KitchenLight

ESP32-C3 based WiFi relay controller for a kitchen light, integrated with Home Assistant via MQTT auto-discovery.

Features

• Controls a relay (active LOW via transistor) on GPIO5
• Connects to Home Assistant as a light entity via MQTT discovery
• Supports ON / OFF / TOGGLE commands
• Publishes availability (online/offline LWT)
• Retains last known state across restarts

Hardware

Component	Detail
MCU	ESP32-C3 (e.g. SuperMini)
Relay	Active LOW via NPN transistor
Relay GPIO	GPIO5

Wiring

ESP32-C3 GPIO5 → NPN base (via ~1kΩ resistor)
NPN collector → relay coil (−)
Relay coil (+) → 5V
Relay NO/COM → light circuit

MQTT Topics

Topic	Direction	Description
home/kitchen/light/set	Subscribe	ON / OFF / TOGGLE
home/kitchen/light/state	Publish	Current state
home/kitchen/light/availability	Publish	online / offline

Setup

1. Copy secrets.h.example to secrets.h
2. Fill in your WiFi and MQTT credentials
3. Flash to ESP32-C3 via Arduino IDE or arduino-cli

FQBN

esp32:esp32:esp32c3

Libraries required

• PubSubClient by Nick O'Leary
• WiFi (bundled with ESP32 Arduino core)