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Computers have always had human interface devices (HIDs), but up until the last few years these devices have barely involved the human directly. Direct human interaction with computers is an exciting new trend in computing and entertainment. Touch input has been one of the most integral parts of this computing movement so far; from Microsoft Surface back in 2008 to Apple’s iPhone and iPad in the recent years touch has been shown to be very powerful as a HID. Group collaboration, touch gaming (E.g. Chess, table tennis, etc), media interaction….the applications are exciting and intuitive.




With this in mind, some touch solutions out currently such as Microsoft’s surface are upwards of $15,000 and only sold to certain clients…this brings us to this weekends project: building a windows 7 mutli-touch table for a “reasonable budget” (say under $500 without the projector and computer needed in the setup). The rest of this blog will outline step by step how in 4 days a small group of us put together a multi-touch table.

The Build

Day 0: Research

The first part of any DIY project is research, and luckily for us there is a large and helpful community of people online at NUIgroup.com that are dedicated to building multi-touch projects. The examples, instructions and community on that site helped our efforts tremendously and anyone looking to do such a project should familiarize yourself with those forums.

After some research we determined that we would pursue a frustrated total internal reflection (FTIR) setup for our multi-touch display. The different setups can be found at NUIgroup.com, but the basic premise is this:

  1. Take a piece of clear acrylic with laser cut (clear) edges. This will be your “screen” so it will be the size you want your screen to be PLUS some extra for mounting, which will be explained in detail later.
  2. A projector will project the computer output straight up or bounced off a mirror threw the acrylic.
  3. The acrylic is clear, so a piece of drafting paper or Vellum is needed to project onto. To make a suitable projection surface, the vellum will need to be prepped with a mix of Xylol and Silicon (see step by step below). The vellum will lay on top of the clear acrylic.
  4. The acrylic will be lined on at least one side (we used 3 sides) with infrared light emitting diodes (IR LEDs) whos wavelength is between 840nm and 890nm preferably.
  5. A PS3eye Toy camera will be opened and the IR filter will be remove. Also, a homemade visible-light filter (that only allows the camera to see IR) is placed in the EyeToy. This visible light filter can be made out of film negatives or a floppy discs magnetic tape. The PS3 eye will look up at the acrylic and the projection and look for IR “blobs” from touchs.
  6. A Windows 7 computer will power the IR LED lights and serve as the computer.
  7. The software for the PS3 eye and the multiotouch service will be loaded on the machine.
  8. The FTIR setup means that the acrylic is filled with IR light, and when a touch if pressing down on the acrylic the IR light inside bounces down off the fingertip and down to the modified PS3 eye which now sees the IR “blobs” created from the pressing down of the acrylic.
  9. This visual input is transfered into mouse control via a software driver.

Simple right? Honestly, it is not as bad as it sounds.

Right off the bat, check out the links on our project bookmarking page located here: http://multitouch32.tumblr.com/ . We found these sites to be useful.

Day 0.5: Ordering Equipment

  • (1x) piece of 24” x32” clear acrylic with laser cut sides from  a local plastics shop ( ACI Plastics in Saint Louis) for $94
  • (100x) IR LEDs – 880NM from DigiKey for $49.77 including tax and 2 day shipping
  • (2x) tubes of silicon from home depot for $8
  • Spools of electrical wire about $10
  • Duck Tape for $5
  • Lumber and construction equip (e.g srews) for $90 from home depot including cuts! See construction section for details.
  • Drafting paper (vellum) for $8 from local retailer
  • (4x) casters for $8 from home depot
  • Windows 7 desktop pc – already aquired (retail cost $500)
  • Optoma GT720 120hz Short throw projector – already owned (retail cost $799)
  • (2x*) PS3 Eye Toy for 39.99/each (*bought two in-case one broke)
  • Soldering iron, drill. solder, and other various tools already owned.

Total cost for us was around $350-$375 bucks in total (not including any man hours), but with the projector and PC this project would have cost around $1700 in total (though I’m sure you could find a cheaper projector or at least a better price…same on the pc if you were on a budget).

Day 1: Drafting paper projection surface and IR LED array prep

The first step we decided to take was to prepare the drafting paper (vellum) that our projector would be projecting onto. In order to create a good compliant surface for our projection and for the eventual “blob” shaped IR dots to show up well we need to coat the vellum with coats of silicon. We decided to use 3 coats with about one hour between coats. There are a few methods to achieving this goal; we decided to go with a method that mixed Xylol (a bad smelling solvent) with clear GE silicon from a caulking gun.

First we cut a piece of vellum from the roll we purchased a local hobby store that was larger than the piece of acyrlic (E.g we had a 24 x 32 piece of acrylic, our vellum was about 24 x 40). Then tape the vellum flat to a solid surface you can apply the silicon mixture on (we used a piece of cardboard). Once have have the vellum secure,  mixed a few millimeters of the xylol with about the same amount of clear silicon and mixed the two until the resulting mixture had a normal consistency and a decent viscosity (sorry for being non-exact…you kinda have to eyeball this, but a 1:1 mixture should work well). Once the mixture is ready, quickly pour it on your vellum. Use a NEW and CLEAN roller brush to apply the silicon/xylol mixture evenly across your vellum. Let sit until dry and repeat with a new coat (we used three coats with about an hour between coats).

DIY Multi-touch Table – Making a Compliant Surface – Coat 2 from Larry Stendebach on Vimeo.

While we where waiting for the silicon to dry to the vellum, we worked on creating the IR LED arrays. Because our current electronics knowledge is limited, we decided to go the easy route when hooking up our LEDs.  Each of our IR LEDs uses 1.5 volts, which is nice because PC power supplies like to provide 12V power to devices which is a mutiple of 1.5 (1.5 x 8 = 12). Thus we can simply solder together 8 IR LEDs in an array (soldering cathode to anode) which would need a total of 12V to power (and very little wattage) and this could be hooked up directly to a PC molex power connector using ONLY the YELLOW and ONE BLACK wires. To achieve this, we hooked electrical wire from the ends of the IR LED arrays (one for positive and one for negative per array) and the electrical wire to a molex power to SATA power connector we had lying around and cut the SATA connector off (See Picture). The negative electircal wire was hooked to black and the positive was soldered to yellow. We decided we wanted the IR LEDs about 1 inch from one another and on three of the 4 sides of the acrylic. Thus we would need 3 arrays of 8 on on side and 4 arrays of 8 on each of the other two sides (we where using one short and two long sides at 24 x 32”). To make the soldering easier, we drilled a board with 8 holes that the IR LEDs fit into that were one inch apart.

While 2 members of the team worked on the IR LED arrays, one of us worked on the PS3 Eye Toy camera. To make the PS3 camera only see IR light, it needs to be opened, the IR filter removed, and a visible light filter is inserted (we made from cut film negatives we pictured up from a local camera shop). Removing the IR filter is ONLY necessary on the old PS3 Eyes, the newer models do not have an IR filter apparently.

To remove the IR filter watch this video (via YouTube) below (It is kind a pain):

After about 30 minutes of cutting, we finally managed to pop the IR filter out…but I accidentally scratch the camera lens…badly. We thought this could mess up the entire project, but as it turns out it did not effect our ability to pick up IR blobs.

Once we had all the IR LED arrays constructed we started taping the IR LEDs to the side of the acrylic pointed inward.

By 3AM we where able to place our acrylic and finished vellum with silicon surface on some saw horses and with a PC rigged precariously below we were able to test the IR LEDs shinning into the acrylic and the PS3 eye working well! All and all a great first day!

Day 2: Building the table

At the start of day two we sat down an drew up the design for our table. We knew a few things: We wanted the table to be about 3-3.5 ft tall, the acrylic surface needs to be flush with the tabletop, and that none of us where carpenters so we wanted this to be as easy as possible.

We decided to use only two types of board: Plywood and 2×4 lumber.

The corners of the box would be made of two 2x4s connected to one another, and inside there would be two supporting inner frames, the topmost of which would be about 3/8” down from the top of the table and the acrylic would rest on the interior support (See picture below).

Once the interior supports where in place we drilled the plywood to each side of the table (including the bottom) and then added 4 casters to the bottom to allow the entire unit to roll.

The acrylic was the set on the top most support to be flush with the top of the table.

Day 3: Mount the projector and modified Ps3 Camera

What may seem like simple steps can prove quite challenging. Mounting the projector inside your table is one of the most important steps in the entire project, as the projector has to be positioned correctly to project onto your surface. The projection needs to be at the correct size and angle, and most projectors require bouncing the image off of a mirror in order to achieve the correct throw distance (to get the correct projected image size). Luckily we had a short throw projector and only need about 24 inches to throw the required image for our table.  The projector was held inside the box while on to estimate the mounting location needed. Once the location was marked, hole where drilled into the side of the table where the projectors mounting screw holes where, and screws where used to hold the projector to the side of the table.

We also used duck tape on the inside edge of the acrylic inside the table to eliminate any leaking IR light.

Day 4: Software and tweaking

Finally we had a day to only worry about software. All of the software we used can be found on NUIgroup.com and mainly focused around Community Core Vision (CCV) and Touchlib. You need 3 things to make the Windows 7 Multitouch driver work:

  1. CCV running and calibrated
  2. Multitouch Driver Service
  3. Multitouch Driver Console

Take a look at this video for more detailed information on the driver install and software you need to run. (Video via YouTube)





It takes a bit of time to get the settings in CCV correct, but stick with it.

To learn more about the install process of CCV (or tbeta) visit:  http://wiki.nuigroup.com/Getting_Started_with_tbeta

Areas to Explore:

Exploring how Multi-touch Input and Data

How can MT input help with data visualization and the users’ experience when working on and with data?
Take a look at the following videos. The first is a demo from Nvidia in 2008, the second is from some open source software that seems to be running multi-touch Google Maps with layers. More research is needed.






Look at 2:50 in the video above for Google Maps with Layers

Exploring Multi-touch Chess

One application I would like to focus on is chess. I think there are some very interesting opportunities with multi-touch interactive chess sets, moreover, this setup is already 3D capable…exploration into a 3D multi-touch chess tabletop application is already underway. Expect more video and write-ups soon:


Looking Forward

I will be adding to this post frequently, with more details, new videos, new multi-touch applications and any improvements I make to this particular table. Please leave me any questions or feedback you may have.

-Larry S.