ESPHome Basics: Build a Custom Sensor with ESP32

Parts list (~$8 total)

Wiring

The AHT10 uses I²C (2 wires + power), the PIR uses a single digital GPIO. Total: 7 wires.

Full ESPHome YAML config

Create a new device in the ESPHome add-on (Home Assistant → ESPHome → New Device) and paste this config. Replace your_wifi_ssid and your_wifi_password with your credentials.

esphome:
  name: room-sensor
  friendly_name: "Room Sensor"

esp32:
  board: esp32-c3-devkitm-1
  framework:
    type: arduino

# Enable Home Assistant native API (no MQTT needed)
api:
  encryption:
    key: !secret esphome_api_key

# OTA updates — push new firmware wirelessly
ota:
  - platform: esphome
    password: !secret esphome_ota_password

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password
  # Fallback hotspot if WiFi fails
  ap:
    ssid: "Room-Sensor Fallback"
    password: "tinkertok123"

# Web dashboard at device IP (optional, comment out to save RAM)
web_server:
  port: 80

# AHT10 temp + humidity via I2C
i2c:
  sda: GPIO4
  scl: GPIO5
  scan: true

sensor:
  # Temperature
  - platform: aht10
    temperature:
      name: "Room Temperature"
      accuracy_decimals: 1
      filters:
        - median:
            window_size: 5
            send_every: 5
    humidity:
      name: "Room Humidity"
      accuracy_decimals: 1
    update_interval: 30s

  # WiFi signal strength
  - platform: wifi_signal
    name: "WiFi Signal"
    update_interval: 60s

# PIR motion sensor
binary_sensor:
  - platform: gpio
    pin:
      number: GPIO2
      mode: INPUT
    name: "Motion Detected"
    device_class: motion
    filters:
      - delayed_off: 30s   # keep "on" for 30s after last trigger

# Status LED (built-in on ESP32-C3 SuperMini)
light:
  - platform: status_led
    name: "Status LED"
    pin: GPIO8

# Uptime and restart button for diagnostics
sensor:
  - platform: uptime
    name: "Uptime"

button:
  - platform: restart
    name: "Restart"

# Log level (reduce to WARNING in production)
logger:
  level: DEBUG

secrets.yaml

ESPHome reads credentials from a shared secrets.yaml file so you never hardcode passwords. Create or update it in the ESPHome config directory:

# /config/esphome/secrets.yaml
wifi_ssid: "YourNetworkName"
wifi_password: "YourWiFiPassword"
esphome_api_key: "generate_one_at_esphome.io/encryption-key"
esphome_ota_password: "choose_a_strong_password"

First flash (USB)

The first flash must be done via USB. After that, all updates are wireless.