Binary Sensor MQTT with JSON

Configuration
,
1

I have a couple of sensors (not binary sensors) that get JSON data via MQTT successfully so I know I’m missing something simple…

Here’s the config:

binary_sensor:
  - platform: mqtt  
    state_topic: "feldman/dryersensor"
    name: "Laundry Dryer"
    value_template: '{{ value_json.sensor }}'

JSON is:

{"sensor":"on","uptime_ms":16928697,"heartbeat":"yes"}

The error I’m getting in the Home Assistant logs is:

No matching payload found for entity: Laundry Dryer with state_topic: feldman/dryersensor

6:02 PM components/mqtt/binary_sensor.py (WARNING) - message first occurred at 6:02 PM and shows up 3 times

Error parsing value: 'value_json' is undefined (value: {"sensor":"on","uptime_ms":16798699,"heartbeat":"yes"}, template: {{ value_json.sensor }})

6:02 PM helpers/template.py (ERROR)

I’m running HA 0.101.3 in a docker container and everything else works great!

Thanks!

2

Have you connected to your mqtt server with something like MQTT Explorer and see what is being posted to this topic?

3 
  - platform: mqtt
    state_topic: "feldman/dryersensor"
    name: "Laundry Dryer"
    value_template: >- 
      {% if value_json.sensor == 'on' %}
        {{'ON'}}
      {% else %}
        {{'OFF'}}
      {% endif %}
1 Like
4

Here is the JSON that’s being posted to the topic confirmed via the MQTT.fx tool (https://mqttfx.jensd.de) :

{"sensor":"on","uptime_ms":16928697,"heartbeat":"yes"}
5

Thanks @francisp. I hadn’t thought of doing if/then.

I tried your suggestion but I still get:

Error parsing value: 'value_json' is undefined (value: {"sensor":"on","uptime_ms":20688697,"heartbeat":"yes"}, template: {% if value_json.sensor == 'on' %}
  {{'ON'}}
{% else %}
  {{'OFF'}}
{% endif %})
6

Strange. I looked at my own config, I get these MQTT messages :
2019-11-10 20:12:41 -> rflink/NewKaku-03a0b800 - {‘SWITCH’: ‘2’, ‘CMD’: ‘OFF’, ‘SWITCH2’: ‘OFF’}

and have this binary sensor :

  - platform: mqtt
    name: sensorTVboven
    state_topic: 'rflink/NewKaku-03a0b800'
    value_template: >- 
      {% if value_json.SWITCH == "2" and value_json.CMD == "ON" %}   
        {{'ON'}}
      {% elif value_json.SWITCH == "2" and value_json.CMD == "OFF" %}
        {{'OFF'}}
      {% else %}
        {{states('binary_sensor.sensorTVboven') | upper}}
      {% endif %}

The only difference I see is that your MQTT uses double quotes, mine single.

7

If the value of sensor is exclusively on or off then this template will convert the values into uppercase which is what a binary_sensor requires. It does the same thing as francisp’s example, just in one line.

    value_template: '{{ value_json.sensor | upper}}'

HOWEVER, this won’t eliminate the error message because it claims value_json is undefined. In other words, it is unable to interpret the received payload as a JSON string. That’s puzzling because the payload you’ve presented appears to be a valid JSON string and Home Assistant should be able to convert it to a JSON object. Only thing I can think of is that there may be an unprintable character terminating the string.

As an experiment, try this template:

    value_template: "{{ 'ON' if 'on' in value else 'OFF'}}"
8

Oooh… Good call @123 !

First off, your test value_template worked:

value_template: "{{ 'ON' if 'on' in value else 'OFF'}}"

But, as you alluded to, looking really closely at the MQTT payload revealed that, due to an off-by-one error in my custom Arduino code, it included the C-string’s null terminator (00) in the message.

This didn’t show up in the text or the pretty views in the MQTT.fx tool. Nor did Home Assistant show it. The way I found it was in hex view in the tool:
39%20PM

Once I updated my Arduino code to remove the trailing character, both the value templates from @123 and @francisp worked. Woo hoo!

Thanks all for the great and very quick help.

P.S. It’s a bit odd to me that “ON” vs. “on” is case-sensitive, but whatever.

1 Like