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I just learned that in analog resistive touchscreen, conducting layers (usually made of indium tin oxide) is placed perpendicular to each other. One on the top flexible film, and one on the bottom, rigid film. On when the end user presses the top film, the conductors touches and a circuit is thus formed.

I previously asked a related question, and Wouter van Ooijen, who answered the comment question, told me that using parallel linings, the conductor will not necessary touch at the point where the user presses the film. But I am not clear how that would happen. So I made a separate question.

Also, what does the conductor looks like? Are they fine conducting strings placed close together?

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When the end user presses the top film, the conductors touches and a circuit is thus formed.

Correct. The controller works by checking which row is touching which column.

The touchscreen controller works as shown by the pseudo code below:

function checkTouch(){
  for each row {              // Switch on each row in turn.
    switch row on;
    for each column {
      if column is on {       // See if column is connected.
        return (row, column); //Contact found.
      }
    }
    switch row off;           // Disable the row.
  }
  return (null, null);        // no touch detected.
}

Turn on each row and see which column gets a signal. For an r x c touch screen this requires r x n pins on the controller.

Also, what does the conductor looks like? Are they fine conducting strings placed close together?

The conductors are transparent conductive coating applied to the screen material. Special edge connectors are used to make contact.

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  • \$\begingroup\$ So you send current through one of the 2 films first (row), and if that film touches the other film, then current pass through the corresponding column on the other film? \$\endgroup\$ – most venerable sir May 17 '16 at 21:50
  • \$\begingroup\$ But the same thing can done if the linings on both films are paralell? \$\endgroup\$ – most venerable sir May 17 '16 at 21:50
  • \$\begingroup\$ You've got the idea. Technically we "apply a voltage" to each row. No current will flow unless a contact is made. The current that does flow will be tiny and we would usually say that "voltage is detected" on the column. \$\endgroup\$ – Transistor May 17 '16 at 21:52
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    \$\begingroup\$ "But the same thing can done if the linings on both films are paralell?" Think about that. Yes, you could tell that a row had been pressed giving you a vertical position on the screen but you would not be able to work out how far across the contact had been made. \$\endgroup\$ – Transistor May 17 '16 at 22:07
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    \$\begingroup\$ This is NOT AT ALL how a modern 4-wire resistive touch screen works. There are no"rows" or "columns", just a single resistive film with exactly two connections on each of the two layers. What you're describing is a much older digital matrix technology. \$\endgroup\$ – Dave Tweed May 18 '16 at 4:59

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