MT table from PeauProductions - LCD LED-LP
Posted: 20 October 2008 09:54 PM   [ Ignore ]
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I am excited today to finally be able to post my own topic in the Showcase forum. 
I have been following multitouch for almost a year now. 
Seeing and playing with cerupcat’s table last Spring really convinced me that I really wanted to build my own table.
I however wanted to do it on a budget and in a smaller form factor than most people here.
This is why I went with an LCD setup, as I couldn’t afford paying for a projector right now.
I also didnt want to worry about compliant surfaces and such, so I decided to go with a Front DI setup.  Well, I am more officially calling it what I think AlexP said: LED-LP, or Gap Method as described on the nuigroup wiki.

Here are the layers top to bottom:
=D LEDs
=Acrylic
=LCD
--Vellum/Backlight diffuser sheet
=Acrylic

notes_cropped.jpg

The bottom piece of acrylic greatly increased the distance that the blobs would appear from even just one side railing of LEDs. 
I could have covered the whole display with only one rail of LEDs, but since it’s a DI setup I went with all the way around:
IMG_1302.JPG
And a top lip to cover the LEDs:
IMG_1303.JPG

And here is what it looks like so far:
1020080001.jpg

The dimensions of the box is about 18x16x20 inches (lxwxh)

Still got some more stuff to do.  Will post pics of the blobs and such soon.
My new blog covers the whole building process step by step.  Check it out.

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Posted: 20 October 2008 11:01 PM   [ Ignore ]   [ # 1 ]
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Really great stuff! I’m gonna have to stop by to see it sometime. It makes me want to build one. I’ve wanted a small one for a while though hehe.

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Posted: 22 October 2008 02:14 PM   [ Ignore ]   [ # 2 ]
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A shot of the new tbeta on my table:

IMG_1320.JPG border=0

Blobs are working great! smile

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Posted: 23 October 2008 01:14 PM   [ Ignore ]   [ # 3 ]
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Quick video showing the table in action using the Photo App here

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Posted: 24 October 2008 07:52 AM   [ Ignore ]   [ # 4 ]
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Looks very nice! Congrats! Am interested to see that the height of your table is only 47cm, is that correct? (with a 17” screen)

Im looking into starting a project to make a coffee table multi-touch screen for my living room so I had thought the low height would definalty cause a problem with a projector and may also cause a problem for the camera to cover the whole screen, but this obviously hasnt seemed to cause a problem for you. Can I ask, do you think at that height of the table do you think that the camera would be able to cover a bigger LCD screen (i.e. 20” or slightly above?)

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Posted: 02 November 2008 11:00 PM   [ Ignore ]   [ # 5 ]
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what does side DI mean?? Looks really cool. I notice your aren’t using a projector at all. How does that work?

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Posted: 03 November 2008 02:12 PM   [ Ignore ]   [ # 6 ]
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Side DI is basically FTIR without the piece of acrylic to bounce the light around, but instead the LEDs shoot out across the top layer and hit your fingers.  It’s similar to LLP (with lasers) but instead uses LEDs.  Check out my blog link in my sig for a whole run down of my process, esp this page which explains some useful stuff:  http://peauproductions.blogspot.com/2008/10/mulittouch-table-prototyping-begins.html

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Posted: 03 November 2008 03:29 PM   [ Ignore ]   [ # 7 ]
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How did you end up doing your back light on the LCD?

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Posted: 04 November 2008 01:32 AM   [ Ignore ]   [ # 8 ]
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For now, it is the backlight out of the LCD, laying on the floor of my box, which is only 47cm or so away from the screen.  I took out one of the diffusers from the backlight, leaving the fresnel lenses and one of the remaining diffusers.  My camera is not officially mounted, nor is my power supply slimlined from a computer ATX power supply to a laptop charger, so both are lying ontop of the backlight, covering probably at least 1/3 of the total surface area of the light.  This though still produces bright enough light to work comfortably, though it can always be brighter.

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Posted: 27 April 2009 02:27 PM   [ Ignore ]   [ # 9 ]
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Looks great Peau. Am looking at building a 32 inch MT. Will LED-LP work for this size in case I put the LEDs all around ? In your experience is any particular wavelength of LEDs better for larger MT tabels ?

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Posted: 27 April 2009 03:33 PM   [ Ignore ]   [ # 10 ]
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After doing this table Ive realized that LED-LP is not the best method to use, unless you dont want to use lasers and are on a tight budget.  If not, then do LLP or DSI which will produce MUCH better results.
Wavelength wise, using something from 850-880nm is usually best.

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Posted: 27 April 2009 07:16 PM   [ Ignore ]   [ # 11 ]
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PeauProductions - 27 April 2009 03:33 PM

After doing this table Ive realized that LED-LP is not the best method to use, unless you dont want to use lasers and are on a tight budget.  If not, then do LLP or DSI which will produce MUCH better results.
Wavelength wise, using something from 850-880nm is usually best.

Is it because of the thinker IR light layer on top of the LCD. What else?
So What do you think will work on a LCD.

Thanks

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Posted: 27 April 2009 09:00 PM   [ Ignore ]   [ # 12 ]
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Yes because of the thick IR beam.  As I mentioned above LLP and DSI are better options, with DSI being my favorite.  The cost is a little higher but well work it.

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Posted: 28 April 2009 01:30 PM   [ Ignore ]   [ # 13 ]
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Thanks Peau. Apart from the thicker beam I am concerned that in case of a 32 inch table, the LED beam as well may not cover the entire area even if the LEDs are put all around. Not comfortable working with lasers. So DSI is the best option I guess. However will it work well with the LCD instead of the projector - I read in the forum that in DSI blobs are hard to detect so how has your experience been with LCD based DSI ? Will it work well in bright areas/morning ?

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Posted: 28 April 2009 01:44 PM   [ Ignore ]   [ # 14 ]
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I havnt tried blobs with it but I have put the Endlgihten over my LCD screen and it showed the image through it very well.  The Endlighten looks very clear and will work well in an LCD setup.  I have plans to build some LCD DSI setups, but not for a couple of months.

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Posted: 07 May 2009 05:45 PM   [ Ignore ]   [ # 15 ]
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PeauProductions - 27 April 2009 09:00 PM

Yes because of the thick IR beam. As I mentioned above LLP and DSI are better options, with DSI being my favorite. The cost is a little higher but well work it.

I continue my journey with the light channel device.

Presenting Now - Light channel LED LLP on a MT coffe table

Now I channeled the light of 21 IR LED array and I got a “light layer” over my lcd with a 3/8” thick max.

If anybody wants more info I will post a new Thread.

here are some picks.

See ya…

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