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How do touch screens work?

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Do they fell body warmth, or electricity or what?

 

I had something on my right hand oh, and rinsed it off in the sink. Cold tap water.

 

After I dried it off I tried to look at something on my phone, and my phone would not react to my hand. I tried with my left hand, which I had not got wet and was still body temperature and everything worked.

 

That seems to say heat. But they have styluses that work with your smartphone, and they are not hot.

 

So what do these things react to?

 

 

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MAGIC

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I believe they work off capacitance. 

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You can read the below link to get a general idea of how they work and the two designs most commonly in use today.

 

Okay, but how do touch screens actually work?

 

The first ones I ever worked on had a grid just above the screen made up of IR beams and corresponding sensors. When you put something close to the screen it interupted the beams path and the system calculated where you were touching the screen. Worked pretty well but it did require the bezel around the screen to be rather large. IIRC it was about 2 or 3 times thicker and 3 to 4 times as wide as the bezel on a current generation computer monitor. Performance outdoors was pretty bad as sunlight tened to overload the IR sensors. 

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I think cell phones work off of capacitance, which is why the wet hands were a problem.  The stylus is made of special material, you can't just take a tooth pick and use it as a stylus.  There are also touch screens that use resistance.  I've seen those in factories and plants.  Those can be used with gloves on or by using any object as a stylus. 

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The touch screen in my car won't work when my hands are wet or if I have gloves on.

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At the bottom of the article about how they work there is a statement about a coffee table size one, The finance manager where I tried to buy a truck had a desktop screen. I signed his desk. Pretty nifty, then the deal went south, having nothing to do with touch screens.

 

Imis 

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Anybody remember MCP in TRON!!

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