I've watched people using them and always wondered how the hell do they do that? The articles I've read have cleared a bit up, but is there anybody who can explain it more simply to me?

I'd suppose every key has a sensor in it, and each sensor adjusts to the correct positions and correct commands when the screen changes.

That's what I think.

The screen has an electrical field going through it that when touched is disrupted. Sensors pick up where the disruption happened and relay the position to the computer. or you could have basically the same thing but with infrared.

Thats just two ways you could have touchscreens work.

What stickciv says is pretty much the simplest way to look at it. If you want to deal with more abstraction on electromagnetic fields, read on:

The entire screen is coated with a very thin, transparent conductor. What this means simply is that you can see through it, but that charge will flow across it easily.

Now, the edges of the screen create some potential, which results in charge being distributed across the screen. Each charge is the same as the other ones, so they try to get as far from each other as possible, that means they spread fairly evenly. This also causes for an overall force on the edge of the screen due to those charges. Think of blowing up a balloon. You cause the air to enter a limited area, it tries to spread out, and it causes a push on the material of the baloon which you can readily see and notice.

So, now we have a bunch of charge that is spread out and REALLY wants to spread out MORE, but cannot quite do so because it is stuck on the screen.

Now, you may have seen some of the globes in Spencer's or some other Novelty store that have "lightning effects" in them, and when you touch the globe surface, the lightning all arcs toward your hand, yes? If so, that is the principle which comes into play when you touch the screen.

When you put your finger on the screen, there is also some charge on your finger. There is ALWAYS charge on your body. When you cause a spark and shock someone, that is actually HUNDREDS of volts, MINIMUM. Typically that is THOUSANDS of volts. At any given moment, you will always have a higher voltage (aka - potential) natually in your body than will exist on the screen. Now, if your potential is opposite that on the screen, then when your finger gets close to the screen it will "pull" many of the charges toward you, allowing more room for the other charges to spread apart from each other. This lowers the force on the edges of the screen (like letting air out of a baloon), but unless your finger is perfectly centered on the screen, it will cause the force on the edges to be different all around (much lower nearer to your finger). This allows the computer to figure out where your finger must be, by measuring the force (potential) all around the screen.

Similarly, if your potential is the same polarity as the screen, you will cause the charges to push away from your finger much stronger than they push away from each other. Like adding air to the baloon. Again, the computer can figure out where your finger is based on the distribution of potential around the edges.


An interesting result of this effect: If you have a much higher potential, you can affect a touchscreen monitor from further away. And if you actually put your finger ON the screen, it is harder for the computer to tell precisely where your finger is at. To see this, rub your feet on a carpet like you were trying to shock someone, then get near a touchscreen.

Conversely, the lower your potential is, the closer to the screen you need to be, and the more accurately the computer can tell where you have placed your finger.

Yup, xienwolf's explanation is good.

Using touchscreens without actually touching them is cool.

So how do they work when I'm using non conductive material like a pencil? Does it still have a very small charge that is affecting the screen?

Yes, there is still a buildup of charge. You would have to use an item which had absolutely no charge in it in order to get no reaction. That would mean no Electrons or Protons anywhere in it, not just a balance of them to make for a neutral charge. How well something conducts or insulates won't enter into the equation at all.

So barring a rod made entirely of neutrons (which is impossible if you think to look up such a thing, any neutron that is not linked in a nucleus with a proton will decay in approximately 17 minutes into a proton), you will always cause the touchscreen to react.

EDIT: Of course, there is a matter of how sensitive the detectors are. An ideal touchscreen will be made to require some certain level of change, which would be difficult for non-charged objects to reach. Well, more accurately probably, you'd have to go out of your way in designing the precision to detect completely neutral objects.

The material covering the screen is a lattice of Piezoelectric material. When you touch (compress) it you generate a potential difference (voltage). The lattice layout means that the location of the contact is known.

I hadn't contemplated using a piezoelectric effect before, so I went ahead and popped Wiki. There are many more approaches to the technology than I had thought of myself :)

What Brennan describes is close to Acoustic Pulse Recognition, though he seems to be indicating something seperate from what Wiki speaks of. More along the lines of what is used in Wacom and other Drawing pads I would think, since it would allow for a high degree of pressure sensitivity.

What I described was close to a capacitive technique when I talked about the electric fields, but since I was picturing not having to use a conductive item it matches better with the Resistive technique.

http://electronics.howstuffworks.com/question716.htm

www.howstuffworks.com is actually a very useful site for these types of questions.

I guess most touchscreens have fairly low sensitivity, because only my skin will work. Not even my fingernail will work. I always thought this had something to do with the electricity flowing through your nerves.

Now, SmartBoards, on the other hand, are completely different! They actually have two layers, one sensor and another that is supposedly a conductor or something. When anything touches the top layer, it presses that part of it to the bottom layer, which is just like any touchscreen. The result is that you can actually have SmartBoard pens in the pen tray that will work for drawing on it without actually having any charge. Pick up a stick would work.

BTW a SmartBoard is, baisically, a computer input device, but you have a projector projecting the computer screen onto the board. So you draw on the board, it draws that on the computer screen, which is shown on the board. Pretty neat!

I guess most touchscreens have fairly low sensitivity, because only my skin will work. Not even my fingernail will work. I always thought this had something to do with the electricity flowing through your nerves.

Now, SmartBoards, on the other hand, are completely different! They actually have two layers, one sensor and another that is supposedly a conductor or something. When anything touches the top layer, it presses that part of it to the bottom layer, which is just like any touchscreen. The result is that you can actually have SmartBoard pens in the pen tray that will work for drawing on it without actually having any charge. Pick up a stick would work.

BTW a SmartBoard is, baisically, a computer input device, but you have a projector projecting the computer screen onto the board. So you draw on the board, it draws that on the computer screen, which is shown on the board. Pretty neat!

Have you ever actually used them? At our school we have them, and they're only useful if:

1) It's aligned correctly.

2) There aren't any flash animations on the software presentation.

3) You're not watching a movie/video/colored image of any sort.

4) The window can be easily viewed under 800x600i resolution.

5) The wires are connected correctly.

They quite the DumbBoards actually.;)

1) Teachers align it every morning.
2) Don't know why that matters, but we never have them.
3) Get a better projector.
4) See number 3.
5) Yeah, it really sucks that you actually have to hook stuff up right. What kind of ancient device needs THAT anymore? :rolleyes:

1) Teachers align it every morning.
2) Don't know why that matters, but we never have them.
3) Get a better projector.
4) See number 3.
5) Yeah, it really sucks that you actually have to hook stuff up right. What kind of ancient device needs THAT anymore? :rolleyes:

1) Not ours.:D

2) Our teachers just have to use them.

3) Our school is too cheap for that.

4) Same as above.

5) When your teachers can't tell firefox and safari apart, think of what they do with cables...:D

You don't really expect me to believe that your teachers installed it, do you?

And I still don't know why SmartBoards won't work with Flash Animations. :confused:

Nope. The computer guy [who can't catch kids screwing around in class on the computers for beans] had to install them.

Only in the SmartBoard tools they won't work. If you put an interactive flash clip into the presentation, then they get all weird and glitchy.

Hm, never noticed that. Oh well, they work fine for us.

Except when teachers (just one) is stupid, and leaves the eraser in the drawer. Also she tried to erase it with a whiteboard eraser, and smudged it.

One of ours wrote an entire sentence in whiteboard marker on it before noticing that it wasn't a SmartBoard marker.:lol:

:vomit: Was it cleanable?

There's still a long gray smudge.:lol:

Heh, lucky ours could clean it up.

I have SmartBoards in two of my 6 classes, but that's only 2 of my 7 periods.

I guess lucky me that our school has hi-def projectors and tablets set up in all classrooms. Kinda makes the SmartBoard seem...obsolete.

How hi-def?

Im not sure which it is exactly, but with a 1280x1024 monitor resolution they dont look crappy at all.

:drool: :yumyum: :suicide:

So how do they work when I'm using non conductive material like a pencil? Does it still have a very small charge that is affecting the screen?A nonconductive material would actually work better, because it holds charge better. A conductor will discharge if it is grounded. If what xienwolf described is accurate, A recently used pencil eraser should work better than a finger.

Do touchscreens work the same as laptop touchpads?

They probably work in a similar fashion, but since you don't have to touch exactly where you want the mouse to go, I guess that when it detects contact on it it centers the movement around that spot. Every time you remove your finger, I would guess that it resets. That's all my guess, you should probably Google (http://www.google.com) it.

Touchpads on a laptop are MUCH easier to work with since you do not need to see what is displayed on the other side of it :) So the mechanism can be similar, but there are FAR more options open, and as such many are used, with pros and cons on each.

They probably work in a similar fashion, but since you don't have to touch exactly where you want the mouse to go, I guess that when it detects contact on it it centers the movement around that spot. Every time you remove your finger, I would guess that it resets. That's all my guess, you should probably Google (http://www.google.com) it.
Um, no, I would think that it just tracks where it was one millisecond ago and where it is now, and moves the pointer accordingly. Because if it wasn't, if you have one with scroll bars on the touchpad, it would think you're touching the center when you're REALLY touching the scroll bar.

Could you rephrase that, I don't quite get your meaning.

I just don't see how touchpads would work any differently from touchscreens. Both of them do one thing: find where your finger is touching.

But on one you move the mouse around using sliding on it, and on the other you simply touch where you want the mouse to go.

The device is still the same, the only difference is the software.

I mean... the touchwhatever just sends coordinates to the computer or whatever, and the computer decides how to respond to that information, either by moving the mouse as you move your finger, or having the mouse jump to a spot on the screen.

Well yes. If you mean in terms of hardware, then yes, they're the same thing. Except for the display part.

I edited my post. ^^ Wasn't fast enough. :(

Pretty sure you can program the touchpad to be a direct location to location pad instead of a relative spot. So it can work the same if you want it to. But the main important difference is the simple fact you don't need to see through the touchpad, so the materials they are able to use are more varied.