A battery-powered, Arduino-driven musical circuit designed to be integrated into a physical wooden box. The system automatically boots up and plays a specific audio track the moment the lid is opened. The primary engineering goal of this project was to achieve an absolute zero-idle-drain power state to maximize battery life, allowing the device to sit on a shelf for months without dying.
Tech Stack & Components
- Microcontroller: Arduino Uno
- Audio Decoding: DFPlayer Mini (HW-247A V0.5.1)
- Storage: MicroSD Card (FAT32, strict folder architecture)
- Actuation: Micro Limit Switch (Normally Closed)
- Output: 0.5W 8-Ohm Speaker
- Language: C++ (Arduino)
Assembly guide & demonstration video.
The project includes a workaround for modern knock-offs of the DFPlayer Mini module (specifically the HW-247A V0.5.1). Because these clones lack the standalone ADKEY trigger functionality of the original YX5200 chip, an Arduino is utilized to handle the logic and send the necessary hex commands via serial communication.
To prevent the 3W amplifier from blowing the delicate 0.5W speaker, the Arduino code incorporates a 1.5-second initialization delay and strictly throttles the startup volume before sending the playback command.