Sauna Controller - ESP32 Firmware

Open-source ESP32 firmware for controlling an electric sauna heater with native Apple HomeKit integration.

Features

• HomeKit Native: Appears as a Thermostat in Apple Home app — control via Siri or Home app
• Temperature Monitoring: Real-time temperature from DS18B20 sensor
• Safety First: Hard temperature limits, session timeouts, fail-safe defaults
• Local Only: No cloud, no accounts, no subscriptions — just your local WiFi

Hardware Requirements

• ESP32 development board (ESP32-WROOM-32 or similar)
• DS18B20 temperature sensor (waterproof version recommended for sauna environment)
• Relay module (5V, appropriate for your contactor coil)
• Contactor rated for your heater (7kW @ 240V = ~30A)

Wiring

ESP32 GPIO 26 ──► Relay IN ──► Contactor Coil
ESP32 GPIO 27 ──► DS18B20 Data (with 4.7kΩ pullup to 3.3V)
ESP32 3.3V    ──► DS18B20 VCC
ESP32 GND     ──► DS18B20 GND, Relay GND

⚠️ WARNING: This project controls high-voltage equipment. Ensure all electrical work is done by a qualified electrician and meets local codes.

Building

Requires PlatformIO.

# Clone the repo
git clone https://github.com/YOUR_USERNAME/sauna-controller-esp32.git
cd sauna-controller-esp32

# Build
pio run

# Flash to ESP32
pio run --target upload

# Monitor serial output
pio device monitor

HomeKit Setup

1. Power on the ESP32
2. Open the Home app on your iPhone
3. Tap "+" → "Add Accessory"
4. The ESP32 will broadcast as "Sauna Controller"
5. Follow pairing prompts (default setup code shown in serial monitor)

Safety Features

• Max Temperature: Heater auto-disables at 110°C (configurable)
• Session Limit: 60-minute hard timeout (configurable)
• Sensor Failure: Heater disables if temperature sensor disconnects
• Fail-Safe Default: Heater is OFF on boot and on any error

License

MIT License — see LICENSE for details.

Contributing

Contributions welcome! Please open an issue first to discuss proposed changes.