Now you may find that in many public places, a computer input device that everyone uses is a computer that allows users to directly operate the screen with their fingers. This computer is actually a touch screen that people often talk about. The touch screen is not only suitable for the national conditions of Chinese multimedia information query, but also has many advantages such as ruggedness, fast response, space saving, and easy communication. Using the touch screen, our users can operate the host computer only by touching the icons or text on the computer display with their fingers, which makes the human-computer interaction more straightforward. This technology greatly facilitates users who do not understand computer operations. . Many large public places such as banks, hospitals, hotels, shopping malls, sales halls, schools, libraries, museums, theaters, exhibitions, stations, large bookstores, tourist resorts, and communities now use touch screen technology. So do you know how the touch screen works? Are you familiar with the operation of the touch screen?
Generally speaking, when we operate the touch screen, we must first touch the touch screen installed on the front of the display with a finger or other objects, and then the system locates and selects the information input according to the icon or menu position touched by the finger. The touch screen is composed of a touch detection component and a touch screen controller; the touch detection component is installed in front of the display screen to detect the user's touch position and accepts the evacuation of the touch screen controller; and the main function of the touch screen controller is to receive touches from the touch point detection device Information, and convert it into contact coordinates, and then send it to the CPU, it can also receive the command sent by the CPU and execute it. In order to efficiently operate the touch screen, we still need to first understand the working principle of each type of touch screen:
1. Working principle of resistive touch screen
The working principle of the resistive touch screen is to realize the operation and control of the screen content through the principle of pressure sensing. The part of this touch screen screen is a multi-layer composite film that is very compatible with the surface of the display. The first layer is glass or plexiglass The bottom layer, the second layer is the interlayer, and the third layer is the multi-layer resin surface layer. The surface is also coated with a transparent conductive layer, which is covered with a hardened, scratch-resistant plastic layer on the outer surface. The conductive layer and the glass layer sensor on the surface of the polylipid are separated by many tiny interlayers; the current passes through the surface layer, and when the surface layer is touched, the bottom layer is touched, and the controller reads the commensurate current from the four corners at the same time And calculate the distance of the finger position. This touch screen uses two highly transparent conductive layers to form the touch screen, and the distance between the two layers is only 2.5 microns. When the finger touches the screen, the two conductive layers that are usually 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 zero. 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 coordinate of the touch point. Similarly, the X-axis coordinate is obtained. It is the most basic principle common to all resistive technology 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 certain medium. This type of touch screen uses acoustic wave generators pasted to the three corners of the screen surface to transmit sound waves and receive them through sound wave receivers. Acoustic waves, then the acoustic wave reflector is responsible for transmitting signals to the touch screen. The acoustic wave generator can send a high-frequency acoustic wave across the surface of the screen. When the finger touches the screen, the acoustic wave on the contact point is blocked, and the received signal is converted into coordinates Value, thus determining the coordinate position of a specific touch point, where the controller can measure the amount of pressure on the touch screen by absorbing the energy of the sound wave, and at the same time return the coordinate value reflecting the magnitude of the touch pressure. On the surface of the surface acoustic wave touch screen, X-direction and Y-direction acoustic wave emitters and acoustic wave receivers are pasted, and 45-degree stripes of reflected acoustic waves are engraved around the glass screen. The controller produces a 5.53MHZ signal, which is transmitted to the transmitting transducer through a cable, and the piezoelectric transmitting transducer converts it into ultrasonic energy and sends it out. After the two reflections of the reflective stripes, they propagate to the receiving transducer and are converted into electrical signals for transmission to the controller. Because the surface acoustic wave touch screen is composed of a touch screen, an acoustic wave generator, a reflector and an acoustic wave receiver, especially the acoustic wave sensor is not affected by environmental factors such as temperature and humidity, and has extremely high resolution, excellent scratch resistance, and long life; High light transmittance, can maintain clear and transparent image quality; there is no drift, only need to be corrected once during installation; there is a third axis (ie pressure axis) response, the most suitable for use in public places.
3. Capacitive touch screen
Capacitive touch screen is a layer of transparent special metal conductive material pasted on the glass surface. This touch screen is composed of five layers. The first layer is the bottom glass layer, the second layer is the conductive layer, the third layer is the glass sensing layer, the fourth layer is the anti-reflective matte or bright surface layer, and the fifth layer is the anti-noise protection layer. When the finger touches the surface of the capacitive touch screen, the induction method is that the voltage is connected to the four corners of the glass layer, and the voltage is spread on the glass layer through the electrode and an unchanging voltage electric field is established, and the capacitance of the contact changes. The frequency of the oscillator connected thereto is changed, and the touch position can be determined to obtain information by measuring the frequency change. Because the capacitance varies 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, thereby determining the exact position of the touch.
4. Infrared touch screen
The working principle of this infrared touch screen is relatively simple, just add a spot frame to the display, no need to add a coating or connection controller to the surface of the screen, and then arrange infrared radiation on the four sides of the spot frame With the receiving sensing element, an infrared detection network is formed on the screen surface. When any touching object touches a certain point on the screen, it will block the two infrared rays passing through the position, and the computer can immediately calculate the position of the touch point. The infrared touch screen is not affected by current, voltage and static electricity, and is suitable for some harsh environmental conditions. Because the infrared touch screen does not have a capacitor charging and discharging process during operation, the response speed is faster than the capacitive type, but the resolution is lower.
After knowing how the touch screen works, let's talk about how to operate the touch screen! In order to better help everyone operate the touch screen, the author summarizes the following operation methods and techniques:
1. If you are using a capacitive touch screen, it is recommended that when you use it for the first time, first install the drivers required for the capacitive touch screen according to the instructions, and then click "Start" on the screen in sequence with your finger / "Program" / "Microtouch Touchware" 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 later, there is no need to calibrate the screen.
2. If you change the display resolution or display mode of the touch screen when you operate the capacitive touch screen halfway, or adjust the refresh rate of the touch screen controller yourself, you must re-touch the touch screen when you feel that the cursor does not correspond to the touch point. The system performs calibration operations.
3. In order to ensure the normal operation of the touch screen system, in addition to ensuring the correct installation of the system software, everyone must also remember not to install two or more touch screen drivers on a host, which will easily cause the system to run A conflict has occurred, making the touch screen system unusable.
4. When using a 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 pressed by other touching objects, for example, once the touch screen is pressed by the display case or cabinet case Staying is equivalent to touching a certain point all the time, then the coordinate position feedback to the controller is inaccurate, and of course the cursor cannot be positioned correctly. If the cabinet case is pressed against the touch area, you can increase the distance between the cabinet and the monitor screen. If the monitor case is pressed against the touch area, you can try to loosen the screw of the monitor case a bit.
5. The author once mentioned that once the system changes the display resolution, adjusts the screen size and installs for the first time, there will be inaccurate clicks or drifts. You need to start the positioning program that comes with the application to reposition, but When you are positioning, it is best to use a thinner pen or fingertip for positioning, which is more accurate.
6. The working environment requirements of the surface acoustic wave touch screen are relatively high. It must be required to work in a clean, dust-free environment, and the dust on the surface of the touch screen must be cleaned regularly. Otherwise, the dust in the air covers the touch screen. Reflection stripes or transducers will affect the correct positioning of the system.
7. Do not let water droplets or other soft things stick to the surface of the touch screen, otherwise the touch screen may easily mistakenly believe that the surface acoustic wave screen is inaccurate due to hand touch. In addition, when removing dirt on the surface of the touch screen, you can carefully wipe it from the center of the screen with a soft dry cloth or detergent, or use a dry soft cloth dipped in industrial alcohol or glass cleaning liquid to clean the touch screen surface.
8. If you touch the surface acoustic wave touch screen with your hand or other touch objects, the touch screen responds slowly, which indicates that the touch screen system is outdated, the internal clock frequency is too low, or the water droplets on the surface of the touch screen are moving. If you want the touch screen to recover quickly, you must replace or upgrade the system, or wipe the water drops on the surface of the touch screen with a rag.
9. The touch screen generally uses the serial port for signal transmission, and the signal is taken from the PS / 2 port, while the TPS screen is directly powered from the host power supply. If the indicator does not light, it means that no signal is obtained, and the PS / 2 cable on the control box may be broken. If the light is on, but still does not flash, it means the control box is broken, so we must replace the control box. If replacing the control box still does not work, it may be that the screen is pressed too tightly and you need to loosen the screws around a little because the touch screen is made of special materials and it is not easy to damage itself. If the serial port is bad or disabled, the driver cannot be installed, because the serial port is automatically found when the driver is installed. Even if it can be installed, the mouse will not move or cannot be positioned. It is best not to use a serial mouse to judge the quality of the serial port. Maybe the 9 serial ports use different methods for them. If the screen is pressed, or the ground wire is not connected properly, it will result in the inability to locate. If some areas cannot be clicked or the response is slow, it may be affected by dust. You need to disassemble the shell to remove the dust.
10. When you touch a certain position on the capacitive touch screen with your finger, and the touch screen does not respond, it is likely that the ITO coating corresponding to the touch position is damaged or scratched. The only way is to buy a new one. touch screen.
11. When you touch a certain position of the surface acoustic wave touch screen with your finger, and the touch screen does not respond, it is likely that the reflective stripes corresponding to the touched position are partially covered or scratched off by a hard object. For the former case Just wipe the touch position clean with a soft cloth. For the latter case, we can only buy a new touch screen.
12. When the user operates the touch screen, the direction of touch movement is to the left, but the cursor of the system moves to the right. This failure may be caused by the connection of the control box and the touch screen is reversed or the left and right positions of the touch screen are reversed. The user only needs to change the direction again.
13. After confirming that the connection to the keyboard port of the host is correctly connected and the serial port number selected during the driver installation is correct to the serial port number actually connected to the touch screen, when the surface acoustic wave touch screen is still not working, you can reformat Hard disk, and install the latest drivers required by the system.
14. When calibrating the surface acoustic wave touch screen, make sure that the MOUSEWARE software pre-installed in the system cannot conflict with the touch screen driver, otherwise the calibration operation will not be performed correctly.
15. When the user operates the capacitive touch screen, if the system is unresponsive, you can check whether the connection of the touch screen is correct. When checking, first take the power part and connect one end to the keyboard port of the host through a keyboard conversion head, and then connect the other end. Connect the computer keyboard, and insert a communication connector with 5V power supply into the serial port of the host.
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