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Topic: Maximum touchscreen voltage (Read 598 times) previous topic - next topic

bobthebanana

What is typically the maximum voltage I should apply between y+/y- or x+/x- on a resistive touchscreen? the resistance is about 300 and 500 ohms for x and y, respectively. I'm asking because I seem to have broken my first touchscreen by using 3v. The resistance between x- and y- became 100 ohms when the touchscreen wasn't pressed (it should have been infinite ohms). I just got a new touchscreen and was also using 3v when the same thing happened. If I disconnect the power and measure resistance it rises up to ~100k over the course of 30 seconds, so it might be something else. Is 3v way to much for the touchscreen? I'd like to drive it directly from an MCU output.

johnwasser

I'd be surprised if even 5V was enough to damage a resistive touch screen.  At 300 Ohms that would be about 16 mA of current or 0.08 Watts.  Make sure your code disconnects Y when powering X and disconnects X when powering Y.
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bobthebanana

Yeah it surprised me too when my first one got shorted. I just redid the less-than-adequate solder job and the problem seems to have gone away; must have been flux residue. However on my first touchscreen the solder job was perfect, yet the short didn't go away over time. Weird.

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