I just finsished (for the most part) a coffee table with 24 individual leds under the glass surface that light up randomly or in a circle pattern. It uses 3 shift registers connected to the Arduino powered by a 9v battery.
I'm at school so I can't get on youtube but search "seth556" as my username or arduino coffee table and I have a video on there of it. If someone will post the link here or I can post it when I get home.
Comments/suggestions for improvement?
It's at:
Very Nice! 
What kind of Leds did you use? "Super Bright" ?
Thanks, I've been working on it a while as I kept waiting for parts to come in. Ordered shift registers from one place then got them and realized they weren't through hole and so they were tiny. Then waited for a bunch and finally got it all wired up. Next time I'll make a board for the shift registers and put all the wires going out first instead of hooking up the wire to the led first one at a time to save wire. That was a stupid idea haha, the wires are a mess.
That glass frosting spray doesn't work so well for large areas, does it....
They make frosting spray? I used sand paper, but I need to do some more work on it.
Ah....try to find someone who has an orbital sander you can borrow. Should frost that up nicely. Even better, a sandblaster
But yeah, you can get glass frosting spray a lot of places, like Home Depot. It's difficult to get an even coat...usually that's okay with spray paint, but the translucency of this stuff depends on the thickness.
I have used the static cling glass frosting film for stuff like this. It's a little too easy to peel off though.
I found a orbital sanding pad that goes into a drill but my drill battery is dead but I'll get that done soon enough.
That glass frosting spray doesn't work so well for large areas, does it....
It can, actually. Just takes ~4 light coats and some care to get it even. It's also crucial that the surface be clean and dry. Especially when using it on Plexiglass where static electricity makes dust especially problematic.
However, if you want a really heavy diffusion paper is often the best bet, and the best thing you can do is move the sources further away from the diffusion material. There's also a certain type translucent foam that works really well even right up against the source, but unfortunately I couldn't tell you what type it actually is.
I did a write up on this and put my source code online here: http://sites.google.com/site/seth556/arduino-projects/round-coffee-table
Also I ordered a few parts to replace the arduino with just a atmega328 chip. I only have one arduino so I've been missing it for a few weeks now haha
