The LCD is perhaps the most annoying hardware component regarding the setup of an LCD DSI table due to the FFC Issue--I will get to this soon. But first, a bit of insight: It is mildly important to understand how LCDs work for the purpose of explaining how the table works. Also, since we are taking one apart, it is important that we understand what each component does.
I. LCD theory
LCDs are an amazing piece of technology that remind us of how amazing and progressed our technological prowess has come. At the core, they rely on Liquid Crystals (LC). LCs are materials that are literally in a state between liquid and solid states of matter--this means that their particles maintain their orientation, yet they are able to move around to different positions akin to liquid state materials. Thus, they are highly sensitive to temperature changes ( they must be at an exact temperature to maintain their odd state). For LCD screens, LC particles are usually arranged in a twisted nematic phase. This only means that they are affected by electric current (nematic) and are naturally twisted. When we apply current to the LC substrate, the LCs untwist varying degrees depending on the voltage--which allows them to react predictably in controlling the passage of light. The orientation of the particles in the natural state depend on either a magnetic field or microscopic grooves. The change in orientation (for most LCDs) is described as either smetic c or chiral nematic. The smetic c orientation holds that the particles are layered in such a way that they tilt slightly in angles with each layer while the chiral orientation sees the molecules untwist slightly from layer to layer.
II. LCD creation
For the LCD screen construction there are 4 factors that are fundamental:
There are many types of LCD screens such as Passive and Active Matrix LCDs, but since we are most likely only dealing with an Active Matrix, I will only explain this one. Active Matrix LCDs depend on Thin Film Transistors (TFT) which are essentially tiny switching transistors and capacitors. They are arranged in a matrix fashion on a glass substrate and to turn a pixel on, the row corresponding to that transistor is turned on and a charge is sent through that column. Since the other rows are off, only the capacitor at that row is receiving a charge--theoretically knowing that Capacitors can change current instantaneously, this is explained and we also factor that the charge can be held until the next refresh cycle. Controlling the voltage, one can untwist the LC enough to moderate the amount of light that passes. This allows for the creation of a gray-scale.
So how do we get color?
Each Pixel has 3 sub-pixels (red-blue-green{RGB}) and they each have their own transistor. each sub-pixel allows for 256 shades within their own gray-scale for a grand total of 16.8 million possible colors on your screen. this is true unless you have a fancy yellow pixel LCD display as we get the possible colors from 255^3 for the 3 sub-pixels.
How many transistors are we talking about?
Depends on the display. A 1024x768 TV has 1024 columns and 768 rows, so if we multiply that by 3 pixels, we get 2,359,296 TFTs etched onto the glass panel. If that doesn't impress you, wait until you see how thin the screen really is and what happens when you turn it on away from its casing!
Why should you care about all of this?
In building your table, you are going to have to make predictions and decisions. You won't always have a perfect display built. Sometimes, you're going to have to figure things out from the fundamentals in order to make sure you didn't just waste $$$$. Also, depending on your setup, you may have to predict the display size of your LCD based on the properties of the screen. More importantly, this is knowledge! so take it in!
III. Things I should worry about in regards to the TV I will use for the table:
What about glare when the LCD is laying down?
The LCD screen comes with a set viewing angle that ensures the best possible picture--most consumer don't know this and miss out on the full experience. A Bias angle is designed to offset this angle. Because of this, your angle of acceptable viewing is made much larger. There is still an area of unacceptable contrast, but you will most likely not reach it.
*You can learn a lot more about LCDs on HowStuffWorks.com:
Link: http://electronics.howstuffworks.com/lcd.htm
As laid out in the previous step, you may want to start thinking about ventilation for your chassis. As pictured above, our simple setup opted for neglecting this step as it was only a prototype. You may want to consider it depending on your component and screen positioning. Remember that IR is also heat, so you may need a system to remedy problems relating to this if they arise. As far as layering for now, consider adding various lips and edges to your table. Remember that you will need a place to house a mouse and keyboard for initial setup and troubleshooting. Also, If you are considering to lay a shell over your box as a design choice (as we did), you'll need a way to support the acrylic. We personally ordered our Acrylic to be larger than our LCD screen in order to have the effect of a floating LCD screen. If you aren't expecting any children or aggressive people to touch your screen--the Endligthen layer is very easily scratched--you may even replace the extruded FF with the abrasion resistant layer. All in all, lay a piece of acrylic for support. If you are a careful person, use the abrasion resistant layer as a support. If you don't want to risk anything going wrong, use the extruded FF.
Recall the last section where I advised you to take pictures of each and every connection. This is where all will come in handy. In this section, we will be essentially rebuilding the LCD TV on your box. How you do this is going to depend solely on how you chose to design your box a couple of sections back. As for our team, we decided to go with designing an inner box that would later be concealed within another outer box. We simply used wood screws to screw the boards onto the back side of the inner box. The important thing to consider is to be careful that you don't crack the boards while screwing them onto the wood. For now, disregard the LCD panel. Do not place it until the next section as we must discuss the layering for the table. However, you do have the option of placing your computer along with the boards of the LCD. There is a great amount of flexibility when choosing a computer. To be honest, as long as it has over 512 MB RAM and is HDMI compatible, the computer will perform nicely. Any recent/decent PC will do--even a laptop if you so wish. We'll talk operating systems later on. For now, just choose your favorite as we have to set everything up.
Assuming that your blobs are perfect, and that you are satisfied with the framerate and all other factors, the final thing to do is to calibrate CCV settings. Once again, Sandler has provided an amazingly detailed guide on the steps for proper calibration. I advise that you go read it here. Once you are done with this step--if successful--you have essentially finished the construction of your setup. Your efforts and money should have (hopefully) paid off, and you will be the proud owner of an LCD-based DSI touch screen table that is fully functional and pleasing.
The best way test your setup? Flash demos of course! Head over to Seth Sandler's Blog for the last time and download some demo applications from NUI folders. Or simply head to the windows store and download a game. If you encounter some problems, you are most likely to find a solution to it via the forums so keep those in mind. Either way, have fun with your new table!
So you've finally completed your table. Feel free to leave any feedback on how this instructable could be made better. Also, feel free to post videos and pics of your setup in the comments below. I'll be sure to add more pics and a couple of videos once I get my setup modded.
If you realized anything from this instructable, let it be this: Multi-touch isn't just a toy, nor is it a technology that we should take too much for granted. Projects like these are gateways to the future of NUI technologies. Multi-touch facilitates the branching toward the naturalization of the human to computer interface. Children are able to become more engaged and willing to learn about technology in this manner--as we are a species that yearns for feedback from our senses--and the elderly and disabled peoples can find more comfort and relief in navigating these devices. More importantly, Multi-touch opens the door to greater technologies such as Pranav Mistry's SixthSense gestural interface (an instructable that may make it's way sooner than you may think) and a host of other interface revisions--some of which I am not able to fully reveal as I am planning on developing. The fact that you've completed this project is truly something to boast about.
**Update: I wanted to take a moment to thank all my viewers and subscribers for voting and allowing me to win my first contest! Can't wait to start on my next large-scale project--after I do some more finishing touches on this one of course.
Of course, not all of us have a huge point to prove. Maybe you want to make a Multitouch table without having to spend so much money. I admit, as time has passed, it has become much easier to develop these devices for a smaller cost, and aside from the size of the display, you won't be losing much at all.
I. Options for building a Multitouch Table with a ~$600 budget
i) Parts if going the camera route:
Camera: one for $80
LEDs WHT: Depends on LCD size (but usually ~$24)
LEDs IR: Determine the size around the screen in meters before buying! this will be up to $99
wood: same as mine (price may go down depending on size)
computer : same
Endlighten: anywhere from $120-200 depending on the thickness you choose and polish.
LED power supplies: $60 from LED supplier.
ii) Parts If going the Frame route:
Add in $50 on wood and lumber from your local hardware store.
Lastly, a computer $0-1000 depending on what you want and whether you already have one (not factored in).
For a grand total of ~$600-700.
II. Options for a $400 or less budget:
All for ~$264. You may end up doing a lot of searching for a frame small enough, but that'll be your only worry.
III. FAQ
"""""""Touch frame (usually comes with glass)"""""""
=================LCD================
~~~~~~~~~~~~~~~SUPPORT~~~~~~~~~~~~~~~
….........................Desired altitude............................
>>>>>>>>>>>>WHT LEDs>>>>>>>>>>>>>>>>