Sunday, March 14, 2010

Pixels by the square foot

We're renovating an apartment, and Ghislaine ViƱas, a friend and interior designer, suggested a mosaic for the wall of a powder room. We looked at mosaics, but they're (a) expensive, and (b) a big commitment – what if you don't like it when it's done? So I thought: wouldn't it be great to have a mutable mosaic – some kind of wall of tile-sized pixels that you could put in any pattern you wanted?


White and RGB LEDs are becoming pervasive – the Oscars had many LED panels on stage showing images and patterns. But they're expensive and power-hungry: e.g. 100-300W for a 2 s.f. panel. Todd Holoubek tracked down Chimera, which consists of LEDs (white or RGB) at a 10mm pitch, individually addressable, on boards that can be cut to any shape. The BMW Museum uses them to great effect. But they turn out to be $650/s.f. all-up.

Plasma and LCD TVs

Here's a spreadsheet of various cheap TVs and their cost per square foot. Bottom-line: a 50" 720p plasma is $170/s.f. This includes $500 for a computer to drive the screen. If you drive it with a cheap device like a DVD player, the cost is $100/s.f.

This seems plausible (and cheaper than mosaic), but there are two problems: power and borders.

Power. 50" plasma screens consume about 300W. If you had a wall of ten screens, you'd generate 3kW of heat. I wondered whether the nominal power usage was real, and whether turning down the brightness would help. so I plugged one into a Kill-A-Watt electricity usage monitor. Sure enough, about 270W. I turned down the brightness, and this dropped to 130W. Unfortunately, the image looked gray and washed out: I couldn't figure out how to drop the brightness without killing contrast. And in any case, 130W is still a lot.

Borders. How closely can you put plasma screens together? If you remove the bezels, could you make it look like a seamless wall (for example, if you put translucent glass in front)? For this, I needed to dismantle the screen. It weighs 75 lb, most of which is a big hunk of glass. I have to say, I'm not a fan of heavy, fragile things... The metal back panel comes off easily (after removing about 30 screws), but it's a cheaply-cut pressed sheet with sharp edges, and I sliced my finger open on it. Having staunched the bleeding, I removed some wires to speakers, IR receiver, etc and undid some more screws:

You can see the driver boards around the periphery, with ribbon cables going to the screen.

Once I lifted the (heavy, fragile) screen out, I could see the edge:

(the ruler, in addition to measuring, demonstrates the beauty of New Zealand native wood...) From the edge of the image to the edge of the glass is about 30mm. So even if you had the bare panels butted up against each other, you'd have 60mm between the images. Not seamless.

Physical pixels

So now I'm driven to desperation. I started thinking about physical mosaic-substitutes. Imagine an x-y plotter that could place lego pieces to create a piece over a few hours. With an automatic color-sorter, it could then take the old pieces out and build a new one. One problem is that there aren't many lego colors.

Or you could build a wall of clear vertical tubes and fill each tube with beads, varying the color to build up the image. Or if you could figure out how to thread the beads on a wire, you could do it even more finely and accurately, with less space between the columns. Then you'd just need an x plotter: the order you drop them in gives you y.

You build a paint plotter, but that would get messy, and not easy to reuse; you'd have to have an easy way to paint over (or maybe you'd get big sheets of white paper, or a huge dry erase board).

I have seen the future, and it is running late

Maybe the time for the huge, low-power image wall has not yet arrived. Let me know if you have ideas that I haven't thought of!