Just when you think the POV thing has run out of gas, along comes [mitxela] to liven things up. In this, he’s taken the whole persistence of vision display concept and literally spun up something very cool: a tiny volumetric “electric candle” display.
As he relates the story, the idea came upon him on a night out at the pub, which somehow led to the idea of an electric candle. Something on the scale of a tea light would fit [mitxela]’s fascination with very small and very interesting circuits, so it was off to the races. Everything needed — motor, LIR2450 coin cell, RP2040, and the vertical matrix of LEDs — fits into the footprint of the motor, which was salvaged from a CD drive. To avoid the necessity of finding or building a tiny slip-ring, he instead fixed everything to the back of the motor and attached its shaft to a Delrin baseplate.
The 8×10 array of surface-mount LEDs stands atop the RP2040 with the help of some enameled magnet wire, itself a minor bit of circuit sculpture. There’s also a 3D-printed holder for a phototransistor and IR LED, which form a sensor to trigger the display; you can see [mitxela] using a finger to turn the display off and move it back and forth. It goes without saying that these things always look better in person than they do in stills or even on video, but we still think it looks fantastic. There’s also a deep dive into generating volumetric data in the write-up, as well as an unexpected foray into the fluid dynamics calculations needed to create a realistic flame effect for the candle.
All in all, this is a fantastic if somewhat fragile project. We love the idea of putting this in a glass enclosure to make it look a little like a Nixie tube, too.
Thanks to [Cutout], [Aaron], and [htky] for the near-simultaneous tips on this one.
That is so cool.
mega kudos
Now do a spinning video screen where AI takes a 2d FaceTime call and changes it to 3d and presto – talk to your friend’s hologram.
Always happy to see the obligatory HaD article per each mitxela video. Each video/project is kickass and it’s great to see recognition of that.
Oh. My. Very cool!
Now that is very simple and fun. Seems like when the goal is to simulate a candle some variety of LED colours would be a good move – doesn’t need to be real RGB or anything that extreme but a candle flame has more than just the orange colours filling out that rough tear drop shape – so replacing a few of those orangey ones in the right places would help that illusion (though also make the volumetric display look odd for that cube/fluid simulation).
May also be worth the hassle of putting the LED in plane with the PCB – help with the balance and if there is a little light leak on the back side when pretending to be a flame that is probably going to further enhance the illusion.
Not worth the hassle. Just populate both sides of the PCB
That would be a substantial increase in pins required for the matrix and power draw and it might also need an extra PCB layer. Not saying its a bad idea, but for such a small battery I think you’d end up getting such a reduction in functional life it isn’t worth it and possibly have to scale the whole thing up physically to get enough I/O on the microprocessor board (or start deadbug soldering to a BGA package micro). At which point their suggestion of just balancing the rotary part nearer the base is probably a better solution.
Lots of ways to skin this cat though (which is a most odd expression).
Possibly extra pins, yes, but power draw and such shouldn’t change because you should be able to spin at half the speed or light each LED half as long per pass.
I like it! Just getting it balaned enough so it doesn’t fly apart is impressive. I used to be able to make small stuff like that, but as I got older….. enjoy it while you can kid.
The compact placement of LEDs as shown for the recent Hackaday Con badge add on could (maybe) be used with this device to fill in the volume of the display better.
Very cool. How long until we see much larger versions of this using RGB LEDs ?
A small, flat, transparent, thin piece of plexiglass glued to the front of the LED panel will shift the center of gravity forward which should allow you to move the whole display backwards while keeping the CG on the axis of rotation. It’ll also allow you to experiment with possibly dulling the surface just a bit for a small amount of blur which might just make the voxels blur together a bit more (which might look better??)
Cool!
IMO, the coolest thing this adds to the PoV display concept is the IR sensor for UI. It controls power, switches modes, and is an intuitive rotation interface, all with only one part!