I designed this project as part of my weekly PCB challenge in 2020. I wanted to prank my coworkers by playing random noises around the office, so I put this together!
The circuit works by reading a random audio file from the SD card, and playing it over the speaker. Once the file is played, the circuit goes to sleep for a random amount of time. The average length of the sleep time can be adjusted with one of the two potentiometers, with the other setting the volume.
The circuit can be powered with a LiPo battery, or with USB-C. When plugged in, the board also charges the attached LiPo battery.