I was inspired by seeing the Sisyphus table by Bruce Shapiro (https://sisyphus-industries.com). I thought it was so cool and wanted to make one of my own.
Underneath the table is a mechanism that moves a magnet. The magnet in turn pulls a steel ball through the sand, making designs. The mechanism has two motors on it - one to move the ball radially in and out from the center using a rack and pinion gear, and another to rotate the arm around 360 degrees. It is essentially a 2D polar plotter.
* How to control motors using the Arduino
* How to decipher and use the feedback signals provided by a motor encoder
* How to design and prepare parts for cutting on a CNC router using Fusion 360
* How to design and prepare parts for 3D printing using Fusion 360
* How to design and send out a PCB for manufacture using Eagle CAD.
It's relaxing and fascinating to watch. I think it also inspires others on how science and engineering can meld with art and meditative experiences.