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Today we will give a brief introduction of the working principles of touch screens.
(1) Touch screens are closely related to people, especially capacitive touch screens.
(2) The relationship between the touch screen and the display is very close.
(3) Typical applications: mobile phones, tablet computers, cashier, and industrial fields.
(1) Common touch screens are divided into two types: resistive touch screen and capacitive touch screen. Resistive touch screens were used in the early days, and capacitive touch screens were invented later.
(2) These two have different characteristics, different interfaces, different programming methods, and different principles.
First of all, it must be clear: the touch screen is a touch screen, which is used to respond to human touch events; the display screen is a display screen, which is used to display.
Why many people confuse these two concepts is mainly because the touch screen and display screen are made together in general products. Generally, the outer layer is a touch screen, which is transparent and very thin; the bottom is a display screen to display images, and the images usually are displayed on the display screen and can be seen through the touch screen.
Before analyzing the principle of capacitive touch screen, let's first understand the working principle of resistive touch screen.
Resistive touch screens mainly use pressure sensing for control. It is composed of a display screen and a resistive film screen closely attached to the display screen. This resistive film screen is usually divided into two layers, one layer is made of glass or plexiglass, and its surface is coated with a transparent conductive layer; the outside of the base layer is pressed with a hardened and scratch-resistant plastic layer that we usually contact directly. There is also a conductive layer inside the plastic layer, and the two conductive layers are separated. When we touch the screen with a finger or other objects, the two conductive layers come into contact, and the resistance changes, and the controller judges the coordinates of the contact point according to the specific change of resistance and performs corresponding operations.
Unlike resistive touch screens, capacitive touch screens work by using the current induction of the human body.
The sensing screen of the capacitive touch screen is a four-layer composite glass screen. The inner surface and the interlayer of the glass screen are each coated with a conductive layer, and the outermost layer is a thin layer of silica glass protective layer. When we touch the sensor screen with our fingers, the electric field of the human body makes the finger and the surface of the touch screen form a coupling capacitor. For high-frequency currents, the capacitor is a direct conductor, so the finger absorbs a small current from the contact point. This current flows from the electrodes on the four corners of the touch screen, and the current flowing through these four electrodes is proportional to the distance from the finger to the four corners. The controller obtains the position of the touch point through accurate calculation of the four current ratios.
Encyclopedi Optoeletronics Technology Co., Ltd (EOTSZ), founded in 2009, is engaged in the R&D and manufacturing of optical display human-computer interaction products. It has a rich team of experts at home and abroad, with an average experience of about 11 years. It has a strict quality management system (ISO9001, TS16949 in progress), a number of industrial patents, and works on analog circuit software. For more information about interactive products, please kindly contact us directly.
