Multi-touch Table

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Introduction: Multi-touch Table

About: Im 17 years old. Member of FIRST robotics and The OLI Hacker space. Currently leading a team converting a wheelchair into a mars rover simulation robot at an explorer post. I love building new things. Please...

Ive looked around for a good in depth instructable on how to make a muti-touch table and I didnt find any I liked. I hope you enjoy making your very own multi-touch table and that my instructions are clear to you. This uses the FTIR (Frustrated Total Internal Reflection) system to track fingers on a screen.

Step 1: Materials

Here is an important list of materials you will need to construct a multi-touch table.
  • Projector (Ebay $70)
  • Clear 100% silicon (Homedepot $5 )
  • Paint thinner (Homedepot $5 )
  • Foam paint roller (Homedepot $2 )
  • Vellum drafting paper (Art supply store $10)
  • Infrared LEDs (Futurlec $15 for 150)
  • Plexiglas (Surplus store $2.25 sq-ft)
  • Angle Aluminum (Homedepot $13)
  • Computer (Had one laying around Free)
  • Web cam (Thrift store $7)
  • Mirror ($5), I used a first surface mirror. This will make it so there isnt any extra reflection in the mirror.  

Step 2: Projector

You need to get a projector with a fairly short throw distance. I got mine off of ebay for about $70 with 130 hours on it. If you already have a projector ready go to projectorcentral and find your projector and use the throw calculator to find the size of your screen and how far away it needs to be. This will be the measurements you will use for the screen size.

Step 3: Modify the Webcam

Most people use a PS3 eyetoy for their webcam the only problem is that there are 2 different models of eyetoys and there very hard to tell apart and one is hack able and the other one isnt. if you go that way here is a website to help you out (nuigroup). To hack the webcam you will need the inside of a floppy disk. This will block out all visible light letting only infrared light in. First you need to cut out the infrared filter. It looks like a small piece of glass that has a red tint to it. Cut out a small square of the floppy disk and put it in the lens. Test the webcam by pointing a tv remote at it and pushing a button.

Step 4: Plexiglas

The Plexiglas will need to be fairly thick for the LEDs to fit into(around 3/8 in). I accidentally got blue tinted Plexiglas but it turned out not to be a problem. I cut my Plexiglas with about a 1/2 in extra on each side to give room for the LEDs and angle aluminum to go around. To cut the Plexiglas I used a table saw which worked great. Make sure to leave the plastic wrap on it until the very last moment!

Step 5: Angle Aluminum

Measure your aluminum to the length of the Plexi and add about 1/8in to it. Mine was 30in by 24in. Cut the aluminum to length using a hacksaw. Now with your aluminum measure and mark every inch along every piece of aluminum. Find the center of your Plexi and add a 1/8in to it for the thickness of the aluminum. Draw a line that high along the aluminum. Where the two lines meet is where you will drill. I used a 3/16in drill bit with a drill press to make the holes for the LEDs. After you drill the holes they will probably have large burrs on the bottom. Use a file or a Dremel with a grinder bit to grind the burrs off.

Step 6: Add the LEDs

The LEDs light up where your finger presses down on the Plexiglas. Now that you have the angle aluminum drilled its time to make the holes in the Plexiglas. Clap the frame together and set up a drill press so you can drill approx 1/4 in down into the Plexiglas. Just make sure the LEDs go all the way in. Once the holes are drilled on all four sides put the LEDs in the holes and solder them together in the schematic you have here is a LED calculator to help with the schematic and power supply. I used a series parallel circuit with 7 1ohm resistors and 1 68 ohm resistor for a 12v power supply. You can test the LED frame by plugging it in and looking at it with the modified webcam from step 3.

Step 7: The Screen

To make the silicon paper I used the Tinkerman method which is mixing paint thinner and silicon and rolling it on the paper. I did about three layers but you can do more. This creates a better connection with the Plexiglas so the infrared light can reflect off the spot you are pressing down on.

Step 8: Box and Frame

This part can be done many different ways. I made a frame that was about two in bigger than the LED frame on each side allowing a half in to cover the aluminum and 1 1/2 in for the wires. I used a router to cut a line a half in from the inside for the aluminum sticking above the Plexiglas to go on.

Step 9: Calibration

Set up the projector and the mirror so it lines up with the screen above. Download ccv for the calibrating and setup for the touch screen. Once its calibrated go to Tuio and find the right software for the computer you have. Tuio allows other programs to use the input of your fingers to move the mouse.I mounted the webcam on the top of the projector at first but there was some weird reflections so i angled it on the side of the box. Depending on the calibration of ccv you can have it very sensitive (tracks very light touches) or less (makes it so you have to push harder).

Step 10: Conclusion

This is a fun toy to mess around with and a great way to show off your to all of your friends. I hope you were successful in your project. I hope to see how all of yours turned out, Thank you.

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    57 Comments

    Dear All!

    Please help us :)

    We try to create a round shaped touch-screen bar-table.

    We tried to follow the instructions from these links:

    http://sethsandler.com/multitouch/

    http://wiki.nuigroup.com/FTIR

    http://sethsandler.com/multitouch/dsi/

    what/how we did:

    860mm diameter, 10mm thick, round shaped plexiglass / 30pcs IR LEDs on sides (in circle surrounding)

    The web camera is 85cm down from the plexiglass
    We experienced good results in recognition, as long as there is no movement.

    When we are moving our fingers, there is no detection. (only when the fingers are still, there is recognition)

    Later we did silicone coating (FBS + xylene). The silicone layer is only a few milimeters thick.

    No significant change (maybe a little result on moving fingers), but the silicone layer is adhesive (picks up dust and dirt) and it wears out fast.

    Then we tried to put a very thin rear projectile film on the silicone coating. (like this MACTAC: http://www.mactac.eu/products-glassmovie-1-2362--2363.htm)

    No significant change happened.

    Can you please help us to create a working touch-screen table? We did everything like we read on forums/blogs...

    What could be wrong ??

    Thank you very much for your help.

    Tamas Gossanyi / Budapest / Hungary

    2 replies

    sir please help me i working on above project.

    so help me.

    can u give me your mail id

    harishkumarvaghela87@gmail.com

    please send me on my mail id

    Is the silicon layer facing up or down? It sounds like your placing it silicon side up. It should be contacting the Plexiglas and it is normally not removed. It could also be the settings on ccv it takes some time adjusting it to work properly. I hope this helps and good luck with your project.

    I am really confused about the LEDs. What do you plug them into, how do you connect it to the computer, how does it even work?

    Thanks

    What were the specifications on the mirror? Should it simply match the size of the screen? Also I am confused as to its purpose, can anyone explain it?

    Is 'Vellum' the same thing as tracing paper (in UK) - as in - translucent paper - partially see-through, which is good for back projection? how do you prevent the paper cockling with the dampness of the silicon and pain thinner? yours looks quite good and flat. Thanks for a great tutorial

    This looks like a great project, well done ! I wondered, - do you think it would work using droplets of water to sense areas on the screen - instead of fingers? (with a waterproof coating on the paper) - or does it need to be something opaque - or with pressure applied? Thanks!

    Nice tutorial. I'm trying to understand this. Would it be possible to used the setup for the LED and RF sensors on a flat screen LCD tv or monitor? I have a glass desk and I was thinking of mounting a monitor underneath it. The sensors would be on top of the glass.

    what is the size of the plexiglass?

    very nice planning on making one soon

    Hi, great project, congrats!

    I´m planning to do something like your table, but detecting objects instead of fingers, do you think is possible? I want to put a PENCIL on table (for exemple), and my software will detect it, and project on the screen a figure of a desk... If I put a FORK, my software will project a knife and a plate on side... Is it possible, do you think?

    1 reply

    I know you can but you will need a different set up than the one I'm using. Try looking for rear DI touch screen. Its a bit harder to make but it is doable.

    I found some scrap that was big enough from a surplus store around where I live. I dont know where you would go to find the right size.

    Another question! In materials it says that 150 IR leds are $15. I wanna know if you actually used all 15 leds.

    Thanks!

    I used a total of 100 LEDs but I knew some would break so i got a few extra.

    I love the project, I may attempt to build one in the spring after I pull together the pieces.

    In hindsight: Is there anything you would do to improve the result of your project?

    The photo looks like the text on the screen was blurred is it just a bad photograph or an effect of the silicon application?

    Have you attempted to use a keyboard app on the screen? How did it work out?

    How much delay between press and system response occurs?

    1 reply

    When making yours just make sure to check your measurements and make sure they are right. Measure twice cut once. Another thing is to angle the web cam off to the side because this light blob was reflecting down from the projector making it all weird. The photos I took with my Iphone so there not the best quality but it displays just fine. I haven't used the keyboard app but I don't see why it wouldn't work. There isnt a noticeable delay in the response but that also depends on the quality of your computer. I would love to see how your project turns out. Feel free to ask me any question if you have any.

    It was around $200 but i got a lot of my stuff used and really cheap.