The touch screen is a device for entering information based on the coordinate principle of perception, which responds to touch. They usually become an alternative to a whole bunch of mechanical buttons, which is very convenient, as it allows you to combine the display and input device. The reliability of such a system is much higher due to the fact that there are no mechanical and moving parts.
The very first models of touch screens were created in the late sixties of the last century, it was then that the scientist Samuel Hurst realized that he did not want to read kilometers of tape recorders. In 1971, he founded the company Elotouch, which released an eliograph, which was the first computing device to have a resistive touch screen. After some time, his company merged with another called Siemens, after which it became known as Elographics. Thanks to this collaboration, touch panels for picture tubes that already existed were developed. In 1982, the world's first television was introduced, which had a touch panel.
At the moment, it is customary to subdivide several types of touch screens depending on the technology by which their sensor functions. The resistive touch screen can be four-wire, five-wire or eight-wire. In addition to it, there are also capacitive, optical, matrix, tensometric screens , based on infrared rays and on the basis of surface-acoustic waves. There are several dozen other patented technologies, however, they are not as popular as resistive and capacitive. Most of them are inefficient or use very outdated technology.
Resistive touch screen
This type of display is the most popular today. The simplest in terms of implementation at the moment is a four-wire resistive touch screen. It includes a glass panel and a flexible plastic membrane with a thin coating of high conductivity. The space between the membrane and the glass is filled with micro-insulators, which reliably protect current-conducting surfaces. Thin metal plates, called electrodes, are mounted at the edges of each layer. In the front layer with resistive material, they are placed horizontally, and in the back layer vertically, which is intended for efficient calculation of touch coordinates. When the resistive touch display is pressed, the panel and the membrane are closed, and the resistance at the point of contact is recorded by a special sensor, which is converted into a signal. Eight-wire touchscreens are more advanced technology. Despite the fact that their accuracy is noticeably higher, their reliability and duration are a little “lame”.
The five-wire resistive touch screen is noticeably more reliable due to the fact that the resistive coating of the membrane has been replaced by a conductive one, which continues to work even when the membrane is damaged. The rear window is covered with a special material with four electrodes at corners that are constantly energized. The fifth electrode serves as a conclusion for the front layer having conductive properties. At the moment the screen is touched, the upper and lower layers collide, and the controller will first record the fact of the touch itself, that is, a change in the front layer. After that, first on the back layer, two horizontal electrodes will be grounded, and then the vertical electrodes will be shorted.
This description of the operation of the resistive touch screen is general, but it should be enough to understand this technology.