A Very Versatile Full-Color PoV Display

Persistence of vision (PoV) is a visual phenomenon that occurs as a result of our eyes’ (or rather brain’s) inability to keep up with fast motion. This is why we see motion blur, like a camera with the shutter left open for a long time. It is also why, for example, you don’t notice your LED light bulbs flickering, even though they probably are — you just see constant light because the flickering happens faster than you can perceive. This is what makes PoV displays possible and this DIY full-color PoV display designed by lhm0 is a very versatile example.

PoV displays like this work just like your LED light bulbs, just with motion. A row of LEDs spins fast enough that you only see a solid plane of light. By modulating the brightness and color of the LEDs in sync with the rotation, it can display images and text.

This design contains 56 RGB LEDs, which is the radial resolution across the diameter. The polar resolution is harder to define, because it is the result of the rotation speed and LED refresh rate.

The great thing about lhm0’s design is that is quite simple from a mechanical perspective. The LEDs, microcontrollers, and most of the other components mount onto the top PCB that spins. The motor and power supply mount onto the stationary bottom PCB. This would normally require something like a slip ring to pass power from the bottom to the top, but that would create friction. Instead, lhm0 integrated wireless power transfer between the boards. That means that the only physical contact the top board makes is with the motor shaft. That motor is for a CD drive. To maintain balance and prevent vibration, lhm0 carefully distributed the components with screws and nuts acting as counterweights.

Because speed is critical for a PoV display like this one, lhm0 used two microcontrollers. The first, a Raspberry Pi RP2040, is dedicated to controlling the LEDs. The second, an ESP32, uses its built-in Wi-Fi adapter to connect to the internet to pull data (like time and weather). It also hosts a web interface where the user can configure settings and select what they want to display.

This is capable of showing all kinds of content, but lhm0’s demonstrations include simple videos, clocks, and weather forecasts.