Every year more and more portable, desktop and embedded technology with touch control appears on sale. The touchscreen is responsible for the operation of buttons or screens, which reads the user's press and performs the appropriate action. In the article we will talk in detail about the types of touchscreens, as well as the principle of operation.

What is a touchscreen

Touchscreen is a transliteration of the English phrase Touch Screen, which translates as a touch screen. Touchscreens are widely used in smartphones and tablets, smart watch and bracelets, reading terminals and communicators. Yet touch screens used in cars and various household appliances.

The use of touchscreens is due to the possibility of simultaneously performing two actions - to display information and work as a button or a full-fledged data input device. Thanks to this, it is possible to use the allocated space more rationally. For example, touch buttons can replace the functions of an additional display. Another example is that the touch screen is capable of acting as a keyboard for data entry in confined spaces such as in cars or terminals.

Over the past few years, large-sized equipment has appeared on sale - laptops and monitors. Such devices provide additional convenience during work for artists, operators in production, etc.

Types of touchscreens

There are two types of touch screens:

1. Resistive.
2. Capacitive.

Resistive type touch screens respond to finger pressure, stylus and other objects. Information input is available when using conventional gloves. At the same time, a certain effort is required to enter information. Often, too much pressure will damage the input surface and cause scratches, and sometimes the display itself will fail.

The capacitive type touchscreen reacts only to the pressure of a finger, as well as other objects that can imitate the touch of a human finger: styluses, gloves, etc. Therefore, the cost of accessories capable of working with such touchscreens is much higher. For that, the data entry process is much simpler, a light touch is enough. Responsiveness and responsiveness are many times higher compared to the resistive type, which provides a comfortable environment for navigating menus or games.

How the touchscreen works

A touchscreen, whether resistive or capacitive, is a transparent panel of glass or plastic on top of the screen. In capacitive screens, a transparent film of resistive material is installed on the inside. And in each corner there is one electrode that conducts low voltage variable type. At the moment when the finger touches the surface, a voltage leak occurs, which catches the controller and makes it clear to the electronics at which point the touch occurred.

Resistive screens are arranged somewhat differently. Instead of a thin film, a flexible membrane is used, which comes into contact when pressed. The controller also detects a change in resistance, after which it transmits information about the coordinates of the touch to the rest of the electronics.

Since touchscreens are not capable of transmitting tactile sensations, a vibration motor is often used as an alternative. With each press, a slight vibration is triggered, making it easy to understand when data is being entered.

IN modern devices Oh and household appliances, resistive touchscreens are rarely used. Typically, this design is found in terminals for reading data, some microwave ovens and other household / non-domestic appliances. Since this design is characterized by high thickness and low responsiveness. While capacitive options are devoid of such shortcomings and are successfully used in netbooks, smartphones, tablets, etc.

It is also worth noting that in order to reduce the overall thickness of the touchscreen and screen, manufacturers began to combine both parts into one design. If earlier a broken touchscreen was easily replaced with an analogue separately. Then, after combining, it is difficult to separate the touchscreen from the working display even with the appropriate equipment. The screen cracks easily, so it is better to replace the whole module.

Output

The touchscreen greatly simplifies the input of information on some devices. Touching with your finger is much easier and faster than typing with the mouse cursor or looking for the right keys on the keyboard. Also, this design helps save space in certain devices. At the same time, the production technology remains costly in terms of money, which hinders the mass production of touch laptops and monitors.

Unlike desktop computers, functions and programs in tablets are controlled by lightly pressing the fingertip on the screen at the desired point. The reaction of the tablet to touch is due to a thin transparent glass plate superimposed on the display screen. When pressing on the glass (touchscreen), depending on the type of sensors, the resistance, inductance or capacitance of the grid applied to the glass changes and thus the tablet receives an indication for a specific action.

The touch glass is very thin, but strong enough to break it with your finger. But if the tablet is dropped on a hard surface or hit with a sharp object, the touch screen cracks, which happened with the glass of the MonsterPad children's tablet shown in the photo.

Testing the tablet with a mouse

The image on the screen was uniform without defects and distortions. The tablet remained operational, since when you pressed the Power button, a window popped up with a menu to turn off the tablet, but it became impossible to control its operation by touching the screen with your finger.

For a complete check of the tablet's performance, and the ability to turn it off before repair, it was necessary to connect a mouse to the Micro USB connector located on the side of the tablet. Mice usually have a connector for USB connections. Therefore, I had to buy a USB-Micro-USB adapter.

When you connect a mouse, the tablet system automatically detected it, and the mouse cursor appeared on the screen in the form of an arrow. Diagnostics showed that the electronics of the tablet is in good condition. Therefore, to repair the tablet, it is enough to replace the touchscreen with your own hands. After diagnostics, the tablet was turned off with the mouse.

In anticipation of purchasing a touchscreen, it is necessary to keep the tablet battery in a charged state, since a deep discharge of it drastically reduces the battery life of the tablet.

Where can I buy a touchscreen for a tablet

Searching for a store to buy a touchscreen for a MonsterPad children's tablet at the lowest cost led to the website of the Chinese online store AliExpress, which I personally tested by time. The site presented a large assortment of sellers of touchscreens for the MonsterPad tablet.

A seller with a lot of positive reviews and a high rating with an average price and free shipping was selected. When choosing a touchscreen, pay attention to the presence of double-sided tape on it. If the screen is without adhesive tape, then replacing it will be complicated by the need to purchase such adhesive tape, cutting it and fixing it.

If you couldn’t find the touchscreen by the name of the tablet, then you can try to search by its marking, which is usually applied to the flat cable coming from the touchscreen.

Touch glasses of many tablet models are interchangeable. The main thing when choosing to pay attention to the type of sensor and its diagonal size, expressed in inches. For example, the MonsterPad tablet requires a 7” touch screen.

The resulting package was a large, in comparison with the size of the touchscreen, foam plastic box completely wrapped with adhesive tape. It is convenient to open such a package by cutting the film along the line connecting the halves of the box with a knife.

The touchscreen was removed from the packaging and carefully examined for defects. Everything was in perfect condition. Trying glass on the tablet confirmed the coincidence of sizes. To test the performance, it remains only to disassemble the tablet and connect the touchscreen to motherboard.

How to disassemble the MonsterPad children's tablet

Before starting the repair of the tablet, in order to prevent scratches on its body and display and dust between the display and the touch glass, wipe the table with a damp cloth and cover its surface with a soft, lint-free cloth. From the tool you only need a knife and a couple of small screwdrivers with a Phillips and a flat sting. After preparing the workplace, you can begin to repair.

The MonsterPad children's tablet is disassembled, thanks to the screw fastening of the back cover is simple. Using a sufficiently sharp object, remove the four end caps glued with adhesive mass and unscrew the four screws with a Phillips screwdriver.

Further, even without the help of a plastic card, grabbing the halves of the case with your nails in the area where the tablet’s power button and connectors are installed, gently spread its halves to the sides. The power and volume buttons must be immediately removed and set aside so that they are not lost and cannot scratch the tablet screen if they fall under it.

The tablet is disassembled enough to start replacing the touch glass. It remains only to remove the cable coming from the touchscreen from the connector. In the photo, the connector is in the far right corner.

If the tablet was disassembled to replace the battery, then its type is clearly visible in the photo. To replace the battery, you first need to unsolder the red and black wires coming from the motherboard from it and carefully remove it, overcoming the adhesive force of the double-sided tape.

To release the touchscreen cable, you need to move the latches with a screwdriver blade a couple of millimeters to the side indicated in the photo by red arrows. After that, the cable without effort can be removed from the connector.

How to check the touchscreen before installing it in a tablet

After removing the back cover from the tablet, it became possible to check the new touchscreen for operability. To do this, without removing the protective film, apply a new touch screen to the broken one, carefully turn the tablet over, and, observing the numbering of the cable, insert it into the connector on the motherboard and return the latches to their place. Then turn the tablet upside down and turn it on using the power button.

After loading software you need to tap on any icon or just work a little on the tablet. If there is a reaction on the display when you touch and scroll through the pages, then everything is in order and you can start replacing the broken glass. Before starting the repair, you must turn off the tablet with the power button and disconnect the cable of the new touchscreen from the connector.

How to remove a cracked touchscreen

To remove a cracked touchscreen, you need to pry it around any of the corners with the end of the knife and try to lift it.

In the MonsterPad tablet, the glass was glued weakly, it was not even necessary to warm up the place of gluing with a hair dryer. The effort of the fingers was quite enough to peel it off. The main thing is not to rush and perform this operation very slowly and smoothly.

Preparing the tablet frame and installing the touchscreen

After removing the cracked touchscreen, use a rag soaked in alcohol to degrease and remove adhesive residue from the frame.

Fortunately, the cracked glass did not crumble into pieces and it was not necessary to blow off its small fragments with a vacuum cleaner or hair dryer. For the same reason, it is not recommended to scrape off adhesive residue with a tool.

In order for the cable not to interfere with the positioning of the touchscreen during gluing, a piece of PVC tube was inserted near the opening of its release, as in the photo.

At the next step, the protective film was removed from the touchscreen from the side of the applied sticky layer to the edges.

It remains to fill the cable into the hole in the frame of the tablet, rest the corner of the touchscreen at the cable in the recess of the frame and slowly attach it to the frame, controlling the accuracy of laying on the opposite corner diagonally.

The touchscreen fit into the recess of the frame exactly, without gaps and displacement on the first try. There is no need to tightly press the glass at this stage of the repair. It is advisable to do this after complete assembly and testing of the tablet.

The cable is quite long, which is convenient for installation. However, so that the cable does not break if it gets between the covers when they are closed, it must be folded in half and pressed a little, avoiding sharp bends.

It remains to put in place the pushers of the buttons for turning on the tablet, adjusting the volume of the sound and snap the back cover to the base of the tablet. Screw the four screws and install the removed plugs on them.

The self-repair of the tablet is successfully completed, it began to work and look like new, and the child can play his favorite games again. Now, I believe, he will be more careful about the tablet and other gadgets. I did not remove the protective outer film from the touch screen, let the owner of the tablet remove it himself and tap (touch) the screen surface first.

Hope given step-by-step instruction will help to cope with the repair of a tablet, smartphone to any home master, even without experience in repairing such devices.

Do-it-yourself tablet touchscreen replacement costs were less than 10% of the tablet's original cost.

What is touch glass (touchscreen)

Touch screen- an input-output device of information, which is a screen that reacts to touching it.

Touch screen is a device for input and output of information through a display sensitive to pressing and gestures. As you know, the screens of modern devices not only display an image, but also allow you to interact with the device. Initially, familiar buttons were used for such interaction, then a no less famous “mouse” manipulator appeared, which greatly simplified the manipulation of information on a computer display. However, the mouse requires a horizontal surface to work and is not very suitable for mobile devices. This is where an addition to the regular screen comes to the rescue. -Touch Screen, which is also known as touch panel,Touchpad, touch film. That is, in fact, the touch element is not a screen - it is additional device, installed on top of the display from the outside, protecting it and serving to enter the coordinates of touching the screen with a finger or other object.

Usage

Today, touch screens are widely used in mobile electronic devices. Initially, the touchscreen was used in the design of pocket personal computers(PDA, PDA), now communicators, mobile phones, players and even photo and video cameras hold the lead.

However, the technology of finger control via virtual buttons on the screen has proven to be so convenient that almost all payment terminals, many modern ATMs, electronic information kiosks and other devices used in public places are equipped with it.

touch screen laptop

It should also be noted that laptops, some models of which are equipped with a swivel touch display, which gives the mobile computer not only greater functionality, but also greater flexibility in managing it outdoors and on weight.

Unfortunately, there are not so many similar models of laptops, popularly called "transformers", but they are.

And finally, the latest mobile computer invention of mankind with a touch screen is tablet computers.

Now they are produced by almost all well-known companies. For example, Apple iPad, HTC, ASUS, Samsung and others.

In general, touch screen technology can be described as the most convenient when you need instant access to device control without prior preparation and with amazing interactivity: controls can change each other depending on the activated function. Anyone who has ever worked with a touch device understands the above perfectly.

Touch screen types

In total, today there are several types of touch displays. Naturally, each of them has its own advantages and disadvantages. We single out four main structures:

• Resistive
• capacitive
• Projected-capacitive

In addition to the above screens, matrix screens and infrared ones are used, but due to their low accuracy, their scope is extremely limited.

Resistive

Resistive touch panels are among the simplest devices. At its core, such a panel consists of a conductive substrate and a plastic membrane with a certain resistance. When the membrane is pressed, it closes with the substrate, and the control electronics determines the resulting resistance between the edges of the substrate and the membrane, calculating the coordinates of the pressing point.

The advantage of a resistive screen is its low cost and simplicity of the device. They have excellent resistance to dirt. The main advantage of resistive technology is sensitivity to any touch: you can work with your hand (including gloves), a stylus (pen) and any other hard blunt object (for example, the top end of a ballpoint pen or the corner of a plastic card). However, there are also quite serious drawbacks: resistive screens are sensitive to mechanical damage, such a screen is easy to scratch, so a special protective film is often purchased additionally to protect the screen. In addition, resistive panels do not work very well at low temperatures, and also have low transparency - they pass no more than 85% of the display's light flux.

Using the Touch Screen Pen

Application:

• PDA - (you can see touchscreens for PDAs)
• Communicators - (touchscreens for communicators)
• Cell Phones - ()
• POS terminals
• Tablet PC
• Industry (control devices)
• Medical equipment
• Car radios - ()
• GPS navigators - ()

Communicator

capacitive

Capacitive touch screen technology is based on the principle that a large object (in this case, a person) is capable of conducting an electrical current. The essence of the capacitive technology is to apply an electrically conductive layer to the glass, while a weak alternating current is applied to each of the four corners of the screen. If you touch the screen with a grounded large capacitance object (finger), current leakage will occur. The closer the touch point (and hence the leakage) to the electrodes in the corners of the screen, the greater the leakage current, which is recorded by the control electronics, which calculates the coordinates of the touch point.

Capacitive screens are very reliable and durable, their resource is hundreds of millions of clicks, they perfectly resist pollution, but only those that do not conduct electricity. They are more transparent than resistive ones. However, the disadvantages are still the possibility of damage to the electrically conductive coating and insensitivity to touch by non-conductive objects, even with gloved hands.

Application:

• In secure premises
• Information kiosks
• Some ATMs

Projected-capacitive

Projection-capacitive screens are based on measuring the capacitance of a capacitor formed between the human body and a transparent electrode on the glass surface, which in this case is a dielectric. Due to the fact that the electrodes are applied on the inner surface of the screen, such a screen is extremely resistant to mechanical damage, and taking into account the possibility of using thick glass, projective-capacitive screens can be used in public places and on the street without any special restrictions. In addition, this type of screen recognizes the pressure of a finger in a glove.

These screens are quite sensitive and distinguish between finger and conductive pen taps, and some models can recognize multiple taps (multi-touch). The features of the projection-capacitive screen are high transparency, durability, immunity to most contaminants. The disadvantage of such a screen is not very high accuracy, as well as the complexity of the electronics that process the coordinates of pressing.

Apple iPhone

Application:

• Electronic kiosks on the streets
• Payment terminals
• ATMs
• Notebook touchpads
• iPod-
• iPad-
• tablet computers

With the definition of surface acoustic waves

The essence of the touch panel with the definition of surface acoustic waves is the presence of ultrasonic vibrations in the thickness of the screen. When touching the vibrating glass, the waves are absorbed, while the point of contact is recorded by the screen sensors. The advantages of the technology include high reliability and pressure recognition (unlike capacitive screens). The disadvantages are poor protection from environmental factors, so screens with surface acoustic waves cannot be used outdoors, and in addition, such screens are afraid of any pollution that blocks their work. Rarely used.

Other, rare types of touch screens

• optical screens. Glass is illuminated with infrared light, as a result of touching such glass, light is scattered, which is detected by the sensor.
• induction screens. Inside the screen there is a coil and a grid of sensitive wires that react to touch with an active pen powered by electromagnetic resonance. It is logical that such screens respond to pressing only with a special pen. They are used in expensive graphics tablets.
• Tensometric - react to the deformation of the screen. Such screens have low accuracy, but are very durable.
• The infrared ray grid is one of the very first technologies to recognize touches on the screen. The grid consists of a plurality of light emitters and receivers located on the sides of the screen. Reacts to the blocking of the corresponding rays by objects, on the basis of which it determines the coordinates of pressing.

Multi-touch

Multi-touch, which everyone is talking about so much and which is only growing in popularity, is not a type of touch screen. At its core, multi-touch technology - which is a loose translation of the phrase multi-touch - is an addition to the touch screen (most often built according to the projected capacitive principle), allowing the screen to recognize multiple touch points on it. As a result, the multi-touch screen becomes capable of recognizing gestures. Here are just a few of them:

• Move two fingers together - reduce the image (text)
• Spread two fingers apart - increase (Zoom)
• Movement with several fingers at the same time - scrolling text, pages in the browser
• Rotate with two fingers on the screen - rotate the image (screen)

Pros and cons:

Touch screens have been around for a long time in handheld devices. There are several reasons for this:

• Ability to make a minimum number of controls
• Simplicity of the GUI
• Ease of control
• Efficiency of access to device functions
• Expansion of multimedia possibilities

However, there are more than enough shortcomings:

• Lack of haptic feedback
• Frequent need to use a pen (stylus)
• Possible screen damage
• Fingerprints and other dirt on the screen
• Higher energy consumption

As a result, it is not always possible to completely get rid of the keyboard, because it is much more convenient to type text using the usual keys. But the touch screen is more interactive, thanks to faster access to menu items and settings of modern gadgets.

Until quite recently, few people could believe that phones with familiar buttons would give way to devices that are controlled by touching the screen. But times are changing and the demand for push-button phones is gradually falling, while for smartphones it is growing.

The term "touchscreen" was formed from two words - Touch and Screen, which is translated from English as "touch screen". Yes, that's right - the touchscreen is the touch screen that you touch when you use your smartphone or tablet. In fact, touch screens are found not only in the world of mobile technology. So, you could see them when depositing funds into the account mobile device through a terminal, at an ATM, at ticket machines, etc.

Touch-screen owes its appearance to Western scientists. The very first samples were born in the second half of the 60s of the last century. Based on this, we can conclude that the touchscreen has been used for more than 40 years. Before the advent of smartphones, they were used in ATMs, etc. At present, every person who uses cellular communication, car navigators, visits banks and shops, encounters this technology, sometimes not even guessing what it is called. So, we figured out what a touchscreen is in phones. In fact, this is the same as the display that responds to the touch of your fingers. It is perfectly used instead of the keyboard and is actively used in mobile technologies. The advantages of the touchscreen include protection from dust, moisture and other adverse environmental factors, as well as a high degree of reliability. If our touch device does not always respond to touch, or even refuses to do it at all, for example, does not want to change the brightness on the iPad, it is most likely that the touch-screen has failed. It is relatively inexpensive (especially if we are interested in a resistive display), and it is easy to replace it.

The basis of the touchscreen

The basis of any touchscreen is a matrix on liquid crystals, which is actually a smaller copy of the one in the monitor. On the reverse side there are backlight diodes, and on the front side there are a number of layers that detect pressing (resistive screen) or touching (capacitive screen).

A person who is well versed in what a touchscreen is understands that most of the devices manufactured use a resistive touch screen. This follows from their low cost and relative simplicity of design. Many Chinese "smartphones" that have flooded the market have a resistive screen type, the manufacturing technology of which, by the way, appeared earlier than capacitive.

Types of touch screens

Touch screens are divided into resistive, matrix, projective-capacitive, surface-acoustic wave touch screens, infrared, optical, tensometric, DST touch screens and induction.

Resistive touch screens

Subdivided into four-wire and five-wire.

The resistive screen sensor consists of two transparent plastic plates with a thin conductive mesh, which are located on the surface of a conventional LCD screen. Between the plates is a transparent dielectric layer. The program displays a graphical interactive interface, which is clearly visible due to the transparent materials on the matrix. Responding to a program request, the user clicks on the desired interface point (for example, the image of a button). - The plastic dielectric diverges, the plastic plates touch, supplying current from the electrode of one to the grid of the other. The appearance of the current is fixed by the registering controller, which, in accordance with the grid of coordinates, will determine the point of pressing. Point coordinates enter the program and are processed according to the established algorithms.

4-wire shield

The resistive touch screen consists of a glass panel and a flexible plastic membrane. Both the panel and the membrane have a resistive coating. The space between the glass and the membrane is filled with micro-insulators, which are evenly distributed over the active area of ​​the screen and reliably isolate conductive surfaces. When the screen is pressed, the panel and membrane are closed, and the controller, using an analog-to-digital converter, registers the change in resistance and converts it into touch coordinates (X and Y). In general terms, the reading algorithm is as follows:

A voltage of + 5V is applied to the upper electrode, the lower one is grounded. The left and right are short-circuited, and the voltage on them is checked. This voltage corresponds to the Y-coordinate of the screen.

Similarly, + 5V and “ground” are supplied to the left and right electrodes, the X-coordinate is read from the top and bottom.

There are also eight-wire touch screens. They improve tracking accuracy, but do not improve reliability.

Five wire shield

The five-wire screen is more reliable due to the fact that the resistive coating on the membrane is replaced by a conductive one (the 5-wire screen continues to work even with a cut membrane). The rear glass has a resistive coating with four electrodes at the corners.

Initially, all four electrodes are grounded, and the membrane is “pulled up” by a resistor to + 5V. The membrane voltage level is constantly monitored by an analog-to-digital converter. When nothing is touching the touch screen, the voltage is 5V.

As soon as the screen is pressed, the microprocessor senses the change in membrane voltage and starts calculating the coordinates of the touch as follows:

+5V voltage is applied to the two right electrodes, the left ones are grounded. The voltage on the screen corresponds to the X-coordinate.

The Y-coordinate is read by connecting both upper electrodes to +5V and both lower electrodes to ground.

Resistive touch screens are cheap and dirt resistant. Resistive screens respond to touch with any smooth solid object: a hand (bare or gloved), a pen, a credit card, a pick. They are used everywhere where vandalism and low temperatures are not excluded: for the automation of industrial processes, in medicine, in the service sector (POS-terminals), in personal electronics (PDA). The best samples provide an accuracy of 4096×4096 pixels.

The disadvantages of resistive screens are low light transmission (no more than 85% for 5-wire models and even lower for 4-wire models), low durability (no more than 35 million clicks at one point) and insufficient vandal resistance (the film is easy to cut).

Matrix touch screens

The design is similar to resistive, but simplified to the limit. Horizontal conductors are applied to the glass, vertical conductors are applied to the membrane.

When the screen is touched, the conductors touch. The controller determines which conductors are shorted and sends the corresponding coordinates to the microprocessor.

They have very low accuracy. Interface elements have to be specially arranged taking into account the cells of the matrix screen. The only advantage is simplicity, cheapness and unpretentiousness. Typically, matrix screens are queried row by row (similar to a matrix of buttons); this allows you to set up multitouch. Gradually replaced by resistive ones.

Capacitive touch screens

A capacitive (or surface capacitive) screen takes advantage of the fact that an object with a large capacity conducts alternating current.

A capacitive touch screen is a glass panel coated with a transparent resistive material (usually an alloy of indium oxide and tin oxide). Electrodes located at the corners of the screen apply a small alternating voltage (the same for all corners) to the conductive layer. When touching the screen with a finger or other conductive object, current leakage occurs. At the same time, the closer the finger is to the electrode, the lower the resistance of the screen, which means that the current strength is greater. The current in all four corners is recorded by sensors and transmitted to the controller, which calculates the coordinates of the touch point.

Earlier models of capacitive screens used direct current - this simplified the design, but with poor user contact with the ground, it led to failures.

Capacitive touch screens are reliable, about 200 million clicks (about 6 and a half years of clicks with an interval of one second), do not leak liquids and tolerate non-conductive pollution perfectly. Transparency at 90%. However, a conductive coating located directly on the outer surface is still vulnerable. Therefore, capacitive screens are widely used in machines that are only installed in a weather-protected room. Not responsive to gloved hand.

It is worth noting that due to differences in terminology, surface and projection-capacitive screens are often confused. According to the classification used in this article, the screen, for example, iPhone is projected-capacitive, not capacitive.

Projected capacitive touch screens

A grid of electrodes is applied on the inside of the screen. The electrode together with the human body forms a capacitor; electronics measures the capacitance of this capacitor (applies a current pulse and measures the voltage).

Samsung has been able to install sensitive electrodes directly between the sub-pixels of the AMOLED screen, which simplifies the design and increases transparency.

The transparency of such screens is up to 90%, the temperature range is extremely wide. Very durable (the bottleneck is the complex electronics that process the clicks). Glass up to 18 mm thick can be used on the POSE, resulting in extreme vandal resistance. They do not react to non-conductive pollution, conductive ones are easily suppressed by software methods. Therefore, projective-capacitive touch screens are widely used both in personal electronics and in vending machines, including those installed on the street. Many varieties support multitouch.

Touch screens based on surface acoustic waves

The screen is a glass panel with piezoelectric transducers (PTs) located at the corners. Along the edges of the panel are reflective and receiving sensors. The principle of operation of such a screen is as follows. A special controller generates a high-frequency electrical signal and sends it to the PET. The PET converts this signal into SAW, and the reflective sensors reflect it accordingly.

These reflected waves are received by the appropriate sensors and sent to the PET. The probes, in turn, receive the reflected waves and convert them into an electrical signal, which is then analyzed by the controller. When you touch the screen with your finger, part of the energy of the acoustic waves is absorbed. The receivers capture this change, and the microcontroller calculates the position of the touch point. Reacts to touch with an object capable of absorbing the wave (finger, gloved hand, porous rubber).

The main advantage of the screen on surface acoustic waves (SAW) is the ability to track not only the coordinates of the point, but also the pressing force (here, rather, the ability to accurately determine the radius or area of ​​pressing), due to the fact that the degree of absorption of acoustic waves depends on the pressure at the point touch (the screen does not bend under the pressure of a finger and is not deformed, therefore, the force of pressing does not entail qualitative changes in the processing by the controller of data on the coordinates of the impact, which fixes only the area that blocks the path of acoustic impulses).

This device has a very high transparency, since the light from the display device passes through the glass, which does not contain resistive or conductive coatings. In some cases, glass is not used at all to combat glare, and emitters, receivers, and reflectors are attached directly to the screen of the display device. Despite the complexity of the design, these screens are quite durable. According to, for example, the American company Tyco Electronics and the Taiwanese company GeneralTouch, they can withstand up to 50 million touches at one point, which exceeds the resource of a 5-wire resistive screen.

SAW screens are mainly used in slot machines, in secure reference systems and educational institutions. As a rule, surfactant screens are divided into ordinary - 3 mm thick, and vandal-resistant - 6 mm. The latter can withstand being punched by an average man or being dropped by a 0.5 kg metal ball from a height of 1.3 meters (according to Elo Touch Systems). The market offers options for connecting to a computer both via the RS232 interface and via the USB interface. At the moment, controllers for SAW touch screens that support both types of connection - combo (data from Elo Touch Systems) are more popular.

The main disadvantage of the screen on SAW are failures in the presence of vibration or when exposed to acoustic noise, as well as when the screen is dirty. Any foreign object placed on the screen (for example, chewing gum) completely blocks its operation. In addition, this technology requires touching an object that necessarily absorbs acoustic waves - that is, for example, a plastic bank card is not applicable in this case.

The accuracy of these screens is higher than matrix ones, but lower than traditional capacitive ones. For drawing and entering text, they are usually not used.

Infrared touch screens

The principle of operation of the infrared touch panel is simple - the grid formed by horizontal and vertical infrared rays is interrupted when you touch the monitor with any object. The controller determines where the beam was interrupted.

Infrared touch screens are sensitive to dirt and therefore are used where image quality is important, such as in e-readers. Due to its simplicity and maintainability, the scheme is popular with the military. Often, intercom keyboards are made on this principle. This type of screen is used in Neonode's abundant phones.

Optical touch screens

The glass panel is supplied with infrared illumination. At the "glass-air" boundary, total internal reflection is obtained, at the "glass-foreign object" boundary, the light is scattered. It remains to capture the scattering picture, for this there are two technologies:

In projection screens, a camera is placed next to the projector.

This is how, for example, Microsoft PixelSense works.

Or an additional fourth sub-pixel of the LCD screen is made photosensitive.

They allow you to distinguish between hand pressing and pressing with any objects, there is a multi-touch. Large touch surfaces are possible, up to the blackboard.

Strain gauge touch screens

Respond to screen distortion. The accuracy of strain gauge screens is not high, but they withstand vandalism very well. The main application is ATMs, ticket machines and other devices located on the street.

Touch screens DST

The touch screen DST (Dispersive Signal Technology) registers the piezoelectric effect in the glass. You can press the screen with your hand or any object.

A distinctive feature is the high reaction speed and the ability to work in conditions of severe screen pollution. However, the finger must move; the system does not notice a fixed finger.

Quite a few years have passed, and almost every second person on Earth has experienced all the delights of new technological advances. More recently, it was possible to observe people dialing SMS or a person's number using buttons, but modernity is making great achievements. Now almost 90% of the population uses simple touches on the screen of a particular technique:

Demand for smartphones over the past 5-10 years has grown by almost 40-45%, which once again proves their uniqueness, versatility, accessibility, interest in everything new.

But when buying any "newly made" equipment, during the story about it by the seller, many are interested in the same question - "touchscreen", what is this detail and what does it serve?

This article will provide extensive information about its appearance, as well as disclose all aspects of its occurrence, types and significance of its use.

Touchscreen, appearance

To begin with, I would like to pay special attention to the most interesting foreign term "touchscreen"? It came from two words, each of which has its own meaning. in this phrase:

• touch- touch, touch, touch;
• Screen- screen;
• touch screen- "touch screen".

Positive and negative qualities

"+" and "-" in pocket devices for communication:

• Ease of use and versatility when pressed;
• Mobile and other devices may not be very large, while the screen will pleasantly surprise with its parameters;
• With manual dexterity and a little training, you can type text of any complexity in a matter of minutes;
• Opportunities are growing every year, which greatly increases the use and sales of these devices.

• There is no tactile screen transmission;
• The battery drains too quickly with prolonged use and an excessively bright percentage;
• With any mechanical impact on the touchscreen, malfunctions may occur;
• The touch screen does not have a high level of hygiene.

"+" and "-" in stationary devices:

• Reliability at the highest level of use of this kind of screens;
• Wear resistance also prevails over other types of screens, has a high level of dust resistance, moisture resistance, protect against small impacts.

• There is no tactile feedback of the screen;
• Working with such devices, which are at the level of your body, leads to frequent hand fatigue, so they are used only occasionally (small, meaningful, with quick work for ease of use);
• When working with , in some cases the screen may be obstructed by a shadow from the hands, or by the hands themselves:
• When working with a small one, errors may occur in calculations, writing, movements on the keyboard;
• When using such displays in public places, there is a risk of contamination, which can also5 lead to a decrease in the performance of the touchscreen. In such a situation, specialized means of protection against moisture, sweat, dust, dirt, etc. are on sale.

During the manifestation of these shortcomings, many developers have come to the conclusion that in addition to touch input, ordinary buttons should also be created (even in the event of a sensor malfunction, you can replenish your account or buy a ticket using button input).

Classification

If you delve deeper into the varieties of the touchscreen, then you can distinguish the following popular types of screens, after which Let's look at each of them:

• resistive;
• Matrix;
• projective-capacitive;
• infrared;
• optical;
• touch screens DST;
• wave;
• induction and many others.

Resistive

The presented view consists of a pair of plates of plastic material, inside of which there is a mesh that conducts current, the width of which reaches no more than 1-2 millimeters. The same grid can be seen when parsing . They can be safely called the "recent past", "on the heels" of which capacitive screens come.

Also, between these plates there is a layer of dielectric material, which makes it possible to carry out a certain set of signals inside any sensor device. software tools, and they already ensure the interaction of all available programs.

That is, when you touch a certain area of ​​the screen, you start a certain process of implementing one or another function of the phone, device, etc. Coordinate touch points on the screen (X and Y) contribute to the launch of a certain, previously programmed algorithm of actions.

Resistive have their subspecies:

four-wire- they consist of one glass panel and a plastic membrane, the surface of which is covered by a resistive screen support. All free space between the panel and the membrane is occupied by insulators. When you press , the panel and the membrane close, which leads to the start of the required touch coordinate, thereby launching one or another phone function (menu, viewing photos, etc.);

five-wire- in this version of the touchscreen, not a resistive support is applied to the membrane, but a conductive one. This gives stronger reliability in use, even if the membrane is damaged in some places, the machine will continue to function.

There are also eight-wire, which, although able to work with your touch more accurately, but in no way are able to increase the level of reliability in use.

Reading process of this type touchscreen is as follows:

• A voltage of + 5V is given to the upper electrode, while the lower one conducts grounding. The left and right are connected shortly and the voltage on them is checked. This voltage corresponds to the Y-coordinate of the screen.
• Similarly, + 5V and “ground” are supplied to the left and right electrodes, the X-coordinate is read from the top and bottom.

The resistance across the touch screen contacts is as follows:

• Y-,Y+=550 Om (without pressing);
• X-,X+=350 Om (without pressing);
• Y +, X + = from 0.5 to 1.35 kOm (measurements were made in different corners of the screen, when pressed, and without touching it - the resistance is equal to infinity);
• Y-,X-=from 1.35-0.5 kOm (measurements were made in different corners of the screen when pressed, and without touching it - the resistance is equal to infinity).
• In different types of touch screens, the resistance can vary from higher to lower.

If we talk about resistive touchscreens in general, then it is worth noting their low cost, ease of operation: you do not need to use only your fingers, you can press it with gloves, and with a plastic card, with a pen to start the action.

Screens of this kind can be observed in medical services, in payment terminals, in industry, PDAs, etc. They are not particularly resistant to temperature changes and awkward movements of the hand or other object.

But resistive screens also have disadvantages:

• rather low degree of penetration of light rays;
• scratches, bumps, cracks, finger stains appear on it faster;
• a small number of clicks to completely exhaust the life of the screen. There are about thirty-four million times;
• not the possibility of implementing multitouch;
• there is no possibility to use the functions of the screen with sliding on it, only a single tap is required.

Matrix

Also one of the inexpensive types of touch screens, which are produced similarly to resistive ones, but have small manufacturing features. The conductors of the horizontal type are applied to the panel, but the vertical type is applied to the membrane.

As soon as you touch any point on the touchscreen, these conductors come into contact, and the required function does its job. During a malfunction of the matrix screen, it is replaced by a resistive one.

Projection-capacitive (PESE) (Capacitive)

At the bottom of the touchscreen there is a grid of electrodes, each of which, together with human heat, is able to form condensate.

It was not difficult to create electrodes of a sensitive type between the sub-pixels of the screen, which makes it possible for it to be more transparent, and the technique more durable in use.

Projection-capacitive screens are transparent by almost 92%, which makes it possible to use them for a long time, and the use of glasses up to 19 mm reduces the risk of their violations. It is for this reason that they are placed even on machine guns and technicians standing in open areas.

infrared

In these types of screens there is a kind of infrared panel in the form of a grid, consisting of vertically and horizontally arranged beams that react to any touch on the screen (any object).

With the help of the embedded controller, the point where the touch was made is fixed for the implementation of a particular program.

Such screens are often used where there is not a lot of dust, dirt, debris - e-books, sensors in the military structure, Neonode brand phones.

Optical

The glass panel has infrared illumination, which on the line between the glass and the air mass can produce 100% reflection inside, and between the glass panel and your finger, the object, the light is scattered. The point is small - to create this picture of dispersion. Scientists were able to create several technologies to make this progress:

1 A camera is installed on the screen next to the projector.

2 Using the auxiliary fourth sub-pixel of the liquid crystal screen, produce a light-sensing process.

3 When using this screen, inside the backlights are able to distinguish the touch of human skin from a foreign object. Thanks to this development, it was decided to expand the boundaries of the size of such touch surfaces (from minimal screens to large school boards).

Dispersive Signal Technology

This type captures the piezoelectric phenomenon in a glass panel. It is possible to touch both with a hand and with any object. It can function in any dusty conditions, but your finger should not be idle.

Wave bright screens (Surface acoustic wave)

These ranges of screens can be safely called our bright, beautiful, unique future!

Coordinate touch points on the screen (X and Y) contribute to the launch of a certain, previously programmed algorithm of actions. At the ends of each of the axes there are their own converters, and each of them has its own principles of influence: one of them transmits information, and the second receives it. In addition to them, there are reflectors on the glass panel that reflect the electricity signal that travels from one converter to another.

Transducers in the form of receivers are pretty smart mechanisms that can "feel" if the screen has been touched, and in which of the exact coordinates it happened (gives a guarantee of long-term use and accurate data entry). The glass panel in this type of screen is completely devoid of metal coating, which is one of the main advantages - a person will see all the colors of the image, without distortion, as well as all the beauty of these colors!

For those, who works on your touch screen device, and their work is connected with small signs, details, graphs, tables, then for them the wave screen is just great option to buy. After all, if we take the above types of screens as an example, one or another figure or value will not be so clearly visible on them, and on the wave screen, even when approaching, you can see even the smallest detail in all its beauty and clarity. In other types of touchscreens, 80% of the image is partially distorted, and all this is directly related to light retention.

induction

This type of touchscreen is intended only for a special pen (a pen for performing any action on the touch screen, often sold with a tablet, pocket PC).

Some distinguishing features of these types of screens

1 Some of the cheapest touch screens are resistive. They are the least accurate to human vision of brightness, clarity, and the most vulnerable of all. Even the most awkward movement can damage it.

2 If we take the most expensive touchscreens, then these are wave ones. They are the brightest, most comfortable, accurate, beautiful.

3 Resistive screens- these are already relics of the past, but wave, capacitive - a solid present and a bright future!

4 When using a resistive screen, it doesn't matter too much what you touch it with pen, card, finger.

5 And here capacitive screens on the contrary, strictly know how to work with them- only objects that conduct current through themselves. 80% of the time it's your fingers.

6 The wave screen is still in terms of use and pressing will be equated to a resistive screen.

Calibration

Since none of the types of touch screens can give you a guarantee of their durability, sensor malfunctions may occur:

• click errors;
• not responding to your touch on the screen;
• incorrect response to pressing a particular function (instead of Menu, you enter Gallery and vice versa, etc.).

With such inconsistencies in the operation of the screen, or when replacing the sensor, many masters will offer touchscreen calibration. This kind of manipulation is not particularly complicated, but the correct operation of the screen response will depend on them.

- this is a set of techniques for improving the performance of the screen's response to your touch, or when using special pens, pens. To find out if your device requires calibration, you should (if it has one) wipe the screen thoroughly.

Then find on your device any bookmarks, sms, documents, and when the keyboard is displayed, press any of the letters. In the event that the pressed letter does not correspond to what you wanted to see on the screen, you will need to calibrate the screen. Each type will require its own calibration:

Resistive. This type of screens, when they are first turned on, must necessarily undergo screen calibration. To do this, there is a programmed inclusion, and you can not avoid this procedure in any way. It is also desirable to calibrate if the resistive screen was hit, dropped, it will be replaced with a new one, a software failure. Almost every device with this type of screen has a built-in program - ts_calibrate, which is located in the phone settings, in the Calibration sub-item. After selecting this program, your screen will darken, and a dot, cross, sign, any color will appear in the center and you need to click on it to start the screen calibration process. You should be careful when pressing, and after the correct input 4-6 times to a given point, the device will save all the correct data, and the phone, tablet, PDA will work properly and accurately.

Capacitive. This type of screen has crashes, but much less frequently than the one described above. The capacitive screen does not already have a built-in program for carrying out this procedure, but you can download it without problems and completely free of charge - TouchScreen Tune. With the help of this program, even the most inexperienced person can easily carry out the entire cycle of procedures.

It should be remembered! Resistive screens are required to be calibrated once every 30-35 days, especially if the screen is constantly used. When carrying out calibration on a capacitive screen, you should be careful, because if the procedure is carried out incorrectly, the touchscreen may fail completely, returning to the initial settings.

This means only the fact that if you are not confident in your abilities, then it is better to entrust this nuance to specialists in this matter!

Is it possible to replace

In the event that it requires replacement:

• broken;
• broken;
• cracked;
• Has ceased to function (does not respond, does not turn on, etc.),

It is not advisable to carry out independent actions, and just as suggested above, turn to specialists who can help you in any situation. We strongly recommend that you replace touchscreens only in service centers, where a quality guarantee will be provided for any work.