WTH stopwatch or timer helper

Archive Month of "What the heck?!" 2022
12

You have a binary_sensor, eg.
binary_sensor.tank_limiter_tank_pump_status, that gives you ‘on’ and ‘off’.
In this case, if a pump is running or not.

Create an input.number helper. f.e input_number.tank_pump_runtime

Then create 2 automations:

automation:
  - id: reset_tank_pump_runtime
    alias: "Reset Tank Pump Runtime on Pump Start"
    trigger:
      - platform: state
        entity_id: binary_sensor.tank_limiter_tank_pump_status
        to: 'on'
    action:
      - service: input_number.set_value
        data:
          entity_id: input_number.tank_pump_runtime
          value: 0
 mode: single

automation:
  - id: tank_pump_runtime
    alias: "Tank Pump Runtime"
    description: "Increase input_number.tank_pump_runtime every second while binary_sensor.tank_limiter_tank_pump_status is 'on'"
    trigger:
      - platform: time_pattern
        seconds: /1
    condition:
      - condition: state
        entity_id: binary_sensor.tank_limiter_tank_pump_status
        state: 'on'
    action:
      - service: input_number.increment
        data:
          entity_id: input_number.tank_pump_runtime
    mode: single

This will give you a counter, which will count up every second of the runtime of this pump. As soon as the pump stops, the last count will stay visible in input_number.tank_pump_runtime.
As soon as the pump restarts, the stopwatch will be set on 0 seconds and the measuring of the runtime will be started again.