Introduction: Multitouch Display (FTIR)

Picture of Multitouch Display (FTIR)
This Instructable will show you how to turn your lcd projector into an interactive multitouch device.
I spend ~185 euro

may you can excuse my bad englisch ;D

Things you will need:

1 beamer
1 webcam - modified this way
1 mirror
~50 IR-LED's I used these ones
stuff to make the LED's work
for example wires,10 resistors and a power supply unit
1 acrylic glass
1 transparency paper
Things you will need to setup the wooden box ,... for example wood ;D
Power glue ;D I used Patex extreme repair
silicon rubber

other great intructions :
by turkey tek
and Christopher Jette

Step 1: How Does It Work ?

Picture of How Does It Work ?

Basically I'm working with infrared light.
LED's placed all around the acrylic glass 'fill' this acrylic glass with infrared light due to the total internal reflection. If you now touch the acrylic glass your finger reflects infrared light and the infrared webcam will see it. you may take a look at the image below to understand.

picture was taken from here

the picture coming from the webcam can now be read by tbeta or your self-made software ;D
this technique makes it possible to read many user interactions at the same time.

for further information on my setup please see the second image below

1) acrylic glass
2) infrared LED.
3) diffuser
4) mirror
5) Webcam
6) Beamer

Step 2: Assembly

Picture of Assembly

Your setup may be very different to mine
but there are some things that are quite important.

first thing:
the degree between the light that falls on the mirror an the light that is reflected should be as small as possible !
otherwise you may see a green shadow on your display.

next thing is that transparency paper is not cheap but worth it, if you have to buy some sheets take the good ones. but may you can get something from a construction business too.

do also take care of your acrylic glass. you can cut it with any saw you like to use but if the saw blade is to small the acrylic glass will melt together immediately.
and if your edges are not totally clear finish them up with some fire or a hot fan.

Step 3: How to Mount the Screen

Picture of How to Mount the Screen

Just glue everything together until you know how big your screen will be

first layer frotm the top to the bottom is the acrylic glass with the led's
next layer to consist of wood, connecting the led's and the acrylic glass
last layer is the transperency paper

I connected 5 led's in a row with a resistor
and this parralel 10 times. therefore i used 50 led's and 10 resistors with 37,5 ohm
everything ist connected to a 12V power supply

Step 4: Software

You can get the basic software at the tbeta homepage
just follow the instructions given there.
for further informations there is a forum

Step 5: Conclusion

this is a very short instruction
but I am looking forward to add some more pictures of my setup the next days.
may there will also be a better video of my screen in action ;D

If you want to learn more you can visit
turkey tek
and Christopher Jette
their explanations are much more detailed.

please tell me if you also realized your multitouch device ;D


Brian407 (author)2014-01-12

The cost in US dollars is 252.71

horatio cheng (author)2009-08-10

the main idea of this project is to allow the camera to see the ir light spot, so could i just make a stick that emit ir light so i can directly point at the whiteboard rather than making the screen

DustyJK (author)horatio cheng2013-10-05

Try an IR laser
# 4 years late

rahi (author)horatio cheng2009-08-11

Yep but make sure that the windows do not let to much daylight shine on your whiteboard ;D

judecru (author)rahi2009-09-01

sir...i found your project is interesting that's why i plan to make one...but i have a little confusion regarding the way you assemble the leds in connection to the glass...sir can you give some advice or points in assembling this project..thank you

rahi (author)judecru2009-09-01

yes this part isn't very easy I glued the LED's with patex on an piece of wood witch was also glued to the glass ,.. Patex is a very strong glue you can buy here in germany ,.. donno if you can get sth like that but it did a great job in my projekt. But I also heard of some people drilling holes inside the glass. In my case the glass wasn't thick enaugh to place the 5mm LED's inside it but if you can do so it would be much better than glue everything together like I did ;D .

cmorano (author)2013-08-03

hi, i just want to ask if i could use the ordinary webcam for this project? i reviewed some of the projects just like this and they used the PS3 eye. I really want to make this project. thanks. :)

f8ie (author)2011-03-15

hi! probably a stupid question...
but does it matter how thick the acrylic glass is?

mesatactil (author)2010-06-08

Hi, I've Made the multitouch display last year and I didn't use the transparency paper, all worked fine, but the light its very strong, now I'm Trying to make a new one but the problem is that I don't know what paper is it, and it's more difficult because I'm from chile and I dont Know the name in spanish (lol). I don't know if you can take some photos to the paper or a specific description :D, I have seen somewhere else that some people use a paper called greaseproof paper (in spanish is "papel vegetal"), do you know if I can use that paper. Thanks! And in my opinion this is one of the best instructable ;)

rahi (author)mesatactil2010-06-10

Thanks for your kind words trancperancy paper is also called tracing paper you can find a wiki entry here the exact translation into spanish is "la transparencia de papel" am I right ? ^^ think you knew that already but google also calls it Standard Vellum Mainly its used in "oficina de arquitectura" ^^ this google translator rocks xD they use it to live Trace "Calco" ?! ^^ hope I could help you otherwise just ask me again =)

mesatactil (author)rahi2010-06-10

Nice man! thanks, now I understand what paper is it :D yeah, it is very similar to "papel vegetal". Thanks again and I will ask you again if needed :D Bye!

judecru (author)2009-09-09

sir.. how about the term you used , "BEAMER" , what exactly is that..does beamer is same as the projector...if so..sir can you give me some specification regarding it...anyway sir thank you for answering my question....

rahi (author)judecru2009-09-10

yes ,... its a computer / video projektor
it dont have to be very expensive ,... just pay some attention to the resolution
its better to be above 800x600 px ,.. but not necessary

by the way its nice that someone is that intrested in what i am doing ;D

m2father (author)rahi2010-03-09

I bought a USB picoprojector  that is much cheaper than traditional projector but with less resolution as 640x480.

Do you think it is workable with your design ? Please advice.

rahi (author)m2father2010-03-09

I think it will work out as well as with an high resolution projector if you use a good webcam. I am just not sure if your image will look very good.

but you know the "trail and error" concept ;D
work on your design and publish your work when finished. i am very intrested in seeing some pics with an usb projector =D

judecru (author)2009-09-11

thanks helps me alot in this the way, hope you don't mind, i still have some questions regarding the angle between the beamer and the mirror, and the value of the resistor should it be exaclty 37.5 ohm or can i use 38 or 39 ohm..and how about the glass can i use ordinary glass for this project..right now i plan to work using 2ft. x 1.5ft ordinary glass sheet possible for this project? sir..again thank you so much for your patience in answering all my questions

masterpj (author)2009-03-25

How did the webcam view trough the mirror?? In that example a big part of the view is blocked by the mirror above it???

rahi (author)masterpj2009-09-01

that example isn't right at all ,.. I planed to place the webcam besides the mirror. Instead I duct taped it on top of the beamer ;D

judecru (author)2009-09-01

sir...i found your project is interesting that's why i plan to make one...but i have a little confusion regarding the way you assemble the leds in connection to the glass...sir can you give me some advices or points in assembling this project..thank you

horatio cheng (author)2009-08-24

thank for the answer.....

mesatactil (author)2009-08-05

hello, with a group of friends, we are buying the things and we have a question... what color have to be the LEDs??. bye

rahi (author)mesatactil2009-08-10

You have to buy UV Leds ,.. 880nm or sth like that ;D

mesatactil (author)rahi2009-08-10

ok, thanks!

JakeTobak (author)2009-02-15

Very kewl, I've always wanted to make on of those myself. I like your design, makes me want to build a desk with a screen on the side of the table top. I'll be moving soon and I only plan to stay at this next place for a couple months, so maybe when I get settled down I can give it a shot.

rahi (author)JakeTobak2009-02-16

Yes this was my intention too but it turned out to be more like a cupboard than a table ;D indeed this was my fault. I have too much space in there

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