Constructing Tiny LED Matrix Earrings

When most people hear the term “wearable technology,” they think of things like smartwatches, augmented reality glasses, and maybe e-textiles. But those of us with piercings consider other possibilities: electronic devices inserted into our bodies for fun and profit. However, this is difficult for makers to pull off, because it requires very small components. Thankfully Tim Alex Jacobs (AKA Mitxela) is very talented and was able to fit entire LED matrices on a pair of stud earrings.

This is a follow-up to Jacobs' LED industrial piercing that we covered recently. That was a single piece of jewelry with a row of LEDs embedded in the stainless steel barbell. This new project is a little different and a lot more versatile. Each earring has an LED matrix consisting of 52 individual LEDs arranged in an 8×8 grid (with corners cut off) forming a roughly circular shape. Microcontrollers provide full control over those LEDs, so it is possible to program patterns, animations, and even scrolling text.

To save some time on labor and avoid custom machining, Jacobs started with a pair of cheap off-the-shelf LED earrings. Each of those had a single LED on the front and a backing that doubles as a battery holder for two LR521 batteries. Jacobs planned to reuse the battery and metal, then replace the single LED with the LED matrix.

This required a very small LED matrix, so Jacobs used surface-mount 0201 LEDs placed as close together as was feasible. Luckily, Jacobs has access to a pick-and-place machine that made assembly easier—it would have been extremely difficult to place the LEDs by hand. Those go on one PCB, with a second PCB forming a sandwich. That second PCB holds the microcontroller — an itty bitty CH32V003 MCU in the QFN20 package. That is a tiny chip, but it has a 32-bit RISC-V processor that can run at up to 48MHz, with 2KB of SRAM, 16KB of flash storage, and 18 I/O ports — enough for an 8×8 matrix with a couple of pins to spare.

Jacobs was able to fit those LED matrix PCBs into the crown mounts that originally held faux gems. The result is fantastic, though reprogramming the LED patterns/animations is tricky. If this is the direction wearable technology is going, then we’re excited for our collective cyberpunk future.