The Wearable Air Quality Pendant is a small, power-efficient device designed to monitor the air you breathe continuously. At its heart is the ultra-low-power STM32U083KCU6 microcontroller, which works alongside the SGP40 gas sensor to detect Total Volatile Organic Compounds (TVOC) in the environment. The sensor is managed using the DFRobot_SGP40 library.

To keep things simple for the user, the pendant provides immediate feedback through a two-color LED (red and green) and a buzzer that plays unique RTTTL melodies depending on the air quality. The system classifies air quality into three levels: Good, Warning, and Critical, each with its own light and sound pattern. If a critical reading is detected or the sensor fails, the device enters a critical mode with flashing red LEDs and an alert tone.

The firmware is designed for efficiency. It uses the ptScheduler library to manage tasks like LED fading, sensor readings, and audio playback without blocking other operations. This makes the pendant responsive and reliable, even on battery power. The entire assembly is fitted into a 3D-printed, pendant-shaped enclosure, making it easy to wear as a pendant.

Whether you're working in a factory, commuting in a polluted city, or just concerned about indoor air quality, this pendant offers a simple and effective way to stay informed and safe.