A classic doorbell can be upgraded into a smart doorbell with just:

• An ESP32
• A doorbell button
• A relay to trigger an existing chime
• Optional ESP32-CAM for snapshots

With Home Assistant you can:

• Keep your physical chime
• Get mobile notifications when someone rings
• Attach an image snapshot from a camera
• Log and automate everything (quiet hours, different sounds, etc.)

This guide covers:

• Simple button + relay wiring
• ESPHome configuration
• Home Assistant automations for chime + notification + snapshot
• An outline of a MQTT version for your usual style

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1. Hardware Overview

Base setup (no camera):

• ESP32 DevKit
• Doorbell push button (momentary switch)
• Relay module (3.3 V logic input, dry-contact)
• Existing low-voltage chime (ideally 8–24 V AC or DC), or a 5–12 V DC buzzer
• Low-voltage PSU (for ESP32 + relay; or reuse doorbell transformer if suitable)

Optional add-on:

• ESP32-CAM module near the door
• 5 V supply for ESP32-CAM
• 3D-printed or weatherproof housing

⚠️ If your doorbell is powered by mains voltage, only work on the low-voltage side of the transformer and follow local regulations. When in doubt, treat anything on 230 V as off-limits and get an electrician.

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2. Concept: How the Smart Doorbell Works

We want three things:

1. Detect button press → ESP32 reads a GPIO from the doorbell pushbutton.
2. Ring a chime
   • Either via relay contacts across the existing chime button input
   • Or by directly powering a low-voltage buzzer
3. Notify Home Assistant
   • Event → HA sends mobile push + (optional) camera snapshot

We’ll do the main implementation with ESPHome & native API.
After that, a quick MQTT variant.

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3. Wiring

3.1 Button → ESP32

Wire the button as a simple contact to ground:

ESP32 GPIO  → one side of button
ESP32 GND   → other side of button

We’ll use the internal pull-up so:

• Button released → GPIO = HIGH
• Button pressed → GPIO = LOW

Example pin: GPIO 32.

3.2 Relay → Chime

Two typical options:

A. Existing low-voltage chime (recommended)

Most wired doorbells have:

• Transformer → low voltage (e.g. 8–12 V AC)
• Chime unit
• Button wired in series

We emulate the button with a relay:

Chime transformer/chime low-voltage line:

[TRANSFORMER] --- [CHIME] ---[PB1]----(button)----[PB2]

Relay COM  → PB1
Relay NO   → PB2

The existing physical button remains in parallel:

PB1 ---- Button ---- PB2
PB1 ---- Relay COM
PB2 ---- Relay NO

ESP32 → Relay module:

ESP32 3.3V  → Relay VCC
ESP32 GND   → Relay GND
GPIO 25     → Relay IN

B. Direct DC buzzer

If you don’t have an existing chime:

• Use a 5–12 V DC buzzer or chime module
• Drive it via relay or MOSFET from a DC PSU
• Logic is the same: ESP32 toggles the relay for ~1 second.

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METHOD 1 – ESPHome Doorbell Node

We’ll create:

• A binary_sensor for the doorbell button
• A switch for the relay / chime
• A doorbell event for Home Assistant
• Optional integration with an ESP32-CAM

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4. ESPHome Base Config

esphome:
  name: esp32-doorbell
  platform: ESP32
  board: esp32dev

wifi:
  ssid: "YOUR_WIFI"
  password: "YOUR_PASSWORD"

logger:
api:
ota:

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5. Relay as Chime Output

We want a momentary relay pulse whenever HA or the ESP32 rings the doorbell.

switch:
  - platform: gpio
    id: doorbell_relay
    name: "Doorbell Chime Relay"
    pin: 25
    restore_mode: ALWAYS_OFF
    icon: mdi:bell-ring
    on_turn_on:
      - delay: 800ms    # ring duration
      - switch.turn_off: doorbell_relay

You can hide this from the UI later if you prefer to trigger via automations only:

    internal: true

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6. Button Input – Doorbell Press

binary_sensor:
  - platform: gpio
    id: doorbell_button
    name: "Doorbell Button"
    pin:
      number: 32
      mode:
        input: true
        pullup: true
    filters:
      - invert: true          # pressed = ON
      - delayed_on: 30ms      # debounce
      - delayed_off: 50ms
    device_class: occupancy
    on_press:
      - logger.log: "Doorbell pressed!"
      - switch.turn_on: doorbell_relay
      - homeassistant.event:
          event: esphome_doorbell_pressed
          data:
            source: esp32-doorbell

Behaviour:

• Short press → ESP32 logs, rings relay, sends an HA event esphome_doorbell_pressed.
• Home Assistant can use either:
  • binary_sensor.doorbell_button state change, or
  • the esphome_doorbell_pressed event as a trigger.

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7. Optional ESP32-CAM Snapshot Integration

You can:

• Use a separate ESP32-CAM running ESPHome with esp32_camera:
• Add a camera entity in HA (e.g. camera.door_camera)
• On doorbell press, request a snapshot and send notification with the image

Example ESPHome for ESP32-CAM (very minimal idea):

esphome:
  name: esp32-doorcam
  platform: ESP32
  board: esp32cam

wifi:
  ssid: "YOUR_WIFI"
  password: "YOUR_PASSWORD"

logger:
api:
ota:

esp32_camera:
  name: "Door Camera"
  external_clock:
    pin: GPIO0
    frequency: 20MHz
  i2c_pins:
    sda: GPIO26
    scl: GPIO27
  data_pins: [GPIO5, GPIO18, GPIO19, GPIO21, GPIO36, GPIO39, GPIO34, GPIO35]
  vsync_pin: GPIO25
  href_pin: GPIO23
  pixel_clock_pin: GPIO22
  resolution: 800x600

(Exact pins depend on module; you’d use the standard ESPHome example for your specific ESP32-CAM board.)

In Home Assistant, this becomes camera.door_camera.

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8. Home Assistant Automations

We’ll use the ESPHome event esphome_doorbell_pressed as the central trigger.

8.1 Basic Doorbell Notification + Chime (redundant, but clear)

If you want HA to also control the relay (instead of ESPHome doing it directly), you can remove switch.turn_on: doorbell_relay from ESPHome and move all logic into HA.

Example automation using the event:

automation:
  - alias: "Doorbell – Chime + Notification"
    trigger:
      - platform: event
        event_type: esphome_doorbell_pressed
    action:
      - service: switch.turn_on
        target:
          entity_id: switch.doorbell_chime_relay
      - service: notify.mobile_app
        data:
          title: "Doorbell"
          message: "Someone is at the door"

If you keep the ESPHome on_press action to ring locally, use this automation only for the notification.

8.2 Snapshot + Notification (ESP32-CAM or Other Camera)

Assuming you have:

• camera.door_camera

Automation:

  - alias: "Doorbell – Snapshot + Mobile Notification"
    trigger:
      - platform: event
        event_type: esphome_doorbell_pressed
    action:
      - service: camera.snapshot
        target:
          entity_id: camera.door_camera
        data:
          filename: "/config/www/snapshots/doorbell_{{ now().timestamp() }}.jpg"

      - delay: "00:00:02"  # Give snapshot time to save

      - service: notify.mobile_app
        data:
          title: "Doorbell"
          message: "Someone is at the door"
          data:
            image: "/local/snapshots/doorbell_{{ now().timestamp() | int - 2 }}.jpg"

Notes:

• /config/www maps to /local in HA URLs.
• The timestamp trick gives a roughly matching filename; you can simplify to a static filename if you don’t care about history.

8.3 Quiet Hours (Do Not Disturb)

Disable chime at night, but still get a silent notification:

  - alias: "Doorbell – Silent Night Mode"
    trigger:
      - platform: event
        event_type: esphome_doorbell_pressed
    condition:
      - condition: time
        after: "23:00:00"
        before: "07:00:00"
    action:
      - service: notify.mobile_app
        data:
          title: "Doorbell (Silent)"
          message: "Someone rang the doorbell during quiet hours"

And update the main chime automation with a time condition to exclude night.

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METHOD 2 – MQTT Doorbell (Your Style)

If you want the ESP32 to speak pure MQTT:

• Button press → ESP32 publishes home/doorbell/button message
• Relay control → HA sends commands to an MQTT switch

9.1 Home Assistant MQTT Entities

Binary_sensor for button:

mqtt:
  binary_sensor:
    - name: "Doorbell Button"
      state_topic: "home/doorbell/button"
      payload_on: "PRESSED"
      payload_off: "IDLE"
      device_class: occupancy

Switch for chime:

mqtt:
  switch:
    - name: "Doorbell Chime Relay"
      command_topic: "home/doorbell/chime/set"
      state_topic: "home/doorbell/chime/state"
      payload_on: "ON"
      payload_off: "OFF"
      retain: false

ESP32 behaviour:

• On button press:
  • Publish "PRESSED" then (optionally) "IDLE" shortly after
• On "ON" command to .../chime/set:
  • Pulse relay and afterwards publish "OFF" to state topic

All the notification/snapshot automations remain the same, just triggered from binary_sensor.doorbell_button instead of an ESPHome event.

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10. Practical Tips

• Debounce: mechanical buttons bounce; ESPHome delayed_on is enough in most cases.
• Local chime even if HA is down: keep switch.turn_on: doorbell_relay in ESPHome’s on_press, so doorbell still rings even if HA/MQTT is offline.
• Camera choice: if ESP32-CAM image quality is not good enough, use any IP camera; you only need a camera entity for snapshots.
• Power: use a reliable PSU; a doorbell that reboots whenever someone presses it is… sub-optimal.

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Summary

With a single ESP32 and relay you get a smart, still-local doorbell:

• Button press detected via GPIO
• Relay triggers existing chime
• Home Assistant sends notifications and snapshots
• Quiet hours and advanced logic are just YAML away

The optional ESP32-CAM (or any IP camera) adds the “who is at the door?” piece without needing an expensive commercial smart doorbell.