sensor values to MQTT in HA.
  3. Read MQTT sensor values in Node-RED.
  4. Regulate and drive outputs from Node-RED using HA nodes.

Option 3:

  1. Receive 433 MHz sensor values in HA.
  2. Convert sensor values to MQTT in HA.
  3. Read MQTT sensor values in Node-RED.
  4. Regulate and push output states to MQTT.
  5. Trigger on output MQTT topics in HA, and drive outputs from HA.

Option 4:

  1. Receive 433 MHz sensor values directly in Node-RED using RFXtrx433/rfxcom palette (was unable to get this installed for some reason).
  2. Regulate and drive outputs from Node-RED using HA nodes.

And so on and so forth…

I’m leaning towards option 2 or 3, since some of the stuff in my home has ready-made plugins for Home Assistant but not for Node-RED.

13

If you mean the advice given to you by the first person to reply, they qualified their response with:

… you are far better off on the HA forum and asking them for the how to on this as your data is originating from there and there are a lot of knowledgeable people on that forum re MQTT interactions

Kudos to that individual for adding that advice because I don’t think they’re aware of node-red-contrib-home-assistant.

node-red-contrib-home-assistant is for interfacing Home Assistant with Node-Red. It makes it very easy to consume data from Home Assistant to build flows in Node-Red. It’s also bi-directional; you can get data from Home Assistant and also send data to Home Assistant.

Option 1 is your best choice if you also plan to use the sensor values within Home Assistant. If not and you only wish to use them within Node-Red then Option 4 is the logical choice. Options 2 and 3 needlessly create more steps in the process of getting from A to B.

Read HA events in Node-RED, and somehow extract values/states.

If the sensor payload is a JSON object, the “somehow” is super easy. Let’s assume this is what the sensor sends: {“temperature”: 24, “humidity”: 45}

  • msg.payload contains everything sent by the sensor (the entire JSON object).
  • msg.payload.temperature contains 24.
  • msg.payload.humidity contains 45.
14

How well would that fit into expanding the system? Are there any downsides with not converting the values to MQTT topics, in regards to e.g. adding InfluxDB/Grafana, offloading services onto a different RPi, or other “that would be a cool thing to do” cases that are likely to come in foreseeable future? :slight_smile:

15

… offloading services onto a different RPi, or other “that would be a cool thing to do” cases that are likely to come in foreseeable future?

If you keep moving the goalposts then eventually there will be something you can’t do with Node-Red. However, for everything you’ve asked for so far, this is the right direction.