I’ve seen videos of them creating beautiful creatures, famous people and even Christmas trees. Do they work? Are there drawbacks? Tell me the good and the bad, please.
They are just LED lights blinked on and off timed to the rotation of the fan blades. They will be limited by the “resolution” of the blade, and while appearing to float like a science fiction hologram are flat images that only look good from a narrow POV.
Plus, touching it would be bad.
Yeah, with a little determination and smarts, you can make one yourself to run with an Arduino. Or you can dig up some code already out there. It’s not that difficult a concept, but takes some math and precise timing to get right.
I once talked to the guy who has the patient on this technique. My partner and I were designing moving message signs, and thought that simplifying the design by spinning a column of LEDs might be interesting (like, on a bicycle tire). The patent holder was willing to license it to us, but also mentioned that he hadn’t made a dime off of it…
I remember there used to be (probably still are) monochrome wands of LEDs that you wave around to write words in the air.
I have one of these clocks, which works on a similar principle, although it has a wand with a row of LEDs on the end that it mechanically waves back and forth instead of rotating. I’m pretty sure I got it in the 1980s, so it’s a pretty old idea.
I’ve seen a clock made from a single column of LEDs. To read the time you had to scan your eyes across it at the right speed. This took a while to get right.
I have one. Sure, it works. It’s just a basic persistence-of-vision device. Obviously devices differ, but it’s common to be able to upload your own images in addition to any default images it comes with. Resolution will depend on the number of LEDs per blade, number of blades, and the rotational speed.
Which is where the cons start. My device pretty much needs to be rigid mounted somewhere for display lest the rotational inertia send it in unexpected directions, especially if jostled. The rotating arms (a bit large and weighty) aren’t dangerous exactly, but will definitely give someone a good whack if not kept out of reach. I have something of a collection of light devices and gadgets I use for parties and events. I’ve never used the hologram fan because I’ve never felt comfortable putting it close enough to people to see well, and mounting it out of the way makes it harder to see and less impressive. It’s turned out to be more of a novelty item than a useful decoration for me. I found the POV display for bicycle tires more useful while it lasted for night riding.