Persistence of vision is a neat optical illusion that you’ve probably seen on toys designed to display text. It works by moving an array of light sources (usually LEDs) very quickly and modulating the light at the proper times to create what your eyes perceive as a solid display. It’s not a particularly practical way to display something, but it does look cool. Over on Hackaday.io, Jarrett has taken the concept even further and built a persistence of vision globe.
Jarrett created Global View for the fun of it, but it’s actually a fairly complicated build and he may end up offering it as a DIY kit. The major component of the project is a custom-designed circular PCB that has side-mount LEDs soldered in a ring around the edge. If you imagine a line bisecting the circular PCB from 0° to 180°, that is the axis of revolution. When the PCB spins, the LEDs light up to show a rudimentary form of each of the planet’s continents.
As you’d expect, coordinating the modulation of those LEDs is the tricky part of this build. Jarrett is using a Hall effect sensor to detect whenever one side of the PCB swings by a magnet mounted on Global View’s stationary stand. That lets a PIC microcontroller sync up the display to maintain the “persistence” part of the equation. With that information, the PIC can control the LEDs via a TLC5947 PWM LED driver. Jarrett may still be working some kinks out, but Global View is already impressive.