Types of touch screens. Which touch screen is better.
The screens of modern devices can not only display an image, but also allow you to interact with the device through sensors. Initially, touch screens were used in some handheld computers, and today touch screens are widely used in mobile devices, players, photos and video cameras, info kiosks, etc. Moreover, in each of the listed devices one or another type of touch screen can be used. Currently, several types of touch panels have been developed, and accordingly, each of them has its own advantages and disadvantages. In this article, we will just consider what types of touch screens are, their advantages and disadvantages, and also what type of touch screen is better.
There are four main types of touch screens: resistive, capacitive, with the definition of surface acoustic waves and infrared. In mobile devices, only two were most widely used: resistive and capacitive. Their main difference is the fact that: resistive screens recognize pressing, and capacitive touch.
Resistive Touch Screens
This technology has received the greatest distribution among mobile devices, due to the simplicity of the technology and the low cost of production. The resistive screen is an LCD display on which two transparent plates are superimposed, separated by a dielectric layer. The upper plate is flexible, as the user clicks on it, while the lower plate is rigidly fixed to the screen. Conductors are applied to surfaces facing each other.
Resistive touch screen
The microcontroller supplies voltage in series to the electrodes of the upper and lower plates. When you click on the screen, the flexible upper layer bends and its inner conductive surface touches the lower conductive layer, thereby changing the resistance of the entire system. The change in resistance is recorded by the microcontroller and thus the coordinates of the touch point are determined.
The advantages of resistive screens include simplicity and low cost, good sensitivity, as well as the ability to click on the screen with your finger or with any object. Of the minuses, it is necessary to note poor light transmission (as a result, you have to use a brighter backlight), poor support for multiple taps (multitouch), they can not determine the pressing force, as well as a rather fast mechanical wear, although this disadvantage is not so much compared to the phone’s life and important, because usually the phone crashes faster than the touch screen.
Application: cell phones, PDAs, smartphones, communicators, POS-terminals, Tablet PC, medical equipment.
Capacitive Touch Screens
Capacitive touch screens are divided into two types: surface-capacitive and projective-capacitive. Surface-capacitive touch screens are glass, the surface of which is coated with a thin transparent conductive coating, over which a protective coating is applied. On the edges of the glass there are printed electrodes that supply low-voltage alternating voltage to the conductive coating.
When touching the screen, a current pulse is generated at the contact point, the value of which is proportional to the distance from each corner of the screen to the point of contact, thus, it is quite simple to calculate the coordinates of the touch point to the controller, compare these currents. Among the advantages of surface-capacitive screens, it can be noted: good light transmission, short response time and a long touch resource. Among the shortcomings: the electrodes placed on the sides are poorly suited for mobile devices, demanding on external temperature, do not support multi-touch and can be touched with fingers or a special stylus, and cannot determine the pressing force.
Application: information kiosks, in secure rooms, in some ATMs.
Projection-capacitive touch screens are glass with horizontal leading lines of conductive material deposited on it and vertical defining lines of conductive material, separated by a dielectric layer.
Such a screen works as follows: on each of the electrodes in a conductive material, the voltage is sequentially applied by the microcontroller and the amplitude of the current pulse resulting from the measurement is measured. As the finger approaches the screen, the capacitance of the electrodes below the finger changes, and thus, the controller determines the place of contact, i.e. coordinates of mowing, these are intersecting electrodes with increased capacity.
The advantage of projection-capacitive touch screens is a quick response speed to touch, multi-touch support, more accurate determination of coordinates compared to resistive screens and determination of pressing force. Therefore, these screens are more commonly used in devices such as the iPhone and iPad. It is also worth noting the greater reliability of these screens, and as a result, a longer life. Of the shortcomings, it can be noted that on such screens you can only touch with your fingers (drawing or writing by hand with your fingers is very inconvenient) or with a special stylus.