The resistive touch screen is controlled by pressure sensing. The main part is a resistance film screen that works very well with the display surface. This is a multilayer composite film, It uses a glass or hard plastic plate as the base layer, the surface is coated with a transparent metal oxide (ITO) conductive layer, and the top is covered with a layer of surface hardening, The smooth and scratch-proof plastic layer (which is also coated with an ITO coating) has many small (about 1/1000 inch) Transparent intervals between them to separate the two layers of ITO conductive layer for insulation. When the fingers touch the screen, the two layers of conductive layers that are normally insulated from each other have a contact at the touch point, because one of the conductive layers is connected to the 5 V even Voltage Field in the Y axis, The voltage of the detection layer is changed from zero to non-zero. After the controller detects the connection, it performs A/D conversion and obtains the Y axis coordinate of the touch point after comparing the obtained voltage value with the 5 V, Similarly, the coordinates of the X axis are obtained, which is the most basic principle shared by all Resistance Technology touch screens. The key to the resistive touch screen lies in the material technology. Commonly used transparent conductive coating materials include: ① Ito, indium oxide, and weak conductive body. The characteristic is that when the thickness drops below 1800 Enis (ER = 10-10 meters), it will suddenly become transparent, the light transmittance is 80%, and the light transmittance decreases when the light transmittance goes down, To 300, the thickness increased to 80%. Ito is the main material used by the touch screen and capacitive touch screen of all resistor technology. In fact, the working face of the touch screen of resistor and Capacitive technology is Ito coating. ② Nickel-gold coating, the outer conductive layer of the Five-wire resistive touch screen uses the nickel-Gold Coating Material with good ductility. The outer conductive layer uses the extended nickel-gold material due to frequent touch. The service life is prolonged, but the process cost is high. Although the nickel-gold conductive layer has good ductility, it can only be used as a transparent conductor. It is not suitable for the face of a resistive touch screen because of its high conductivity, In addition, the metal thickness is not very uniform, and it is not suitable for voltage distribution layer. It can only be used as a probing layer. 1. Five-wire resistance touch screen: The base layer of the Five-wire resistance technology touch screen adds the Voltage Fields in both directions to the conductive working surface of the glass through the precision resistance network, we can simply understand it as two-direction Voltage Field time-sharing. Work on the same working surface, while the outer nickel-gold conductive layer is only used as a pure conductor, the touch point position is measured by the method of detecting the voltage value of the X and Y axes of the inner Ito contact point after the touch. Four leads are required for the inner layer of the 5-wire resistive touch screen. Only one conductor is used for the outer layer. There are 5 leads for the touch screen. Another proprietary technology of the 5-wire resistive touch screen is to correct the linearity problem of the inner Ito through a precise resistive network: the voltage distribution may be uneven due to the thickness and thickness of the conductive coating. Resistance screen performance features: ① they are all completely isolated from the external working environment, not afraid of dust, water vapor and oil stains ② can be touched by any object, can be used to write and draw, this is their big advantage ③ the accuracy of the resistive touch screen depends only on the accuracy of A/D conversion, so it can easily reach 4096*4096 • Relatively speaking, the five-wire resistance is superior to the four-wire resistance to ensure resolution accuracy, But the cost is high, so the price is very high. Improvement of the 5-wire resistive touch screen: first, the surface of the 5-wire resistive touch screen is conductive glass instead of conductive coating layer. The process of conductive glass greatly improves the life of the surface and improves the light transmittance. Secondly, the five-wire resistive touch screen gives the work surface tasks to a plane with long service life, while the B plane is only used as a conductor and adopts a nickel-gold transparent conductive layer with good ductility and low resistivity. Therefore, The service life of Plane B is also greatly improved. Another proprietary technology of the 5-wire resistive touch screen is to correct linear Problems on the plane through a precision resistive network: the voltage field is unevenly distributed due to the possibility of uneven thickness in the Process Engineering, The precision resistance network flows through most of the current at work, so it can compensate for possible linear distortion on the working face. The five-wire resistive touch screen is currently the best Resistance Technology touch screen, most suitable for military, medical, industrial control applications. 2. The four-wire resistive touch screen is attached to the display surface and used together with the display. If the Coordinate Position of the touch point can be measured, you can obtain Knows the intention of the touch. The resistive touch screen is widely used in embedded systems. The resistive touch screen is a 4-layer transparent composite film screen, as shown in Figure 2. The bottom is glass or organic glass. The top layer of the base layer is a plastic layer that is hardened to smooth and scratch-proof. The middle layer is a two-layer metal conductive layer, which is located on the base layer and the plastic layer respectively, in the two conductive There are many small transparent isolation points between layers to separate them. When you touch the screen with your finger, the two conductive layers touch each other at the touch point. The two metal conductive layers of the touch screen are the two working surfaces of the touch screen, A silver gel is coated at both ends of each working face, which is called a pair of electrodes on the working face. If a voltage is applied to the electrode on a working face, a uniform and continuous flat is formed on the working face. Line Voltage Distribution. As shown in 1, when a fixed voltage is applied to the electrode in the X direction, and the electrode in the Y direction is not pressed, the voltage value at the contact can be The Y + (or Y-) electrode shows the X coordinate value of the contact by measuring the voltage of the Y + electrode to the ground. Similarly, when voltage is added to the Y electrode pair, and the X electrode does not have a voltage applied to the Y electrode, By measuring the voltage of the X + electrode, you can know the Y coordinate of the contact. Four-wire resistive touch screen defects: the B-side of the resistive touch screen should be often touched, and the B-side of the four-wire resistive touch screen should adopt Ito. We know that Ito is a very thin oxide metal. during use, soon it will produce small cracks, Once a crack occurs, the current flowing through the area is forced to bypass the crack, and the voltage that should have been evenly distributed is damaged. The touch screen is damaged, and the crack points are inaccurate. As cracks increase and increase, the touch screen gradually becomes invalid. Therefore, the long service life is the main problem of the four-wire resistive touch screen. |
