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:
1. Working principle of resistive touch screen
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 insulating conductive layers 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 the controller detects this connection, it 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.
2. Surface acoustic wave touch screen
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.
3. Capacitive touch screen
Capacitive touch screen is a transparent special metal conductive material pasted on the glass surface. This inductive touch screen is composed of five layers. The first layer is the glass bottom layer, the second layer is the conductive layer, the third layer is the glass sensing layer, the fourth layer is the anti reflective fog surface or bright surface layer, and the fifth layer is the anti noise protective layer. When the finger touches the surface of the capacitive touch screen, the induction mode is that the voltage is connected to the four corners of the glass layer, the voltage is dispersed in the glass layer through the electrode, and an unchanged voltage electric field is established. At the same time, the capacitance of the contact will change, so that the frequency of the oscillator connected to it will change. The touch position can be determined by measuring the frequency change to obtain information. Because the capacitance changes with temperature, humidity or grounding conditions, its stability is poor and drift often occurs. In addition, when the surface layer is touched, the current is collected from the four corners of the glass layer, and the controller calculates the distance from the current to the position of the finger, so as to determine the accurate position of the touch.
4. Infrared touch screen
The working principle of this infrared touch screen is relatively simple. It only needs to add a light spot distance frame on the display without adding a coating or connecting a controller on the screen surface. Then, infrared transmitting and receiving sensing elements are arranged on the four sides of the light spot distance frame to form an infrared detection network on the screen surface. When any touching object touches a point on the screen, It will block the horizontal and vertical infrared rays passing through the position, and the computer can calculate the position of the touch point immediately. The infrared touch screen is not disturbed by current, voltage and static electricity, and is suitable for some harsh environmental conditions. Because the infrared touch screen has no capacitor charging and discharging process during operation, the response speed is faster than the capacitor type, but the resolution is lower.
After knowing the working principle of the touch screen, let's talk about how to operate the touch screen! In order to better help you operate the touch screen, the author summarizes the following operation methods and skills:1. If you are using a capacitive touch screen, it is recommended that when you use it for the first time, first correctly install the driver required for the capacitive touch screen according to the instructions, and then click "start" / "program" / "microtouch touchware" on the screen with your fingers to run the screen calibration program. After the calibration is completed, The system automatically stores the calibrated data in the register of the controller. After restarting the system, there is no need to calibrate the screen.2. If the display resolution or display mode of the touch screen is changed again during the midway operation of the capacitive touch screen, or the refresh frequency of the touch screen controller is adjusted by itself, and it is felt that the cursor cannot correspond to the touch point, the touch screen system must be calibrated again.
3. In order to ensure the normal operation of the touch screen system, in addition to ensuring the correct installation of the system software, we must also remember not to install two or more touch screen drivers on a host, which will easily lead to conflicts during the operation of the system, so that the touch screen system can not be used normally.
4. When using the resistive touch screen, if you find that the cursor does not move or can only move in a local area, you can check whether the touch area of the touch screen is always dominated by other touch objects. For example, once the touch screen is pressed by the display shell or cabinet shell, it is equivalent to a point has been touched all the time, and the coordinate position fed back to the controller is inaccurate, Of course, the cursor cannot be positioned correctly. If the cabinet shell presses the touch area, you can increase the distance between the cabinet and the display screen. If the display shell presses the touch area, you can try to loosen the screw of the display shell.
5. The author mentioned earlier that once the system changes the display resolution, adjusts the screen size and is installed for the first time, there will be inaccurate clicking or drift. It is necessary to start the positioning program in the application to reposition. However, when positioning, it is better to use a thin pen or fingertip for positioning, which is more accurate.6. The working environment of the surface acoustic wave touch screen requires high requirements. It must work in a clean and dust-free environment, and the dust on the surface of the touch screen must be cleaned regularly. Otherwise, when the dust in the air covers the reflection stripes or energy converters around the touch screen, it will affect the correct positioning of the system.7. Do not allow water droplets or other soft things on the surface of the touch screen to stick to the surface, otherwise the touch screen is easy to mistakenly think that there is hand touch, resulting in inaccurate surface acoustic wave screen. In addition, when cleaning the dirt on the touch screen surface, you can carefully wipe it from the center of the screen with a soft dry cloth or detergent, or clean the touch screen surface with a dry soft cloth dipped in industrial alcohol or glass cleaning solution.
8. If the touch screen reacts slowly when touching the surface acoustic wave touch screen with hands or other touch objects, it indicates that the touch screen system is very old, the internal clock frequency is too low, or there are water droplets moving on the touch screen surface. In order to restore the rapid response of the touch screen, the system must be replaced or upgraded, Or wipe the water drops on the surface of the touch screen with a rag.