Template trigger for attribute, how to use 'from:' 'to:'

Configuration
1

I have this automation which triggers with a value_template for an attribute:

  trigger:
  - platform: template
    value_template: '{{is_state_attr(''sensor.crow_alarm_system'',''mains'', True) }}'

what i want is this to trigger when the attribute ‘mains’ goes from ‘False’ to ‘True’. However when i restart HA, it fires even when going from ‘Unknown’ to ‘True’ also.

In short, how do i set this trigger so that the ‘mains’ attribute triggers when going from ‘False’ to ‘True’ only?

2

The documentation says Trigger state Object offers this:

trigger.from_state will return the previous state object of the entity.

We can use that in a condition to reject the case where the previous value of mains was ‘unknown’.

  trigger:
    platform: template
    value_template: "{{ is_state_attr('sensor.crow_alarm_system','mains', True) }}"
  condition:
    condition: template
    value_template: >
      {{ trigger.from_state and 
         trigger.from_state.attributes.mains | lower != 'unknown' }}

The condition’s first test:

trigger.from_state

confirms the Trigger State Object has a from_state.

The second test checks that the previous value of mains was not ‘unknown’.

trigger.from_state.attributes.mains | lower != 'unknown'
3

Actually, I think the way to do it (i.e., prevent the automation running on a state change where the old state did not exist) is simply to check trigger.from_state. Also, since the attribute is already a bool the trigger can be simplified, too. @febalci try:

  trigger:
    platform: template
    value_template: "{{ state_attr('sensor.crow_alarm_system', 'mains') }}"
  condition:
    condition: template
    value_template: "{{ trigger.from_state }}"

I think that should work. :slightly_smiling_face:

1 Like
4

But that would also trigger on true to false post withdrawn because author was being an idiot

1 Like
5

I see. I hadn’t considered the possibility that if the previous state was ‘unknown’ then trigger.from_state isn’t defined (and that’s all the condition needs to test).

6

@123 and @pnbruckner thanks a lot for your help. This was a two way automation to understand whether mains power is Off or On. “{{ trigger.from_state }}” alone did not work in ‘False’ to ‘True’ condition. So i combined both your suggestions and made some changes like:

- alias: Power Back On
  trigger:
  - platform: template
    value_template: '{{state_attr(''sensor.crow_alarm_system'',''mains'') }}'
  condition:
    condition: template
    value_template: >
      {{ trigger.from_state is defined }}

and

- alias: Power Cut
  trigger:
  - platform: template
    value_template: '{{is_state_attr(''sensor.crow_alarm_system'',''mains'', False) }}'
  condition:
    condition: template
    value_template: >
      {{ trigger.from_state and 
         trigger.from_state.attributes.mains | lower == 'true' }}

and this works. On Power Cut trigger i tried to make the same structure but don’t know how to use ‘not’ on boolean in data and value_templates.

Anyway thanks to you both…

1 Like
7

Not exactly sure why had to make the changes you did, but then again I don’t know the full behavior of sensor.crow_alarm_system either. As long as it works for you, that’s the main thing.

Generally when quoting a template that also uses quotes inside, you should quote the entire template with one kind of quote, and use the other inside. The typical way is use double-quotes for the entire template and single quotes inside. So:

    value_template: "{{state_attr('sensor.crow_alarm_system','mains') }}"

For your Power Cut automation, you could do the trigger this way:

    value_template: "{{ not state_attr('sensor.crow_alarm_system','mains') }}"
8

with an extra quote at the beginning ?

(we’ve all been there ! :rofl: )

1 Like
9

After some trials (about 20-30 tries :grinning:), come up with the following for both power cut and power back on:

Create a template sensor for the attribute:

sensor:
  - platform: template
    sensors:
      home_power:
        friendly_name: "Home Power"
        device_class: power
        value_template: "{{ is_state_attr('sensor.crow_alarm_system', 'mains', True) }}"

Automation:

- alias: Home Power
  trigger:
  - platform: state
    entity_id: sensor.home_power
  condition:
    condition: template
    value_template: >
      {{ trigger.from_state.state != 'unknown' }}
  action:
  - service: notify.pushover
    data_template:
      message: >
        {% if is_state('sensor.home_power','True') %}
        Power On...
        {% else %}
        Power Off!!!
        {% endif %}

I also found out (at last) how to write to log file for automation debugging purposes:

action:
  - service: system_log.write
    data_template:
      message: "The state of the switch is from: {{trigger.from_state.state}} tgo:{{trigger.to_state.state}}"
      level: warning
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