Electronics notes/Touch screen notes

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Types

http://en.wikipedia.org/wiki/Touchscreen#Technologies

Resistive

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Most simpler touch screens are resistive. For a good time they were the rather cheaper option -- largely though economy of scale.

They need more force than the later capacitive type, and may require a stylus to be useful.

Can have pretty decent resolution, but may not.

Each axis, when touched, will give a particular resistance in a range (usually interfaced with an ADC), so can report only a single touch - touching on multiple places (e.g. resting a palm while drawing) will typically mis-report.

There's 4-wire, 5-wire, 7-wire, 8-wire and more. These relate to different accuracies, and some to variants that won't lose as much accuracy over timeTemplate:Verfiy

Capacitive

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Capacitive sensing can sense various materials nearby, which includes fingers or anything with a conductive tip - from specific styluses to sausages in latex gloves.

Designs usually focus on a specific range of capacitive effect, and will then respond fewer things that aren't fingers and closeby.

Capacitive tricks went from being there in only a few devices (e.g. nineties trackpads) to increasingly common (in MP3 players, and phone touchscreens) in the late noughties, to uniquitous in phones and tablets since.

Has a few subtypes -- see capacitive sensing.

One of them can be multi-touch, and multi-touch tablets and phones are very usually capacitive.

Capactive touchscreens can be built in a more robust way than resistive (sensors are under the top glass, not part of the top layer as in resistive).

Capacitive touch can also be faster and more responsive than resistive. Some of the simpler/cheaper designs are less accurate than resistive, though; some handwriting recognition devices actually stuck with resisitive.