h a l f b a k e r y
Not so much a thought experiment as a single neuron misfire.

meta:

account: browse anonymously, or get an account and write.

 user: pass:
register,

# ElectroMechanical Billboard Display

Based on "flipping clock digit" technology
 (+7, -2) [vote for, against]

See link for details of a "flip clock" digit-display unit.

The starting-point Idea here is, instead of displaying a square with a digit on it, we display a square with a color on it, such as yellow or black or blue or white.... Depending on just how many "flaps" can be mounted on the mechanical wheel at the heart of the device, we could have quite an assortment of colors available. (Also see the "Rolodex" link.)

Note that in many clock mechanisms it is typical for digits to be connected to each other by gears, so that one full rotation of one digit-wheel causes one incremental partial rotation of the next wheel. We don't want that here. Instead we want each of these color-display units to have a "stepper motor" (see link) built into it. One electrical pulse through the unit's control-wires causes one incrementation, and displays the next color in the available sequence.

We now take many thousands of these display units and mount them next to each other as closely as possible, covering the surface of a billboard with them. This is the part that makes this Idea half-baked. Consider a largish billboard 10 meters long by 5 meters high, and suppose each "pixel" unit fits in 1 square centimeter. That's 500,000 pixel units to buy!

Note that these pixels are significantly larger than the pixels of an ordinary printed billboard image. However, because more colors are available for each pixel here, it is less important for the eye to be able to merge neighboring pixels to see a combined color. It means that the larger pixels of this billboard can still produce a good-quality large image.

We connect all their control wires to a computer. Something known as "multiplexing" (see link) makes this task less formidable than you might at first think. Note that if a factory makes 1-square-meter modular panels, each containing 10000 pixel units and an appropriate demultiplexer, the task of assembling the overall billboard becomes somewhat easier.

Those panels will likely be fairly heavy, so perhaps a smaller size (say 32 pixels square or 1024 per panel) might be better. Binary counting also makes demultiplexing more logical, even if it means the overall large billboard won't be an exact number of whole meters tall or wide. There are always trade-offs!

The computer is programmed to know which color is being displayed by each pixel unit in the billboard. The computer also knows the sequence of colors that will be displayed as the mechanical flaps are flipped by the stepper motor. Therefore it can figure how many stepper pulses are needed to change any pixel in this overall "display device" from one particular color to another.

Remember, this is a billboard, a device for displaying one image for a significant time. It is not intended for fast-motion video. But thanks to its computer control and the flexibility of its pixel units, the displayed image can be easily and fairly quickly changed, for the next static image (making it good competition for an ordinary billboard). And, of course, the computer can simply be turned off in-between image-changes, saving electricity, whenever an advertiser pays for a long-term display.

 — Vernon, May 28 2011

Flip Clock http://en.wikipedia.org/wiki/Flip_clock
As mentioned in the main text. [Vernon, May 28 2011]

Stepper Motor http://en.wikipedia.../wiki/Stepper_motor
As mentioned in the main text. [Vernon, May 28 2011]

Multiplexing http://en.wikipedia.org/wiki/Multiplexing
As mentioned in the main text. [Vernon, May 28 2011]

//attract and hold eyeballs// http://en.wikipedia.../Liane_the_Wayfarer
[mouseposture, May 28 2011]

Ku-Damm Bildwand, old and new http://super-screen-media.com/14.html
The old one used cubes, the new one just uses LEDs. (German "Würfel" = cube.) [jutta, May 28 2011]

[discontinuuity] linked this to one of my ideas that is similar to this. http://www.smoothwa...m/danny/mirror.html
[2 fries shy of a happy meal, May 28 2011]

Rolodex http://en.wikipedia.org/wiki/Rolodex
For a better idea of how many colors each pixel unit might be able to display. [Vernon, May 28 2011]

Peter Wegner artrork at Stanford Graduate School http://articles.lat...rd-project-20110522
Color display using electromechanical panels [rmutt, Jun 02 2011]

Do you mean like this? http://tacomachambe...ds-may-come-to.html
[xandram, Jun 02 2011]

 Imagine the job of the ElectroMechanical Billboard Display Repair Technician.

Indoors, not too big, preferably somewhere people had time to kill (an airport would be perfect) this might attract and hold eyeballs <link> well enough to justify the added complexity, relative to similar, all-photoelectronic technology [+].
 — mouseposture, May 28 2011

The AVNet bildwand at the Ku-Damm Eck in Berlin worked by rotating colored cubes. There were often broken pixels, but it wasn't as altogether fragile as I'd expect if I hadn't seen it work. This was in 1988. It burned down on July 8th 1990 in a fireworks accident. (Nowadays, the replacement just uses LEDs.)
 — jutta, May 28 2011

This does have the notable advantage that it continues to display the programmed messag even in case of a total power failure.
 — 8th of 7, May 28 2011

 Excellent point. [Vernon] could it be built with a default message, which displayed in a power failure?

 "We are experiencing technical difficulties. Thank you for your patience."

 "Please walk, do not run, to the nearest exit."

 "Keep calm, and carry on."

"We are the Borg. You will be assimilated. The queue forms to your right."
 — mouseposture, May 28 2011

Kind of baked in electromechanical railroad station arrival displays. See link to Peter Wagner artwork using colored panels.
 — rmutt, Jun 02 2011

I think I've seen these before...[see link]
 — xandram, Jun 02 2011

[rmutt] and [xandram], no, those are LED (light-emitting-diode) displays. Each pixel in them is electronic, not mechanical.
 — Vernon, Jun 03 2011

 If this were done in a Steampunk style, all brass and polished mahogany, it would be a sight to behold.

(Supported on a couple of massive cast-iron Corinthian columns, painted green and highlighted with red paint and real gold leaf, like any proper Beam engine).
 — 8th of 7, Jun 03 2011

Thanks for explaining [Vernon]! I thought those blocks that flipped over were mechanical.
 — xandram, Jun 03 2011

 [xandram], I did not see any indication of "blocks flipping" when I looked at the link you provided. I did see "electronic" and "digital" mentioned. For the link [rmutt] provided, I was able to Google for more details, and am confident that that one, at least is an LED display.

 I might mention that there is an existing type of mechanical billboard display that involves a lot of vertical slats. Think of long triangular tubing; each slat is one side of the triangle. So, by mounting a bunch of these slat-triangles side-by-side, and rotating all the triangles 1/3 turn, a new image can be displayed as new slat-faces are rotated to become the overall surface of the billboard. But it can only do 3 images, and 1/3 of all the slats need to be replaced, if you want to show a new image.

I note that simple geometry should make it impossible to rotate cubes or squares that are surrounded by other cubes or squares, so I want to see more information about claims concerning such billboards.
 — Vernon, Jun 03 2011

 Nope, it is mechanical. Did you read the article?

"He spent months perfecting the 80 different colors in each spinning module (picture a mini-Rolodex with colored polycarbonate flaps instead of white paper cards) that makes up each cell on the grid. "
 — rmutt, Jun 04 2011

[rmutt], I apologize. When I first saw the link I stopped scrolling at the first advertisements in the middle of the text, thinking that was all there was. So I tried Google to learn more, and an LED display came up (which I now see is also mentioned in the article). His mechanical display is indeed rather similar to what I thought up here. The pixels are a lot bigger, though...and his purpose is to constantly change the image it displays. Not like the use I described here.
 — Vernon, Jun 04 2011

 [annotate]

back: main index