Build a smart garage door opener with an ESP32 and ESPHome

An ESP32, a relay and a $3 magnetic reed switch turn almost any garage door opener into a Home Assistant cover: open and close it from your phone, see whether it's open, and get a warning when it's left open at night.

First, check your opener

This build works by doing exactly what the wall button does: briefly connecting its two terminals. That works on most older openers and on Genie and many other brands, which use a simple dry contact button.

Newer Chamberlain, LiftMaster and Craftsman openers with Security+ 2.0 (often with a yellow learn button) use a digital wall button instead, and shorting the terminals does nothing. For those, use a ready-made ESPHome board built for that protocol, such as ratgdo, which talks to the opener over its own wires and also reports door position without a reed switch.

A quick test: with the wall button disconnected, touch a short piece of wire across the two button terminals on the opener. If the door moves, this guide is for you.

Parts

• An ESP32 DevKit and a 5 V USB power supply.
• A 1-channel 3.3 V relay module (or a 5 V module that accepts 3.3 V input).
• A wired magnetic reed switch, the kind sold for alarm systems, with normally-open contacts.
• Two-conductor bell wire for the relay-to-opener and reed-switch runs.

Wiring

Mount the reed switch on the frame near the bottom of the door and the magnet on the door itself, about 1 cm apart when closed. A switch at the closed position is the most useful single sensor: "closed" is the state you care about at night.

The ESPHome config

Add this to an ESP32 config (the config generator makes the base). It defines the relay as an internal momentary switch, the reed switch as a sensor, and a cover that ties them together:

switch:
  - platform: gpio
    id: garage_relay
    pin: GPIO26
    restore_mode: ALWAYS_OFF
    internal: true
    on_turn_on:
      - delay: 500ms
      - switch.turn_off: garage_relay

binary_sensor:
  - platform: gpio
    id: door_closed
    name: "Garage door closed"
    pin:
      number: GPIO27
      mode:
        input: true
        pullup: true
      inverted: true
    filters:
      - delayed_on_off: 200ms

cover:
  - platform: template
    name: "Garage door"
    device_class: garage
    lambda: |-
      return id(door_closed).state ? COVER_CLOSED : COVER_OPEN;
    open_action:
      - if:
          condition:
            binary_sensor.is_on: door_closed
          then:
            - switch.turn_on: garage_relay
    close_action:
      - if:
          condition:
            binary_sensor.is_off: door_closed
          then:
            - switch.turn_on: garage_relay
    stop_action:
      - switch.turn_on: garage_relay

A few details matter here:

• The relay is internal and momentary. It turns itself off after half a second, just like a button press, and ALWAYS_OFF means a reboot can never leave it held closed.
• Open and close check the door first. Pressing "open" on an already-open door does nothing, instead of closing it.
• Stop is just another press, which is how most openers behave mid-travel.

Home Assistant automations

Left-open reminder

Trigger when Garage door has been open for 15 minutes after 9 p.m., and send a phone notification. Most people find this the most valuable part of the whole project.

Auto-close, carefully

If you add an automatic close, make it announce itself first. Commercial openers flash a light and beep before an unattended close, and you should do the same: flash a light in the garage or play a sound for at least 10 seconds before triggering the relay, and only close when nobody's presence sensor in the garage is active.

Upgrades

• Add a second reed switch at the fully-open position to tell "open" from "stuck halfway".
• Add an LD2410 presence sensor so automations know if someone is in the garage.
• Add a leak probe under the water heater if it lives in the garage — same ESP32, one more GPIO.