Building A Touch Screen For My Final Year Project

[mekman]

i am buliding a touch screen (4 wire resistive) for my final year project in university. and i need some help to point me in the right directions.

i now understand they are 3 parts to the project
1. building of the touch screen itself
2. creating a controller for it
3. the software interfacing

my problem is as follows

for the first part (building of the touch screen itself)
i know i need ITO coating on a glass or some sort of plastic
does anyone know where i could order this somewhere in the uk?
2. should get the coating with the most resistance?
3. i am going to have problem with noise either form the lcd screen i am mounting on or the plate itself and how do i resolve this?

for the second part (creating a controller for it)
any idea for a cheap 4 wire controller or chip to be used to make this controller to work through the RS232 port?
please any schematics?

for the software part
how do i get it to actually move the mouse in windows xp.
and do i need to create a driver?

any help you give me is appreciated and thank you for taking time to read my request.
anthony

 

[Oznog]

I don't think you can MAKE a touch screen.
Touch screens are complicated to manufactured and AFAIK it's not something you can make at home.

Typically there are 3 components here: the physical touch screen, a controller which interprets the analog electrical voltags as a logical location, and a microcontroller (or PC) which queries the controller for touch screen activities.

There are infrared LED touch screens which are not based on a coating but rather a frame around the screen, consisting of simply many infrared (invisible) transmitting LEDs on one side and many receivers on the other side, giving a low-resolution X-Y location of your finger by seeing which row/column receivers see a reduction in light exposure. There are issues of light spread, a finger will probably block the light to more than one receiver and light spreading off adjacent rows/columns will probably still illuminate the desired receiver some. It may be best to use highly focused LEDs but I really don't know.

 

[mekman]

i am not making this at home

I don't think you can MAKE a touch screen.
Touch screens are complicated to manufactured and AFAIK it's not something you can make at home.

Typically there are 3 components here: the physical touch screen, a controller which interprets the analog electrical voltags as a logical location, and a microcontroller (or PC) which queries the controller for touch screen activities.

There are infrared LED touch screens which are not based on a coating but rather a frame around the screen, consisting of simply many infrared (invisible) transmitting LEDs on one side and many receivers on the other side, giving a low-resolution X-Y location of your finger by seeing which row/column receivers see a reduction in light exposure. There are issues of light spread, a finger will probably block the light to more than one receiver and light spreading off adjacent rows/columns will probably still illuminate the desired receiver some. It may be best to use highly focused LEDs but I really don't know.

i am studying computer systems and electrical engineer. and i am doing this at university. we have all the tools need to make it happen

 

[Helder Ferreira]

Look at the microchip.com site, they have an apnote on touch sreens. It's quite easy to work and with a little dedicated microcontroller you can use it's UART to comunicate with the PC. To interface the touch screen all it's needed is, 4 pins from the uC. 2 outputs and ADC channels. About every Pic micro has those.

 

[Helder Ferreira]

Another way to make a "virtual touch screen" is to use 4 small load cells on a base on to wich you mount the monitor. If you press the screen at different points, the relation between the cells change and it's different from each other. After calibration it will serve as a pretty good touch screen.

 

[ClydeCrashKop]

Microsoft DirectX SDK will let you intercept/modify mouse droppings with examples in the direct input section.

 

[Hero999]

You could consider Linux as opposed to Windows, not only for reliability's sake but also, being open source, you can tweak it to get it working they way you want.