This project is built around the STM32L0 series of ultra-low-power microcontrollers, paired with the X-Y MBD40A Bluetooth module from XinYi Technology, an AHT20 temperature and humidity sensor, and an SG90 servo motor, along with a dedicated mobile app. It enables functions such as turning lights on and off, reading temperature and humidity data, and achieves an ultra‑low standby power consumption of just 100 µA. Powered by a 1000 mAh lithium battery, the device can operate for up to one year on a single charge, with charging supported via a Type‑C port.
The primary focus of this product has been on power consumption optimization—progressing from an initial standby current of 400 µA down to just 100 µA today. To further enhance performance, potential improvements could include fine‑tuning the STM32’s standby mode, minimizing leakage current in the servo signal lines and between the STM32 and its power supply, as well as optimizing the Bluetooth module’s advertising interval.

The PCB design and firmware are open source—link available Bluetooth Light Off Device – Temperature and Humidity Feedback – Charge Once, Use for a Year – Lichuang Open Source Hardware Platform.