Introduction: 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

Step 2: Prepare 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 four LED lights to shine light into a sheet of Lexan, where it will bounce around without escaping, due to the index of refraction. This is called Total Internal Reflection. When pressure (such as that from a finger) is applied to the Lexan, it compresses a little, changing the index of refraction, and allowing the light to escapes. The places where the light escapes will only be where the surface is compressed, making nice glowing blobs where something is pressing on the Lexan.

This is where the webcam comes in! You can watch the blobs with a webcam, and with special software use them as input into your computer, like a mouse or keyboard.

For this project (and most multitouch displays) the light being used for touch detection is in the infrared range and the webcam must be modified to see in the infrared range. This is easily done by exchanging your existing webcam lens for one which can 'see' infrared light..

The LED used by the mini-multitouch interface, at 880 nm frequency, is within the range of 'night vision' surveillance cameras. You can swap your existing webcam lens for a 'night vision' lens, and you'll be ready to go. If you are using the recommended SPC900NC, you can use any 4.3MM x 4.3 MM CCTV Camera IR lens. Try searching e-bay or a local security camera shop.

Before removing the existing lens on your webcam, install the webcam software on your PC and test the webcam, to make sure the camera works. Note: it is critical to do this BEFORE voiding your warranty by opening it up and changing the lens! Once you've successfully taken a few pictures and ensured that the webcam works nicely, you are ready to switch the lens.

To replace the lens on the SPC900 camera (or other comparable cameras), you first need to pry off the ring around the lens using a screwdriver. Once that ring is gone, it is easy to replace the regular lens with a 'surveillance' lens by carefully (but firmly) unscrewing the lens.
The ring is just for looks, so you can put it back on, or leave it off. I

After you've swapped the lens, check the webcam to make sure it still works using the webcam software. You may also need to adjust the focus of the new lens. The images you get back from the webcam won't look like they do with a regular lens, this only means that it is working as expected.

Finally, if the camera has a built-in light to shine on what it's filming, cover the light with some duct tape to block it. If you don't, it will add some light 'noise' and will make your display have 'ghost' touch points.

Step 3: Build 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 found for the frame is 'Tile Divider', which comes in 6- to 8-foot strips and can be purchased in the molding section of most home repair stores. See the images below for a visual description (rather than try to explain here!).

The frame will fit the Lexan very closely, so you can cut the Tile Divider exactly to size: cut two 8-inch strips, and two 10-inch strips. Once the strips are cut, you should use a T-Square to cut the ends of the short strips to bevel inward at a 45% angle. This will make them fit neatly and snugly as a frame around the Lexan.

You will be mounting the four LED lights on one 8-inch side of the frame. They need to be mounted so they are touching the Lexan through holes in the strip, and spread out evenly along the edge.

It is important to place the holes near the top of the strip, as shown below, so that the light shines into the edge of the Lexan only, and NOT down onto the camera below. Mark the locations of the four holes at about 1-inch, 3-inch, 5-inch and 7-inch along the edge of one 8-inch Tile Divider strip.

Because the Tile Divider is made of soft plastic, you'll need to drill the holes in several incremental sizes to avoid bending or warping the plastic too much. First, drill a small hole (1/16"), then drill one a little larger (9/64"). Finally, drill a 3/16" hole, which is the ideal size for the LEDs to fit through.


Step 4: Prepare 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 edges of the Lexan touchsurface must be made very smooth (this is where the LEDs will make contact with the touchsurface). Ideally, you'll use three materials: 400 grit sandpaper, 800 grit sandpaper, and brass polish. If you don't have brass polish available, you can use just the 400 and 800 grit sandpaper, but the results will be less than spectacular.

Fold a piece of 400 grit sandpaper over a block of wood (or even a small paperback book), and run it back and forth three or four times along one 8-inch edge of the Lexan touchsurface. You should see small white flakes coming off. Repeat this with the 800 grit sandpaper. After each pass with the sandpaper, you should be able to see that the scratches and blemishes on the edge of the Lexan are growing smaller and smaller: this indicates that you're doing a proper job (and isn't that encouraging!). After sanding down the blemishes and bumps, polish the edge of the Lexan (only the edge!) using your brass polish (follow the instructions on the brass polish container).

Admire how smooth and shiny your Lexan edge has become.

Step 5: Fit 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 the Lexan, check to ensure the frame fits the 8-inch by 10-inch Lexan touchsurface by sliding the Tile Divider strips (from Step 3) onto the edges of the touchsurface: it should fit nice and snug in its happy new frame. Also, check to be sure that there are no plastic burrs left in the Tile Divider from drilling the LED holes, as these can make the frame fit poorly. Once you've checked the fit, it's time to glue the frame and the Lexan together into a single unit.

Remove the Tile Divider frame, and peel the protective covering back about one inch back from the edges of the Lexan, taking care not to remove it completely. Then, slide the frame back onto the Lexan, without the covering in between the two. Be sure that the frame section that has the LED holes is put on the Lexan edge that was polished smooth!

When all the sides of the frame are on adjusted to your liking, use some crazy glue (or any glue) to glue the corners of the frame to each other. Try to glue frame sections to each other not to the Lexan. If some glue gets on the Lexan, it's not a big deal and shouldn't affect your touchsurface.

Now that the frame is mounted to the Lexan, it's time to mount the LEDs to the frame.
Before permanently gluing the LEDs through the holes in the frame) try a few test runs to make sure you have them positioned properly. For best quality 'blobs' the LEDs shouldn't face straight into the edge of the Lexan, they need to be mounted at a slight angle to the edge of the Lexan: about 20-30 degrees angle off of horizontal (see image for more detail). The angle will help make the light the escapes where the Lexan is compressed brighter and clearer.

To position the LEDs for easier wiring later: be sure to mount all of the LEDs so they are rotated to have the ground pin (the longer pin) on the top.

Once you are satisfied with the angle and position of the LEDs, mount them permanently in the frame by holding the LED in place and applying crazy glue around the outside of the LED where it touches the frame. Hold those LEDs in place until they dry completely! (This is why we recommend using crazy glue).

Now that the LEDs are in place, it's time to start doing the wiring.

Step 6: Wiring 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 this Instructable assume you are using a 200mA 3.3V DC power supply (such as a 'wall wort' or hobby power supply). You may need to adjust the wiring of your LEDs based on what power supply you have -- check with someone familiar with electronics if you are not sure how to adjust your wiring.

Solder the LEDs together as shown in the picture below... if you need some practice with soldering, do a test run using some LEDs that are NOT glued into the frame. To test the LED wiring, connect the power supply and point them towards the (IR-filtered) webcam. Run your webcam software: if the webcam is picking up the infrared light, you should see a bright red light on the webcam display (although you won't see any light coming from the LEDs themselves, cause it's infrared!).

Now back to the mini-multitouch display. Once you've wired up the LEDs using your soldering iron (according to the diagram below), point the IR-filtered webcam at the mini-multitouch box from above. Run your webcam software now if you do not already have it running: you should see a glow on the webcam display, along the frame when the infrared LEDs are mounted (but, again, you won't see any light from the actual LEDs!). If you can't see the glow you will need to check your wiring, and possibly consult someone familiar with electronics if you aren't sure how to fix the LED hookup.

A quick note: the glow described above is light-leak, and it is undesirable: we will be taking care of that in the next step so that the only infrared light emitted from the touchsurface is the light that comes from touching it. But, for now, it is a good way to check that your LEDs are wired correctly.

You are so close to having a mini-multitouch display!

Step 7: Finish 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 (light-leak) can cause problems. This extra light can bounce off nearby objects such as walls, screens, ceilings, etc., creating areas of infrared glow that will show up on your webcam display as false touch points. The best way to fix this problem is to add a little extra opaque material above and below the edges of the Lexan touchsurface to block this up-glow and down-glow.

Cut a flat 8-inch by 10-inch frame mat out of cardboard, approximately 1-inch thick and sized to fit just below the touch surface. The inside dimensions of this mat should be 6 by 8 inches, making it basically a rectanglular border 1-inch thick that fits snugly into the space right below the Lexan. If these directions are unclear, take a look at the expanded diagram in Step 5, which includes a drawing of this cardboard mat. This will take care of the down-glow.

Repeat the process on the top side of the touchsurface to block up-glow. If you have the time, it looks more professional to use something nicer looking (like some floor or ceiling edge molding) for the up glow blocker, but we just used a second cardboard mat and it works just fine! At this point, you have a touchsurface sandwich, with the Lexan and frame in the middle, and the up-glow and down-glow blockers on the top and bottom, fit snugly into place and held there by crazy glue if desired.

To finish your hardware setup, you just need to place the webcam. It needs to sit approximately 1.5 to 2 feet from the touch surface, pointing at the 'bottom' side of the Lexan (eg. the side not being touched). You can accomplish this by using a cardboard box. Stand the box up so that its height is 1.5 to 2 feet (which side you stand it on will depend on how big your box is). Your webcam will sit inside the box, and your touchsurface will sit on top of the box, so you will need to cut a hole in the top of the box that is approximately the size and shape of the exposed portion of the Lexan (only the exposed portion, not the entire frame!). See the image below for a visual example.

Run the webcam cord out of the box, set the touchscreen on top, and admire the beauty of your completed hardware setup! Now you can peel that protective coating off of the Lexan, if you haven't done so already.

Congratulations! You have finished the hardware for your Mini-Multitouch! If you run your webcam software, you should be able to see the touch surface light up where you put pressure on it, ideally with your fingers.

On to the last step: software.

Step 8: Set 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 way to start is to work using the 'vvvv' graphics toolkit. The vvvv toolkit is available freely, for non-commercial uses. Unfortunately, because it is based on Microsoft's DirectX software (for speed), vvvv is only available for Windows. Our apologies!

To obtain a copy of the vvvv toolkit, go to the vvvv vvvv download page and unzip the package to a directory of your choice (I recommend c:\Program Files\vvvv as the prefect place).

vvvv has no install or setup program, you simply run vvvv.exe when you want to run vvvv. You will see a swaying tree demo by default upon running vvvv - this is where you can launch the tutorial and get a feel for what vvvv is capable of, and what it can be used for. We recommend starting with this tutorial! And, a bit of troubleshooting advice: if you get a 'dll error' when you try to run vvvv.exe, you probably need to upgrade DirectX on your machine to version 9.0c or newer.

Once you have run through the vvvv tutorial, follow the links below and do the first two (short) vvvv tutorials before continuing. The vvvv Tutorial Introduction and the Hello World Tutorial will teach you most of the basic skills you need for using vvvv, and are very highly recommended.

Once you've run those two tutorials, you have one last step before experiencing mini-multitouch magic! It's time to check that your webcam is working with vvvv. You can test whether or not vvvv automatically detects your webcam using the vvvv VideoIn Tutorial. This tutorial comes with instructions on how to test your webcam in vvvv: follow these instructions! Before going on to the final step, use the VideoIn Tutorial to make sure that you are getting images and that your camera is generally working with vvvv properly. If your camera is not working with vvvv, go to the vvvv forums and seek help with setup and configuration.

If you have gotten this far, you finally have all of the pieces working, built, and installed: it's time for the payoff. Download the Touch_demo_3.v4p file and robot_image.jpg (located at the bottom of this Instructables page) to your desktop: these two files are a simple mini-multitouch demo we created based on the hardware setup you've just built. If you already have vvvv running, you can run Touch_demo_3.v4p just by clicking on it. In Touch_demo_3, like in VideoIn Tutorial, just connect the VideoIn connector to run the program.

After connecting up the VideoIn, you should see two display windows in the vvvv user interface: one window will display the infrared 'blobs' that are emitted when you put pressure on the touchsurface, and the other window shows a video feed, where each blob has been replaced by an image (robot_image.jpg - the file you downloaded a few paragraphs back). You may want to start tinkering with vvvv and your mini-multitouch by replacing our robot image with an image of your own choosing, by editing the Image node in the vvvv interface.

Another troubleshooting note: if the window displaying the infrared 'blobs' appears all-black or all-white whether you are touching the touchsurface or not, change the threshold levels in input pin 2 on the Contour node of the vvvv interface (for this step, we assume you've done the vvvv tutorials, and both know where the Contour node is, and how to change the threshold. If you do not, go back and complete the tutorial!). Since vvvv runs in real-time, you can see your changes take place in the display windows immediately. This makes for quick and fun experimentation (hint, hint)!

'Tada! You now have a mini-multitouch interface. You can manipulate those infrared 'blobs' in your vvvv display to behave in myriad ways: the outputs from the vvvv Contour node give you all sorts of great 'blob' data to use in creating your own mini-multitouch toys.

Comments

author
App Programmierer made it! (author)2012-05-08

thanks for that intresting guide. Just had a few ideas by reading it.

author
sunnyy made it! (author)2012-02-09

sir plzz tell me that how this interface works with the software. . what software i have to install and how it install. . this is also my final year project.and im started on working on it. plzzz tell me the complete detail and description. . . i shall be so grateful to you

author
tinker234 made it! (author)2011-08-27

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

author
tinker234 made it! (author)2011-08-23

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

author
tagadac made it! (author)2010-10-22

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

author
7577122 made it! (author)2010-02-06
Can we use IR camera directly instead of converting webcam into IR camera??? Thanks.
author
theXmaker made it! (author)theXmaker2010-09-10

yes sure u can

author
TheIronHobo made it! (author)2010-07-08

did you make the one in the video?

author
MK2MR2 made it! (author)2010-06-24

^ I'd like to know that as well

author
horatio cheng made it! (author)2009-07-15

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?

author
systemic_anomaly made it! (author)systemic_anomaly2009-11-08

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.
 

author
Spypro made it! (author)Spypro2010-02-12

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. :)

author
earl_kim made it! (author)2009-09-04

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

author
josheee12 made it! (author)2009-08-17

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

author
UbuntuNinja made it! (author)2009-03-28

Nice diagrams!

author
muthukumaran_m made it! (author)2007-10-17

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

author
Earl Jr. made it! (author)Earl Jr.2008-07-10

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

author
sambam2006 made it! (author)2008-06-30

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

author
fangtastic made it! (author)2008-05-29

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

author
StrangeRover made it! (author)2008-04-25

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

author
imarzouka made it! (author)2008-03-22

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

author
jak06 made it! (author)2008-03-19

what works better? lexan or acrylic

author
efko made it! (author)2007-11-23

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?

author
FarMcKon made it! (author)FarMcKon2007-11-24

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

author
efko made it! (author)efko2007-11-25

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!

author
FarMcKon made it! (author)2007-07-15

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.

author
RiddleOfSphinx made it! (author)RiddleOfSphinx2007-10-22

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

author
legsmacgee made it! (author)legsmacgee2007-10-21

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.

author
nuiman made it! (author)2007-10-19

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

author
shadowsrevenge made it! (author)2007-10-03

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

author
FarMcKon made it! (author)FarMcKon2007-10-04

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.

author
digilevi made it! (author)2007-09-13

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

author
J50Nunlimited made it! (author)2007-09-06

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

author
FarMcKon made it! (author)FarMcKon2007-09-06

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.

author
J50Nunlimited made it! (author)J50Nunlimited2007-09-07

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?

author
FarMcKon made it! (author)FarMcKon2007-09-09

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.

author
J50Nunlimited made it! (author)J50Nunlimited2007-09-11

thanks!

author
Neodudeman made it! (author)2007-09-05

lol. icanhascheezburger?

author
cheesemaker101 made it! (author)2007-07-11

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

author
askjerry made it! (author)askjerry2007-08-22

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

author
carlton stedman made it! (author)carlton stedman2007-08-22

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.

author
mrdspecs made it! (author)mrdspecs2007-07-26

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.

author
FarMcKon made it! (author)FarMcKon2007-07-14

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.

author
treize7 made it! (author)2007-08-06

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?

author
FarMcKon made it! (author)FarMcKon2007-08-06

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!

author
treize7 made it! (author)treize72007-08-07

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

author
FarMcKon made it! (author)FarMcKon2007-08-09

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 "

author
treize7 made it! (author)treize72007-08-07

ya thx great project!

author
marilialb made it! (author)2007-08-04

Hi, do you think is possible to bay a webcam with night vision and it'll work properly?

author
francoisp made it! (author)2007-07-16

As far as I understand it, the plastic frame is only there to keep the infrared light inside the lexan while it spreads ? So couldn't we simply use sume duct tape / black electrical tape to cover the side have pierce a small hole on a small part of the tape ? Am I wrong ?

About This Instructable

90,489views

186favorites

License:

More by FarMcKon:Mini-Multitouch Interface
Add instructable to: