Introduction: Multi-touch Table

Picture of Multi-touch Table

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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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.

Comments

Amphibion04 (author)2016-07-07

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

hulenc (author)2015-10-14

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?

kathyhinde (author)2015-04-14

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

kathyhinde (author)2015-04-14

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!

velez9658 (author)2015-01-15

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.

marcosb2 (author)2014-11-17

what is the size of the plexiglass?

comins (author)2014-05-08

very nice planning on making one soon

tomibudapest (author)2014-02-24

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

2bigbros (author)tomibudapest2014-02-24

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.

rroglio (author)2014-01-28

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?

2bigbros (author)rroglio2014-01-28

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.

fmfootball38 (author)2014-01-12

Where did you find the plexiglass?

2bigbros (author)fmfootball382014-01-13

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.

fmfootball38 (author)2bigbros2014-01-19

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

Thanks!

2bigbros (author)fmfootball382014-01-20

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

SirRahKnight (author)2014-01-13

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?

2bigbros (author)SirRahKnight2014-01-14

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.

bertwert (author)2014-01-13

How much is the final cost?

2bigbros (author)bertwert2014-01-13

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

ile (author)2014-01-03

Nice work. You forgot to mention the mirror on your list of materials. Did you use a regular mirror? If you did, do you have a double reflection on the image?

2bigbros (author)ile2014-01-03

I could of sworn i put it in there. Well Ill make sure I put in there.

aternes (author)2014-01-02

Great instructable! am I right in thinking that the "throw distance" of the projector dictates what height you create the surface at?

2bigbros (author)aternes2014-01-02

yes i have a link in my instructable where you can choose your projector and calculate the throw distance.

akatzbreaker (author)2014-01-02

At the last step, what should I download from the TUIO Website?

2bigbros (author)akatzbreaker2014-01-02

it depends what you want to use it for but in general go to the bottom at the Input bridges and get the multi touch visita.

A P3RS0N (author)2014-01-01

After just playing Frozen Synapse, I can only imagine how interesting playing a game like that would be when the other person is sitting across from you.

ToolboxGuy (author)2013-12-31

Nice build! I have to agree w/ lurkingdevil that we could all use a bit more detail on the build itself.
1) How/where is the webcam installed in the unit?
2) Is TUIO doing the translation from what the webcam "sees" to x,y coordinates for input?
3) Are the IR LEDs just being used for the lighting to show where the touches are occurring, or are they somehow mathematically included as relative positions?
4) More about IR - is it reading a change in "shape" of the plexiglass, or temperature changes? I'd hate to put down a cup of tea on this and WHOOSH! 3,287 unprintable symbols are instantly typed.
5) how well does this work with tasks like sliding/scrolling?
6) how much pressure is applied to be identified as an action?

2bigbros (author)ToolboxGuy2013-12-31

Oh sorry, I forgot to add that. Ill update the inscrutable with more info.

ToolboxGuy (author)2bigbros2014-01-01

LOL! Making the inscrutable more like an instructable!

beowulf_ (author)2013-12-31

Cool project, but you lost me at, "floppy disk." It's not listed in the parts list, and there are a couple of formats of "floppy" disk. The first generation is the original, thin, black, actually "floppy" disk, and the second generation were the smaller, rigid plastic shell (unfloppy) type with a metal shutter. I don't recall either type having any kind of lens built into them since they were magnetic media, not optical. Can you please clarify on exactly why type of disk is needed and, in this age of everything is downloadable, where one can be found? Thanks for trailblazing such a great DIY project!

beowulf_ (author)beowulf_2014-01-01

Thanks guys. Understand now. Would've never guessed that floppy disk media can be used in this way!

yellowcatt (author)beowulf_2014-01-01

The magnetic media is being used as a cheap IR-pass filter.

https://www.instructables.com/id/Poor-Mans-Cell-Phone-IR-Filter/

2bigbros (author)beowulf_2013-12-31

I found mine at my school they had lots of extras. Try finding one at a thrift store or computer store.

2bigbros (author)beowulf_2013-12-31

Im not very familiar different types of floppy disks but I used a 3 in floppy disk. I think most floppy disks have the plastic middle part you use for the lens for the webcam. Ill add a picture of it.

Marik I. (author)2014-01-01

What can you use the multi touch table for?

2bigbros (author)Marik I.2014-01-01

You can use it for displays or just something fun to use to surf the internet or play games. Here is a video of someone playing star craft on one (http://www.youtube.com/watch?v=TEt7R6Jn2mQ)

mhjii (author)2014-01-01

could you use irled strips I feel like that would be a faster method than soldering up an ungodly amount of leds

2bigbros (author)mhjii2014-01-01

Yes you could but its a bit more expensive and you would have to polish the edges of the Plexiglas. I was on a budget so I used LEDs but a LED strip would be a lot easier.

davyrob (author)2014-01-01

Excellent project - very nicely engineered and a great way to build the screen. May I suggest that anyone looking should read this http://wiki.nuigroup.com/FTIR on how the tech works.

lurkingdevil (author)2013-12-31

This instructable is more about building it but no information on the technology behind it and how it works.. Its an interesting project but lack of detail..

spikec (author)2013-12-31

Wow, this is one badass project. Awesome!

1littlebros (author)2013-12-31

Thats my bro yea it is really cool. You should make.

2bigbros (author)1littlebros2013-12-31

Yeah... Thanks for the comment little bro.

Mokeymark (author)2013-12-31

This is a great project! I wish there was a lot more detail. Does this work with Windows 8? I didn't see any screen shots with an actual OS in use. What is Tuio? What operating systems does this work with? Thanks!

2bigbros (author)Mokeymark2013-12-31

It does work with windows 8 but im not sure how it works with the windows 8 gestures. Tuio allows programs to use the inputs from ccv. On the Tuio web sight there are many different programs to work will all sorts of OS.

danzo321 (author)2013-12-31

Could you explain to an old guy, what a multi-touch table is and does? Thanx!

2bigbros (author)danzo3212013-12-31

It uses a modified web cam to track fingers on a surface and it uses those inputs to control the mouse. Its a easier way to make a touch screen.

strongman98 (author)2013-12-31

Ok thanks!!

ssamc (author)2013-12-31

Nice job, congrats

strongman98 (author)2013-12-30

This is so cool!!! About how much did it cost!?

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Bio: 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 ... More »
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