Local check for sensor failure

ESPHome
1

I’m building my own sauna controller and one of the safeties I want to add is to shut off the oven if my main temperature sensor fails. But how can I check if the sensor gave a recent reading? Can I check for unavailability? Can I check for last updated value?

When I google or search on this community I get a lot of stuff about unavailability of the device not a singel sensor, or i find solutions that involve home assistant, but for safety I need this to be fully local on the device.

The best thing I could think of till now is to have an on_value part in the dallas sensor that updates a global variable with a timestamp and then a time sensor that triggers every minute and me checking the global variable. But this seems ugly to me. Any elegant solutions you could steer me towards?

Thanks!

2

No reactions, too bad… For anyone ending up here. This is my resolution:

For the temperature sensor I did this:

globals:
  - id: global_main_temp_sensor_updated_min_ago
    type: int
    restore_value: no
    initial_value: '0'

sensor:
  - platform: dallas
    address: 0x5b00000f0f1eb328 # temp_sensor_6
    # address: 0x3600000f12ebcc28 # original
    name: "Onboard Temperature"
    id: onboard_temp
    on_value:
      then:
        - lambda: |-
            if (!isnan(id(onboard_temp).state))
            id(global_main_temp_sensor_updated_min_ago)=0;

and then I already had a logic that checked all kinds of stuff every minute so there I have:

time:
  - platform: homeassistant
    id: homeassistant_synced_time
    timezone: Europe/Amsterdam
    on_time:
      # Every minute
      - seconds: 0
        minutes: /1
        then:
          - lambda: |-
              if (id(climate_pid).mode==climate::CLIMATE_MODE_OFF) {
                // something not relevant for this post was here
              }else{
                id(global_main_temp_sensor_updated_min_ago)++;
                // If no temperature is read for 1 minutes then turn of heater
                if (id(global_main_temp_sensor_updated_min_ago)>=2){
                    auto call = id(climate_pid).make_call();
                    call.set_mode("OFF");
                    call.perform();
                    ESP_LOGE("temp_sensor_update_check", "Turning heater off, because temperature sensor had no new value for more than 1 minute.");
                  }
              }

Hope this helps someone some day!

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