Set boolean based on equation

I have no doubt that this has been answered before but I am apparently not using the right search terms. I suppose I should also mention that I recently switched from Vera to HA so I am still very much a beginner on the learning curve with HA.

I have a number of automations that I want to apply a condition to based on the Lux reported from a light sensor. It occurs to me that in the long run, referring to a more generic boolean value, say named “dark” would be simpler than constantly referencing a specific light sensor and testing if the value is below a certain number. This is even more so the case since I quickly realized that I want a light sensor that is far more active in updating the Lux value than the battery operated one I have now so I will be changing the sensor I want to use in the automations and if I had the aforementioned boolean value set up I’d only have to change the device reference in that one item instead of in each of the automations I create that use the value.

So can someone point me in the right direction with how I should go about doing this?

Thanks in advance.

Create a Template Binary Sensor that reports on when it’s dark (when your light sensor’s value is below a threshold you’ve chosen), otherwise it reports off. The resulting Template Binary Sensor can be referenced in automations, scripts, etc.


The following configuration defines an entity named binary_sensor.is_dark

  - binary_sensor:
      - name: Is Dark
        state: "{{ states('sensor.your_light_sensor') | int(0) < 50 }}"

wow, that was too easy - well, for someone that has a clue what they are doing. I was thinking it’d be more complicated than that.


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You’re welcome!

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