How to make a touch screen controller ?

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I'm a student and would like to build my pc monitor into a touch screen one. Please tell me a good site that give a good resource for it. Thanx a lot !!

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Please, we need more information.

Spanish "En el infinito todos calvos".
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Best regards

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It's very hard to make your own. For best results it has to conform to the curve of the monitor tube. It's much easer to put one on an LCD, and it's better still to pick up a monitor that already has one installed. The easiest kind to get are open frame, made for kiosks or similar equipment. The industry leader for touch screens is Microtouch. I'm sure there are dozens of places to get monitors but I happen to know Wells Gardner does them with touch screens. IMHO the best touch screens are the surface acoustic wave screens from ELO, but they are also very expensive.

A resistive touchscreen, the kind on a palm pilot, is very cheap by comparison. It has two conductive plastic sheets with microscopic spacers holding them apart. First you apply a DC voltage left to right on one sheet, and measure the voltage you read on the other; this gives you the X coordinate. Then apply a DC voltage top to bottom on the other sheet, and measure the voltage on the first one; this gives the Y coordinate. There are chips that do all this automatically and give you a serial output.

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Elographics (ELO) also sells monitors with screens mounted. I have used hundreds
of their SAW screens, and they are absolutely the best. Rock stable, and the clear
glass does not interfere with image clarity. You also have Z axis functionality.

Microtouch's capacitive screens are useless (or worse).

You can easily use an Avr with a/d as a resistive screen controller.

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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As Peret says, resistive touch screens are actually a sandwich made of two outer sheets of protective plastic then two inner sheet of a plastic coated with a layer of Indium Tin Oxide which has the property of having the same refractive index as glass/plastic sheet but being conductive (it's also what the segments on STN LCDs are made from). Having the same refractive index makes it (close to) invisible. The two more delicate plastic layers are held apaprt by "microspheres". When you press the sheet with a stylus the spheres deform and the two ITO sheets touch passing a voltage fed into one into the other. The resistance of the circuit gives an indication of the position where they have touched. This is scanned once in the X direction then once in the Y to get an (x,y) coordinate pair.

It would be impossible to make your own such sensor so you really need to buy a pre made touch pad then just worry about interfacing it to an AVR or whatever.

Cliff

PS The reason I know perhaps more than it is healthy to know about ITO touch panels is that back in 1991-1993 I was responsible for this:

http://www.old-computers.com/museum/computer.asp?st=1&c=876

which was the world's first ever touch screen, hand writing recognising PDA that was available 3 months before the Apple Newton back in 1993. Back then this cost £299 - about $450. These days you can get something equivalent for about £20/$35 !!

 

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To use a standard desk/laptop LCD monitor for touch screen use may be a bad idea. They're very fragile, not intended to be touched. You may find that tapping a screen too hard may initiate cracks causing failure or at the very least wearing the plastic surface of the screen. However if you intend to make a transparent touch panel that rests over the LCD screen, such that it would not receive any force during panel touching, there should not be a problem.

Stan

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Nice to know that the new users have learned to read in the time 'Freaks was down :roll:.

OP: This would be better in the Off-Topic forum. Can one of the mods move it please.

- Dean :twisted:

Make Atmel Studio better with my free extensions. Open source and feedback welcome!