Hey everyone,
just finished a new sensor node build and wanted to share the setup. I was looking for a clean, highly accurate indoor air quality monitor that doesn’t look like a breadboard mess on the desk, so I built a custom node around the Sensirion SEN66.
Hardware used:
- Sensor: Sensirion SEN66 (measures PM1.0-PM10, VOC, NOx, Temp, Humidity)
- MCU: ESP32-C3
- Display: 1.28" GC9A01 Round LCD
Software & Theme Engine: Everything runs locally via ESPHome and drops straight into HA. Since dealing with raw display coordinates and drawing components can get tedious if you just want to change a color or layout, I integrated a custom theme engine into the ESPHome YAML. It makes tweaking the UI for the GC9A01 straightforward without having to rewrite the core display logic.
Choose from all values for the 3 arcs, the big number and 6 value slots. Setup min/max and range levels. Choose text and background color for light/dark theme as well as backlight brightness.
Enclosure: I designed a custom, compact 3D-printable case to fit the C3, the SEN66, and the round display.
If you want to replicate the build or grab the code for your own round display projects:
- Full build guide & Theme Engine details: https://www.360customs.de/en/2026/02/esphome-air-quality-sensor-system-sen6x/
- YAML on Github: https://github.com/doctormord/SEN6X_ESPHOME
- STLs for the enclosure: https://www.thingiverse.com/thing:7298235
Let me know if you run into any issues compiling the display component or have questions about the SEN66 integration!
