Physics of Capacitive Touchscreens
Projected Capacitive Touchscreen
Basically, a capacitive touchscreen is made out of a single capacitive layer which is also coated with a conductive material and glass. The finger or other conductive materials that come in touch forms a second capacitive layer. Let's look at that in further detail.
Remember, the definition of capacitance,
where, e = electric permittivity of free space, A = area , d = the separation of plates.
Therefore, the larger the area, the bigger the capacitance and as the distance implies, the thinner the layer, the bigger the capacitance will be.
Voltage is applied through the layer and that creates a circuit with a single capacitor. When a conductive object is touched, it acts as a second capacitor parallel to the existing capacitor.
Therefore, the larger the area, the bigger the capacitance and as the distance implies, the thinner the layer, the bigger the capacitance will be.
Voltage is applied through the layer and that creates a circuit with a single capacitor. When a conductive object is touched, it acts as a second capacitor parallel to the existing capacitor.
Parallel capacitors, so the total capacitance is calculated as
Ct = Cp + Cf
Different mechanisms can be built to to detect any of the change and to locate the X and Y coordinates of the touch.
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