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Topic: Ttp223 , Cs capacitor value (Read 189 times) previous topic - next topic

endrithoxha123


hello,
I need to put a touch pad on the glass, the thickness of the glass will be 4mm, the dimensions of the touch pad will be 1x1cm copper,
what value should the capacitor Cs set

Grumpy_Mike

Cs is shown as a variable capacitor. It should be about the same capacitance as the pad. But until you physically make the pad you can't measure its capacitance so you don't know what value to make it.

Paul__B



Page 4 of the datasheet.

You do not need "Cs" at all, indeed you absolutely do not want it unless the touch area is excessively sensitive and responding to movement around the sensor that you do not want to be detected.

If you were to have spurious sensitivity to movement behind the touch area, you would want to place a grounded shield behind, but not too close to it.

Wawa

You do not need "Cs" at all, indeed you absolutely do not want it unless the touch area is excessively sensitive...
+1
A parasitic capacitor makes things less sensitive.

4mm glass shouldn't be a problem, unless you're on battery power.
Make sure you also have a ground plane near that sensor field.
Leo..

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