Tim Alex Jacobs Builds the Ultimate LED Candle — with a 3D Volumetric POV Display
Simplifying the build of a spinning 3D POV volumetric display by literally spinning the whole thing lets Jacobs shrink the project down.
Maker Tim Alex Jacobs has built a battery-powered tea light candle that's actually a 3D volumetric display, spinning rapidly enough to use the persistence of vision (POV) effect to create a hovering image.
"I was recently fortunate enough to find myself in the pub with some very creative and talented people. The discussion turned to electronic candles, and how one might create something that would look like a flickering candle from any angle," Jacobs explains.
"I suggested a persistence-of-vision display, but the general consensus was that those require too much in the way of supporting machinery to make them work: bearings, and probably slip rings and so on. Afterwards I had a think and figured that if the motor and battery were small enough, the whole thing could spin."
A typical spinning persistence of vision display uses, as Jacobs' friends correctly stated, a static base with a rapidly-moving array of individually-addressable LED lights. At a large scale, that's reasonably simple to implement — but at the scale of a tea light candle, things become a lot more challenging.
Throwing a simple circuit design onto an existing PCB order and putting the resulting boards onto a pick-and-place machine, Jacobs put together an 8×10 array of 80 surface-mount LEDs. This is connected to the recently-launched Waveshare RP2040-Tiny, a compact alternative to the Raspberry Pi Pico, and powered by a LIR2450 lithium-ion button-cell battery in a 3D-printed housing.
The resulting prototype, which mounted the LED matrix diagonally across the RP2040-Tiny board, was the mounted on a motor — which spins the entire assembly, battery, motor, and all, to simplify the POV part of the operation. An infrared sensor mounted at the front monitors the speed of the display — which, as it's spinning in a circle around its vertical axis, creates the effect of a three-dimensional display.
The core concept behind the tiny display is the same as that shown off on a much larger scale by maker James Brown back in October — though for an improved effect Brown's version used either lenticular lenses or 3D-printed collimators to restrict view of the off-axis LEDs.
For the volumetric data, Jacobs turned to blender and rendering 3D wireframe cubes and fluid simulations — the latter providing an animated flame which brings the project back to its origins of attempting to create an LED candle which would look flame-like from all angles.
Jacobs' full write-up is now available on the Mitxela blog, with wiring schematic; the source code is available on GitHub under an unspecified license.