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I am doing a physics project for my high school course. My project is to explain how a resistive touchscreen works.I have no engineering knowledge.

From a description I found on computerworld.com (it's the most elaborate one I could find)...

It consists of a top flexible, bendable film and a rigid bottom film (usually glass), separated by a air gap. The two films are lined with transparent conducting materials (usually ITO), perpendicularly placed to one another.

It's analog resistive ("analog"-measures a change in value, not limited to the binary choice between complete presence or absence)

When pressed, the top and bottom films (more specifically, the conducting linings) make contacts, and thus a circuit is formed.

The voltage is measured. Assuming the current that goes through this "circuit" is constant, the resistance varies proportionally with the voltage.

This is the tricky, kinda shaky part that the author just glossed over: with the voltage measured, the X and Y coordinates of the touch position is calculated based on the amount of resistance at the point of contact.

QUESTION

What determines the voltage measured (and thus the resistance calculated from voltage and current)?

What are the conducting layers lined perpendicularly?

If the whole resistive touchscreen is "analog resistive", why then "this analog voltage is processed by analog-to digital converters (ADC) to create a digital signal that the device's controller can use as an input signal from the user"? (ALSO, ISN'T "DIGITAL" THE OPPOSITE OF ANALOG?)

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"What determines the voltage measured (and thus the resistance calculated from voltage and current)?"

The voltage mesaured is determined by the location of the touch. No resistance is calculated explicitly.

"What are the conducting layers lined perpendicularly?"

To make sure that they touch only at the location where the user touches the screen.

If the whole resistive touchscreen is "analog resistive",

that is correct

why then "this analog voltage is processed by analog-to digital converters (ADC) to create a digital signal that the device's controller can use as an input signal from the user"?

Because the device software can handle only digital values.

(ALSO, ISN'T "DIGITAL" THE OPPOSITE OF ANALOG?)

That depends on what you mean by OPPOSITE.

What you don't seem to have picked up is how a tochscreen actually works. If it is your assignment to do that, you will have to do some more study, especially the concept of "voltage divider". A basic understanding of Ohm's law as used for series and parallel circuits will also be handy.

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  • \$\begingroup\$ But why does the location of touch affect the voltage. Is there a battery that supplies constant voltage? Then, would total voltage in the circuit be constant, the only variables being resistance and current? \$\endgroup\$ – most venerable sir May 17 '16 at 19:58
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    \$\begingroup\$ "why does the location of touch affect the voltage": do read up on "resistor voltage divider". The voltage is in the end supplied by the power of the device (battery or mains or other), but there is a trick required to get both X and Y coordinates. \$\endgroup\$ – Wouter van Ooijen May 17 '16 at 20:01
  • \$\begingroup\$ I cant imagine how parallel linings will touch at a different locations. Can you maybe draw a pic? \$\endgroup\$ – most venerable sir May 17 '16 at 20:33
  • \$\begingroup\$ So the point of touch is like a resistor?What is that thing in the touchscreen that measures the current and the voltage across this resistor? \$\endgroup\$ – most venerable sir May 17 '16 at 21:01
  • \$\begingroup\$ Now that I read and know about voltage divider, can you tell me what that "trick" is? \$\endgroup\$ – most venerable sir May 17 '16 at 21:11

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