Generally speaking, when operating the touch screen, we must first touch the touch screen installed in the front of the display with our fingers or other objects, and then the system will locate and select the information input according to the icon or menu position touched by our fingers. The touch screen is composed of a touch detection component and a touch screen controller; The touch detection part is installed in front of the display screen to detect the user’s touch position and accept the evacuation touch screen controller; The main function of the touch screen controller is to receive the touch information from the touch point detection device, convert it into contact coordinates, and then send it to the CPU. At the same time, it can receive and execute the commands sent by the CPU. In order to operate the touch screen efficiently, it is very necessary for us to understand the working principle of various types of touch screens first:
The working principle of the resistive touch screen is mainly to realize the operation and control of the screen content through the pressure sensing principle. The screen body of the touch screen is a multi-layer composite film that fits well with the surface of the display, in which the first layer is the bottom layer of glass or plexiglass, the second layer is the spacer layer, the third layer is the surface layer of multi-component resin, and the surface is also coated with a transparent conductive layer, It is covered with a layer of smooth scratch resistant plastic layer with hardened outer surface. The conductive layer and glass layer on the surface of polybasic grease are separated by many tiny compartments; When the current passes through the surface layer and lightly touches the surface layer, it contacts the bottom layer. The controller reads the corresponding current from the four corners and calculates the distance of the finger position at the same time.
The touch screen is composed of two highly transparent conductive layers, and the distance between the two layers is only 2.5 microns. When the finger touches the screen, the two conductive layers normally insulated from each other have a contact at the touch point. Because one of the conductive layers is connected to the 5V uniform voltage field in the y-axis direction, the voltage of the detection layer changes from zero to non-zero. After detecting this connection, the controller performs a / D conversion, and compares the obtained voltage value with 5V to obtain the y-axis coordinates of the touch point, Similarly, the coordinates of the X axis are obtained, which is the most basic principle common to all resistive touch screens.
The working principle of the surface acoustic wave touch screen is mainly based on the principle that mechanical waves propagate on the surface of a medium. The touch screen transmits sound waves through the sound wave generator pasted on the three corners of the screen surface, receives sound waves through the sound wave receiver, and then transmits signals to the touch screen through the sound wave reflector, The sound wave generator can send a high-frequency sound wave across the screen surface. When the finger touches the screen, the sound wave on the contact is blocked, and the received signal is converted into coordinate value, so as to determine the coordinate position of the specific touch point. The controller can measure the pressure of the touch screen by absorbing the sound wave energy, At the same time, the coordinate value reflecting the touch pressure is returned.
On the surface of the surface acoustic wave touch screen, the acoustic wave transmitter and acoustic wave receiver in X direction and Y direction are pasted, and 45 degree stripes reflecting acoustic waves are engraved around the glass screen. The controller produces 5.53mhz signal, which is transmitted to the transmitting transducer through cable, and the piezoelectric transmitting transducer converts it into ultrasonic energy. After two reflections of the reflection fringe, it is transmitted to the receiving transducer and converted into an electrical signal to the controller. Because the surface acoustic wave touch screen is composed of touch screen, acoustic wave generator, reflector and acoustic wave receiver, especially the acoustic wave sensor is not affected by environmental factors such as temperature and humidity, with high resolution, excellent scratch resistance and long service life; High light transmittance, which can maintain clear and bright image quality; No drift, only need to be corrected once during installation; With the response of the third axis (i.e. pressure axis), it is most suitable for use in public places.