# A 3D-printed marble clock that scrolls text

Marble clocks are well explored, so one maker asked what happens when you swap digits for a scrolling text wheel. Black and white marbles, a lot of 3D printing and a lot of retries.

- Category: Hardware (build)
- Made by: [Ivan Miranda](https://www.youtube.com/watch?v=wKQOMW56auA) on YouTube
- Original: https://www.youtube.com/watch?v=wKQOMW56auA
- On Afterware: https://afterware.xyz/p/a-3d-printed-marble-clock-that-scrolls-text

## Can I build this?

- Difficulty: Advanced
- AI-buildability: 3/5 (AI can write the stepper control, homing and text-to-marble sequencing code, but the large mechanical design, printing, tuning and sensor debugging are hands-on work.)
- Time: A month or more
- Cost: $150–300
- Parts: Stepper motor, IR sensor, Steel ball bearings, PLA filament
- Tools: 3D printer

Estimates based on the original write-up. How the AI-buildability score works: https://afterware.xyz/ai-buildability

## Build sheet

- Drive: Stepper motors (wheel + selector)
- Sensing: IR sensors
- Body: 3D-printed, bolted
- Marbles: Black and white steel balls

## Starter prompt

```
Based on "A 3D-printed marble clock that scrolls text" on Afterware: https://afterware.xyz/p/a-3d-printed-marble-clock-that-scrolls-text

Write Arduino firmware for an ESP32 that drives two stepper motors through a TB6600 or similar driver: one rotates a ring of marble channels, the other moves a selector arm. Use two IR sensors to detect the home position on the wheel and the selector. Given a text string, convert each letter to a sequence of black and white marble slots, then step the wheel so each slot receives the correct color.
```

## Story

Marble clocks show time with fixed digits. Ivan Miranda wanted text with no digit limit, so the build became a big round wheel of marble channels. Inner steel ball bearings drop black or white marbles into the slots, and the wheel's stepper motor lines up each channel. A second stepper on an inner selector picks the right color for each slot, so the wheel builds the target sequence one marble at a time.

The whole structure is 3D printed and bolted together, and it's a big one. It took several rounds of trial and error, including IR sensors that got confused by daylight. It now mostly works. The wheel still has to be homed by hand before each run, and the black-to-white ratio can leave gaps in the final text. The text is still legible, and the scroll never runs out of room.

## Resources

- [Build video](https://www.youtube.com/watch?v=wKQOMW56auA)

Tags: marble display, 3d printed, stepper motor, scrolling text, ir sensor, kinetic display

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