Resistive screen: what is it and what are its features? Your phone's touchscreen is resistive, capacitive, or projected capacitive.
Or as they are also called - tablets, based on the operating room Android systems are some of the fairly new gadgets that will allow you to chat with your friends, view World Wide Web (Internet), as well as watch movies and listen to your favorite music. They are usually small flat shape, have lost a significant part of their mass and a rather voluminous keyboard, which is now associated with their older brother, the laptop. If there is no keyboard, you ask, then how to work with them?
Every tablet has a touch screen. This is a screen that responds to your touch, just like Touchpad at the laptop. This way, instead of clicking on icons with your mouse, you can simply touch them with your finger or stylus (looks like a pen, but without the ink).
Exist different kinds touch displays, so let's figure out what they are and what the differences are between them:
Resistive touch screen
Resistive touch screen looks like a sandwich consisting of layers, if we speak by analogies. When you press the screen, it closes with the membrane, the device registers the change in resistance and converts it into coordinates, so your tablet knows that you pressed here and reacts accordingly. For example, opens an application or pauses the game. Their strengths are that they are quite durable, as they are made from various types of fiberglass. Considering that this is enough simple development, resistive screen It also has a relatively low cost, so it will reduce your costs. The disadvantage of the resistive type of screen is that some people feel that they are not sensitive enough, since the tablet has to wait a short time for your finger or stylus to close the layers. In addition, it is highly recommended to have a stylus or a long fingernail, since simple touches with your fingertip are not always recognized by the device.
Capacitive touch screen
Capacitive touch screen consists of flat and thick glass covered with a layer electrical conductor. The human body is also good guide electric current, so when you touch the glass it appears electrical connection, which is recognized as if you were clicking the mouse. Strengths of this type touch screens are that they produce a brighter and clearer picture than resistive ones, they are also made of glass, there is no plastic there, so they recognize touches quite accurately and quickly, thus eliminating the need for a stylus. Flaws capacitive screen take place here too. Since the production of such displays is quite complex, the price touch screen significantly more than resistive ones, and since they are made of glass they are susceptible to damage, for example when the tablet falls to the ground.
So which one should you choose? To be honest, there's no clear winner here, but it might be worth considering whether you'll be using a stylus or your finger. Capacitive displays tend to be brighter, so if you're going to watch movies on a tablet, a capacitive screen is preferable. They are also great for gamers, due to the ability to respond more quickly to touch. If you are not attracted by the above, and you just want to find yourself a tablet based on Android OS for browsing the Internet, Email, listening to music, then you can certainly save money without sacrificing performance and buy a tablet with a resistive display.
An information input device, which is a screen that responds to touches. There are many different types touch screens that operate on different physical principles. But we will consider only those that are found in mobile phones and other portable equipment.
How resistive touch screens work
Resistive touch screens come in two types, four-wire and five-wire. Let's consider the operating principle of each type separately.
Four-wire resistive screen
Operating principle of 4-wire resistive touch screen
A resistive touch screen consists of a glass panel and a flexible plastic membrane. A resistive coating is applied to both the panel and the membrane. 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 with analog-to-digital converter registers the change in resistance and converts it into touch coordinates (X and Y). IN general outline The reading algorithm is as follows:
- A voltage of +5V is applied to the upper electrode, and 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, and the X-coordinate is read from the top and bottom.
Five-wire resistive screen
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 through membrane). The rear glass has a resistive coating with four electrodes at the corners.
Operating principle of 5-wire resistive touch screen
Initially, all four electrodes are grounded, and the membrane is “pulled up” by a resistor to +5V. The voltage level on the membrane is constantly monitored analog-to-digital converter. When nothing is touching the touch screen, the voltage is 5V.
As soon as the screen is pressed, the microprocessor detects the change in membrane voltage and begins to calculate the coordinates of the touch as follows:
- A voltage of +5V 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 to ground both lower ones.
How capacitive touch screens work
A capacitive (or surface capacitive) screen takes advantage of the fact that an object large capacity conducts alternating current.
Operating principle of a capacitive touch screen
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 amount of energy to the conductive layer. AC voltage(same for all corners). When you touch the screen with your finger or other conductive object, current leaks. Moreover, the closer the finger is to the electrode, the lower the screen resistance, which means the greater the current. The current in all four corners is recorded by sensors and transmitted to the controller, which calculates the coordinates of the touch point.
In earlier models of capacitive screens, D.C.- this simplified the design, but bad contact the user with the ground led to failures.
Capacitive touchscreens are reliable, about 200 million clicks (about 6 and a half years of clicks every second), do not leak liquids, and tolerate non-conductive contaminants very well. Transparency at 90%. However, the conductive coating is still vulnerable. Therefore, capacitive screens are widely used in machines installed in protected areas. They do not respond to a gloved hand.
Operating principle of 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; the electronics measures the capacitance of this capacitor (supplies a current pulse and measures the voltage).
Operating principle of projected capacitive touch screen
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 clicks). POE can use glass up to 18 mm thick, which results in extreme vandal resistance. They do not react to non-conductive contaminants; conductive contaminants are easily suppressed using software methods. Therefore, projected capacitive touch screens are used in outdoor machines. Many models react to a gloved hand. IN modern models The designers have achieved very high accuracy - however, vandal-resistant versions are less accurate.
PEEs even react to the approach of a hand - the response threshold is set by software. Distinguish between pressing by hand and pressing with a conductive pen. Some models support multi-touch. Therefore, this technology is used in touchpads and multi-touch screens.
It is worth noting that due to differences in terminology, surface- and projected-capacitive screens are often confused. According to the classification used in this article, the iPhone screen is projected capacitive.
Conclusion
Each type of touch screen has its own advantages and disadvantages; for clarity, let’s look at the table.
| Resistive 4-wire | Resistive 5-wire | Capacitive | Projected capacitive | |
|---|---|---|---|---|
| Functionality | ||||
| Hand in glove | Yes | Yes | No | Yes |
| Solid conductive object | Yes | Yes | Yes | Yes |
| Solid non-conductive object | Yes | Yes | No | No |
| Multi-touch | No | Yes | Yes | Yes |
| Pressure measurement | No | No | No | Yes |
| Ultimate transparency, % | 75 | 85 | 90 | 90 |
| Accuracy | High | High | High | High |
| Reliability | ||||
| Lifetime, million clicks | 10 | 35 | 200 | ∞ |
| Protection from dirt and liquids | Yes | Yes | Yes | Yes |
| Resistance to vandalism | No | No | No | Yes |
The article was written based on materials from the site
If you are not one of those savvy technically users and you will soon be faced with a question of choice mobile phone or a smartphone with a touch screen, you are likely to come across terms such as “capacitive screen” or “resistive screen” when reading the specifications of mobile devices. And then it will come to your mind completely logical question– which one is better: resistive or capacitive? Let's find out how touch displays differ, what types exist, and what their advantages and disadvantages are.
RESISTIVE SCREENS
If we talk accessible language, avoiding wise technical terms and phrases, a resistive touch screen is a flexible transparent membrane on which a conductive (in other words, resistive) coating is applied. Under the membrane there is glass, also covered with a conductive layer. The principle of operation of a resistive screen is that when you press the screen with a finger or stylus, the glass closes with the membrane at a specific point. The microprocessor records the change in membrane voltage and calculates the contact coordinates. The more precise the press, the easier it is for the processor to calculate the exact coordinates. Therefore, with resistive screens it is much easier to work with a stylus.
The main advantages of resistive screens are that they are relatively cheap to produce, and also that this type of display responds to pressure from any object. This is very useful when making presentations, especially since the prices of projectors today are falling every day.
The disadvantages of resistive screens are: low strength; low durability (about 35 million clicks per point); impossibility of implementation; a large number of errors when processing gestures such as sliding and flipping.
So which screen is better: resistive or capacitive?
If you read carefully this article, then you can draw your own conclusion without any problems. I will only say that this dispute is doomed to failure. Some users like to work with a stylus and are not comfortable with capacitive displays. But most people are more comfortable operating a device equipped with a capacitive screen - it’s more convenient, and the multi-touch feature makes a big difference. It's not all for nothing modern smartphones and tablets running under Android control, have capacitive displays.
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At first, touchscreens (touch screens) were quite rare. They could only be found in some PDAs and PDAs (pocket computers). As you know, devices of this kind never became widespread, since they lacked the most important thing, that is, functionality. The history of smartphones is directly related to touchscreens. That is why at the present time a person with “ smart phone“You won’t be surprised by a touch screen these days. The touchscreen is widely used not only in fashionable expensive devices, but even in relatively inexpensive models modern phones. What are the principles of operation of the 3 types of touch screens that can be found in modern devices Oh.
Types of touchscreens
Touch screens are no longer too expensive. In addition, touchscreens today are much more “responsive” - they recognize user touches simply perfectly. It was this characteristic that paved the way for them to a large number users all over the world. Currently, there are three main designs of touchscreens:
- Capacitive.
- Wave.
- Resistive or simply “elastic”.
Capacitive touchscreen: operating principle
In touchscreen designs of this kind, the glass base is covered with a layer that acts as a charge storage container. The user, with his touch, releases a part at a certain point electric charge. This reduction is determined by microcircuits that are located in each corner of the screen. The computer calculates the difference in electrical potentials existing between different parts of the screen, and the detailed touch information is immediately transmitted to the touchscreen driver program.
A rather important advantage of capacitive touchscreens is the ability of this type of screen to retain almost 90% of the original display brightness. Because of this, images on a capacitive screen appear sharper than on touchscreens that have a resistive design.
Video about capacitive touch screen:
The future: waveform touch displays
At the ends of the axes grid There are two converters located on the glass screen. One of them is the transmitter, the second is the receiver. There are also reflectors on a glass base that “reflect” the electrical signal that is transmitted from one converter to another.
The converter-receiver “knows” absolutely exactly whether there was a press, as well as at what specific point it occurred, since the user interrupts with his touch acoustic wave. At the same time, the glass of the wave display does not have a metal coating - this makes it possible to preserve 100% of the original light in full. Due to this, wave screen represents best option for those users who work in graphics with small details, because resistive and capacitive touchscreens are not ideal in terms of image clarity. Their coating blocks light, which results in significantly distorted images.
Video about the operating principle of surfactant touch screens:
Past: about resistive touchscreen
A resistive system is ordinary glass, which is covered with a layer of electrical conductor, as well as an elastic metal “film” that also has conductive properties. Between these 2 layers, using special spacers, there is empty space. The surface of the screen is covered with a special material that provides it with protection from mechanical damage eg scratches.
An electric charge passes through these two layers as the user interacts with the touchscreen. How does this happen? The user touches the screen at a certain point and the elastic top layer comes into contact with the conductive layer - only at this point. Then the computer determines the coordinates of the point that the user touched.
When the coordinates become known to the device, a special driver translates touches into commands known to the operating system. IN in this case you can draw analogies with the driver of the most common computer mouse, because it does exactly the same thing: it explains to the operating system what the user specifically wanted to tell it by moving the manipulator or pressing a button. As a rule, special styluses are used with screens of this type.
Resistive screens can be found in relatively old devices. The IBM Simon, the oldest smartphone known to our civilization, is equipped with just such a touch screen.
Video about the operating principle of a resistive touch screen:
Features of different types of touchscreens
The cheapest touch screens, but at the same time the least clearly transmitting the image, are resistive touchscreens. In addition, they are also the most vulnerable, because absolutely any sharp object can seriously damage a fairly delicate resistive “film”.
The next type, i.e. wave touchscreens are the most expensive among their kind. At the same time, the resistive design most likely belongs to the past, the capacitive design to the present, and the wave design to the future. It is clear that absolutely no one knows the future one hundred percent and, accordingly, at the present time one can only guess what technology will have great prospects for future use.
For a resistive touchscreen system, it does not make any special difference whether the user touches the device screen with the rubber tip of the stylus or simply with a finger. It is enough that there is contact between the two layers. At the same time, the capacitive screen only recognizes touches by some conductive objects. Often, users of modern devices operate them using their own fingers. Wave design screens in this regard are closer to resistive. It is possible to give a command with almost any object - you just need to avoid using heavy or too small objects, for example, a rod ballpoint pen not suitable for this.
18.01.2011What is the difference capacitive screens, used in iPhone and other modern mobile devices, from other types of touch displays? And is this the future?
I have been convinced many times that regular users are completely unaware of the existence of different types of touch screens and learn with genuine amazement that the lack of response of the display of a newly purchased communicator to the usual poking with a pencil is not at all a sign of a malfunction. It's just a different screen, built on a different technology. Even some sellers are confused in the readings, attributing to displays of one type the properties of others. So first we will conduct brief educational program, after which you will be able to distinguish different types of screens literally by touch. And then we’ll talk about which of them is the future.
Modern mobile devices - smartphones, communicators, players - use two types of touch screens: resistive And capacitive. Moreover, more than 90% of all touch screens today are of the resistive type, although there is already a clear trend toward an increase in the share of capacitive screens.
To stop getting confused, just remember: Resistive screens are pressure sensitive, while capacitive screens are touch sensitive. This difference is due to the design of the displays, and it is in principle impossible to train, for example, a capacitive screen to recognize pencil presses.
A resistive screen is a glass liquid crystal display on which a flexible membrane is applied. A resistive composition is applied to the contacting sides, and the space between the planes is divided by a dielectric. Electrodes (four or eight, five or six and seven) are attached to the edges of the plates. It is easy to guess that when pressed, the screen and the membrane come into contact at the point of pressing, the coordinates of which are calculated by sequentially applying current to the upper and lower plates and measuring the voltage at the point of contact of the plates. That is why you can press such a screen with any hard object - from a fingernail and a stylus to a pencil or a match, and it will work.
Due to their design, resistive screens and, especially, their conductive layer are subject to gradual wear, which is why there is a need for periodic calibration of the screen. The simplest and cheapest four-electrode screens can withstand only 3 million clicks on one point. Several times more reliable - up to 35 million clicks - are five-wire ones, where four electrodes are located on the screen plate, and the fifth is on a membrane coated with a conductive composition and serves only as a kind of “probe”. In addition, five-wire and its modifications 6 and 7-wire screens continue to work even if part of the membrane is damaged.
The disadvantages of resistive screens also include low light transmission - no more than 70-85%, which requires increased backlight brightness. But these screens are extremely cheap to produce, which explains their wide distribution.
A capacitive touch screen is generally a glass panel on which a layer of transparent resistive material is applied. Electrodes are installed at the corners of the panel, supplying low-voltage alternating voltage to the conductive layer. Since the human body is capable of conducting electricity and has some capacity, when you touch the screen, a leak appears in the system. The location of this leak, that is, the point of contact, is determined by a simple controller based on data from the electrodes at the corners of the panel.
There are no flexible membranes on the screen, which ensures high reliability and allows you to reduce the brightness of the backlight. Unfortunately, you cannot poke them with a stylus or fingernail, since the command simply will not be recognized. Only with your finger. Such a screen also does not like negative temperatures: at best, the accuracy of determining coordinates decreases; at worst, it simply stops responding.
Unfortunately, on the simplest capacitive screen, which is now installed in the cheapest “touch” phones, it is impossible to organize a fashionable “multi-finger” multi-touch interface - four electrodes in the corners are capable of recording only one click at a time. Projected capacitive displays, in which reverse side the screen has a whole grid of conductors (or rows of electrodes), to which a weak current is applied, and the place of contact is determined by the points with increased capacity. By the way, such screens are capable of reacting even to the approach of a hand (and therefore to a gloved hand) - it all depends on the sensitivity settings.
Many experts, not without reason, believe that resistive screens are a thing of the past, and capacitive screens are the future. Indeed, just the transition from a mechanical-electrical input system to a purely electrical one is certainly progress. Reliability and accuracy of coordinate determination have increased, the need for calibration has disappeared, and a “multi-finger” interface has appeared.
The abandonment of resistive displays stimulated the development of truly convenient user interfaces, optimized for finger control. In modern communicators, you no longer need to aim a sliver at microscopic interface elements inherited from the “big ones” operating systems. Please note, the latest Windows Phone 7 is absolutely nothing like the rest of the family of “mobile windows” of previous generations, in which there was nothing to do without a tiny stylus.
Skeptics will note that you can no longer draw on a capacitive screen with a regular plastic stylus or some random object, or write down a memo by hand. To do this, you will have to buy a special stylus with an electrical capacity. HTC even patented such a capacitive stylus and asks about $30 for it. But how often do we draw on our phones or use handwriting? As they say in certain circles, a little less often than never. But touch tablets for drawing use completely different technologies, and they are not going anywhere.
The only reason why resistive screens still occupy the lion's share of the market is because they are extremely cheap. In addition, over the course of several years, all the largest vendors managed to produce such a number of very diverse and not at all cheap handsets with resistive displays that it would be like death for them to immediately write them into the category of obsolete. In any case, devices with capacitive screens will become more and more, and with resistive ones - less and less. In a few years, we won’t even remember that we once poked special thin slivers into the screen of smartphones.