What it is
The Sand Garden is a little round table filled with fine sand. Underneath, a magnet on a moving arm drags a steel ball through the sand, and the ball leaves a trail. The trail turns into swirly patterns. It's like a robot that doodles for me. (Placeholder text — real version coming soon.)
How it works
My Sand Garden is a two-axis polar drawing robot. A magnet under the sand pulls a steel ball along a path, and the whole design is generated by code running on a microcontroller. It looks like magic, but every swirl is really math and motors.
1. The ball is the pen
A steel ball sits in a round bed of sand. As it moves it carves a groove behind it, so the ball is basically a pen and the sand is the paper. There's no ink — the line is the trail it leaves.
2. A hidden magnet does the pulling
Underneath the table is a magnet on a moving arm. Magnetism reaches right through the base, so wherever the magnet goes, the ball follows. The ball never touches the machine — it's guided entirely by an invisible force.
3. Two motors = a polar coordinate system
Instead of moving left/right and up/down (X and Y), this robot uses angle and distance from the center — that's a polar coordinate system. One stepper motor rotates the arm (the angle), and another slides the magnet in and out (the radius). Together they can reach any point in the circle.
4. Stepper motors move in tiny exact steps
Regular motors just spin. Stepper motors turn in hundreds of tiny, precise clicks, so the code always knows the exact position of the ball. That precision is why the patterns come out clean and repeatable instead of wobbly.
5. Code turns shapes into coordinates
A pattern (like a flower or spiral) is really a long list of (angle, radius) points. The program calculates those points with math, then interpolates — fills in the in-between steps — so the motors glide smoothly from one point to the next instead of jumping.
6. Hacking it = making my own art
It ships with 10 built-in patterns, but the real fun is editing the code. By changing the math and the helper functions, I can design brand-new patterns the kit has never drawn. The robot handles the motion — I control the algorithm.
Sand Garden kit by CrunchLabs / Hack Pack — built and coded by me!
Why I built it
After my other builds I wanted something more precise and calm. The Sand Garden uses stepper motors, which move in tiny exact steps, and I really wanted to feel how much more accurate they are than regular motors. Plus the patterns are just so pretty. (Placeholder — my real story goes here.)
What it teaches
My build steps
Build the round base
I started with the bottom plate and the walls that hold the sand. I made sure everything sat flat so the patterns wouldn't come out crooked.
Mount the two stepper motors
I attached the motors that move the arm. One spins the whole arm around, and the other slides the magnet in and out toward the center.
Attach the magnet arm
I connected the arm that carries the magnet under the sand and checked that it could swing all the way around without bumping anything.
Wire it up and load a pattern
I connected both motors to the brain board, plugged it into my computer, and loaded a program that draws a simple spiral first.
Add sand and watch it draw
I poured in the sand, dropped in the steel ball, and started the pattern. Then I tweaked things until the lines came out smooth.
What I learned
I learned that stepper motors are amazing for precise drawing, but they're picky — they need a level table and a smooth track. I also learned that polar coordinates (an angle plus a distance from the center) are a really natural way to describe circles and spirals. (Placeholder — more to come.)
Want to build your own Sand Garden?
Grab the official kit and build along with me — about $66+.