How a Graduate Turned His Cap into a Rust‑Powered Light Show

As U.S. graduation ceremonies begin, Purdue senior Eric Park decided to customize his cap by connecting LED strips to a microcontroller and controlling them with Rust code, creating a moving light display that lights up when the tassel slides.

The hardware consists of LED strips, a spring‑loaded switch, a magnet to activate the switch, and a Digispark ATtiny85 board. Because the design must stay lightweight and removable, Park powers the system with an external power bank; he originally wanted an integrated 21700 battery but lacked a boost converter.

Park wrote the firmware in Rust, spending a few hours on the code. He notes that using Rust felt faster for him than switching to the Arduino library or a different board, even though an ESP32 would have been over‑engineered for the task.

Assembly took just over three hours, mainly because he worked with household tools rather than a full lab setup. All components are affixed with double‑sided tape and Kapton tape, allowing quick attachment and removal without damaging the cap fabric.

The complete project, including source code, is open‑sourced on GitHub (https://github.com/ericswpark/gradcap-rs), enabling other students to replicate or extend the design for their own ceremonies.

Park does not plan to wear the illuminated cap at the ceremony, citing a rental agreement that forbids burning or damaging rented caps, and he acknowledges the device might look odd to some observers.