Build Your Own Multitouch Surface Computer
Posted 04/07/09 at 12:00:00 AM by Alex Castle
It all started while we were researching an article on future user interfaces. Touch interfaces are hardly futuristic at this point, but multi-touch hardware like the Microsoft Surface or the iPhone is just starting to become a big deal, and we decided to see what big things are going on in that field. What we found that surprised us the most wasn’t anything about the future of multitouch; it was about something that people are doing right now.
There is, it turns out, a whole community of very smart folks out there on the internet perfecting the art of building DIY multi-touch surfaces. The process isn’t exactly simple, but the results we saw were stunning: multitouch surfaces with responsiveness rivaling Microsoft’s $12,000 offering, built in a garage on a shoestring budget. “Future UI article be damned,” we thought, “we’ve gotta build one of these for ourselves.”
And so we did. We documented the whole process, from start to finish, so that you can try building one of your own, if you’re so inspired. We’re not going to claim to have done everything perfectly the first time, so think of this article as more of a build log than a definitive how-to. Still, we’re very pleased with how the table turned out. We’re so pleased, in fact, that we put together a video showing the table in motion. Check it out, and read on to find out how we did it!
First, some acknowledgments are in order. Virtually all the techniques used to create this table were discovered at the Natural User Interface Group website, which serves as a sort of repository for information in the multitouch hobbyist community. If you find the technology shown in this article interesting, you owe it to yourself to check out their forums, where you can participate in the development of multi-touch hardware and software.
The Theory
Before we can get into the actual, physical construction of the table, it’s important to understand just how it works.
There are several different ways to make a multi-touch surface, but we’ll focus on the one that we employed: the FTIR screen. An FTIR (short for Frustrated Total Internal Reflection) setup involves three vital components: a sheet of transparent acrylic, a chain of infrared LEDs, and a camera with an IR filter. The LEDs are arranged around the outside of the sheet of acrylic so that they shine directly into the thin side surfaces.
Once the IR light is inside the acrylic, it strikes the top and bottom surfaces of the acrylic at a near-parallel angle, and is subject to the effect known as total internal reflection. This causes it to be wholly maintained in the acrylic. This is a little tough to describe in words, so we’ve made a simple diagram:
The net effect of the setup described above is a sheet of acrylic full of internally reflecting infrared light. When a finger is pressed against the acrylic, it causes some of the light to be reflected down, through the acrylic and into the cabinet, where it is detected by the webcam. This effect, called frustrated total internal reflection is a little complicated, and involves something called an evanescent wave, but you don’t really need to understand why it happens, just that it does happen, as illustrated in this diagram:
The webcam, which has been modified to detect only infrared light, sees this reflected light as white spots on the screen; something like this:
From that picture, software running on a nearby computer extracts a map of where fingers have been pressed on the screen, and uses that data to control multi-touch applications.
The Screen
An FTIR multi-touch table’s screen is comprised of three basic components: The acrylic sheet, the LED lighting, and the projection surface. Each one requires a bit of work, so we’ll discuss them one by one.
The Acrylic
The foundation of the screen is the sheet of acrylic which serves as the medium for the infrared light. Why acrylic? Acrylic has several properties that make it a good fit for our project. First, it has the right optical properties, allowing for an excellent FTIR effect. Additionally, it’s lightweight, strong, and very clear (more so than glass).
We constructed our screen from a 24” X 30” X 3/8” acrylic sheet, which we bought at local plastics dealer TAP plastics. Acrylic can also be purchased on the web, although high shipping costs mean that it’s best to try and find a local plastics dealer. For a 24” X 30” sheet, 3/8” is thick enough to prevent any noticeable sagging in the sheet, even when firm pressure is applied to the middle of the screen. A larger screen would, of course, require thicker acrylic for stability.
Most acrylic comes with saw-cut edges, which are rougher and therefore more opaque. Because we wanted to shine infrared light into the acrylic from the sides, we needed to do something to guarantee a clear edge. We had two options:
1. Buy laser-cut acrylic. Most large plastics stores will have the capability to do this, though they generally charge extra. Because we here at Maximum PC always have our mind on our money and our money on our mind, we decided to go with option number 2:
2. Buy saw-cut acrylic, then polish the sides ourselves. To do this, we simply gave the edges a thorough sanding with 200-grit sand paper, then went back over each edge with Dremel rotary tool using the buffer attachment and a polishing agent. This certainly took a little while, and involved inhaling more acrylic dust than is probably healthy, but the result was a nice, clear edge.
Smoothing the edges with 200 grit sandpaper
Polishing to a sheen with a Dremel and buffer bit
Can't get the IR filter out
Submitted by tornato7 on Tue, 08/17/2010 - 5:13pm
Great info on building this, and i am attempting to, but i can't get the darn IR filter out of the PS3 eye lens. I might have a newer ps3 eye? where can i get the old ones? Thanks!
Also, get rid of the advertising replies
Submitted by lowqiumei on Thu, 05/13/2010 - 11:53pm
I am having some problem with the camera's orientation. My LED calibration everything was perfect and alright. But i am having some problem with the camera image orientation. When i open the "demo_smoke" application, after doing my calibration, when i touch on the left on my acrylic, on my laptop it shows that i am touching on the right, how can i flip it?
Submitted by JuliaDee on Thu, 02/18/2010 - 7:46am
Instead of soldering all those LED's you can just wire-wrap directly to the LED leads (assuming they're square or rectangular in cross-section. I wouldn't recommend a hand-wrapping tool, you want an AC-powered gun, or if you can't afford that, a battery-op one. Mouser sells the wire and I think the tools as well. Wirewrap has been around for 40 years and is a great technique but unfortunately has become a bit of a "lost art" in this era of CAD and fast-turnaround PCB service houses.
Submitted by touch screen mate on Thu, 02/18/2010 - 8:29am
Do you know what the wires are for tho what is there aim?
Submitted by touch screen mate on Wed, 02/17/2010 - 11:41am
Hi guys,
im excited at the prospect of making this for my epq on touch screen technology!
I was just wondering what the white wires on pages 1&2 which seem to be attaching the led chain together are for and what way to put them together.
Thanks!
PLEASE HELP =)
Submitted by jersten on Mon, 02/01/2010 - 10:29pm
ok so i am interested in building one and certainly going to start soon as i kinda know what im doing haha but when i get to the computer part, if i use a regular desktop computer from dell...will i be able to operate the regular windows applications like browse the internet and click on the desktop icons and stuff like you would be able to with a mouse or in order to do this do i need to do something special with the table?
Submitted by SCPRedMage on Thu, 02/04/2010 - 5:19pm
The system Maximum PC built did not support using multitouch to interact with normal applications, because at the time, there wasn't any software available to pass TouchLib's data over to Windows.
Of course, time makes all things possible: http://multitouchvista.codeplex.com/
Submitted by Gamgigo on Sun, 07/04/2010 - 12:20am
So then yu can use it with normal windows apps, so go on paint or something? Is there something for Linux to do this (other than running it on Wine)?
Submitted by sparky81795 on Sat, 01/30/2010 - 9:47pm
sorry for the double post, if the ps3 eye can see IR without removing the IR filter, why remove it? does it see a broader range of IR afterwards? i just wonder since i have a ps3 and use my toy from time to time. thank you.
Submitted by kaaden on Wed, 01/27/2010 - 9:50am
i mounted the leds with two sided tape
[IMG]http://img62.imageshack.us/img62/3018/getattachmentaspxay.jpg[/IMG]
but now when i connected all leds in series of 8 and put the webcam below and put the plexiglass plate in it doesn't work. The webcam doesn't see your fingers when you pres on the plexiglas surface but it does see the infrared leds when i hold them above my webcam and they are on. What did i do wrong??
Submitted by matroska on Tue, 02/02/2010 - 11:49pm
Your camera does not see when you press a surface?!
Submitted by robertsimon212 on Thu, 08/12/2010 - 12:47am
It all started while we were researching an article on future user interfaces. Touch interfaces are hardly futuristic at this point, but multi-touch hardware like the Microsoft Surface or the iPhone is just starting to become a big deal, and we decided to see what big things are going on in that field. What we found that surprised us the most wasn’t anything about the future of multitouch; it was about something that people are doing right now.
Xbox Live Code Generator baggy cycling shorts pressure washer polyurethane casting
Submitted by wr31LUCY on Sat, 01/23/2010 - 9:26pm
Some times happens that we would like to know close to this topic and in that situation that is good to find an assistance at the good essay writing services and buy an essay right there.
Submitted by MEC on Fri, 01/15/2010 - 4:50am
steps for the modification of the Molex connector and 12v rail?
Submitted by monitor stands on Mon, 12/14/2009 - 11:04pm
Is there a tripod monitor stand available to have a computer monitor displayed from a high position?
<a href="http://www.colebrookbossonsaunders.com.au">monitor stands</a>
Submitted by Tech Computers on Thu, 12/03/2009 - 7:45pm
Is this software or idea copywrited? waz up?
Submitted by ethereal_fire on Sat, 11/14/2009 - 5:04pm
Would it be possible to do this with a projector like this one:
http://www.costco.ca/Browse/Product.aspx?Prodid=10322635&search=Pocket%20projector&topnav=&Mo=0&cm_re=1_en-_-Top_Left_Nav-_-Top_search&lang=en-CA&Nr=P_CatalogName:BCCA&N=0&whse=BCCA&Dx=mode%20matchallpartial&Ntk=Text_Search&Dr=P_CatalogName:BCCA&Ne=4000000&D=Pocket%20projector&Ntt=Pocket%20projector&No=0&Nty=1&Ntx=mode%20matchallpartial
Submitted by adyrcz on Mon, 11/09/2009 - 4:10pm
What was the part number for the LED's you purchased from Digi-Key?
Submitted by matroska on Wed, 09/16/2009 - 1:15am
Greetings to all))) People, huge requests... Who can help with this question I will is grateful.
Please, who did this project?? Help me!!!
There is any circuit of assemblage of this device? How all to connect?? Many gathered, please help!!!!
Who agrees to me to help, write, here e-mail Vera.krylova@mail.ru
In advance thanks (In advance I apologise - English language I know not so well)
Submitted by Riiich on Thu, 08/13/2009 - 11:41am
PLEEASE post some pictures of inside the box, im having real trouble on where to place the webcam, mirror and projector. or if anyone else knows of any good websites that show this please let me know! Email: AceRiiich@hotmail.com
Submitted by DOS_equis on Wed, 08/05/2009 - 1:01pm
Well it looks like microsoft has a version of this as a prize in a mobile app contest.
Check it out here:
http://www.mobilethisdeveloper.com/?CR_CC=100185013&CR_ID=P100023634799621#meteor=1R7qhtiY4W5
I wonder if someone in Redmond saw this article and copied it for this contest. Looks like a more polished version of the one MPC did.
Submitted by willcapellaro on Tue, 08/04/2009 - 7:51pm
Tell me why you didn't just sand the acrylic?
Submitted by s3kShUn7 on Wed, 07/22/2009 - 11:29am
I'm 15, and after looking for a multi-touch monitor solution and coming up empty, i remembered that I had seen this article's title, and thought I might be able to find a little more info. Now, thanks to you, I have the funding (from my parents) to complete the project. And, I thought I might put up my used parts list, so that other people may get a handle on more compatible divices, and find a solution that works well for them.
Toshiba TDP-ET10U Projector. $375 on Amazon
- Playstation Eye Camera. $40 at bestbuy
- Table Material= Dark Stained Plywood, 3/8in thick. Table Height=2.5ft.
- Acrylic, Laser Cut, Dimensions=33.85in.x19.35in. (16:9 ration matches projector). $62
- Laminated Vellum, from local Art Supply Store.
- Caulk Gun, From Ace Hardware≈ $12
- Narrow Dimmable LED Ribbon Flex by the 5-meter reel (High Density Infared 850nm). $207 from environmentallights.com
- 60 Watt 12 VDC Power Supply. $49.99 at environmentallights.com
- A DEEP Alluminum Shower Door Channel from local store, (midered to make a good frame).≤$100
- A good deal of patience, and roughly $850 available.
- Over 50 hours of thourough research.
Hope this helps some people who weren't sure exactly what to get, or what to do to make it work well. My best advice: Choose the Projector First, and base your table off of it's abilities.
Submitted by touch screen mate on Thu, 02/18/2010 - 8:30am
How did that work out for you? Got any pictures to share with us? ESpecially the inside of the box!
=)
Submitted by matroska on Sat, 09/12/2009 - 1:15am
You couldn't help me? I write from a far city of Almaty, not so well I know English language.
You have written that have collected this device. And how you have arranged chambers? And the Mirror? If not difficultly you can answer here this address vera.krylova@mail.ru
Submitted by argniest on Sat, 07/18/2009 - 1:18am
I have been following the Microsoft Surface computer for a while now. I cant believe you all built this thing in the garage!
Can you please post more specific instructions. I will pay you 100's of dollars if you will do that. And I am sure lots of other people will too.
I want to build one this summer, but I need more detailed, pretty much, step by step instructions. A detailed parts list, sequence to build it, a video of putting each portion of the system together, and more detailed information about the software loading side of thngs.
I have built pc's for a long time. But nothing like this.
This is THE COOLEST THING I HAVE ever seen. I loved the microsoft surface, but what you have done blows that away because of the cost of how you have gone about it.
Submitted by sitting on Fri, 06/26/2009 - 12:56pm
WOW awesome! I will make one of those for my school project. But I wounder how it look like inside the box, make possble to show some pic inside?
Submitted by oceania68 on Sun, 06/21/2009 - 8:47am
This is definately the way of the future in technology. I have been saying this for years... the prospects are almost limitless... Consider space craft... no keyboards no mice less weight, but with all the familars of a computer at home without the bulk.. A star trek initiative. Give it time and incentives from goverments and businesses to developing this kind technology, we could see plenty of these in homes and cars etc... Couple with voice activation recognition software... whoa the ideas flood... You can have all this already .... for a price.... and thats typical... But building your, gives you satisfaction of accomplishment and pride... and when it works, enthusiam. I am going to build one, using the guide shown here, but with my own mods.... for example.. an old video game table (remember the first space invaders machine, something like that would be good.
I shall give it a go and see what happens...
cheers guys and thanks for the information
Submitted by perceptee09 on Fri, 06/19/2009 - 4:54am
It very informative and nice to read
Submitted by Boyobejaminhere on Sun, 06/07/2009 - 9:11pm
Hi,
Im going to build one of these this summer and im a little stuck. As other people have said, this article is vague in some parts and detailed in others. What is missing that i desperatly need are pictures. I need pictures that easily show what goes where, the only diagrams I see show pieces of this device and not where they go. Something else that is missing is (like in other How to articles) the materials guide. After reading it a few times I've got an idea of what I need but im pretty sure there is an item or two missing from my list. So if those could be posted or added in that would be awesome =D
Thanks,
Boyo
Otherwise this is an excellent article and I'm trying to get my school to let us (students) build a few of these for ourselves and for the school =D
Submitted by jameyscott on Wed, 05/20/2009 - 3:06pm
i would so buy one of these please sell them or make kits for us to make them on our own i want one so bad
Submitted by carlosmessi on Sun, 05/17/2009 - 8:33am
Very good and very long article. I like it but unfortunately I don't have time and money to try it. I think if you opt to buy materials online for that project you can find them on Shop Carefully. Good luck in building the table.
Carlos Messi
www.shopcarefully.com baby.
Submitted by patjam on Sat, 05/16/2009 - 11:04am
Hello!
Can you show some photos of inside of this computer?
Yours sincerely
Patryk
Submitted by szore on Tue, 05/05/2009 - 2:47pm
You see a little eye candy and you all cream your pants
Submitted by Boyobejaminhere on Mon, 06/08/2009 - 10:06am
Hey man show some respect. These guys spent two weeks on building this machine (probably even more to plan it all out) and they ended up with a kickass machine. Sure you could probably use some of the aplications on a tablet pc but where is all the fun in that? Why go out to buy a small tablet pc for 3000 freakn dollars when you can build a kickass multitouch surface computer for about $350 plus an old computer? I say this is worth the time, worth the effort (especially when you convince someone to give you community service hours for school to build one of these =D), deserves some respect, and a couple thank yous while your at it
btw: thanks for makin this kickass article =D
Submitted by bmjones66 on Wed, 04/29/2009 - 8:21pm
Are there any pictures of inside the cabinent all put together? I would like to see the mounting of the camera along with the projector/mirror.
Submitted by nsk chaos on Thu, 04/30/2009 - 3:32pm
so i did some (okay maybe a lot) of researching and found most of the parts i needed and a pretty good guide to go along with the project: http://www.instructables.com/id/SCR2H4QF3ER7VQK/ the most valuable part of this guide are the pictures (the catch is a 15 sec registration).
enjoy!!! and good luck too =)
Submitted by nsk chaos on Wed, 04/29/2009 - 7:49pm
i am very curious how you guys managed to get a l * w * 3/8... all i could find was a 24*48*0.220
please help thx!
website for the one i found: http://www.thegreathardwarestore.com/Plaskolite-24x48x-220-Acrylic-Sheet-1AG2196A-p/196843.htm
P.S.: when they say u must order in X4 is this 4 for $54.13 total or 4 for $54.13 each?
P.S.S.: what color led works best? im thinking blue but idk if it matters though...
Submitted by nsvander on Mon, 06/01/2009 - 2:29pm
You have to use IR LEDs, they are the only ones that will work.
In Magazine
Submitted by linkmaster6 on Tue, 04/28/2009 - 5:27am
Hey Alex Castle why not do a full article in Max PC some issue and answer some of the questions we've got about this.
Submitted by qryptiq on Mon, 04/27/2009 - 1:07pm
These LED's may be by far the easiest to install
http://www.oznium.com/led-flex-strips
Submitted by qryptiq on Mon, 04/27/2009 - 12:14pm
From what i understand and on TED.com the Wii remote is infrared ready and cost $39 dollars...
Alex, do you think this would work fine?
Submitted by famiccomputers on Sun, 04/26/2009 - 4:38am
I'm currently studying electronics and think this is a great project. I have read through it 3 times and get most of it apart from one bit in two sections; 1. Where on earth do you get a table of that size made in that same way? Am I meant to build it from scratch? and 2. I don't get where you put the Infra-red leds, do they get soldered and stuck to wood like in p.2 or stuck to a metal strip like on p1 and the bottom of p2? Thanks.
Submitted by drmitch on Mon, 04/20/2009 - 6:40am
LEDs in series-parallel with no resistor? That's bad juju
Submitted by xRadeon on Mon, 04/20/2009 - 7:36pm
What do you mean? I'm not good at all with resistors and things like that. I really think I'm going to make one of these, what kind of resistor would I need and why?
Submitted by radrat on Sat, 04/18/2009 - 6:37pm
I found some simular diodes fo a whole lot cheaper.
here is the link
http://www.newark.com/vishay-semiconductor/vsmg3700-gs08/ir-emitter/dp/31M2973?_requestid=250017
Submitted by xRadeon on Mon, 04/20/2009 - 7:03pm
Good job, I spent so long trying to find good priced IR LEDs, thanks, and I'm pretty sure these will work just fine too. Thanks. Pretty sure at these prices you could have IR LEDs touching each other around the whole edge and not even brake your pocket change.
Submitted by QuadCoreAbe on Thu, 04/16/2009 - 11:40am
....Nerdgasm....
by the way, it would be great to have a checklist of parts and components so that we dont have to read the whole article fifteen times before going to home depot. Thanks
Connect with Maximum PC
|
|
|
|
|
|
|
|
|
Must Read Articles
-
Feature -
Feature -
Review -
Feature -
Feature
This Month's Issue
FEATUREDream Machine 2010FEATUREMatch Wits with the Geek QuizHOW TO Merge Multiple Music LibrariesFEATUREBe an Android Power User!WHITE PAPERAll You Need to Know about HDMI 1.4
Maximum PC on Facebook
© 2010 Future US, Inc. All rights reserved.