Touch screen?

[totokan]

If I were to buy some IR receivers (4 or 8, i suppose) and place them in the corners (and sides?) of a 7" or so screen and use an ir LED, would the change in brightness of the led by moving it across the screen be measurable to accurately predict the position? If not, any better ideas for a cheap touchscreen for a small screen?

[phantom92opera]

http://www.instructables.com/id/Back-pr ... television./

http://www.instructables.com/id/Mini-Mu ... Interface/

the closest thing to ir touch screen ive seen is huge multitouch displays

[tom61]

If I were to buy some IR receivers (4 or 8, i suppose) and place them in the corners (and sides?) of a 7" or so screen and use an ir LED, would the change in brightness of the led by moving it across the screen be measurable to accurately predict the position? If not, any better ideas for a cheap touchscreen for a small screen?

Not really, most IR 'receivers' (photo diodes, photo resistors, etc.) aren't that accurate. For industrial touch screens using IR, there are matched pairs of sender/receiver for a rough sampling of where the finger/object is, probably on the order of 40 pairs for semi-decent touch resolution on a 8" screen.

Using a full-on camera sensitive to IR (or modded to be that way) is a much better option: http://eduard.metzger.googlepages.com/webcam-whiteboard I've was contemplating similar for a while now, most recently for the EEE, as the webcam is fairly sensitive to IR without modding.

[APHawkes]

If you need to make a touch screen just buy an overlay with controller. Check out http://www.tvielectronics.com/ to see what they have. I've not bought from these people myself, but have heard of others who had a good experience with them.

[totokan]

Thanks guys, but I was trying to do it for cheap (everything besides a controller would be less then $10) and on a small, portable scale (The best comparison I could come up with is a tablet PC screen). The ones on Instructables I've already seen, the majority of which are using the same idea, that is, they all use ir leds bounced through a pane of glass and a camera to detect when those paths are broken. This, while useful in applications where you are not moving the device, is impractical on the small scale. Also, TVI Electronics, although they offer a large amount of screens, seem to be a little expensive. Why does it cost 50 dollars for it? The components can't cost more then 10-15 dollars...

[tom61]

Thanks guys, but I was trying to do it for cheap (everything besides a controller would be less then $10) and on a small, portable scale (The best comparison I could come up with is a tablet PC screen). The ones on Instructables I've already seen, the majority of which are using the same idea, that is, they all use ir leds bounced through a pane of glass and a camera to detect when those paths are broken. This, while useful in applications where you are not moving the device, is impractical on the small scale.

A reflector on a finger, the IR LEDs as you planned to lay them out, and small camera slightly elevated above the screen should work with the software in the link of the IR based whiteboard, or similar.

What platform are you intending to use this with?

Why does it cost 50 dollars for it? The components can't cost more then 10-15 dollars...

Research and development costs amortized over a small number of units. There's more than just electronics that goes into a project... You might be able to use a resistive touchscreen with an AVR, but you'd have to figure out the programming yourself.

[totokan]

If at all possible, I was going to try for platform independent, using a microcontroller to relay the data back to the computer, probably as a mouse x,y coordinate. Even if that wasn't enough information, I figure data could be interpreted by a C program, but the main computer is windows.
A resistive touch screen seems much more useful in this small-scale application, but the only information on it is from the people trying to sell theirs, and very limited because of it.
I am attempting to build a wireless PC interface, that is, a monitor and some form of input powered by batteries. The monitor part is simple enough, but the input is what I'm having difficulty with. A trackball was my initial idea, but then I decided that a touch screen would be much more user-friendly, and supposedly simple and cheap to build.