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Between the Apple iPhone and Microsoft's interactive table, multi-touch displays are all the rage. This instructable will show you how to turn your l...
This multitouch display screen design is based on the description in Jeff Han's paper,Han, J. Y. 2005. Low-Cost Multi-Touch Sensing through Frustrated...
The primary component to be constructed is the screen itself. This is a piece of acrylic, with a frame which holds the diffuser and IR leds in positi...
The leds are mounted in extruded aluminum c-channel, pressed into holes. The channel serves to hold the leds in place as well as providing a baffle t...
I used 88 infrared leds I ordered surplus online. Their maximum output was 10mW @ 940 nm. Each led needed 100mA at 1.45V so i wired sets of 8 in ser...
It is valuable to polish the edge of the acrylic to maximize the light that enters from the diodes. Some folks advocate drilling holes in the edge so...
Once the frame, rails and acrylic are prepared you are ready for the final assembly. Clamp the layers together for easy drilling and bolt them in pla...
In order to image the infrared light, we need an infrared camera. Fortunately CCDs in cheap consumer cameras are quite sensitive to IR, so sensitive ...
A key aspect of my design is the projector mount. It allows dual use, whereby the projector can be used with a standard projection screen, or swivele...
Last but not least, build some framing to support the screen. I started from a coffe table frame as a base and a couple wood planks to get the screen...
The key thing to making this all work is really the software that converts the detected blobs of light where your fingers are into awesomeness...of co...
Excluding the projector, the total material cost is on the order of $100-200 depending on what you already have lying around. Construction time was a...
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Flame polishing is really the best, and potentially fastest, but you should really practice on a similar thickness scrap first because you risk burning if you move the flame too slowly. I recommend using an oscillating power sander with 200 grit, then 600 grit til the edges are silky smooth. Then use a MAPP or hotter (for best results, we even used to use oxy-propane smallllll tip) torch to *QUICKLY* run the furthest tip of the feather of the flame around the edges at a backwards angle (so the cone is pointed opposite the direction you are moving) - after all dust and masking is cleared from the edges. You'll see the hazy sanded area turn clear and reflective very quickly if you are looking at the right angle.
If you miss a spot, or if some deeper sanding scratches remain, you can retouch with quick swipes keeping the flame even further back; if you burn it (and its VERY easy to do if you don't keep it moving) just resand the edge with 600 grit, and use some soap and water with a cotton (or preferably microfiber) rag to remove any scuz from the faces of the acrylic sheet. NEVER USE PAPER TOWELS ON ACRYLIC - they have wood pulp and will scratch it, eventually turning it cloudy...
This will give you nice crystal clear (acrylic is of course clearer than glass...) edges that will transmit wayyy more of your IR light!
Good luck!
i know what i wanted to ask is out of line but believe me i wouldn't ask if this was not my last chance .
I really really need to have the PDF version of this multi-touch screen here coz i took it as my major project and i have to build it in a week time and to be honest i don't have the money to be a pro member and since i'm a student i don't have any visa card as well.
I was wondering to ask if possible can you downloaded it for me and send it to my mail i would mean a lot to me .
THANK you so much
vhk_karimi@yahoo.com
I haven't tried it specifically for LEDs transmitting into acrylic, but in college I took a machining class that involved making an acrylic screwdriver handle. We used Brasso, available at most grocery stores (in the US).
See the results for yourself:
http://www.eng.hmc.edu/E8/Tools/ScrewdriverIndex.htm
This will also eliminate any tiny scratches you might get in the surface... but don't be too liberal, the metal polish is dissolving the acrylic so you can remove more material than you intend if you go overboard.