Mini-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.

Step 1 Parts 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
soldering iron
T-Square

Materials:
Webcam (Phillips SP900 Recommended) - Available for purchase on the web
Windows PC (sorry Atari, the vvvv toolkit is Windows-only.)
4.3 x 4.3 mm Infrared (aka nightvision) lens - Available for purchase on the web

Infrared LED's (SFH485 recommended) - available from digikey.
A power supply (output 3.3v DC at 220mA recommended) - Available at most hobby/craft shops
Fast setting crazy glew (any brand, and get it in a brush on bottle) - Available at most hobby/craft shops

Sandpaper, 400 grit and 800 grit - Available at hardware store
Brass Polish - Available at hardware store
8 x 10 sheet of Lexan standard thickness (0.85) - Available at hardware store
8ft strip of "Tile Divider" - Available at hardware store
A cardboard box, at least 1.5 feet tall on one side (we used 1.5' x 1' x 1') - Available at hardware store (or just laying around!)
Small bits of wire. If you don't have wire laying around, get a small spool of 20 or 22 gauge wire, in both red and black.- Available at most electronics/hobby shops

Comments

[tinker234]

hey could i use a PS3 camera i heard they work great

[tinker234]

hey could i do alyer of infreid leds then a reciver so that on the surface i can just touch anywhere

[tagadac]

I think it's possible. But it's less expensive to turn a webcam to an IR camera...

[7577122]

Can we use IR camera directly instead of converting webcam into IR camera??? Thanks.

[theXmaker]

yes sure u can

[TheIronHobo]

did you make the one in the video?

[MK2MR2]

^ I'd like to know that as well

[horatio cheng]

the idea of this project is to allow the webcam to see the infrared light right? so could i just make a stick that emit infrared light ratter than make the screen?

[systemic_anomaly]

short answer - yes.

one problem - working out how your going to hold multiple IR-emitting pens in one hand. this of course opens up the possiblility for a multi-touch display without an actual box. you could simply wave the pens around in the air in front of an IR camera, and have the pointers show on a monitor.
 

[Spypro]

You can create a glove with ir leds on it, and position the camera so it will react only to some distance in the space (so you can use shut them down like click, or make an button that shut downs the led's when you fully straignten the finger, every one of them, or when you bend them to certain degree. :)

[earl_kim]

nice work! but it couldn't download example patch anymore. anybody has it email me that?

[josheee12]

i personally sanded with 400 grit, 800 grit, and the classic "blowtorch method".

[UbuntuNinja]

Nice diagrams!

[muthukumaran_m]

Please let me know the size of the sheet, thinkness, length and breath.

[Earl Jr.]

Sheet size is limited only by the brightness of the light source. As for thickness, I've heard 1/4" works the best.

[sambam2006]

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

[fangtastic]

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

[StrangeRover]

I may be wrong, but couldn't you now use the Wii remote in place of the video camera? (a la Johnny Lee.)

[imarzouka]

Use this led calculator to calculate the resistors you will need for your ir led array
http://ledcalculator.net/

[jak06]

what works better? lexan or acrylic

[efko]

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?

[FarMcKon]

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

[efko]

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!

[jak06]

(removed by author or community request)

[FarMcKon]

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.

[RiddleOfSphinx]

Wow, not bad, affordable enough for anybody to make...I like it :D !!

[legsmacgee]

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.

[nuiman]

Check out http://nuigroup.com to learn more :) great tutorial thanks!

[shadowsrevenge]

When modifying the webcam is it possible you could brake the computer?

[FarMcKon]

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.

[digilevi]

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

[J50Nunlimited]

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

[FarMcKon]

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.

[J50Nunlimited]

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?

[FarMcKon]

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.

[J50Nunlimited]

thanks!

[Neodudeman]

lol. icanhascheezburger?

[cheesemaker101]

hi how do you power the LEDs becaue i attached mine to a 1.5v battery and they blow up

[askjerry]

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

[carlton stedman]

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.