Let’s be honest– smartphones are the best thing since sliced bread. We use them for almost everything (except toasting sliced bread). You’re probably even reading this on your smartphone right now or have one nearby. But have you ever wondered exactly how your phone works? Like, how does it do the things it does?
Take the display, for example. Back in the early days of cell phones, the screen and the keypad were two separate parts of a phone. Now you can use the screen as the keypad using touch input. Ever wondered…
How does the touchscreen on a phone work?
The idea behind touchscreens is very simple. Smartphones have electrical currents running through their screens. When you place your finger or stylus on the screen, it changes the flow of the current. The smartphone’s system measures the changes in the electrical current, and uses that information to detect the exact location of the touch and responds to the input.
However, different electronic devices use different methods to detect a person’s input on a touchscreen. The two most common methods found on smartphones are resistive touchscreens and capacitive touch screens.
Types of touchscreens
Resistive touchscreens rely on pressure being applied to the screen in order to determine the point of contact. Capacitive touchscreens, on the other hand, don’t rely on pressure. They only respond to input from an object that holds an electric charge, your finger being one of them.
Resistive touchscreens may have been common in the early days of mobile phone touch screens, but today it’s more likely that your smartphone uses a capacitor touchscreen than a resistive touchscreen.
So,…
How exactly do they work?
Here’s a little breakdown of the more technical details of how the different touchscreens work.
How a resistive touchscreen works
(1) Polyester Film, (2) Upper Resistive Circuit Layer, (3) Conductive ITO (Transparent Metal Coating), (4) Lower Resistive Circuit Layer, (5) Insulating Dots, (6) Glass/Acrylic Substrate, (8) Touch controller.
Resistive smartphone touchscreens rely on a touch overlay, which is essentially made up of a flexible top layer and a hard bottom layer. The inside of these two layers is coated with a conductive transparent metal oxide coating, which is responsible for running an electric current through both layers.
The flexible upper resistive circuit layer and the rigid lower resistive circuit layer are separated by insulating dots. The whole setup is attached to a touchscreen controller, which is responsible for determining the location of the touch input.
An electric current runs through the flexible top layer and the rigid bottom layer while the phone is operational. When your finger or stylus touches the flexible top layer, the pressure is applied to the layer and it bends until it comes into contact with the bottom resistive circuit layer, thus creating a circuit switch at the point of contact.
The touchscreen controller registers the change in current between the top and bottom circuit layers and then converts them into digital X and Y coordinates of the activated area. From there, the phone’s processor carries out the instructions associated with that particular area on the screen.
Advantages of resistive touchscreens
The biggest advantages of resistive touchscreens are their durability and their relatively low cost. This makes them ideal for any input device without driving the costs up too high.
Disadvantages of resistive touchscreens
The biggest disadvantage of resistive touchscreens is that they can only handle one-touch input at a time. That means you can’t do things such as a two-finger zoom, which is pretty much expected in today’s mobile devices.
How a capacitive touchscreen works
Capacitance refers to the ability of something to hold an electric charge. For example, your body has capacitance. When you shuffle your feet across a carpet, your body stores the electric energy generated from the carpet, which leads to a static shock when you touch a metal object. Capacitive touchscreens rely on this principle in order to work well.
In the capacitive touchscreen system, the touchscreen panel is made of glass, coated with a layer of transparent conductor material. In most cases, this material is indium tin oxide, and it is responsible for storing the electric charge.
Capacitive touchscreens come in two different types– surface and projective. A surface capacitive touchscreen has sensors at each corner of the screen, which it uses to measure changes in the electric charge. A projective touchscreen, on the other hand, uses a grid of rows and columns with a separate chip for sensing.
With both types of capacitive touchscreens, when you touch the screen, the electric current is transferred to your finger because the human body is also a conductor of electricity. This transfer decreases the amount of electrical charge in the capacitance layer.
Once the system has determined the location of the touch input, the relevant instruction will be processed and executed by the processor.
Advantages of capacitive touchscreens
One advantage capacitive touchscreens have, especially over resistive ones, is that they transmit almost 92% of the light that comes from the screen, whereas resistive touchscreen systems only transmit about 75%. This greatly impacts the picture quality of the display.
Perhaps the biggest advantage of capacitive touchscreens is that they can register multiple touch inputs. This makes gestures such as finger zoom possible. Also, capacitive touchscreens respond very quickly.
Disadvantages of capacitive touchscreens
The biggest drawback of the capacitive system is that it does not respond to input from non-conducting objects. So, if you’re wearing gloves or using a plastic stylus, you will not be able to use the touchscreen.
The best way to deal with this issue is to invest in a special capacitive stylus or a pair of gloves that are fitted with conductive thread.
Super AMOLED/ In-Cell
The above explanations refer to what is known as an on-cell touchscreen, because of the different layers of the display that work together to display images and respond to touch input.
A different type of touch screen is the in-cell touchscreen. What’s cool about it is that it combines the layers of the touchscreen into one. What results is a more responsive touchscreen that is much thinner with fewer moveable parts.
Samsung calls this technology Super AMOLED and has used in their smartphones from as far back as the first Galaxy S smartphone released in 2010. Since then, other manufacturers have included in-cell displays in their smartphones.
Conclusion
Touchscreen technology is nothing new or exclusive to smartphones but it has made a major impact in the industry. And just when you thought it couldn’t get any better, innovative companies come up with new versions that offer greater flexibility and benefits.
What the future holds for smartphones and touchscreen technology, only time will tell.
