Linear Pendulum Assembly

I made this in a weekend.

My interview for Heirloom required a presentation on a project that I was passionate about. Realizing that it had been a long time since I worked on my college projects (and I didn’t really find them interesting), I decided to put this together the weekend before my presentation. It ultimately got me the job.

• Mechanical design was all done in Fusion 360. I obtained the extrusion and hardware on McMaster and electronics from Digikey and Amazon. The black plastic parts seen in the images were 3D printed.

• Motor control was done using an ESP32 microcontroller via the Arduino IDE. I used this DC gear motor that, in hindsight, was a pretty lousy choice for this application. The motor driver I sourced from Amazon was also particularly bad, containing blatant errors in its documentation that took several hours to debug and identify.

• Closed-loop control was achieved using a rotary encoder attached to the belt on the side opposite to the motor, in addition to two simple limit switches on either end of travel.

This project taught me a lot of what not to do when designing a belt-driven linear motion system, e.g. using load-bearing 3D printed parts, adding almost no adjustability for things like motor mounting, sizing a motor based entirely on “intuition,” and using a non-standard (i.e. not an Arduino) microcontroller because my older brother who is a computer engineer at Rivian said it would be cool.