Mini-Multitouch Interface

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introMini-Multitouch Interface

This Instructable shows you how to create a mini-multitouch interface out of simple parts you can order online or purchase at a typical construction/hardware store.

Multitouch interfaces are surfaces that can register multiple 'touch points' at the same time,
meaning users can use natural hand movements to manipulate digital objects. Most multitouch systems also project the screen image onto the touch surface, making interaction more intuitive.


Since big multitouch systems are expensive to build, this instructable teaches you how to build a simpler and smaller multitouch system for $50-150 using easy to find parts. A Mini-Multitouch.

Mini-Multitouch works by the same principles as larger systems, and is handy for all sorts of hack-ish or art-ish uses (think fingerpainting, music-by-touch, or other gesture-based interactions).

This Instructable is being submitted as part of the "Win a Laser Cutter" contest on behalf of Make:Philly, in the hope that we might be able to kick off the creation of our new community workspace with the introduction of a shiny new laser cutter :)

Enjoy!

Difficulty: Intermediate (or intrepid beginner). Requires basic knowledge of soldering, use of hacksaw and utility knife, software installation, and following software tutorials. Passing familiarity with these topics and a willingness to learn will get you through this Instructable!

Build Time: 8-10 hours for an expert in above topics; 16-20 hours for beginner/intermediate.


Mini-Multitouch Interface
vvvv_final.JPGmulti_final.pngmini_final.png

step 1Parts and preparation

Step one: get your parts! Below, you will find recommendations on where to purchase items from the materials list. Tools: hacksaw knife cordless drill and drill bits…

step 2Prepare the webcam to detect infrared light

This step describes the setup of the webcam used to record the blobs of infrared light emitted when you touch the touch surface. This mini-multitouch display relies on…

step 3Build the touchsurface frame

This step covers the building of the frame that will house the Lexan, as well as the preparation necessary to mount the LED lights in the frame. The best material I foun…

step 4Prepare the Lexan touchsurface

This step covers the sanding and polishing of the Lexan touchsurface, for maximum light distribution. To get the most light into the touch surface, one of the 8-inch edg…

step 5Fit the frame to the touchsurface, mount the LEDs

This step covers the installation of the Lexan touchsurface and LED lights into the frame built in Step 3 of this Instructable. Before permanently affixing the frame to …

step 6Wiring the LEDs

This section covers all of the wiring you have to do, and covers connecting the LEDs to a power source. We recommend using 1.5 V 100 mA LEDs, and for the purposes of thi…

step 7Finish the touchsurface, position the webcam

This is the last step in the hardware build. Some light from the LEDs will tend to glow upwards and downwards instead of directly into the Lexan, and that extra glow (li…

step 8Set up vvvv toolkit and play!

This final step describes the software setup used to interact with your multitouch display. Now it's time to start using your new mini-multitouch system! The easiest wa…

46 comments
Oct 17, 2007. 7:08 PMmuthukumaran_msays:
Please let me know the size of the sheet, thinkness, length and breath.
Jul 10, 2008. 9:31 PMEarl Jr.says:
Sheet size is limited only by the brightness of the light source. As for thickness, I've heard 1/4" works the best.
Jun 30, 2008. 6:20 AMsambam2006says:
For the people who are after IR leds then go here. I got mine from there. They come in strips. Easy installation took me five minutes. Shipping takes over a week. Contact him and leave him a message of your requirements etc.

http://youshare.co.uk/iphoneworld/form1211626325.php
May 29, 2008. 4:32 PMfangtasticsays:
the download is working it's just being renamed weirdly, right click and do a 'save link as' or whatever your browser has as a similar option.

it will then give the file name as 'FH1S374F3KMNVOY.tmp' just go ahead and save to the desktop, or note where you saved it to.

when its downloaded just rename it to Touch_demo_3.v4p and you should be good to go :-)

Also many thanks for the instructible it's fascinating how many ways people are going about this, I had contacted a london based company that specialises in bar's to try and buy their system but their customer service has been so poor, I decided to research further and found this and many other far more exciting ideas. It's not so difficult and I'll get exactly what i want, so now instead of buying I'm going to build!!!

I'm off to the shed, and I won't be back till breakfast :-D
Apr 25, 2008. 2:49 PMStrangeRoversays:
I may be wrong, but couldn't you now use the Wii remote in place of the video camera? (a la Johnny Lee.)
Mar 22, 2008. 11:57 AMimarzoukasays:
Use this led calculator to calculate the resistors you will need for your ir led array
http://ledcalculator.net/
Mar 19, 2008. 1:46 PMjak06says:
what works better? lexan or acrylic
Nov 23, 2007. 2:26 PMefkosays:
very nice! i've got a questions...
1) how about latency/responsiveness of such a thing... can it be used for real-time live music, for entering beats, controlling effects etc.?
i'm considering building it, but maybe it want perform enough for what i would use it...
2) are there some requirements for lighting? that is can it be usable under any lighting condition? what about some club interiors, sometimes they love to use these UV lamps, do you think it can affect this somehow?
Nov 24, 2007. 12:45 PMFarMcKonsays:
There is low latency on this, it's only limited by how fast your PC can process the video. IT should do OK under black (uv) lights, but it does not do so well in light that has a lot of Infra-red (ie, bright dayligt, outdoors). I hope that helps
Nov 25, 2007. 3:26 AMefkosays:
Thanks! Though don't know what "low" exactly means:-) It's clear, that the processing machine probably won't do much more useful stuff then multitouch handling... But that could be OK. Anyway thanks for nice guide!
Jul 15, 2007. 11:50 AMjak06says:
(removed by community request)
Jul 15, 2007. 1:55 PMFarMcKonsays:
t can be done cheaper, but my costs were
Webcam - $70
Lexan and misc. parts - $30
IR lens & electronics- $20

You can get an OK webcam for about $30, but the other costs are pretty constant.

This was built as a demo for doing a full multitouch display, with projector. I thought the other project was a lot of 'what I have' and I wanted to do something more 'how to make one'.

I'll be doing a full build for a 30x28 in. mulitouch table with projector over the next few weeks, and I hope to have the instructable for that done in a month.
Oct 22, 2007. 7:56 PMRiddleOfSphinxsays:
Wow, not bad, affordable enough for anybody to make...I like it :D !!
Oct 21, 2007. 1:10 PMlegsmacgeesays:
I got a decent webcam for 12 dollars. You don't need amazing resolution for this project. If you get it on ebay, etc., I'm sure it can go down even from there. Otherwise, the cost of parts depends on what you already have, and what you can get cheap/free from other people.
Oct 19, 2007. 12:29 AMnuimansays:
Check out http://nuigroup.com to learn more :) great tutorial thanks!
Oct 3, 2007. 1:24 PMshadowsrevengesays:
When modifying the webcam is it possible you could brake the computer?
Oct 4, 2007. 6:50 PMFarMcKonsays:
Not at all, there is 0.001$ chance of breaking the computer. Even if you work on it plugged in (DON"T do that) you would at most ruin the one USB port you are plugged into.

Now, having letting something fly across the room because you were prying too hard, that is possible. Don't work on this right next to you LCD monitor, for example.
Sep 13, 2007. 3:24 AMdigilevisays:
HI FarMckon,
this is a very good instructable, however i`ve some questions.

1) can i see my desktop on the table top?
2)shouldi run vvv together with the appz i want to manipulate(ex. photoshop)?
3) can u give us a demo video in manipulating some popular appz.

thanks. more power to you

cheers
Sep 6, 2007. 5:37 AMJ50Nunlimitedsays:
so with this handy stuff i can like control my computer? like something i can use during a powerpoint presentation to control the pc without walking back and forth? and will more LEDs increase performance or accuracy? how many should i use?
thanks
Sep 6, 2007. 5:06 PMFarMcKonsays:
Yes, using this you can control you PC, but not a 'walk away' type of thing. It's like a homebrew Lemur Pad.

For my 8in x10in demo, I used 5 LED's and it worked great. An LED every 2 inches or so works for small boards, I can't recommend something for board over 15in or so, since I've not built one yet.
Sep 7, 2007. 11:01 AMJ50Nunlimitedsays:
what do you mean by "not a walk away type"..."homebrew"?? does this mean like i CANT use the touchscreen to click the start menu and stuffs?
Sep 9, 2007. 9:29 AMFarMcKonsays:
I mean that your hand has to be in contact with the touch surface to use it. You can't wave your hand a few feet away and have it accept commands. If you are using it in a projector room, you would need to have a long USB cable connecting your touch-box (sitting next to you) to the computer/projector you are using (sitting somewhere else).

In this case "Homebrew" means it works similar to a commercial product, but it's built at home a lot cheaper. In this case, it not as good quality as the commercial product either.. You can use it to click start, etc, but it's more useful for situations that need multiple inputs at once. Such as playing digital piano/keyboard, various video games, etc.
Sep 11, 2007. 3:08 AMJ50Nunlimitedsays:
thanks!
Sep 5, 2007. 12:36 AMNeodudemansays:
lol. icanhascheezburger?
Jul 11, 2007. 5:00 AMcheesemaker101says:
hi how do you power the LEDs becaue i attached mine to a 1.5v battery and they blow up
Aug 22, 2007. 12:32 PMaskjerrysays:
An LED is designed to run at a certain voltage and to draw a certain amount of current. If you exceed this rating it will overheat and burn out. When you get your LEDs they will have a specification sheet usually on the back of the package, or you can look them up online.

Let's say that your LED runs on 2.2vdc and is supposed to draw 20mA of current. (That's 0.020 amps) So... how do you connect it without it blowing?

Let's say you have a 5 volt power supply...

5 volts minus 2.2 volts is 2.8 volts.

We know that we need to control this additional 2.8 volts to never exceed the 20 mA (0.020 Amps).

2.8 volts divided by 0.02 is 140.

So we will need about 140 ohms of resistance... a quick trip to Radio Shack or other supplier and we find that the nearest resistance is 150 ohms. This will work just fine.

In the discussion below... if we were to insert a 1K (1000 ohm) resistor, the formula would be...

2.8 volts divided by 1000 is 0.0028 amps... or 2.8 mA far below the operating current specified... they would be VERY dim indeed!

Jerry
Aug 22, 2007. 5:58 AMcarlton stedmansays:
Agree with mrdspecs, you need a current-limiting resistor. 1k sounds a little high, typically regular LEDs will take 5-10 mA, at 1.5V means you want 300-150 Ohms, respectively. Just put it in series with the LED, so +battery -> resistor -> led -> -battery.
Jul 26, 2007. 5:35 PMmrdspecssays:
You need to put some sort of resistance in there. You can't just run the battery through the LED because all your electrons get out. Get like a 1k resistor at radioshack.
Jul 14, 2007. 11:00 PMFarMcKonsays:
What are you seeing that indicates they are burnt out? Are they getting extremely hot when they do that? What type/brand of battery are you using, just a standard AA battery?

I'd like to help, but I don't have enough info to go on from your post so far.
Aug 6, 2007. 7:08 PMtreize7says:
Woah Wait so this interface doesn't really project the images that you are palying with on the device you built, you only see it on the comp? And I have read this and i am very intriqued to do this, but i haven't really grasped the concept of the leds and how this works with the vvvv programs?
Aug 6, 2007. 9:20 PMFarMcKonsays:
Yes, in this version the image aren't projected onto the touch-surface. It's still a cool toy, it's much like using a mouse without looking, since your feedback is right on the computer screen.

The LED's are to shine infrared light (IR) into the touch surface, so the camera can pick up the IR to see where you are touching the surface.

VVVV is just a quick (and sweet) tool to get something running where you can see the feedback. VVVV will automaticlly detect most windows webcam drivers, so you can simply install a regular webcam, start vvvv, and easily do image processing on the camera video feed.

I hope that helps clear some things up!
Aug 7, 2007. 6:28 PMtreize7says:
So whtat basically happend is tht the light is detected from the webcam and transmitted to the computer where vvvv compiles it into its code and you can do touch screen stuff with it? srry bout the amt of question im 15 new to all this
Aug 9, 2007. 9:09 PMFarMcKonsays:
Yes, that is what it does. I think it would be cleared to rephrase that ".... where vvvv WATCHES THE VIDEO, and then you can do touch "

Aug 7, 2007. 4:03 PMtreize7says:
ya thx great project!
Aug 4, 2007. 9:54 AMmarilialbsays:
Hi, do you think is possible to bay a webcam with night vision and it'll work properly?