I’ve been working on this project for the last few months, and finally got to the point where I can finally declare it done. Mercator is a spherical

Mercator: An ESP32-based spherical persistence-of-vision display

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2021-07-20 18:30:18

I’ve been working on this project for the last few months, and finally got to the point where I can finally declare it done. Mercator is a spherical persistence-of-vision display based on a ring of DotStar programmable LEDs and the Adafruit HUZZAH32 ESP32 dev board. As the LEDs spin around, the pattern changes to display pretty much anything:

The whole project is open source and the source code and design files can be found here. In this post I’ll walk through the design and explain it in some detail.

Do a Google search for “persistence of vision globe” and you’ll come up with a bunch of similar projects on the Internet, including some impressive YouTube videos. I wanted to build something based on my favorite dev board (the AdaFruit HUZZAH32), and using primarily 3D printed and/or lasercut physical components (rather than, say, CNC milled aluminum). Mercator is the result.

There are three main components to Mercator: The base, the clear acrylic shield, and the 3D printed LED ring. The base is laser cut out of 3mm thick wood. The shield cut from 3mm clear acrylic. The shield is there for two reasons: first, to prevent injuries (in case one of my kids decided to stick their hands in front of the spinning ring), but also to hold the top axis of the LED ring upright. I use two 12mm shaft diameter ball bearings, one mounted in the top face of the shield, and another in the top face of the base, to hold the LED ring. The shield has notches that align with matching holes in the top face of the base to hold it in place, so it is easy to lift the shield off if needed.