ESPHome Air Quality Sensor System Sensirion SEN66

ESPHome Air Quality Sensor System (SEN6x)

A high-end Air Quality Monitor based on the ESP32-C3 and Sensirion SEN66, featuring a fully dynamic GC9A01 round display dashboard. This project goes beyond standard ESPHome configurations by allowing real-time UI customization directly from Home Assistant without re-flashing.

Software Repo: https://github.com/doctormord/SEN6X_ESPHOME

🚀 Features

• Dynamic Dashboard: Round UI with three configurable arcs and six data slots.
• Real-time Customization: Change sensor assignments, arc ranges, and update intervals on the fly via Home Assistant.
• Dynamic Theming: Support for Light and Dark modes with user-definable HEX colors for backgrounds, text, and UI elements.
• Advanced Sensor Handling:
  • Anti-Reset Logic: Specialized 24h-polling trick to prevent the Sensirion gas engine (CO2, VOC, NOx) from resetting, ensuring stable long-term data and proper warm-up.
  • Custom Calibration: Offset sliders for Temperature and Humidity.
• Intelligent Backlight: Automatic day/night brightness adjustment based on sun elevation (Sunrise/Sunset).
• Health Monitoring: Visual color-coded alerts (Green/Yellow/Orange/Red) based on three-stage configurable thresholds for every pollutant.
• WiFi Diagnostics: On-screen signal strength indicator (%) and auto-reboot logic for weak connections.

• 💧 Dynamic Humidity Compensation

  Relative Humidity (RH) is highly dependent on the ambient temperature. When applying a temperature offset (e.g., to compensate for internal device heat), the raw RH value from the sensor becomes physically inaccurate.

To solve this, the firmware implements a real-time compensation logic using the Magnus-Tetens Formula. It calculates the saturation vapor pressure to maintain a consistent dew point, ensuring that the displayed humidity remains accurate even after temperature calibration:

• Vapor Pressure Consistency: The system ensures that the calculated actual vapor pressure remains constant while the temperature is adjusted.
• Physics-Based Correction: Instead of a simple linear offset, we use the exponential saturation curve.
• Accurate Environment Data: This ensures that your humidity readings don't "drift" just because the temperature calibration was adjusted.

🛠 Hardware