Working with a touch screen. Touch screen: resistive or capacitive - what's the difference?

Resistive screen.

The simplest type is a four-wire one, which consists of a special glass panel as well as a plastic membrane. The space between the glass and the plastic membrane must be filled with microinsulators that can reliably isolate conductive surfaces from each other. Electrodes, which are thin plates made of metal, are installed over the entire surface of the layers. In the rear layer, the electrodes are in a vertical position, and in the front layer - in a horizontal position so that coordinates can be calculated. If you press on the display, the panel and membrane will automatically close, and a special sensor will sense the press, converting it into a signal. The most advanced type are eight-wire displays, which differ high level accuracy. However, these screens are different low level reliability and durability. If it is important that the display is reliable, you need to choose a five-wire type.

1 - glass panel, 2 - resistive coating, 3 - microinsulators, 4 - film with conductive coating

Matrix screens.

The design is similar to a resistive display, although it has been simplified. Vertical conductors were specially applied to the membrane, and horizontal conductors were applied to the glass. If you click on the display, the conductors will definitely touch and close crosswise. The processor can track which conductors are shorted, and this helps detect the coordinates of the click. Matrix screens cannot be called high-precision, so they are already for a long time do not use.

Capacitive screens.

The design of capacitive screens is quite complex, and it is based on the fact that the human body and the display together form a capacitor that conducts AC. Such screens are made in the form of a glass panel, which is covered with a resistive material so that electrical contact is not hampered. The electrodes are located at the four corners of the display and are alternating voltage. If you touch the surface of the display, then AC leakage will occur through the aforementioned “capacitor”. This is recorded by sensors, after which the information is processed by the device’s microprocessor. Capacitive displays can withstand up to 200 million clicks, they have an average level of accuracy, but, alas, they are afraid of any influence of liquids.

Projective capacitive screens.

Projected capacitive screens can, unlike the previous types discussed, be able to detect several clicks at once. On inside There is always a special grid of electrodes, and during contact with them a capacitor will certainly be formed. IN this place the electrical capacitance will change. The controller will be able to determine the point where the electrodes crossed. Then the calculations take place. If you press the screen in several places at once, not one capacitor will be formed, but several.

Screen with a grid of infrared rays.

The principle of operation of such displays is simple, and to some extent it is similar to a matrix display. In this case, the conductors are replaced with special infrared rays. Around this screen there is a frame in which there are built-in emitters, as well as receivers. If you tap on the screen, some beams will overlap and they cannot reach their own destination, namely the receiver. As a result, the controller calculates the contact location. Such screens can transmit light, they are durable, since there is no sensitive coating and there is no mechanical touch at all. However, such displays present moment do not meet high accuracy and are afraid of any contamination. But the diagonal of the frame of such a display can reach 150 inches.

Touch screens based on surface acoustic waves.

This display is always made in the form of a glass panel, into which piezoelectric transducers are built, located at different angles. There are also reflective and receiving sensors around the perimeter. The controller is responsible for generating signals whose frequency is high. After this, the signals are always sent to piezoelectric transducers, which can convert the incoming signals into acoustic vibrations, which are subsequently reflected from the reflective sensors. The waves can then be captured by receivers, re-sent to piezoelectric transducers, and then converted into electrical signal. If you press the display, the energy of the acoustic waves will be partially absorbed. Receivers are sensitive to such changes, and the processor can calculate the touch points. The main advantage is that touch screens based on surface acoustic waves track the coordinates of the point of pressing and the force of pressing. Displays of this type are durable, because they can withstand 50 million touches. Most often they are used for slot machines, help systems. It should be taken into account that the operation of such a display may not be accurate in the presence of ambient noise, vibration, or acoustic pollution.

To control modern gadgets, there is no longer any need to press buttons; you just need to touch the screen. This became possible thanks to the touchscreen (among experts it is simply called “touch” or “touch panel”), which has become an integral part of smartphones and tablets, including iPhones and iPads. It is not surprising that due to frequent use it often breaks down and becomes a headache for the owner of the device. If you understand what this component is and by what principles it works, you can quickly detect a malfunction and avoid awkward situations when contacting a service center.

What is a touchscreen

This term was formed from two English words - touch and screen, which literally translates as “touch screen”. The history of its appearance is long and occurred in several stages. The world's first finger-controlled display was invented and described in his scientific works American E. A. Johnson in 1965. Five years later, Dr. Samuel Hurst, through experiments, developed resistive touch screen, and the physical production of the product itself began only in 1973.

Currently, city residents deal with touch panels almost every day: not only smartphones and tablets are equipped with them, but also ATMs, information terminals and payment acceptance points. Touchscreen connects to display and is sensitive to any touch. It can be described as an information input device that serves to replace a keyboard.

It is important to know that the touchscreen is only part of the overall design, responsible only for the sensor. To transfer an image a display is used, which is a liquid crystal matrix. The unity of these two elements is called display module, which is practically the main component of any high-tech device.

How the touch panel works

The principle of operation of the touchscreen is simple - any touch on it triggers some function or entails certain actions. The physical features of its operation directly depend on the type of touch panel. There are seven of them in total, but the most common today are three of them.

The cheapest to produce, resistant to dirt and temperature changes. Consists of glass panel and plastic membrane, between which insulators are located. Any pressure causes the glass to push through the micro-insulator, and the membrane and panel close. After this, a special controller reads the changes and converts them into contact coordinates. Weaknesses This model has low light transmission, short service life and a high risk of damage if dropped.

Capacitive screen

More reliable and durable, but vulnerable to bad weather, water and pollution. It uses a special touch glass, coated with resistive material. An alternating current passes through it, which is supplied by electrodes located at the corners of the screen. That is, when you touch the touchscreen, a current leak occurs, which is detected by special sensors. They register these changes and transmit them to the controller.

Surface acoustic wave sensor

One of the most complex screens. The peculiarity of its work is that in the thickness of the glass there are ultrasonic vibrations. When you press the touchscreen, the waves are absorbed and converted into an electrical signal, which is then transmitted to the controller. The advantage of this technology is its long service life, equal to at least 45 million touches. The main drawback is that the screen is extremely sensitive to dirt and electromagnetic interference.

In addition to this, there are several more varieties touch panels. These include:

• Projected capacitive. On the inside of such screens there is a grid of electrodes, which, when pressed, forms a capacitor, the capacitance of which is measured by electronic sensors.
• Infrared. Along their edges there are light emitters and receivers in the IR range; when you touch the screen, part of the light is blocked and thereby the location of the click is determined.
• Tansometric. They are based on simple fixation of screen deformation, are resistant to damage and are often installed outdoors.
• Induction. Inside them there is an inductance coil and wires; when such a screen is touched with a special tool, the voltage of the existing magnetic field changes.

How to check the touchscreen

The touchpad may not work correctly due to physical damage mobile device, so for no apparent reason. The following factors indicate that the problem is in the sensor:

There may be several reasons for such a malfunction:

1. Display dirty. If you do not wipe the sensor promptly by special means, then during operation it becomes abundantly covered with fingerprints and greasy marks, which can reduce its sensitivity.
2. Violation temperature regime . Too tall or low temperatures, as well as their strong drop - common reason touchscreen malfunction.
3. Damage to the cable. It can peel off from the glass due to mechanical damage, thereby disrupting the connection between the latter and the touch coating.
4. Moisture ingress. If there is liquid inside the gadget, oxidation of the contacts may occur. Sometimes the problem can be solved with a hair dryer.
5. Crash software. In this case, you need to reflash the device; for this you will need a USB cable and the software itself.

How to replace the touchscreen on your phone yourself

Before removing the touch screen, you should turn off your smartphone, remove the battery and SIM card. It is important to remember the disassembly sequence so that you can later put the device back together without damaging the internal elements. Some models may require full analysis housing, which requires special knowledge. To replace the touch screen on your phone with your own hands, you need to prepare special equipment in advance, namely:

The process of replacing the touchscreen is as follows:

1. Take off back cover telephone;
2. Screwdriver remove all bolts along the perimeter of the body;
3. Carefully insert the spatula between the housing fastening and pry;
4. Hairdryer warm up the glue connecting the sensor to the matrix up to a maximum temperature of 80 °C;
5. Pin to display suction cup, which will allow you to separate the touchscreen from the matrix;
6. Apply thin layer of glue and install a new touchpad;
7. Carefully press it and remove any remaining glue;
8. Reassemble the device in reverse order.

What is the difference between touchscreen and display

The display is the part of the smartphone on which the image is displayed. It is he who is the conductor of visual information and makes it accessible to the human eye. A touchscreen is a touch glass, the main purpose of which is to call a particular function. That is, he is only information input tool, but no conclusion.

If the phone is broken and cobwebs appear on it, but the screen continues to work and you can clearly see the picture, then only the sensor needs to be replaced. When the device distorts the image and shows blots, you will have to change the display, which is more time-consuming and cash procedure.

Tablets, many smartphones, as well as monitors, displays on household appliances equipped with touch screens. This technology pleases, firstly, with its attractive design, secondly, for its functionality and simplicity. In addition, now there is no need to waste space on placing buttons, which is also very convenient. Read about the types of screens, their structure, operating principles, pros and cons in our article.

The most popular types of sensors

Resistive sensors

The resistive sensor consists of a plastic membrane (the first layer) and a panel made of glass (the second layer). A micro-insulator is laid between these layers, designed to protect conductive surfaces from each other. Electrodes are located on the surfaces of the layers (in the first layer they run horizontally, in the second – vertically). By pressing on the screen, you provoke the closure of the layers; a special sensor reads your press and converts it into a signal that is transmitted to the processor. As a result, the screen reacts to the task set by your touch - for example, it starts a video, opens a document, etc.

This technology is considered quite simple, and therefore not too much money is spent on the production of resistive screens. As a result, products with them often end up in the budget price segment, which is the main advantage of equipment with resistive screens. Equipment with resistive displays is presented in large quantities and assortment. Among the disadvantages of this type of sensors are the lack of support for multi-gestures, poor visibility in the sun/in bright light, low wear resistance, and low accuracy.

Capacitive sensors

This technology is more advanced - it supports multi-touch, has decent visibility in bright light, better wear resistance, and a higher level of accuracy. Disadvantages include the higher price of devices with capacitive screens, negative reaction to exposure to liquids.

How does the touch screen work? of this type? The key role here is played by electrodes located in the corners of the display and transmitting alternating flows of electricity to each other. As a result, a kind of current grid is formed. By pressing on the screen, a person shifts the direction of the current, which allows the system to determine the location of the press and accordingly calculate and execute the required command. In this case, the human body, together with the screen itself, act as current conductors. The display consists of glass coated with a resistive material that provides effective electrical contact.

Infrared sensors

The screen frame (made of glass) includes receivers and emitters of infrared rays. When working, they form an infrared grid on the surface of the display. By clicking on the screen, we will block access to certain rays - the system will calculate this location and calculate the corresponding task that it will need to perform.

Disadvantages include not very high accuracy (especially in bright light), “fear” of contamination and the high cost of products with infrared displays. Among the advantages are good visibility in the sun and durability.

Less popular types of sensors

Matrix sensors

The matrix system is similar to how the sensor works in resistive display models. Only vertical current conductors are applied to the membrane, and horizontal current conductors are applied to the glass. Pressing causes a closure, which the system calculates and then converts into performing a particular task.

Matrix screens are rarely used today because they are considered very inaccurate and therefore unproductive.

Surface acoustic wave screens

Piezoelectric transducers are built into different corners of the glass panel. Along the perimeter of the display there are sensors that receive and reflect signals. A special controller provides high frequency signal generation. Pressing the display initiates the execution of a task.

There is constant debate about which phone has the better screen. Especially between owners Apple technology and those who prefer devices on the Android platform.

This simple infographic beautifully breaks down all the benefits of each type of touchscreen. I hope that when you buy your next smartphone, it will help you do right choice and don’t overpay a tidy sum.

So, there are three types of touch screens: Resistive, Capacitive and Infrared.

Resistive

Phones with resistive screens: Samsung Messager Touch, Samsung Instinct, HTC Touch Diamond, LG Dare

How do they work? Small dots separate several layers of material that transmit current. When the upper flexible layer presses against the lower layer, electric current The location of the impact, that is, the touch, changes and is calculated.

How much does it cost to manufacture? The cost of manufacturing resistive touch screens is not very high - $ .

Screen material. A layer of flexible material (usually a polyester film) is placed on top of the glass.

Tools of influence. Fingers, gloved fingers or stylus.

Visibility on the street. Poor visibility in sunny weather.

Possibility of multi-gestures. No.

Durability. For its price, the screen lasts quite a long time. Easily scratched and susceptible to other minor damage. It wears out quite quickly and requires replacement.

Capacitive

Phones with capacitive touch screens: Huawei Ascend, Sanyo Zio, iPhone, HTC Hero, DROID Eris, Palm Pre, Blackberry Storm.

How do they work? The current is broadcast from the corners of the screen. When a finger touches the screen, it changes the direction of the current and thus the location of the touch is calculated.

How much does it cost to manufacture? Quite expensive - $$ .

Screen material. Glass.

Tools of influence. Only fingers without gloves.

Visibility on the street. Visibility on a sunny day is good.

Possibility of multi-gestures. Eat.

Durability.

Infrared

Phones with infrared touch screens: Samsung U600 (heat), Neonode N2 (optical).

How do they work? In order for the heat-sensitive screen to react, you need to touch it with a warm object. An optical screen uses a grid of invisible sensors directly above the screen. The touch point is calculated based on the point where the x-y axis was violated.

How much does it cost to manufacture? Very expensive - $$$ .

Screen material. Glass.

Tools of influence. Optical - fingers, gloves and stylus. Heat-sensitive - warm fingers without gloves.

Visibility on the street. Visibility in sunny weather is good, but strong sunlight affects productivity and accuracy.

Possibility of multi-gestures. Yes.

Durability. Lasts quite a long time. Glass breaks only from serious damage.

Smartphone users who do not speak English well are puzzled when they hear the name “touchscreen” - what part of the phone is this? This is usually the name given to any touch screen, regardless of what device it is installed on. Currently, such displays are used not only for mobile gadgets, but also built into various self-service terminals.

What is a touchscreen?

This term comes from the merger of two English words: touch and screen, which means “touch screen”. This display responds to touch and makes it easier to control equipment. However, it is worth distinguishing between several types of equipment, since the principle of their operation is not entirely similar.

IN modern gadgets, for example, on the iPhone, capacitive and projected-capacitive displays are installed. The latter type can be called more advanced, since it is capable of reading a certain number of touches simultaneously. In themselves, such touchscreens are glass panels with a layer of resistive material and electrodes.

There are also displays on which a flexible membrane is applied. Between it and the glass there are micro-insulators, pressing on which provokes a change in resistance. It is captured by the controller and converted into coordinates, resulting in control of the device.

The main difference between these types of technologies is that a capacitive display does not respond to touch with any object or even a simple stylus, which cannot be said about resistive touchscreen. Thus, locking a smartphone on it works much better than on its outdated “brother.”

How different screens work

There are only 3 types Touch Screen, 2 of which have already been briefly described:

• capacitive;
• wave;
• resistive.

It's worth starting with the most used one, i.e. capacitive display. How does such a screen work on a phone? It's quite simple. The resistive layer serves as a charge accumulator that the electrodes pass through, while the user, with his touch, pushes out some of the energy at a certain point. This works due to the fact that there is also current in the human body. When the charge level decreases, this change is recorded by the microcircuits and transmitted to the touchscreen driver.

The main advantage of such displays is that they are quite wear-resistant. Over time they do not lose their original brightness and are able to transmit clearer images.

Operating principle resistive screen was stated above. If we look at this in more detail, we should say that a flexible membrane is an elastic metal plate that passes current. Between it and the conductor layer there is empty space. When interacting with the display, the user presses lightly on its surface, closing the membrane with the conductor at this point. Then everything happens according to the same scheme: the system reads the coordinates, and the driver issues commands to the OS.

Resistive displays have not been popular for a long time, since their functionality is somewhat limited compared to capacitive touchscreens. Such screens can only be found in very outdated technology or various terminals, but less often.

What is a wave touchscreen? It is also a glass surface with a coordinate grid and transformers. One of them transmits impulses, while the other receives signals reflected by the reflector. Thus, the charge “walks” through the transducers, creating an acoustic wave, which the user interrupts by pressing. This is how the location of the touch is determined.

This type of display is the best option for artists and graphic designers, because it does not distort the image due to the lack of metal coating. It is also the most expensive, while many attribute it to the technologies of the future, believing that even a capacitive display will go into oblivion, giving way to wave technology.

Video review: types of touchscreen