Print an Arduino-powered color mechanical television | Hacker News Reader

Print an Arduino-powered color mechanical television

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96 pointssohkamyung13 comments

Hmmm, it's tiny... but what about a bigger matrix of LEDs that can be moved around just a little bit. The idea I guess is time-multiplexing lights in space... So if you have a big board with a grid of LEDs and shake it around a bit, you can do the same thing but with less movement and more lights... You get more pixels for the same number of lights.

(Hopefully someone can visualize what I mean.)

There are little toy fans with 8 or so leds on the blades that do this...show a word while the fan spins.

Ans SUPER expensive ones that appear to make a 3D hologram in the air.

However, wouldnt it make sense to change the shape from a square to a wedge/arc that more accurately follows the arc of its orbit and resulting in a tighter pitch between scan line?

There used to be cheap LED wand displays you could wave in the air to display messages. Once popular with ravers.[1]

[1] http://www.houseofrave.com/skyliner_message_writer.html

Better yet, move the matrix in the normal axis to put your pixels in 3D space.

https://www.google.com/search?q=swept+volume+display

For something less cutting edge, you can spin a bar with individual LEDs instead of a disk full of holes. Also makes for a good DIY project now that we have the microcontrollers to do it without specialized slip rings. But contrary to popular use, neither of these is a 'holographic display' as they don't use holography!

check out the suspected new displays in the next oculus headset https://www.androidcentral.com/gaming/virtual-reality/quest-...

I worked for a company (2009-10) that made big spinny ones for outdoor advertising (they got a few deployed in the UK) and were working on a 8'x5' billboard-style one which had 8 huge rotors, each with 4 arms, coated in (of the time huge) LEDs.

When it span up, it sounded like a steam-powered 747 trying to take off.

Thankfully (because the potential for catastrophic disintegration was huge) the company went bust before any of these got deployed anywhere near the public.

I was surprised it looks as good as it does. Amazing.

That's cute. I considered doing that back when I was doing steampunk props.

I'd like to see someone revive Scophony.[1] That was the best of the mechanical television systems. It's a much brighter system, because a whole line is illuminated once, not just one pixel at a time. 9' x 12' projectors were built, at 405 lines. The "super-sonic light valve" is the only hard part. That's a long, narrow liquid tank with a transducer at one end. You could probably use a prism from an old laser printer for the fast scanning direction, and 3-phase drone motors to drive the mirrors. Keeping the mechanics in sync would not be hard with modern motor controllers.

[1] https://en.wikipedia.org/wiki/Scophony

Any reason a belt with holes couldn't replace the disk with holes for a more compact and rectangular viewing surface? Should be easy enough to test with a belt sander.

The closest thing from the time was mirror drums but those don't sound too similar, and they had mirrors for some reason.

https://youtu.be/LmISP_fAAws?t=15

I find the images gorgeous and could watch this for longer. Anyone know if there's more footage anywhere?

Also how big could one theoretically / practically scale this up? How big a wheel would you need for a public display?

This reminds me of the recovery of original Baird recordings (made on phonograph-style discs) which couldn't be played back at the time, but modern technology came to the rescue:

http://www.tvdawn.com

There was a project in the 1980s in one of the electronics mags to make a mechanical TV. I didn't build a unit, but the bit I remember was the need to sacrifice a 12" LP for the disc and drilling a spiral of holes in it.

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