During the Xmas holidays, I began construction on the cabinet with my Dad and had a lot of fun doing it. I left it in his capable hands for painting, sanding, and the installation of the interior frame and handles. Here is the result. Looks rather awesome. The height is important as one needs to make sure the camera can see the entire top of the box. Also, there needs to be space for the various electronics that will be installed in the bottom along with a 4 Gang. the height is also just about right for the table to be used standing.
Here is the EyeToy. I used the PS3 eyetoy as it came recommended by the guys on the NUIGroup Forums. It runs at 640x480 at 30fps, has two aperture settings and space for a filter. There is a problem with removing the infrared filter. Most cameras have one and you need to remove it. On my cheap logitech this was easy because it was simply a piece of plastic that fell out. With the Eyetoy, it's a piece of ground glass, set into the plastic. You need to gouge it out and be careful with it too as the lens is right behind it! There is a good video here on how to do this.
You need to get a filter that matches your LEDs. In my case, I bought a small 880nm filter from eBay. I can't remember the guys name but if you search on eBay you'll find a guy in the states who sells these small, round filters for this exact purpose. It works really well. Once you've put that in, you are ready to go.
The PS3 sits on top of the light that came with the LCD panel. Since this light was obviously right next to the LCD itself, you need to extend the cables that come from this light using solder and some extra wire. It is important that when you take apart the panel, you remember which plug goes where. Take photos at every stage!
Here are the innards of the LCD Panel. Some of the wires needed extending also as they tend to be jam packed inside the original Dell Case. They are mounted on some wood except for the light's power supply which I have yet to attach. The more recessed you can make these the better as they will show up on the screen if you don't which makes the effect a bit naff.
On the left, you can see the wires that go up to the LED arrays. You need to link these to an adaptor. Check out old mobile phone chargers as they are dead handy for this sort of thing. For my circuit, I needed a 5V supply capable of around 1.5 amps. I managed to find a charger that did 5V and up to 2 Amps which turned out to be perfect.
This photo shows the annoying, overlapping PCBs that fall on both sides of this LCD screen. This means that about an inch from two sides of the LCD panel are obscured which is very annoying. The only thing stopping this from being fixed is the current configuration of the box and the small L shaped plastic track that links the two PCBs together. If I could get a longer, flat plastic cable I'd be in business. At the moment, it doesn't affect things to much to be fair but it makes calibration with the NUIGroup tool impossible at present. I'll aim to sort it manually.
Here is the top of the table with the lid attached. Looks good no? The plastic came from a place called Barkstons in Leeds. You need to go to their "plastic people" / yellow site as they will do decent perspex cut to any size you like for a decent price, delivered. Make sure you go for at least 8mm (I used 8mm) and have the edges polished. At first I was unsure whether or not this would make a decent wave guide but it appears that it does.
Lots of people talk about Endlighten and other fancy perspex, or a compliant surface made of silicon. I've had no problems with this cheap stuff and ordered two pieces in case one was damaged. Its still all good.
PS. Ignore the thing on the top left of the photo! :D
With the lid off, you can see the LED arrays. They are arranged on the aluminium frames and connected together. The circuit was designed with the help of this handy calculator. Some people link the whole thing up in parallel; indeed, I did this for the first mini table. The problem with that is that it uses a lot of power and needs a heavy resistor. All you need to know is this:
V = I x R
Yup, that good old equation. Checking the RS Data sheet for my LEDs I found that each one requires 100mA and drops 1.5V. That means, with a 5V supply, we can only have a maximum of 3 LEDs in series (1.5 x 3 = 4.5V). Now, to get 100mA over each one we do some maths. V = I x R . Rearrange to get V / I = R . Substitute the numbers: 0.5 / 0.1 = 5 Ohms. What did we do here? Well, we need to go from 5V, down to 0V after going through 3 LEDs. Since each LED drops 1.5, we are left with half a volt to sort out and 100mA of current to send. So 0.5 / 0.1 = 5 Ohms. The closest rated is 5.6 Ohms and you can buy these cheap from either Farnell or RS Components.
I managed to get my Mum, who is a much better solderer than me to do this bit! :P Shrink sleeving and everything. A quality job well done.
You can get a better view of the internals here. You can see that the LEDs line up quite well with the perspex and that is indeed the trick. With all that done, you need to power it up and grab the software from the NUIGroup and play till your hearts content.
This project was a lot of fun and it still isn't over. There are a few funky things I'd like to add, though I need to do some boring things like putting the shelf in and calibrating the screen but there are many other things in the pipeline.
Total costings:
Bandpass Filter from Ebay: £15.17 54 LEDs from RS: £22.46 Perspex Sheets from Barkston - £31.68 MDF, Aluminium Track, Hinges, Drill-bit, Handles - £23.58 Maplin Wire and Solder - £12 RS Components Resistors - £8 PS3 EyeToy from eBay - £20.51 Grand Total: £133.40p
Of course, I had to scrounge the LCD panel and there is no mac mini involved but damn, its cheap! :D
Overall, it was hard to get solid answers on certain questions like "Is this a good wave guide?", "Is the infrared leaking?", "exactly how good is the eyetoy with this?" etc etc. Generally, the best advice is just go for it with the guides and providers I've mentioned and you can't go far wrong. I guess I got lucky with the plastics and the spacings of the LEDs and the filters etc, but generally, it doesn't seem too hard to get a good result.
But of course, no tutorial would be complete without a proper video showing some funky touch software:
Some Resources
The VIRTTable. If you look at no other page, you should definitely check this guy out.
Hak5 On Multitouch. A good overview though they don't go into specifics as they are keeping it hush hush for business purposes (which I've just blown I guess! :S)
