This Ornament Contains a Tiny Diorama Complete with a Working Model Train

Can we all share a moment of honesty and admit that Christmas tree ornaments are kind of boring? Sure, they can be very sentimental, but they don’t really do anything and that’s a shame. To correct that yuletide drudgery, Sean Hodgins built this ornament that contains a tiny diorama complete with a working model train.

This is a pretty normally sized ornament — no trickery there. Inside the transparent globe of the ornament is a little scene featuring mountains, trees, houses, and a PCBWay office building. Winding around that tiny town is an itty-bitty train track on which a minuscule train rides. The diorama was 3D-printed and there isn’t much to talk about with that, but making such a small model train move was a fascinating challenge.

Hodgins experimented with different ideas to pull that off, because it wasn’t a trivial problem. On top of being small, the diorama also hangs from a tree and can move around. The train needed to run reliably, even when tilted.

The solution that worked was based on magnets. The train has a stiff wire on its bottom to keep it riding in the groove of the track. Then underneath the diorama, a motor pulls a belt that has a magnet attached to it. That magnet attracts another magnet on the train, causing the train to follow the belt path as it loops around. That works under the control of an Adafruit Feather ESP32 V2 development board on a custom PCB. Hodgins even threw in some LEDs to light up the scene.

Now Hodgins has an ornament that is sentimental and that actually does something. His future holidays are sure to be much more entertaining. And if you want to build this ornament yourself, he posted a detailed build guide on Instructables.