Maths in conditions for automation

Configuration
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1

I’m struggling to understand the syntax for simple maths in value templates for conditions.
I have a DHT22 sensor in the bathroom that turns the extractor on if the humidity is above a limit held in an input_number on a lovelace card. This works well, and has turned on the fan after showers etc. The condition logic to compare the value returned by the humidity sensor and the input_number value is fine.

The fan has some speed setting jumpers, and I’d like to be able to run slow and then medium speed. I currently have this operatiing using two input_number set points, but would like to just use one, and trigger slow speed at say a humidity that is 10% under the medium speed setpoint.

I’m struggling to understand the syntax to make this work. The basic comparison works fine like this:

  value_template: '{{ states.sensor.bathroom_humidity_2.state >= states.input_number.high_speed_humidity.state}}'

I’ve tried to add the simple subtraction like this:

  value_template: '{{ states.sensor.bathroom_humidity_2.state >= states.input_number.high_speed_humidity.state - 5}}'

The result is that the condition simply appears to never operate. Similarly these also don’t seem to work:

  value_template: '{{ states.sensor.bathroom_humidity_2.state >= states.input_number.high_speed_humidity.state|int - 5}}'
  value_template: '{{ states.sensor.bathroom_humidity_2.state >= states.input_number.high_speed_humidity.state|float}}'

Any pointers about what I’m doing wrong and how this is supposed to work would be gratefully received. I’m a mechanical engineer, without a significant background in languages that work anything like Jinja, and its proving to be real struggle to get to grips with it.

2

What do you receive when you put any of those templates into the template editor/tester?

3

any state is a string. If you want to compare number numerically, they need to be cast as a specific type. Both need to be cast. In all your attempts, you only cast one side.

  value_template: '{{ states.sensor.bathroom_humidity_2.state | int >= states.input_number.high_speed_humidity.state | int - 5}}'
4

Thanks @petro, that makes sense ! It’s curious that the greater than and less than comparisons work even on the strings.

I can’t log in from here at work except from my phone (that’s another thread). I’ll try this when i get home.

Tim

5

Yes, characters have a value associated to them. The comparison starts left to right and compares each character. You can get into shit situations becasue 9 is greater than 10 if you start left to right.

6

In my limited forays into C and PLC code I’ve always steered clear of strings, with enough grief from casting between byte, long, signed/unsigned etc. Now I’m even more glad !

7

well anyways, I guess you’ll just have to update them:

This should emulate a 3+ way switch. I’d have to test it but can’t at the moment.

trigger:
- platform: state
  entity_id: switch.a
- platform: state
  entity_id: switch.b
action:
- service_template: >
    {% set switches = ['switch.a', 'switch.b'] %}
    {% set target = trigger.to_state.state %}
    {% set total_target = states | selectattr('entity_id', 'in', switches) | selectattr('state','eq', target) | list | length %}
    {% if total_target == switches | length or total_target == 0 %}
      light.turn_off
    {% else %}
      light.turn_on
    {% endif %}
  data_template:
    entity_id: light.a, light.b
8

There’s a whole lot that I don’t know about yet. I’ve only just started setting up what i want HA to do with value templates, and now I see service templates and data templates in your example, along with a syntax involving % that reads much more logically to me - I’ll need to dig around some more !

9

You can’t make a 3 way switch without that logic. Just add the automation and test it out. If it doesn’t work report back and I can help you tailor it. Otherwise this will be an uphill slog. You don’t need to understand it to use it :wink: . But the templating syntax is Jinja, so look that documenation on google or look here. As for the trigger.to_state.state, that documentation is located here. And normal templating documentation is here.

10

I chickened out on the more complex stuff I’m afraid. casting both the sensor and input_number to numbers worked a treat. I have two tests, one to turn the fan on, and a second to turn the speed up if the humidity rises too far. Seems to be working a treat - many thanks @petro