Build Your Own Multitouch Surface Computer
Posted 04/07/09 at 12:00:00 AM by Alex Castle
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The Lights
The array of infrared LEDs is what floods the acrylic with light and creates the vital FTIR effect. The exact construction of the array can differ greatly from one table to the next: which LEDs to use, how far apart to space them, how many sides of the screen to wire were all variables we had to consider. For our table, we decided to cover all four sides with LEDs spaced just a little more than an inch apart.
Like with the acrylic, there is an easy way and a hard way to connect the LEDS. The easy way is to buy premade infrared LED ribbons. Right now, the only source for IR LED strips that we could find was a company called Environmental Lights. These strips can be installed around the edges of the acrylic using an aluminum channel such as this one. Both the Ribbon and the channels run on the pricey side.
The hard way is to buy LEDs in bulk and solder them yourself. Once again, because we were committed to putting this project together on as tight a budget as possible, we opted to go for the cheaper option. We bought 110 IR LEDs (850nm wavelength, not 940nm—it’s easier for the camera to pick up) from www.digi-key.com for about 40 bucks, and whipped out the old soldering iron.
Now, we won’t lie to you, readers; soldering and wiring the LEDs was a pain in the ass. Not only is soldering 96 LEDs together tedious to begin with, but the LEDs’ leads had an unpleasant tendency to break under even slight force, requiring quite a bit of LED repair work. Also, even though our table worked just fine in the end, we would probably try to use even more LEDs in a future build. Because the premade ribbons pack more LEDs per inch and are much easier to use, we would probably go with those the second time around.
Because the voltage drop across each LED is 1.5V, and we’re using a 12V rail from a PC power supply to run them, we soldered the LEDs in chains of 8 (for a total 12V drop), then wired 12 chains up in parallel (leaving us with a handful of spare LEDs, which is absolutely vital). To make it easier to solder, we drilled 8 holes in a line in a piece of scrap wood, just big enough to hold the LEDs in place as we soldered them together.
There are different ways the LEDs can be mounted around the acrylic. Some people choose to drill holes into an aluminum or wood strip in order to make a frame to hold the LEDs in place. Since we were committed to doing things on the cheap, and also on a very tight schedule, we simply used electrical tape to hold all the LED chains in place, three on each side, shining into the acrylic. Sure, it’s not the prettiest solution in the world, but it was effective, and because the outer two inches of the acrylic are covered by wood, the tape doesn’t show up on the finished screen.
The Surface
Now we’ve got our acrylic, and the LEDs are set up to shine into it, but our setup has still has two problems.
For one, acrylic is very clear. More so than glass, even. This is nice if you’re building a window out of Plexiglas, but it also means that if we tried to project onto the acrylic the light would pass right through. To solve this problem we’re going to use a sheet of drafting vellum, which is essentially a high-quality, durable tracing paper. This will act as a reasonable projection surface, and is fairly cheap. We got a 36” by 24” sheet for about 5 bucks at San Francisco art supply superstore FLAX. If you don’t live near a huge art store, you might have to do some calling around to find a sheet, or you can order them online, usually in somewhat larger quantities.
In our experience, the vellum worked very well as a projection surface, but gave the surface a distinctly "papery" look and sound, and it was sometimes difficult to make it lay flat. In a future revision of the build, we would like to experiment with having the vellum laminated before using it as a construction material.
The other problem with the acrylic surface isn’t really noticeable until you turn on the lights and camera and watch what happens when you actually touch the screen. On the bare acrylic, or the acrylic with the vellum, pressing your fingers down causes the FTIR effect to occur, reflecting light into the camera. However, if you try dragging your fingers on the screen, the effect gets much weaker, or disappears completely. To solve this problem, we need to create a “compliant surface” to enhance the FTIR effect. We made our compliant surface out of silicon sealant.
When it’s spread on with a foam roller, the silicon creates a thin coating of “microblobs,” with a very rough, rubbery texture. This is ideal because it allows the vellum to lie lightly on top of the acrylic, silicon side down. When you press down on the vellum sheet, the silicon squishes onto the acrylic, momentarily bonding with the surface, which alter the way light bounces around inside the screen and allows more to escape down into the camera.
To create the compliant surface, we first taped the vellum to a flat surface with painters tape, then applied silicon onto the sheet with a caulk gun in a loose grid. After that, we quickly used a dense foam paint roller to spread the silicon evenly across the vellum. We waited about an hour for the silicon to set, then repeated the process. We waited another hour, then applied a third and final layer. As an experiment, we also readied an additional sheet of vellum with only a single coat of silicon. During our testing we found that the 3-coat compliant surface created a dramatically more responsive surface.
Would it be possible to do
Submitted by ethereal_fire on Sat, 11/14/2009 - 4:04pm
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
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Submitted by adyrcz on Mon, 11/09/2009 - 3:10pm
What was the part number for the LED's you purchased from Digi-Key?
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How all to connect??
Submitted by matroska on Wed, 09/16/2009 - 12:15am
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 - 10:41am
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
MS version
Submitted by DOS_equis on Wed, 08/05/2009 - 12:01pm
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 - 6:51pm
Tell me why you didn't just sand the acrylic?
Submitted by s3kShUn7 on Wed, 07/22/2009 - 10:29am
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 matroska on Sat, 09/12/2009 - 12:15am
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 - 12:18am
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 - 11:56am
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 - 7:47am
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 - 3:54am
It very informative and nice to read
Submitted by Boyobejaminhere on Sun, 06/07/2009 - 8:11pm
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 - 2:06pm
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
Very good
Submitted by carlosmessi on Sun, 05/17/2009 - 7:33am
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 - 10:04am
Hello!
Can you show some photos of inside of this computer?
Yours sincerely
Patryk
Submitted by szore on Tue, 05/05/2009 - 1:47pm
You see a little eye candy and you all cream your pants
Submitted by Boyobejaminhere on Mon, 06/08/2009 - 9:06am
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 - 7:21pm
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.
so i did some (okay maybe a
Submitted by nsk chaos on Thu, 04/30/2009 - 2:32pm
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 - 6:49pm
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...
Blue Wont Work
Submitted by nsvander on Mon, 06/01/2009 - 1:29pm
You have to use IR LEDs, they are the only ones that will work.
Submitted by linkmaster6 on Tue, 04/28/2009 - 4:27am
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 - 12:07pm
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 - 11:14am
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 - 3:38am
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 - 5:40am
LEDs in series-parallel with no resistor? That's bad juju
Submitted by xRadeon on Mon, 04/20/2009 - 6:36pm
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 - 5:37pm
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 - 6:03pm
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 - 10:40am
....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
Submitted by comptech08 on Tue, 04/14/2009 - 7:44pm
I am looking at parts and I have a question. Could I use a pico projector? I notice they have low lumens, is that going to be a big facter if the lights in the room have to be on or off?
Submitted by s3kShUn7 on Wed, 07/22/2009 - 9:55am
Go with the TDP ET-10u. Extremely Short Throw Projector
Submitted by I8NY on Sat, 04/11/2009 - 4:33am
This is fantastic! Thanks MaximumPC. I have an 11 year old non-verbal Down's son who is slowly learning to use a touch screen on a conventional PC, but his motor skills are poor and it is still difficult and he gets frustrated. This large format may be just the ticket for him. My three year old Daughter would freak, too! I think I have enough skills to build this if I can manager to scrape up the $ for all the parts.
I also rely on MaxPC for the best of the best freeware - you guys are awesome! Thanks again.
Submitted by Mr_Gone on Fri, 04/10/2009 - 7:42pm
After falling in love with this video... i was wondering can i mix/match methos of doing this?
i want to mix the LLP method with LLP and RDI (FDI) methods.. (laser lights VS rear or front diffusion)
but would that even work..
Submitted by jeremfromfrance on Fri, 04/10/2009 - 2:12pm
I guys ! I'm trying to build that wonderfull stuff with one of my friend ! it's just awesome!
could it be possible to run 3 or 4 or much tables with only one OS?
Submitted by s3kShUn7 on Wed, 07/22/2009 - 9:57am
Submitted by lbclofy on Thu, 04/09/2009 - 8:17pm
would you be able to use a rear projection screen tv instead of a projector?
Submitted by Devansh on Thu, 04/09/2009 - 7:59pm
Hey ppl. i must thank Maximum PC for their efforts on this remarkable machine. I am planning to make it as my Final year project at School. Can you guys tell me where you got the applications you have shown in the video as well as the bonus section?? thanks a ton. and once again, a great job!!
Submitted by MAJORzer0 on Thu, 04/16/2009 - 12:43am
The links are included into the article.
This is a great bit of fun. I wish I had the time to tinker with it.
~No one said it would be easy....they just said it was worth it...~
Submitted by linkmaster6 on Thu, 04/09/2009 - 9:50am
Love the idea of this project and so do the guys I work with but I've noticed a couple things that are missing that would be nice to see.
First would be how the LEDs are connected to the acrylic. Looking at the steps I see the LEDs being soldered together from in hole in a board but a in later shots of the acrylic it looks like they are embedded or stuck to it.
Second would be the position of the camera. Call me stupid but is it suppose to be set like the leds? underneath looking up at the acrylic?
Third would how the projector is mounted, where the mirror is set. Is it hung dead center looking down at the mirror? A model of the projector would be nice, that way others would know what to look for.
Fourth. More specs on the computer used would be nice, such as OS, videocard used, PSU Wattage
Well thats the end of my rant. My boss has been looking to do something likes this for our store.
Submitted by robtom on Thu, 04/09/2009 - 7:51am
no that is using it as something else it doesn't link to your computer as a camera it becomes an HID which is Human Interface Device. I did that project too.
Submitted by nsk chaos on Wed, 04/08/2009 - 5:45pm
i think i had an orgasm when i first read this lol =) its good to know that DIY touch screen is within my budget hahahaha.
great article ++rep to MPC
What about the Wii Remote?
Submitted by winmaster on Wed, 04/08/2009 - 2:52pm
You guys went through a lot of trouble to build a touch screen when you could have just used the camera on a Wii Remote and an IR light source. You don't even have to actually buy a Wii, you can just connect the Wii Remote to the PC using Bluetooth. More info here:http://www.youtube.com/watch?v=5s5EvhHy7eQ.
--------------------------------------------------------------------------------------------------
The quick brown fox jumps over the lazy dog.
Submitted by ccshou on Wed, 04/08/2009 - 11:30am
I think I would need one whole year to build one for myself lol.
Hope to see it on market with reasonable price soon.
Submitted by robtom on Wed, 04/08/2009 - 6:26am
Actually with FTIR it works quite well. There is also a way to do it without using custom IR LED strands. IR lasers are possible one of the neatest ways to do it. My friend made one and with it you don't really have to worry as much about the room being dark and having no lights on. The lasers are so bright that they pretty much block the effects of ambient lighting.
Submitted by Paulfo on Wed, 04/08/2009 - 6:49am
That's cool. Do you have a link to the laser parts used?
Thks!
Paul
wotudo.net
Submitted by Paulfo on Wed, 04/08/2009 - 6:07am
I recently showed my mutli-touch machine at Maker Faire UK.
Rather than using FTIR I used the rear IR diffused method. This required no custom electronics because I used the CCTV IR illuminators as my IR source. I then modified an Xbox Live Camera to have a IR Band filter and then it was just the table I had to build. I did the whole thing for less then £90 (so about $140) because I had the Xbox camera (but almost any web cam will do) and I borrowed a projector from work!
I made a video of it, you can see how I put it all together at http://www.youtube.com/watch?v=izwb_uCitxU
I also used an multitouch application built by members of the NUIGroup with XNA. This gives a great user experience - very Surface like :-)
Its all in the video so please take a look! My blog has more details - I'd be happy to help others looking at doing this sort of thing so ping me if you need help!
Paul
wotudo.net
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