We live in era of smartphones. Almost each one of us owns one. Have you ever wondered that which feature makes it different from the conventional devices; yes of course it is the touchscreen. Touchscreens really made our life simpler. Now a day, even a 3 year old kid can easily handle phone. Swiping, magnifying, playing and controlling the game on fingers etc have been possible only because of touch screen. So this article is all about working of a touch screen.
So firstly we should be clear that all the touches are not same. You will be surprised to know that there are 18 different touch technologies available. But they differ in durability, accuracy, cost etc. there are two technologies which are generally used:
- Resistive touchscreen
- Capacitive touchscreen
What is Resistive touchscreen?
In simple words, what is touch? It is applying negligible yet detectable force by your finger on anything. And this resistive force detected by touchscreen. Resistive touchscreen consists of two electrically conducting layers. One of them is resistive and other is conductive in nature. These layers are covered by grid of electrical conductors. They are separated by a small gap which is called spacer. So basically current flows through these layers all the time but when we touch a force act and one layer bends and touches the other and so the current changes at the point of contact. The software detects the change in current and hence that spot is identified. And the function associated with that point or spot is carried out. Such touch screens are found in ATMs.
Advantages of Resistive Touchscreen:
- They are durable and consistent
- They are inexpensive.
- We can use anything to touch like fingertip, finger nails, gloves.(but that should not be sharp otherwise screen may get damaged.)
Disadvantages of Resistive Touchscreen:
- These touchscreens need re-calibration of touch panel from time to time.
- Spacers present in such screens increase the width of device (now we know there is a trend of thinner devices).
- These spacers are also responsible for poor display in outdoors.(that occurs due to refraction)
- The biggest disadvantage is that only one touch is detected at a time. If we touch the screen at two places , the resultant or the combined effect of both the point will be some other point differing from previous two points.(we can make those resistive screen which detect more than one touch but they will be very costly.)So here comes a need of using other touchscreen.
What is Capacitive Touchscreen?
They are further divided in two categories:
- Surface capacitive touchscreens
- Projective capacitive touchscreens
In surface touchscreens, sensors are present at corners and a thin evenly distributed film is present across the surface and projective touchscreens consists of grid made of rows and columns and sensors are distributed throughout the screen. Now a day’s projective touchscreens are used and are called PROCAPS.
The working is completely different from resistive touchscreens. These screens can be operated by anything (which should be conducting, human bodies are conducting in nature that is the reason why we are able to operate them). When we touch the screen charge moves through our body as circuit is completed resulting in a voltage drop on that point of contact. . The software detects the change in voltage and hence that spot is identified. And the function associated with that point or spot is carried out. This is used in smartphones.
Advantages of Capacitive Touchscreen:
- Multiple touches are allowed.
Disadvantages of Capacitive Touchscreen:
- It is costly as expensive controller are used in it (they detect touch was hard or soft or it was unintentionally done so needs to be ignored).
Only fingertips can be used. (after wearing gloves we can’t use them as they are non conducting).
About Author: This Article was originally submitted by Ms. Priya pursuing B.Tech in Electronics.