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Project: DirtyGirl (LCD LLP)
Posted: 01 May 2010 05:59 PM   [ Ignore ]
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This is the first in a series of posts recording the construction of DirtyGirl, our first attempt at a multitouch LCD screen built into my cheap-o IKEA Ramvik table.  It’s going to be used as a total HTPC-A/V jukebox system.  [This build log is meant for general computer fora with more mainstream users, so it goes in to a depth that many of you will find pedantic.  Some of the explanations will be obvious to you.] So without further ado, fear my MSPaint skills:
schematicw.jpg

The techniques applied here come from the vast http://www.nuigroup.com forums.  Thanks to them [YOU!] for their tireless efforts in recording their pursuits.  Nearly everything you need for this table is available from http://www.peauproductions.com.  Nolan’s site is a store and educational resource that aggregates basic MT knowledge into one easy-to-follow (and purchase!) system.  It’s actually the cheapest place I found to buy the multitouch goodies, and shipping was quick.  He’s been of great help to me during this process, and continues to contribute to the NUI group as part of their forum.  Without further ado, here’s the what makes DirtyGirl tick:

$199 - Acer 23” LCD Display (http://www.bestbuy.com/site/Acer+-+23"+Widescreen+Flat-Panel+LCD+Monitor+-+Black/9183224.p?id=1218049006792&skuId=9183224)
$260 - 2x PS3 Eye, M12 mount, 850nm filter, custom Peau enclosure ($130 each) http://peauproductions.com/store/index.php?main_page=product_info&cPath=1_6_10&products_id=15)
$30 - 2x 3.6mm lenses ($15 each) (http://peauproductions.com/store/index.php?main_page=product_info&cPath=4&products_id=28)
$116 - 4x 850nm lasers ($29 each) (http://peauproductions.com/store/index.php?main_page=product_info&cPath=16&products_id=38)
$12 - 4x line lenses ($3 each) (http://peauproductions.com/store/index.php?main_page=product_info&cPath=16&products_id=39)
$8 - First Surface Mirror sample (http://firstsurfacemirrors.com)

$625 Total Component Cost ($426 if you dismember your own LCD).  Depending on your setup, you can definitely get away with three lasers and line lenses instead of four (I purchased one extra just in case) and one eye instead of two.  You only need the first-surface mirrors if your setup requires you to reflect the lasers.  These trade-offs will, of course, be dependent upon your setup and tolerance for inaccuracy in the touch events.

Now a bit about these components.  First up, the victim.  The IKEA Ramvik is a cheap, modern coffee table that Lady NYCEsquire has been trying to get me to replace.  I’m doing her one better:

p1020311.jpg

We chose the 23 inch Acer because it was cheap.  $199 for 23 inches?  Yes, please:

p1020348g.jpg

Unfortunately, you get what you pay for.  It’s a low-grade TN panel, so the viewing angles are not impressive.  This is a fairly critical point, since DirtyGirl will almost always be viewed from an angle while sitting on an adjacent couch.  If we had mo dollaz we’d have picked up an IPS or equivalent panel that would remedy this issue.  Still, the Acer has no “FFC” issues (see below), and this should make for an easy build. The stripped-naked LCD enclosure - nary a fig leaf:

p1020298r.jpg

(My little helper made it into the shot, as well).  In some other panels, the Flat Flexible Cable connecting the LCD panel to the driver board is sometimes connected in such a way that it can’t be bent away from the back of the screen.  The Acer takes a bit of wiggling to get apart, but is easy on the DIY front from there.

The PS3 Eye is a godsend to the multitouch hobbyist.  It does 640x480 at 60 fps for fast finger-response times.  It’s relatively cheap and well-documented compared to other webcams.  We need two because the Ramvik is so short, we’re forced to place the LCD very close to the camera.  Much of the LCD at this short distance would be outside the frame of a single Eye.  This setup is pricier of course, but we didn’t have much of a choice, and it has the added benefit of tracking at double the resolution of a single camera.  Here’s one of them stripped of the pesky OEM shell:

p1020301.jpg

The PS3 Eye, like most webcams, includes a filter that blocks infrared light.  Since we need to detect infrared light, these filters [chrisrock] have got ta go [/chrisrock] .  Without it, the Eye is open to all visible and all infrared light.  But this doesn’t end our modification.  We need to block out all light, save one particular wavelength on the IR spectrum, so we install a bandpass filter at 850nm.  This will, as the name suggests, allow only light at the 850nm wavelength to pass.  Here’s a closeup:

p1020303j.jpg

Now that we’ve done this, we’ve screwed up the optics of the Eye pretty badly - to the point where the image is almost unusably blurry.  The aftermarket M12 Mount and lens bring us back into focus, and restricted to the spectrum we want:

p1020300g.jpg

The peauproductions custom enclosure is precisely machined from onyx acrylic and fitted with a magnetic cover that snaps into place to protect the delicate Eye hardware.  Muy sexy.  Most importantly, it allows the easy switching of lenses and mounting vertically or horizontally on any surface and in either direction.  It’ll save you a ton of frustration and is well worth the extra cash:

p1020302.jpg

The lasers emit light at the 850nm wavelength.  We chose 850nm over another, cheaper, 780nm version because it’s less likely to be affected by interactions from visible light.  The included lenses focus the dot into a flat, razor thin beam:

p1020341x.jpg

They’ll be mounted under the table vertically, forming a verticle plane.  What we need is a horizontal plane just over the glass top of the table, so we use a first-surface mirror at a 45 degree angle to reflect the beam.  A regular mirror would give some refraction, sending errant IR into the camera.

That’s all for today.  Next up:cutting and installation!

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Posted: 01 May 2010 06:34 PM   [ Ignore ]   [ # 1 ]
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ahh your using the same monitor which I am using… Sadly, yes, the viewing angles aren’t *great*, but they suffice for my table. I’ve also found that you can view it at a greater angle upside-down. Anyway, your project looks great, and nice and thin. Hope everything goes well!

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Posted: 01 May 2010 06:34 PM   [ Ignore ]   [ # 2 ]
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Looking good man, can’t wait to see more progress.

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Posted: 01 May 2010 08:22 PM   [ Ignore ]   [ # 3 ]
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hillbilly - 01 May 2010 06:34 PM

ahh your using the same monitor which I am using… Sadly, yes, the viewing angles aren’t *great*, but they suffice for my table. I’ve also found that you can view it at a greater angle upside-down. Anyway, your project looks great, and nice and thin. Hope everything goes well!

Thanks for the tip, hillbilly.  Have you had any luck actually using it upside down?  Do you just flip the image in the drivers?

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Posted: 01 May 2010 09:00 PM   [ Ignore ]   [ # 4 ]
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Very nice . Cant wait to see more..
I would like to do my next setup LLP
and set the laser up in the same
manner you have above.  Keep us posted.

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Posted: 01 May 2010 11:22 PM   [ Ignore ]   [ # 5 ]
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No, I actually, haven’t tried it but instead, I just recently noticed that so I haven’t had time enough to try. I would imagine that all you’d have to do it flip the image in the drivers though… i don’t know for sure though…

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Posted: 02 May 2010 06:10 AM   [ Ignore ]   [ # 6 ]
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Really hope the laser mirrors work - may encourage me to try the same…

Good luck.

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Posted: 02 May 2010 07:32 AM   [ Ignore ]   [ # 7 ]
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Very nice setup NYCEsquire and well documented

Absolutely cracked me up when I read the label in the diagram “...Frickin ‘Laser’...” wink

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Posted: 02 May 2010 09:02 AM   [ Ignore ]   [ # 8 ]
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Paolo - 02 May 2010 06:10 AM

Really hope the laser mirrors work - may encourage me to try the same…


Good luck.

Thanks! Do you have any reason to believe that they won’t work?

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Posted: 02 May 2010 09:06 AM   [ Ignore ]   [ # 9 ]
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No reason at all - it’s something I’ve never got around to trying…

very keen to see the outcome :o)

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Posted: 09 May 2010 05:22 AM   [ Ignore ]   [ # 10 ]
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I hope that’s supposed to be your finger touching the surface in the diagram wink

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Posted: 09 May 2010 06:24 AM   [ Ignore ]   [ # 11 ]
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Paolo - 09 May 2010 05:22 AM

I hope that’s supposed to be your finger touching the surface in the diagram wink

tongue laugh

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Posted: 09 May 2010 11:51 AM   [ Ignore ]   [ # 12 ]
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I admit, the “next time, on Project:DirtyGirl” part of my last entry was a lie, just like the cake.  Next up is not cutting and installation, but preparation and preparation.

My plan is to position the lasers vertically and reflect them at a 45 degree angle so that they create a plane over the table.  I want to embed the mirrors into the raised edge along each side.  But as you can see, the Ramvik doesn’t leave much room for error here.  The edge barely rises above the glass.  To make matters worse, the mirrors were pretty thick.  How is this supposed to fit?

p1020313j.jpg

When life gives you lemons, shave them down.  Also do this if it gives you acrylic first surface mirrors:

p1020344.jpg

With skinnier mirrors, I should have better flexibility in placing them in the Ramvik.  On a meta-project note, you’ll see that I’m using a Dremel tool for just about everything, from shaving the mirror to plunge-routing a cutout into the Ramvik for the LCD.  Or at least I’m hoping to.

The lasers ( http://peauproductions.com/store/index.php?main_page=product_info&cPath=16&products_id=38 ) are rated at 3.2v.  The manufacturer supposedly includes some voltage-regulating hardware in the housing to allow these to accept 5v, but since they’re $30 each, I’m not taking any chances.  I included a small resistor and wired them up in parallel to the 5v source on my HTPC’s PSU.  They only draw about 4mW each, so I’m not worried about the overhead:

p1020444n.jpg

Next up: cutting, hopefully.

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Posted: 10 May 2010 10:31 AM   [ Ignore ]   [ # 13 ]
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I admit, the “next time, on Project:DirtyGirl” part of my last entry was a lie (*ahem*cake). Next up is not cutting and installation, but preparation and preparation.

My plan is to position the lasers vertically and reflect them at a 45 degree angle so that they create a plane over the table. I want to embed the mirrors into the raised edge along each side. But as you can see, the Ramvik doesn’t leave much room for error here. The edge barely rises above the glass! To make matters worse, the mirrors were pretty thick. How is this supposed to fit?

p1020313j.jpg

When life gives you lemons, shave them down. Also do this if it gives you acrylic first surface mirrors:

p1020344.jpg

With skinnier mirrors, I should have better flexibility in placing them in the Ramvik. On a meta-project note, you’ll see that I’m using a Dremel tool for just about everything, from shaving the mirror to plunge-routing a cutout into the Ramvik for the LCD. Or at least I’m hoping to.

The lasers ( http://peauproductions.com/store/index. ... ucts_id=38 ) are rated at 3.2v. The manufacturer supposedly includes some voltage-regulating hardware in the housing to allow these to accept 5v, but since they’re $30 each, I’m not taking any chances. I included a small resistor and wired them up in parallel to the 5v source on my HTPC’s PSU. They only draw about 4mW each, so I’m not worried about the overhead:

p1020444n.jpg

Next up: cutting, hopefully.

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Posted: 15 June 2010 07:04 PM   [ Ignore ]   [ # 14 ]
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For Great Progress! Cutting has commenced. Sloppy, nasty, dremel-through-MDF cutting, that is. I’ll be placing the cameras on the lower-most panel where the Dremel is now, so I cut through both layers with a router attachment for my trusty Dremel multitool. Let me tell you, that was not as fun as it sounds. I went through two bits (you can see the cut became horridly jagged where the bit dulled) and had to finish with a handsaw. The Dremel, though “trusty”, isn’t made to handle such thick work. No worries, though. I’ll be using a custom cut picture frame mat (matte?) to neatly outline the LCD on the upper layer under the glass top. There will be no visual evidence of my pathetic router skills:

p1020844i.jpg

After gutting the LCD, I found that the cables giving power to the backlight were simply too short for the distance between the LCD panel and the floor, where the backlight will reside. I’ve endeavored to lengthen them. Original cable on the left. My work on the right:

p1020845m.jpg

Next up, the guts of the DirtyGirl all set up!

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Posted: 19 June 2010 09:00 AM   [ Ignore ]   [ # 15 ]
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UPDATE: Backlight woes! First, the backlight emits quite a bit of IR in addition to visible light. This is a bad, bad thing, since the backlight washes out any IR transmitted through the LCD from the lasers. If I use the backlight I’m going to have to use some IR film to filter the light.

But this probably won’t even ben an issue since, second, extending the backlight cables dimmed the level of the light output such that it isn’t usable in daylight at all. Must be a resistance issue?

Anyway, unless you guys have better suggestions, I’m going to dump this backlight and use a couple of fluorescent tubes I have lying around. I’ll wrap them in the IR window filter a few times to block out the offending spectrum.

My main concern at this point is getting the IR from the lasers to pass through the LCD/Fresnel/Diffuser layers. My vision software isn’t picking up anything at all. It’s referred to as “not getting any blobs” on the NUI group forums. I think that either the fresnel or the diffuser is blocking the the IR from the lasers.

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