If you’ve put in all the necessary practice to learn bike tricks, you’d probably like an appropriately dramatic soundtrack to accompany your stunts. A team of students working on a capstone project at the University of Washington took this natural desire a step further with the Music Bike, a system that generates adaptive music in response to the bike’s motion.

The Music Bike has a set of sensors controlled by an ESP32-S3 mounted beneath the bike seat. The ESP32 transmits the data it collects over BLE to an Android app, which in turn uses the FMOD Studio adaptive sound engine to generate the music played. An MPU9250 IMU collects most position and motion data, supplemented by a hall effect sensor which tracks wheel speed and direction of rotation.

When the Android app receives sensor data, it performs some processing to detect the bike’s actions, then uses these to control FMOD’s output. The students tried using machine learning to detect bike tricks, but had trouble with latency and accuracy, so they switched to a threshold classifier. They were eventually able to detect jumps, 180-degree spins, forward and reverse motion, and wheelies. FMOD uses this information to modify music pitch, alter instrument layering, and change the track. The students gave an impressive in-class demonstration of the system in the video below (the demonstration begins at 4:30).

Surprisingly enough, this isn’t the first music-producing bike we’ve featured here. We’ve also seen a music-reactive bike lighting system.

Thanks to [Blake Hannaford] for the tip!

This little audiobook player is a stellar example of the learning process behind a multifaceted project blending mechanical, electrical, and software design. [Mario] designed this audiobook player, dubbed Boxie, for his 3-year-old son to replace the often-used but flawed Toniebox.

The inspiration for Boxie was the Toniebox, a kid-friendly audiobook player. While functional, the Toniebox had drawbacks: it required internet connectivity, limited media selection, and had unreliable controls. Enter Boxie, a custom-built, standalone audiobook player free from web services, designed to address these issues with superior audio quality and toddler-friendly controls.

Boxie’s media is stored on microSD cards inserted into a slot on the device. To make this manageable for a toddler, he designed a PCB with a standard microSD card interface, ensuring easy swapping of audiobooks. The enclosure, crafted via 3D printing, is durable and compact, tailored for small hands.

The cartridges slide into the body of the Boxie. This presented a problem, most cartridge media utilize edge connectors. Strictly speaking, his DIY cartridges didn’t have those and couldn’t use traditional cartridge reader components. First trying pogo pins, he ran into several issues, most notably the inability to hold up to the wear and tear of a 3-year-old. A clever hack to add robustness was achieved when he switched to using a series of battery springs to interface with the cartridge.

Inside the Boxie lives an ESP32-S3 microcontroller, which provides the smarts to read all the controls, play audio from the inserted cartridge. The main housing also contains the battery, DAC, amp, and speaker. Mario faced a fair number of new challenges on this project, including designing a battery charging circuit and building his own ESP32-S3 board with support for charging NiMH batteries.

All of the 3D designs, PCB files, and source code are available on his GitHub account. If you’re interested in making a Boxie for a young one in your life, be sure to go check out his detailed write-up. If you enjoyed this project, be sure to check out the other DIY audio players we’ve featured.