The rectifier also provides a signal that the assembly has completed a rotation, so you can maintain image stability based on actual position, rather than guessing how long a cycle is.

Transmitting power via induction might work, but I was never able to deliver it efficiently enough, so to make it work I had to turn up the source voltage so high that I worried about fires.

This advice comes from my 2001 Burning Man art project. A very sad early prototype is pictured here: https://github.com/sowbug/tqw/blob/master/photos/side.jpg. The final installation worked great.

A TI DLP DMD can modulate at those high speeds, and there's readily available driving circuitry for it. However, it's a small reflective based display designed for projectors, and you would then need a light source to reflect off of it.

MicroLEDs would let you increase your pixel pitch with fast modulation frequency, but the display area is still small at the moment because of low yields. You also need a custom chip to drive the microleds at the required high framerate.

It makes me wonder how different LIDAR vendors manage it.

1: https://www.adafruit.com/product/1407 2: https://www.adafruit.com/product/2162

Given that the results are so compelling even when pulled together by hand out of relatively primitive discrete components, I’m wondering why we shouldn’t expect to see full color, high resolution versions from every random 7-letter drop shipper on Amazon next Christmas?

But they're mostly kind of just toys. When you're limited to transparent glowing surfaces and you can't even touch them, there's really not a whole ton you can do. You can see a much larger non-spinning version made of LEDs suspended on cables [2] and it's very cool, but the novelty kind of wears off after a while, and you realize it's not the kind of display you're going to use for anything productive.

If you actually want real 3D visualization that can render anything at high quality and that you can interact with, it seems like VR/AR headsets are the way. (Though there are also the new 3D monitors that don't require glasses, but not a lot of people have gotten to see those in person yet.)

Maybe there's some kind of toy you could make with them to sell on Amazon though? Not really sure if there's a "killer app" for these things.

[1] https://en.wikipedia.org/wiki/Volumetric_display#Swept-volum...

[2] https://www.ledpulse.com/

It would actually make a fantastic Princess Leia message toy!

https://mitxela.com/projects/hardware

Personal favorite: the MIDI slide whistle.

[0] https://mitxela.com/projects/headphone_amps

https://youtu.be/bT716nyK0AY

[1] https://www.180studios.com/

It really makes a huge difference in what you can get done with side projects. You probably have more interesting ideas than you think you do, but if having them doesn’t line up with having the time and energy to act on them (or even to just expand on them), they’ll fade away.

It's also ok to have really """bad""" ideas. They're always funny to read back (a month/year) later. They're fun to share with friends and strangers. And sometimes they lead to good ones as you think about what made you think the bad ones were bad in the first place.

I have no problem coming up with, and remembering, cool projects. I just rarely have the energy or the lasting enthusiasm to actually follow through.

One thing that I really like about this site is that the creator spends a ton of time on documenting it all. I am usually so busy with projects I don't get around to it. Another problem is that, especially for larger projects, that you need to store and maintain them. And that gets old pretty quickly when you're lugging around 200 pound windmills and such.

Most dangerous times: when the administration needs to be brought up to date for the tax man. Then I really have to force myself. Fortunately I've been able to off-load most of that but even the little bit that remains is enough to get me to spend 30 hours on something else to avoid 1/2 an hour of work.

(Ear training exercises are fun. I just built an ear training module into the beta of pianojacq.com and it's a hoot, what's also interesting is that it seems to have an immediate effect on playing ability, I really didn't expect that)

I second taking note of stuff; like most things, genuinely practicing means you will get better.

Something that's also overlooked often is (1) Technical knowledge, (2) Methodical invention (3) Motivation!.

Technical knowledge helps you know which projects are possible (or just economically feasible), and map the roadblocks on the way; impossible inventions are not really useful.

Methodical invention means methodically looking at things instead of just randomly inventing. So you analyze a problem, like: (a) I want to make a volumetric display, (b) I want to bring (virtual) 3D objects to life. Notice the subtle difference between the two. Volumetric displays (a) can range from a lightfield display, which is a very elegant theoretical foundation (and can be realized in a number of ways), to volumetric persistence-of-vision displays like the own shown here. It's likely you will eventually arrive at whatever solutions are possible when you deeply research about a problem domain. Bringing a 3D object to life (b) can mean anything from digital fabrication, VR glasses, haptic interaction, robots, and more. It's a much wider problem domain.

Motivation is also really important. Understanding why you're inventing, and what you what you want to bring to life is also significant. Are you going to bring people joy, is it just very cool, is it a useful medical device that can save lives, etc.. Focusing on worthy subjects is also something you can study and that will really increase how good you are at inventing. Of course making stuff just because [we like it] is also important and valid :)

And for me the most important part is to have fun while you're at it...

I wonder if a cheap oled display could be updated fast enough to achieve a much higher resolution. It might work but could look worse since the space between radial slices would be much larger than the pitch of the pixels, most likely.

And even there, 12 Hz is probably pushing it in terms of flicker.

For a 1 meter diameter and height cylinder at 60Hz voxel refresh and say 1mm resolution at the edge one would need the plane rotating at obviously 3600 rpm, and edge pixels switching at about 380KHz. Since rgb is nice to have that's 10 gigabit for a somewhat coarse display. Nothing impossible, but not a DIY territory yet.

I think one'd want the LEDs either on the receding or the advancing halves of the plate, depending on which is best for the cooling -- not all on the same side or on both -- that would be just a waste.

Or even just on one half of the plate, the other being just a countermass. This way cuts the bandwidth in two.

All in all, this is what makes it interesting, no? 1x1 meter holo tank, not those tiny Voxon shakers.

The edge of such a display would also be moving at several hundred miles per hour, which creates it own whole set of problems.

You would still need a bare minimum of 1-2 kHz, and a lot of screens, and balancing every layer would be super difficult, but I don’t think anything about it is fundamentally impossible with current technology.

Are phone screens (minus the phone etc) transparent?

And we can't reduce RPM.

Get it light enough and you don't even have to center it that good.

https://news.ycombinator.com/item?id=38406824

Each pixel on such a setup travels along a circle. Spinning at 1200 rpm = 20/second, a 1000 Hz display would have a resolution of 50 segments along this circle. With a 10 cm diameter, this would make the outer "pixels" in the virtual 3D display around 6mm long.

The outer edge of the display would also experience a force of 80 G at that point, so bigger and/or faster spinning quickly becomes challenging (although it's only linear).

Driving monochrome OLED displays at 500+ Hz has already been done https://blog.adafruit.com/2012/02/03/adafruit-ssd1306-monoch...

This gave me a wild idea: what if you could encode a low-resolution 3D video on the left channel of a stereo vinyl groove? [1] A special record player with a spinning plexiglass plate could then play holographic albums. The hologram would stay perfectly in sync with the music if you changed speeds or did turntable scratching.

[0] If anyone can find a link to the original spinning hard drive hologram project please drop it!

[1] I assume this wild idea isn't feasible given vinyl data rates?

Data rates go up if you spin the disk faster, and can get fast enough for 2D video. I don’t think it was vinyl, but https://en.wikipedia.org/wiki/Television_Electronic_Disc:

“Program information was stored in the form of ridges in the surface of a thin, flexible foil disc, which was claimed to be sufficiently robust to withstand being played 1,000 times. The main technological breakthrough was the vertical recording method that reduced the track pitch to 0.007 mm, and increased the rotation speed to 1,500 rpm, making it possible to record 130–150 grooves per millimeter, compared with the typical 10–13 grooves on an audio disc. This increased the available bandwidth from around 15 kHz to 3 MHz.”

When each pixel actually represents multiple pixels in a circle, you need a much higher refresh rate than 60 Hz.

https://mitxela.com/projects

I wonder how they respond to being dunked in epoxy.

https://thepihut.com/products/ito-indium-tin-oxide-coated-gl...

Here's another cool one I found a while ago: https://www.youtube.com/watch?v=wM_Byrv9iBI

compatible with the exact same pick-and-place machines, you just need to drill a hole in the PCB

The code is lean too, seems like one could learn a lot by trying to do this themselves.

Need one the size of a 5gal bucket.

As it is, I'd stick one on my gimcrack cabinet.

Edit found another video showing it starting up https://www.youtube.com/watch?v=SMz4bJA47Js

Now that I think about it, I suppose if you match the resonate frequency of the display component and its carrier it should be fairly efficient. Really cool stuff.

https://www.forbes.com/forbes/2007/0723/060.html?sh=3c183bcb...