[tomclancey]

Hello all! It's Anthony again with another project! I started this along with my Poplar/Pine Computer Desk project. (Yay for shameless plugs!)

This time though a buddy is helping me construct it! It all started when we were starting up a D&D group and I saw something that caught my eye. RPMaptools! It seemed to revolutionize the way people could play D&D. Then I saw someone use a multi-touch screen and I'm thinking to myself, I think I found my new project!

Initially I had mulling around my head an FTIR (frustrated total interior reflection design) where an array of IR LED's would be lined up along side 3/8" acrylic (or 1/2") and blast IR light throughout the acrylic with no leakage.

The only problem is they don't detect fiduciary markers, and it would cost almost 3 times as much. $120 for the LED's (on the cheap end) and $98 for the acrylic. Ouch.

The more common alternative that can do both multi-touch fingers and fiducial markers is Read-DI! Or diffused illumination.

Essentially it works by covering the entire bottom side of the with IR light (I'm using four 48-LED arrays that are normally used for outdoor security lights). From what I've read and seen it's a lot cheaper then using IR LED bars. That would set me back almost $300 in strips alone!

Project costs so far:
Projector:
Dell 3300MP - FREE
Computer:
Junker Dell PC - FREE
IR lighting:
4x 48 IR LED array - $57
Lumber:
4x 1" x 12" x 6' pine-sheets - $25
4x 1" x 2" x 3' cherry - FREE
4x 3/4" x 30" x 48" plywood - FREE
1x 3/4" x 60" x 40" plywood - FREE
1x 1" x 2" x 98" maple - FREE
Compliant surface:
36" x 5' Vellum - $17
Acrylic:
1x 3/16" x 30" x 30" - $27
IR Camera:
1x PlayStation 3 EYE - $25 (IR converted!)

It all comes out to about $151! Not bad for something like this.

(Oh, if anyone lives in the tri-state area, Queen City Polymers is an awesome acrylic distributor! Great prices, and they get orders done fast!)

So yeah, enough of me blabbering, here are some pictures!

Here are some renders of the desk:

What the renders don't show is the mirror, projector and PS3 Eye. The project will mount under the screen, bounce onto a mirror and project through the acrylic onto the vellum. The PS3 Eye which has been converted to only capture IR light with pickup any hot spots left by fingers and the fiducial markers. (The hot spots show up because they reflect IR light instead of it diffusing into the surrounding area.)

Photos!
The cherry "clamps" that will hold the vellum taught across the acrylic.

Measuring depth of the acrylic on the shelf piece.

Routing the last shelf.

Still routing!

All four done.

All four of the edge pieces cut. Those were a pain! And we still had fitting issues so I recut them later.

Shot of the jig and rip saw used to cut the angled table-top pieces.

Dry-fitting of the top pieces. As you can see, lots of errors! Those were fixed-ish later.

Post-fix. Much better! And we can reuse the scrap for joinery. Win-win!

Oh, it was also my birthday today (well, yesterday technically). The big 18!

Friend and I screwing on the shelf pieces for the acrylic. Got the corner-braces attached too.

Top done!

And there's a behind shot! Got the 4 corner braces (going to add some in between them and the corner of the acrylic though). The 4 "shelf" units and the 8 stops for the table-legs.

Stay tuned for more!

 

[tomclancey]

Update! I finally found the time to pickup the parts from my friends house. He's going on vacation and I wanted to get this done while he's away!

The holes in the bottom have since been patched. I'm also going to be sealing the corners with some spare MDF. It's going to be one ugly desk, but functional!

I'm also changing the design to make it more portable. I'm going to cut off the corners of the table top and detach them from each other. Instead they're going to be hinged to the tops of the legs and will swing down to about a 45 degree angle. It'll discourage users from putting their weight on it, plus it'll be much smaller form factor for transportation!

That, and those angle cuts look awful.