Hi,
I'm designing a Control Panel composed by a screen and a key pad.
I noticed that Resistive and Capacitive Touch Screen Films are getting popular because they can replace silicon keypads.
I know almost nothing about those 2 technologies.
Can anybody tell me how they work and what kind of electrical interface they have.
Thanks in advance, Enrico
I know resistive panels are usually 4 pins for pairs of resistance in the X and Y directions (touch to reference points).
Perhaps capacitance s for capacitive panels?
Usually Wikipedia is a good entry point. A general overview:
The detailed description with a diagram for resistive touchscreens is available in German, only:
Maybe someone wants to enhance the English page:
But there are some links on the Wikipedia page, e.g. this one for the capacitive concept:
-- Frank Buss, http://www.frank-buss.de piano and more: http://www.youtube.com/user/frankbuss
If you need 'turn-key' hardware, you could try an 'evaluation kit' from WinSystems.com . I think they have a couple of different sizes too.
Are you deliberately limiting yourself to these two technologies?
Do you need "fine resolution" and a large number of "screen locations"? Or, will all of your "buttons" be in fixed places on the screen? (perhaps you can use real buttons adjacent to the screen and just
*label* them on the screen... "soft keys")What sort of environment are you working in (temperature, humidity, vibration, etc.)? How concerned are you re: ESD, etc.?
Do you just want bistable sensing (i.e., pressed vs. not pressed)? Or, do you also want to be able to sense how *hard* the screen is being pressed?
Do you want to be able to sense a "gloved" finger, also? Or, even a
*plastic* actuator??How tolerant will you be of "multiple (concurrent) touches"?
How concerned are you of the actual display (image portion) being "damaged" by way of normal usage?
My (current) favorite technology is SAW as it seems to give me the greatest flexibility -- though it is ill-suited to portable devices, etc.
Most people should probably avoid capacitive touch screen technologies unless you find a good partner to work with, that can sell in low volume.
Low volume is < 250 ku/year
Reason is that the touchscreen film manufacturers only start to get interested when you have that kind of volume.
I dont think that they maintain a distribution network either, so you have to find those few companies which have competence and a channel into the touchscreen film manufacturers.
Best Regards Ulf Samuelsson
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