Information

Mon, 01 Jan 0001 00:00:00 +0000

Visit the to download the example code and get the latest version.

A custom WS2812 LED badge powered by a and written in .

The PCB hosts 20 RGB LEDs arranged in a 4 rows × 5 columns grid behind a frosted 3D-printed diffuser. A single button cycles through lighting effects.

Hardware

Component	Note
Hikari PCB	in hardware/pcb folder
3D printed files	in hardware/STL folder
Flathead screw 2.1x10	4x
20 × WS2812 LEDs (4 rows × 5 cols)	D6
Tactile button	D3
Qwiic / StemmaQT connector	D4 & D5 (I²C)
Passive buffer	D7

Effects

Each press of the button advances to the next effect. The sequence cycles endlessly.

#	Name	Description
1	Rainbow	All 20 LEDs show the same colour; the hue cycles slowly through the full spectrum (~20 s per revolution)
2	Row sweep	One row lights up at a time and sweeps downward; the hue drifts continuously
3	Column sweep	One column lights up at a time and sweeps rightward
4	Stars	8 LEDs at random positions fade in with a random colour then fade out; when a star dies a new one appears elsewhere
5	Breathing	All LEDs pulse with a triangular brightness envelope (~5 s per breath); the hue shifts slowly between cycles
6	Rainbow rows	Each row shows a different hue (90° apart on the colour wheel); all hues advance together
7	Wave	A bright column chases across the grid with a two-column fading trail

Flash

tinygo flash -target=xiao-esp32c3 -stack-size=8KB .

Requires TinyGo ≥ 0.41 and v0.35.

Build

Step 1 — Bare PCB

The back side of the custom PCB. Footprints for the 20 WS2812 LEDs are arranged in the 4 × 5 grid.

Step 2 — Qwiic / StemmaQT connector

We’ll start with the SMD Qwiic / StemmaQT connector since it’s the trickiest to solder. It is not really needed, but a cool way to extend the board with sensors. Use the help of some flux if needed.

Step 3 — Soldering the button

The tactile switch is soldered to its footprint on top of the board. Easier than the stemmaQT.

Step 4 — PCB fully populated

All 20 LEDs and the button in place. The XIAO BLE/RP2040/ESP32C3/… plugs in on the left edge. It’s the easier one to do, and the last one to be done since it goes over one LED.

NOTE: Make sure all the LEDs are correctly soldered since once we solder the board there’s no way to fix the LED behind it.

Step 5 — PCB seated in the frame

The board drops into the back shell. The silkscreen on the rear shows the Go gopher pattern.

Step 6 — 3D-printed back cover

The black back shell printed in PLA. The XIAO slides into the slot on the side for USB access. Use 4 screws on the holes.

Step 7 — Frosted diffuser panel

A white PLA diffuser snaps onto the front of the frame to spread the light evenly across the grid. You could print different models of the diffuser!

Step 8 — Finished

Fully assembled and running. The diffuser softens each LED point into a smooth glow.

光 Hikari badge | Go Education Project