How to build a Multi-Touch surface

Step 6: Attach IR strip

The IR strip lighting should be wrapped around the edges of the EndLighten acrylic layer.  You should cut the IR strip once you have gone around, since it tends to get pretty hot when left in a coil at the end.  If you are just building a test setup, tape will work fine to adhere the IR strip to the acrylic layer.  Otherwise, I recommend purchasing/building a u-channel frame and adhering the IR strip to the frame.  That way your acrylic layers will be permanently aligned and in one simple unit that you can drop into your enclosure.

Comments

[philmont21]

I think this might work. www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay

let me know what you think.

[philmont21]

I'm sorry, i was stating my intentions incorrectly. I was hoping to put a u-channel around all three acrylics and simply adhere the ir strip inside of that u channel. Suggestions? Thanks so much!

[philmont21]

Do you have any ideas where i could purchase the u-frame to hold the ir strip on?

[jck112]

 Try here.

[SpikezHackz]

 How do you supply power to the LED's?

[jck112]

 Hey sorry I forgot to include that.  You can either power the LED's off of a 12V rail on the computer power supply or by purchasing a stand alone power supply like this.

[SpikezHackz]

 Thanks, also is it really necessary to use all these layers of acrylic or could you just use one layer and cover it with a silicon solution like so:www.maximumpc.com/article/features/maximum_pc_builds_a_multitouch_surface_computer

[jck112]

 The technique they are using in that article is called FTIR (Frustrated Total Internal Reflection), whereas the technique I am using is called DSI (Direct Surface Illumination).  The FTIR technology requires a compliant layer (the vellum covered with silicon solution you mentioned) to be the top layer on the surface, this layer however is delicate and not desirable in a high use environment.

In the DSI solution, you can have a layer of glass or abrasion resistant acrylic on top, which protects the surface and makes it much more durable.  It is possible to forgo this layer and directly touch the diffusion layer (the rear projection acrylic sheet), but then you might as well go with FTIR.

You can read about the various technologies as well a list of their respective pros and cons: here.

[SpikezHackz]

 Once again, thanks for your help, but i'm in the uk and i have no local places that i can get these acrylic sheets. Could you please direct to me to a website that sells the materials i need...

[jck112]

 This is the same place I bought my materials from, but they have a store specifically for the UK (i think they are based out of Germany).

[SpikezHackz]

 Thanks i had already found this site, but they don't have the Rear Projection layer, and as it seems it is the most important layer....

[jck112]

 They don't have the exact same rear projection layer, but these ones they offer should work fine as well.

[SpikezHackz]

 Thanks so much for all your help, looks like i've got all i need now!

[cthomas10uk]

Sorry to be a bit dim, but do the LEDs light up the table so its easy to see? Could you point me in the right direction on were to get the LEDs in the UK. Also are there only one way the LEDs fit ?
Thx
Chris

[jck112]

 So the LEDs use IR light which is not visible to the naked eye.  It is however visible to the camera located underneath the surface.  The IR LEDs illuminate the surface through the DSI effect, which is the basis for how the entire system works (See Step 2).  I believe this place ships internationally; I don't know where you could purchase them locally though.