This fun PCB from [Nick Brown] features a miniature railroad implemented with 0805-sized LEDs. With an eye towards designing his own fun interactive PCB badge, the Light-Rail began its journey. He thoroughly documented his process, from shunting various late-night ideas together to tracking down discrepancies between the documentation of a part and the received part.

Inspired by our very own Supercon 2022 badge, he wanted to make a fun badge with a heavy focus on the aesthetics of the final design. He also wanted to challenge himself some in this project, so even though there are over 100 LEDs, they are not laid out in a symmetrical or matrix pattern. Instead, it’s an organic, winding railroad with crossings and stations throughout the board. Designed in KiCad the board contains 144 LEDS, 3 seven-segment displays, and over a dozen buttons that all come together in use for the built in game.

The challenges didn’t stop at just the organic layout of all those LEDs. He decided to use Rust for this project, which entailed writing his own driver for the seven-segment displays as well as creating a tone library for the onboard buzzer. As with all projects, unexpected challenges popped up along the way. One issue with how the oscillator was hooked up meant he wasn’t able to use the ATmega32U4, which was the brains of the entire railroad. After some experimenting, he came up with a clever hack: using a pogo pin jig to connect the clock where it needed to go while programming the board.

Be sure to check out all the details of this journey in his build log. If you love interactive badges also check out some of the other creative boards we’ve featured.

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