Capacitive screens in telephones

If you go to a modern mobile phone store and get acquainted with the offered products, then in the specifications for most devices in the windows will be indicated: "Screen type - capacitive". For those who change their mobile communication devices often, this term is well known, but what if the person did not seek to buy all the new things, preferring proven solutions? He can only get lost in conjecture: "Capacitive screen - what is it?"

Data Entry Technology

The principle of touch set is now used everywhere. For example, ATMs or devices for making various types of payments, on the panels of which there are at least a few buttons, and entering the desired figures occurs by clicking on the corresponding image, you can find in almost every major store. Capacitive screens were first proposed in the seventies, but they did not get propagation because of insufficient accuracy of recognition of the pressing zone and complexity of implementation. But work to improve this decision continued.

Sensors in telephones

When there were models of mobile communication devices with large screens, immediately the question arose about ergonomics. Of course, it was possible to reduce the already small block of buttons, but on the convenience of use it would have affected the most negative way. Compromise solutions were used - the so-called "sliders", but this too thickened the device and made it less reliable due to the need to use a mechanical mobile connection. Manufacturers began to search for a solution. And it was found. They were touch screens, by that time substantially improved and ideally suited for phones.

Resisting pressure

The first models of such screens were made according to the resistive principle. Due to a number of features, such sensors are used now. The structural-resistive screen consists of two completely transparent plates: the outer plate, on which presses are applied, is made flexible, and the inner one, on the contrary, is rigid. The space between them is filled with a transparent dielectric material. An electrically conductive layer is deposited on both plates on the inner sides by sputtering. It is specially connected to the controller by the conductors, which constantly supplies low voltage to the layers. All this "sandwich" is fixed on the main display. When a person presses a portion of the screen, the plates touch at a certain point, a current appears. Having determined the resistance values along two Cartesian axes, it is possible to determine with sufficient accuracy exactly where the depression occurred. These data are transferred to the running program, which processes them further. Resistive sensors are inexpensive in production, work well at low temperatures.

Capacitive screens

Sensors working on a capacitive principle are much more perfect. Touchpad in laptops is a vivid example of such solutions. On foreign sites in the characteristics of phones with this technology is indicated "Capacity". In contrast to the above-described resistive solution, here the mechanical pressing is completely unimportant. In this case, the property of the human body is used to accumulate an electric charge, acting as a classical capacitor. Capacitive screens are more durable, have excellent "responsiveness". There are two ways to implement: surface and projection. In the first case, a transparent layer of conductive material is applied to the surface of the glass or plastic. It constantly has electrical potential from the controller. It is enough to touch your finger to the point of the screen, as there is a leak from the battery into the human body. It can be easily determined and the coordinates transferred to the running program. Projective capacitive screens work differently. Behind the outer glass of the display is a grid of transparent sensor elements (they can be seen at a certain angle and illumination). If you touch the point, in fact, a capacitor will be formed, one of the plates of which is the finger of the user. The capacity in the circuit is determined by the controller and is calculated. This solution allows the implementation of the multi-touch technology.