Many people have used power sensors to detect when a washing machine or dish washer has finished its cycle and needs to be unloaded. This typically monitors a standard current sensor using a smart plug, and triggers based on a change/fall in the current. I felt this was inelegant as it relied upon Home Assistant to continuously check the state of the current, when there is a perfectly good microcontroller which can do that for us.

The following ESPHome excerpt turns a typical smart plug into a sensor which will report on the state of a washing machine.

<code>
- platform: hlw8012
    sel_pin:
      number: GPIO12
      inverted: True
    cf_pin: GPIO4
    cf1_pin: GPIO5
    model: BL0937
    initial_mode: CURRENT
    change_mode_every: 4294967295
    update_interval: 2s
    current:
      name: "HLW8012 Current"
      internal: true
      on_value_range:
      - below: 0.02
        then:
          - text_sensor.template.publish:
              id: machine_state
              state: "Off"
      - above: 0.02
        below: 0.1
        then:
          - text_sensor.template.publish:
              id: machine_state
              state: "Standby"
      - above: 0.1
        then:
          - text_sensor.template.publish:
              id: machine_state
              state: "Running"

text_sensor:
  - platform: template
    name: "Washing Machine"
    update_interval: 10s
    icon: "mdi:washing-machine"
    id: machine_state
</code>

It should be noted that this hides all of the regular power reporting sensors from Home Assistant. This suited my use-case, however it would be possible to make a hybrid sensor and expose this alongside the washing machine state. For my switch I also hid all of the regular smart controls, and configured the switch to always be on.