How Does A Capacitive Touch-Screen Work??

– Rohit Bhaskar

– Chirag Trasikar

We all use mobiles everyday, almost continuously. And we pretend to have control over how much we use it :) But do we ever stop and think about how the screen of our devices actually work? For most of us out there, i am guessing its still ‘black magic’. So I am hoping that this small post will help everyone understand!!

Parts:

Capacitive touch screen actually consist of 3 different layers or screens.

The first layer is the conducting transparent sheet. (The first layer is a glass like panel) The second layer is the capacitive grid, or mesh of conductors, or just a thin conducting sheet. The third is the sensor layer or the capacitance measuring layer.

Working:

In the next image we can see that when we bring our finger (any conductor) close to the 1st layer, the field generated by the 2nd layer is disrupted. This in turn causes a change in capacitance at that point (since capacitance is directly related to the voltage at the point). After that come the use of the 3rd layer which senses the position of the variation in capacitance and sends corresponding data to the processor to process further.

Types:

Even capacitive touch screens are of 2 types, but their main 3 layers still remain the same, even if they work differently. The 2 types are:

1. Surface
2. Projective

The main difference between them is that surface capacitive uses sensors at the corners of the screen to find out where you have clicked and a thin evenly distributed film across the surface (as pictured above) whereas projective capacitive uses a grid of rows and columns with a separate chip for sensing the position.

That’s It!! I hope you guys understood and I also hope I helped you bust this ‘magic’ phenomenon!