how to develop simple touch screen mechanism

At a minimum, you'll need switchable drivers (simple) and a decent A-D.

I suggest reading about the operation of touch panels (in case you don't know) as there are a number of types. That assumes, of course, that you are going to use a commercial touch panel.

Try the Wolfson data sheet (has a decent explanation of touch panel operation) for their combination AC97 / touch panel controller

Cheers

PeteS

NO! What are you trying to accomplish? When you say "build", what do you mean? What do you mean by touch? Finger? stylus? For a small display a finger might be too big. The technology used may be critically dependent on what you're gonna use to "touch" it. The bottom line is that while conceptually simple, it's unlikely that you could build one for less than what it costs to buy one.

When you say "alpha numeric", I infer that you need less than full position reporting. If all you want is selection with soft buttons, one way is to position a line of buttons under the display with labels that are dispayed above on the LCD. You have context sensitive buttons without any touch input at all.

If you have the ability to deposit transparent conductive material on plastic, you have a lot of other options. If that material happens to be uniformly resistive, you have more options.

Then there are other technologies. All simple conceptually, but requiring specialized equipment to fabricate.

What you do depends a lot on what you're trying to accomplish.

mike

Yes.

Graham

No ?

You're talking rubbish.

This is one of my fave areas.

A certain company I worked for wasn't called Touchscreen Technology by accident.

It's a mature technology and great fun.

Also very easy to use. Expensive though ! :-(

Now pls - ask the more detailed question.

Graham

So, you're saying that it's easy to build a touchscreen if you're a touchscreen manufacturing company? Whooda thunkit!! I'm flabbergasted by this revalation. I have to sit down until my heart palpitations subside...I may even have an orgasm...

Do please elaborate on how someone who didn't have the resources of a touchscreen company might "build" such a device (for less than the cost to buy one). I gots my soldering iron hot too. Let's do it.

mike

we are developing a small LCD touch screen, but it may be a couple of months before it will be marketed.

Don...

ISTR a Byte magazine article, a long time ago, that used strobed leds and optical sensors around the edge of the screen. Even a PIC could do that if you are daft enough to use one

martin

I am not clear if the OP wanted to make a touch screen or acquire a commercial one and simply drive it properly. Depending on other local circuitry, even that can have plenty of it's own pitfalls ( I know - I have one very close to a cold cathode backlight inverter ;)

Cheeers

PeteS