How does touchscreen work?
In: Technology
There are two kinds, but I’ll explain capacitive touch because it’s cooler and easier to use. There are electrons being rapidly pumped into and out of a bunch of transparent wires on your screen. When something comes near the screen, it makes it easier for these electrons to move into the screen since they’re attracted to the something. The computer senses this easier movement, and knows there is something there. If the movement is too easy, it’s probably just a piece of metal. If the movement is too hard then there’s probably nothing there or something with a lot of resistance (not a finger).
theres resistive and capacative
The idea is that you have a extra layer on the screen that uses a physical atribute to detect you touching the screen
Resistve it was 2 layers that had a grid of dots, so depending on which dots from the 2 layers touched, you could tell where someone was touching.
Capacitive is similar but with 1 grid and 1 layer, the grid has a low voltage electric current through it, and when something conductive like your finger touches it, it creates a capacitor (basically a buildup of electricity there), by measuring that you can calculate where a use is touching.
Electrically conductive materials that are near each other make a capacitor. If you use a battery you can charge a capacitor up to full charge very quickly. If you put a resistor in the path of the electricity it will slow down the charge up process enough that you can measure the charge up time to see how much capacity it has.
Touch screens have a grid of thin wires. The left-right wires never touch the up-down wires, but are very close. Picking a left-right wire and an up-down wire lets you pick a capacitor at some location on the screen (since you have two electrical conductors near each other.)
The touch screen scans across every “capacitor” in the grid and measures the capacity.
Your skin isn’t very conductive. However, your blood is very conductive. When you bring your finger close to one of these capacitors, the meat-bag conductor increases the capacity nearby, and that will be picked up by the scan. (You can activate a sensitive touch screen without even physically touching it if you have steady hands.)
Fun facts:
The bits and bobs inside your phone and tablet make the capacity of these little wire-pair capacitors vary across the screen, so the screen needs to learn in the factory what no one touching it looks like, generally after the device is fully assembled.
I’ve been told that Apple holds a patent on square wire grids, so everyone else uses a diamond pattern, and does a little extra math to put it into screen positions.
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