tft lcd screen meaning free sample

A thin-film-transistor liquid-crystal display (TFT LCD) is a variant of a liquid-crystal display that uses thin-film-transistor technologyactive matrix LCD, in contrast to passive matrix LCDs or simple, direct-driven (i.e. with segments directly connected to electronics outside the LCD) LCDs with a few segments.

In February 1957, John Wallmark of RCA filed a patent for a thin film MOSFET. Paul K. Weimer, also of RCA implemented Wallmark"s ideas and developed the thin-film transistor (TFT) in 1962, a type of MOSFET distinct from the standard bulk MOSFET. It was made with thin films of cadmium selenide and cadmium sulfide. The idea of a TFT-based liquid-crystal display (LCD) was conceived by Bernard Lechner of RCA Laboratories in 1968. In 1971, Lechner, F. J. Marlowe, E. O. Nester and J. Tults demonstrated a 2-by-18 matrix display driven by a hybrid circuit using the dynamic scattering mode of LCDs.T. Peter Brody, J. A. Asars and G. D. Dixon at Westinghouse Research Laboratories developed a CdSe (cadmium selenide) TFT, which they used to demonstrate the first CdSe thin-film-transistor liquid-crystal display (TFT LCD).active-matrix liquid-crystal display (AM LCD) using CdSe TFTs in 1974, and then Brody coined the term "active matrix" in 1975.high-resolution and high-quality electronic visual display devices use TFT-based active matrix displays.

The circuit layout process of a TFT-LCD is very similar to that of semiconductor products. However, rather than fabricating the transistors from silicon, that is formed into a crystalline silicon wafer, they are made from a thin film of amorphous silicon that is deposited on a glass panel. The silicon layer for TFT-LCDs is typically deposited using the PECVD process.

Polycrystalline silicon is sometimes used in displays requiring higher TFT performance. Examples include small high-resolution displays such as those found in projectors or viewfinders. Amorphous silicon-based TFTs are by far the most common, due to their lower production cost, whereas polycrystalline silicon TFTs are more costly and much more difficult to produce.

The twisted nematic display is one of the oldest and frequently cheapest kind of LCD display technologies available. TN displays benefit from fast pixel response times and less smearing than other LCD display technology, but suffer from poor color reproduction and limited viewing angles, especially in the vertical direction. Colors will shift, potentially to the point of completely inverting, when viewed at an angle that is not perpendicular to the display. Modern, high end consumer products have developed methods to overcome the technology"s shortcomings, such as RTC (Response Time Compensation / Overdrive) technologies. Modern TN displays can look significantly better than older TN displays from decades earlier, but overall TN has inferior viewing angles and poor color in comparison to other technology.

The transmittance of a pixel of an LCD panel typically does not change linearly with the applied voltage,sRGB standard for computer monitors requires a specific nonlinear dependence of the amount of emitted light as a function of the RGB value.

Less expensive PVA panels often use dithering and FRC, whereas super-PVA (S-PVA) panels all use at least 8 bits per color component and do not use color simulation methods.BRAVIA LCD TVs offer 10-bit and xvYCC color support, for example, the Bravia X4500 series. S-PVA also offers fast response times using modern RTC technologies.

TFT dual-transistor pixel or cell technology is a reflective-display technology for use in very-low-power-consumption applications such as electronic shelf labels (ESL), digital watches, or metering. DTP involves adding a secondary transistor gate in the single TFT cell to maintain the display of a pixel during a period of 1s without loss of image or without degrading the TFT transistors over time. By slowing the refresh rate of the standard frequency from 60 Hz to 1 Hz, DTP claims to increase the power efficiency by multiple orders of magnitude.

Due to the very high cost of building TFT factories, there are few major OEM panel vendors for large display panels. The glass panel suppliers are as follows:

External consumer display devices like a TFT LCD feature one or more analog VGA, DVI, HDMI, or DisplayPort interface, with many featuring a selection of these interfaces. Inside external display devices there is a controller board that will convert the video signal using color mapping and image scaling usually employing the discrete cosine transform (DCT) in order to convert any video source like CVBS, VGA, DVI, HDMI, etc. into digital RGB at the native resolution of the display panel. In a laptop the graphics chip will directly produce a signal suitable for connection to the built-in TFT display. A control mechanism for the backlight is usually included on the same controller board.

The low level interface of STN, DSTN, or TFT display panels use either single ended TTL 5 V signal for older displays or TTL 3.3 V for slightly newer displays that transmits the pixel clock, horizontal sync, vertical sync, digital red, digital green, digital blue in parallel. Some models (for example the AT070TN92) also feature input/display enable, horizontal scan direction and vertical scan direction signals.

New and large (>15") TFT displays often use LVDS signaling that transmits the same contents as the parallel interface (Hsync, Vsync, RGB) but will put control and RGB bits into a number of serial transmission lines synchronized to a clock whose rate is equal to the pixel rate. LVDS transmits seven bits per clock per data line, with six bits being data and one bit used to signal if the other six bits need to be inverted in order to maintain DC balance. Low-cost TFT displays often have three data lines and therefore only directly support 18 bits per pixel. Upscale displays have four or five data lines to support 24 bits per pixel (truecolor) or 30 bits per pixel respectively. Panel manufacturers are slowly replacing LVDS with Internal DisplayPort and Embedded DisplayPort, which allow sixfold reduction of the number of differential pairs.

The bare display panel will only accept a digital video signal at the resolution determined by the panel pixel matrix designed at manufacture. Some screen panels will ignore the LSB bits of the color information to present a consistent interface (8 bit -> 6 bit/color x3).

Kawamoto, H. (2012). "The Inventors of TFT Active-Matrix LCD Receive the 2011 IEEE Nishizawa Medal". Journal of Display Technology. 8 (1): 3–4. Bibcode:2012JDisT...8....3K. doi:10.1109/JDT.2011.2177740. ISSN 1551-319X.

K. H. Lee; H. Y. Kim; K. H. Park; S. J. Jang; I. C. Park & J. Y. Lee (June 2006). "A Novel Outdoor Readability of Portable TFT-LCD with AFFS Technology". SID Symposium Digest of Technical Papers. AIP. 37 (1): 1079–82. doi:10.1889/1.2433159. S2CID 129569963.

A thin-film transistor liquid crystal display (TFT LCD) is a type of liquid crystal display (LCD) that makes use of thin-film transistor technology in order to improve qualities such as contrast and addressability. TFT technology means that an individual transistor is used to drive each individual pixel, allowing for faster response times.

Thin-film transistor liquid crystal display technology uses "field-effect" transistors, which are built by layering thin films on a glass substrate, hence the name. This technique is commonly used for creating microprocessors. The TFT in the LCD controls individual pixels in the display by setting the level of the electric field across the three liquid crystal capacitors (one for each sub-pixel of red, green and blue) in the pixel in order to control the polarization of the crystal material. The amount of polarization in the crystal determines the amount of light that reaches the color filter from the backlight. Because of this ability to directly and quickly control each pixel, TFT is also called active-matrix LCD technology.

A TFT LCD,  or a thin film transistor liquid crystal display, is one of the fastest growing forms of display technology today. The thin film transistor (TFT) is a type of semiconductor device used in display technology to enhance efficiency, compactness, and cost of the product. In conjunction with its semiconductor properties, the TFT LCD is an active matrix display, controlling pixels individually and actively rather than passively, furthering the benefits of this semiconductor device.

The TFT LCD is built with three key layers. Two sandwiching layers consist of glass substrates, though one includes TFTs while the other has an RGB, or red green blue, color filter. The layer between the glass layers is a liquid crystal layer.

The Architecture of a TFT Pixelbelow) from the other substrate layer of the device and control the amount of voltage applied to their respective sub-pixels. This layer also has pixel electrodes between the substrate and the liquid crystal layer. Electrodes are conductors that channel electricity into or out of something, in this case, pixels.

The outer sides of the glass substrates (closest to the surface or closest to the back) have filter layers called polarizers. These filters allow only certain beams of light to pass through if they are polarized in a specific manner, meaning that the geometric waves of the light are appropriate for the filter. If not polarized correctly, the light does not pass through the polarizer which creates an opaque LCD screen.

The twisted nematic effect is one of the cheapest options for LCD technology, and it also allows for fast pixel response time. There are still some limits, though; color reproduction quality may not be great, and viewing angles, or the direction at which the screen is looked at, are more limited.

The light that passes through the device is sourced from the backlight which can shine light from the back or the side of the display. Because the LCD does not produce its own light, it needs to use the backlight in the OLED) have come into use as well. Typically white, this light, if polarized correctly, will pass through the RGB color filter of the surface substrate layer, displaying the color signaled for by the TFT device.

Within an LCD, each pixel can be characterized by its three sub-pixels. These three sub-pixels create the RGB colorization of that overall pixel. These sub-pixels act as capacitors, or electrical storage units within a device, each with their own independent structural and functional layers as described earlier. With the three sub-pixels per pixel, colors of almost any kind can be mixed from the light passing through the filters and polarizer at different brightness based on the liquid crystal alignment.

1971 – Lechner, F. J. Marlowe, E. O. Nester, and J. Tults demonstrated a 2-by-18 matrix display driven by a hybrid circuit using the dynamic scattering mode of LCDs

2020 – TFT LCD display technology dominants the display market now. Within the last 20 years, it has wiped out the market of CRT (cathode-ray tube) and Plasma. The only challenges are OLED (organic light-emitting diode)and Micro LED (Maybe, still in lab).

TFT LCD Display (Thin-Film-Transistor Liquid Crystal Display) technology has a sandwich-like structure with liquid crystal material filled between two glass plates. Two polarizer filters, color filters (RGB, red/green/blue) and two alignment layers determine exactly the amount of light is allowed to pass and which colors are created.

Each pixel in an active matrix is paired with a transistor that includes a capacitor which gives each sub-pixel the ability to retain its charge, instead of requiring an electrical charge sent each time it needed to be changed.  The TFT layer controls light flow a color filter displays the color and a top layer houses your visible screen.

Utilizing an electrical charge that causes the liquid crystal material to change their molecular structure allowing various wavelengths of backlight to “pass-through”. The active matrix of the TFT display is in constant flux and changes or refreshes rapidly depending upon the incoming signal from the control device.

The pixels of TFT displays are determined by the underlying density (resolution) of the color matrix and TFT layout. The more pixels the higher detail is available.Available screen size, power consumption, resolution, interface (how to connect) define the TFT displays.

The pixels of TFT displays are determined by the underlying density (resolution) of the color matrix and TFT layout. The more pixels the higher detail is available. Available screen size, power consumption, resolution, interface (how to connect) define the TFT displays.

The TFT screen itself can’t emit light like OLED display, it has to be used with a back-light of white bright light to generate the picture. Newer panels utilize LED backlight (light emitting diodes) to generate their light and therefore utilize less power and require less depth by design.

In this article, you will learn how to use TFT LCDs by Arduino boards. From basic commands to professional designs and technics are all explained here.

There are several components to achieve this. LEDs,  7-segments, Character and Graphic displays, and full-color TFT LCDs. The right component for your projects depends on the amount of data to be displayed, type of user interaction, and processor capacity.

TFT LCD is a variant of a liquid-crystal display (LCD) that uses thin-film-transistor (TFT) technology to improve image qualities such as addressability and contrast. A TFT LCD is an active matrix LCD, in contrast to passive matrix LCDs or simple, direct-driven LCDs with a few segments.

In Arduino-based projects, the processor frequency is low. So it is not possible to display complex, high definition images and high-speed motions. Therefore, full-color TFT LCDs can only be used to display simple data and commands.

There are several components to achieve this. LEDs,  7-segments, Character and Graphic displays, and full-color TFT LCDs. The right component for your projects depends on the amount of data to be displayed, type of user interaction, and processor capacity.

TFT LCD is a variant of a liquid-crystal display (LCD) that uses thin-film-transistor (TFT) technology to improve image qualities such as addressability and contrast. A TFT LCD is an active matrix LCD, in contrast to passive matrix LCDs or simple, direct-driven LCDs with a few segments.

In Arduino-based projects, the processor frequency is low. So it is not possible to display complex, high definition images and high-speed motions. Therefore, full-color TFT LCDs can only be used to display simple data and commands.

In electronics/computer hardware a display driver is usually a semiconductor integrated circuit (but may alternatively comprise a state machine made of discrete logic and other components) which provides an interface function between a microprocessor, microcontroller, ASIC or general-purpose peripheral interface and a particular type of display device, e.g. LCD, LED, OLED, ePaper, CRT, Vacuum fluorescent or Nixie.

The LCDs manufacturers use different drivers in their products. Some of them are more popular and some of them are very unknown. To run your display easily, you should use Arduino LCDs libraries and add them to your code. Otherwise running the display may be very difficult. There are many free libraries you can find on the internet but the important point about the libraries is their compatibility with the LCD’s driver. The driver of your LCD must be known by your library. In this article, we use the Adafruit GFX library and MCUFRIEND KBV library and example codes. You can download them from the following links.

Upload your image and download the converted file that the UTFT libraries can process. Now copy the hex code to Arduino IDE. x and y are locations of the image. sx and sy are size of the image.

In this template, We converted a .jpg image to .c file and added to the code, wrote a string and used the fade code to display. Then we used scroll code to move the screen left. Download the .h file and add it to the folder of the Arduino sketch.

while (a < b) { Serial.println(a); j = 80 * (sin(PI * a / 2000)); i = 80 * (cos(PI * a / 2000)); j2 = 50 * (sin(PI * a / 2000)); i2 = 50 * (cos(PI * a / 2000)); tft.drawLine(i2 + 235, j2 + 169, i + 235, j + 169, tft.color565(0, 255, 255)); tft.fillRect(200, 153, 75, 33, 0x0000); tft.setTextSize(3); tft.setTextColor(0xffff); if ((a/20)>99)

while (b < a) { j = 80 * (sin(PI * a / 2000)); i = 80 * (cos(PI * a / 2000)); j2 = 50 * (sin(PI * a / 2000)); i2 = 50 * (cos(PI * a / 2000)); tft.drawLine(i2 + 235, j2 + 169, i + 235, j + 169, tft.color565(0, 0, 0)); tft.fillRect(200, 153, 75, 33, 0x0000); tft.setTextSize(3); tft.setTextColor(0xffff); if ((a/20)>99)

In this template, We just display some images by RGBbitmap and bitmap functions. Just make a code for touchscreen and use this template.  Download the .h file and add it to folder of the Arduino sketch.

Let us start with the basics first; refresh the knowledge about TN and LCD displays in general, later we will talk about TFTs (Thin Film Transistors), how they differ from regular monochrome LCD displays. Then we will go on to the ghosting effect, so we will not only discuss the technology behind the construction of the TFT, but also some phenomena, like the ghosting effect, or grayscale inversion, that are important to understand when using an LCD TFT display.

Next, we will look at different technologies of the TFT LCD displays like TN, IPS, VA, and of course about transmissive and transflective LCD displays, because TFT displays also can be transmissive and transflective. In the last part we will talk about backlight.

Let us start with a short review of the most basic liquid crystal cell, which is the TN (twisted nematic) display. On the picture above, we can see that the light can be transmit through the cell or blocked by the liquid crystal cell using voltage. If you want to learn more about monochrome LCD displays and the basics of LCD displays, follow this link.

What is a TFT LCD display and how it is different from a monochrome LCD display? TFT is called an active display. Active, means we have one or more transistors in every cell, in every pixel and in every subpixel. TFT stands for Thin Film Transistor, transistors that are very small and very thin and are built into the pixel, so they are not somewhere outside in a controller, but they are in the pixel itself. For example, in a 55-inch TV set, the TFT display contains millions of transistors in the pixels. We do not see them, because they are very small and hidden, if we zoom in, however, we can see them in every corner of each pixel, like on the picture below.

On the picture above we can see subpixels, that are basic RGB (Red, Green, Blue) colors and a black part, with the transistors and electronic circuits. We just need to know that we have pixels, and subpixels, and each subpixel has transistors. This makes the display active, and thus is called  the TFT display. TFT displays are usually color displays, but there are also monochrome TFT displays, that are active, and have transistors, but have no colors. The colors in the TFT LCD display are typically added by color filters on each subpixel. Usually the filters are RGB, but we also have RGBW (Red, Green, Blue, White) LCD displays with added subpixels without the filter (White) to make the display brighter.

What is interesting, the white part of the RGB and RGBW screen will look exactly the same from a distance, because the lights are mixed and generate white light, but when we come closer to the screen, we will not see white light at all.

Going a little bit deeper, into the TFT cell, there is a part inside well known to us from the monochrome LCD display Riverdi University lecture. We have a cell, liquid crystal, polarizers, an ITO (Indium Tin Oxide) layer for the electrodes, and additionally an electronic circuit. Usually, the electronic circuit consists of one transistor and some capacitors to sustain the pixel state when we switch the pixel OFF and ON. In a TFT LCD display the pixels are much more complicated because apart from building the liquid crystal part, we also need to build an electronic part.

That is why TFT LCD display technologies are very expensive to manufacture. If you are familiar with electronics, you know that the transistor is a kind of switch, and it allows us to switch the pixel ON and OFF. Because it is built into the pixel itself, it can be done very quickly and be very well controlled. We can control the exact state of every pixel not only the ON and OFF states, but also all the states in between. We can switch the light of the cells ON and OFF in several steps. Usually for TFT LCD displays it will be 8-bit steps per color, so we have 256 steps of brightness for every color, and every subpixel. Because we have three subpixels, we have a 24-bit color range, that means over 16 million combinations, we can, at least theoretically, show on our TFT LCD display over 16 million distinct colors using RGB pixels.

Now that we know how the TFT LCD display works, we can now learn some practical things one of which is LCD TFT ghosting. We know how the image is created, but what happens when we have the image on the screen for a prolonged time, and how to prevent it. In LCD displays we have something called LCD ghosting. We do not see it very often, but in some displays this phenomenon still exists.

If some elements of the picture i.e., your company logo is in the same place of the screen for a long period of time, for couple of weeks, months or a year, the crystals will memorize the state and later, when we change the image, we may see some ghosting of those elements. It really depends on many conditions like temperature and even the screen image that we display on the screen for longer periods of time. When you build your application, you can use some techniques to avoid it, like very rapid contrast change and of course to avoid the positioning the same image in the same position for a longer time.

Another issue present in TFT displays, especially TN LCD displays, is grayscale inversion. This is a phenomenon that changes the colors of the screen according to the viewing angle, and it is only one-sided. When buying a TFT LCD display, first we need to check what kind of technology it is. If it is an IPS display, like the Riverdi IPS display line, then we do not need to worry about the grayscale inversion because all the viewing angles will be the same and all of them will be very high, like 80, 85, or 89 degrees. But if you buy a more common or older display technology type, like the TN (twisted nematic) display, you need to think where it will be used, because one viewing angle will be out. It may be sometimes confusing, and you need to be careful as most factories define viewing direction of the screen and mistake this with the greyscale inversion side.

We know already that TN (twisted nematic) displays, suffer from grayscale inversion, which means the display has one viewing side, where the image color suddenly changes. It is tricky, and you need to be careful. On the picture above there is a part of the LCD TFT specification of a TN (twisted nematic) display, that has grayscale inversion, and if we go to this table, we can see the viewing angles. They are defined at 70, 70, 60 and 70 degrees, that is the maximum viewing angle, at which the user can see the image. Normally we may think that 70 degrees is better, so we will choose left and right side to be 70 degrees, and then up and down, and if we do not know the grayscale inversion phenomena, we may put our user on the bottom side which is also 70 degrees. The viewing direction will be then like a 6 o’clock direction, so we call it a 6 o’clock display. But you need to be careful! Looking at the specification, we can see that this display was defined as a 12 o’clock display, so it is best for it to be seen from a 12 o’clock direction. But we can find that the 12 o’clock has a lower viewing angle – 60 degrees. What does it mean? It means that on this side there will be no grayscale inversion. If we go to 40, 50, 60 degrees and even a little bit more, probably we will still see the image properly. Maybe with lower contrast, but the colors will not change. If we go from the bottom, from a 6 o’clock direction where we have the grayscale inversion, after 70 degrees or lower we will see a sudden color change, and of course this is something we want to avoid.

We will talk now about the other TFT technologies, that allow us to have wider viewing angles and more vivid colors. The most basic technology for monochrome and TFT LCD displays is twisted nematic (TN). As we already know, this kind of displays have a problem with grayscale inversion. On one side we have a higher retardation and will not get a clear image. That is why we have other technologies like VA (Vertical Alignment), where the liquid crystal is differently organized, and another variation of the TFT technology – IPS which is In-Plane Switching. The VA and IPS LCD displays do not have a problem with the viewing angles, you can see a clear image from all sides.

Apart from the different organization of the liquid crystals, we also organize subpixels a little bit differently in a VA and IPS LCD displays. When we look closer at the TN display, we will just see the subpixels with color filters. If we look at the VA or IPS display they will have subpixels of subpixels. The subpixels are divided into smaller parts. In this way we can achieve even wider viewing angles and better colors for the user, but of course, it is more complicated and more expensive to do.

The picture above presents the TN display and grayscale inversion. For IPS or VA technology there is no such effect. The picture will be the same from all the sides we look so these technologies are popular where we need wide viewing angles, and TN is popular where we don’t need that, like in monitors. Other advantages of IPS LCD displays are they give accurate colors, and wide viewing angles. What is also important in practice, in our projects, is that the IPS LCD displays are less susceptible to mechanical force. When we apply mechanical force to the screen, and have an optically bonded touch screen, we push the display as well as squeeze the cells. When we have a TN display, every push on the cell changes the image suddenly, with the IPS LCD displays with in-plane switching, different liquid crystals organization, this effect is lesser. It is not completely removed but it is much less distinct. That is another reason IPS displays are very popular for smartphones, tablets, when we have the touchscreens usually optically bonded.

Now, let us look at the backlight types. As we see here, on the picture above, we have four distinct types of backlight possible. The most common, 95 or 99 per cent of the TFT LCD displays on the market are the transmissive LCD display type, where we need the backlight from the back. If you remember from our Monochrome LCD Displays lecture, for transmissive LCD displays you need the backlight to be always on. If you switch the backlight off, you will not see anything. The same as for monochrome LCD displays, but less popular for TFT displays, we have the transflective LCD display type. They are not popular because usually for transflective TFT displays, the colors lack in brightness, and the displays are not very practical to use. You can see the screen, but the application is limited. Some transflective LCD displays are used by military, in applications where power consumption is paramount; where you can switch the backlight off and you agree to have lower image quality but still see the image. Power consumption and saving energy is most important in some kind of applications and you can use transflective LCD displays there. The reflective type of LCD displays are almost never used in TFT. There is one technology called Low Power Reflective Displays (LPRD) that is used in TFT but it is not popular. Lastly, we have a variation of reflective displays with frontlight, where we add frontlight to the reflective display and have the image even without external light.

Just a few words about Low Power Reflective Displays (LPRD). This kind of display uses environmental light, ambient light to reflect, and produce some colors. The colors are not perfect, not perfectly clear, but this technology is becoming increasingly popular because it allows to have color displays in battery powered applications. For example, a smartwatch would be a case for that technology, or an electrical bike or scooter, where we can not only have a standard monochrome LCD display but also a TFT LCD color display without the backlight; we can see the image even in

strong sunlight and not need backlight at all. So, this kind of TFL LCD display technology is getting more and more popular when we have outdoor LCD displays and need a low power consumption.

On the picture above, we have some examples of how transmissive and reflective LCD displays work in the sunlight. If we have a simple image, like a black and white pattern, then on a transmissive LCD display, even with 1000 candela brightness, the image probably will be lower quality than for a reflective LCD display; if we have sunlight, we have very strong light reflections on the surface of the screen. We have talked about contrast in more detail in the lecture Sunlight Readable Displays. So, reflective LCD displays are a better solution for outdoor applications than transmissive LCD displays, where you need a really strong backlight, 1000 candela or more, to be really seen outdoors.

To show you how the backlight of LCD displays is built, we took the picture above. You can see the edge backlight there, where we have LEDs here on the small PCB on the edge, and we have a diffuser that distributes the light to the whole surface of LCD screen.

In addition to the backlight, we have something that is called a frontlight. It is similar to backlight, it also uses the LEDs to put the light into it, but the frontlight needs to be transparent as we have the display behind. On the example on the picture above we can see an e-paper display. The e-paper display is also a TFT display variation, but it is not LCD (liquid crystal), it is a different technology, but the back of the display is the same and it is reflective. The example you see is the Kindle 4 eBook reader. It uses an e-paper display and a frontlight as well, so you can read eBooks even during the night.

TFT displays are also known as an “Active Matrix TFT LCD module” and have an array of thin film transistors fabricated on the glass that makes the LCD. There is one of these transistors for each pixel on the LCD.

LCDs use voltage applied to a field of microscopic liquid crystals to change the crystal’s orientation, which in turn changes the polarization of the liquid crystal which creates light or dark pixels on the display.

Beautiful, complex images: All of our TFT modules are full-color graphic displays. Unlike standard monochrome character displays, you can create complex images for an imaginative user experience.

Single Supply: Most of the TFTs use an integrated controller with built-in voltage generation so only a single 3.3v supply is needed for both the panel power and logic voltage.

Many of our character LCD modules use a standard HD44780 controller, so they can be quickly integrated into a new product or used as a replacement in your existing products.

Many of the LCD controllers on board our graphic LCD display modules also include a CGROM (character generator ROM) which allows for easy character information as well as full bit-mapped graphic information to be shown.

Some of the graphic LCD displays have the ability to render graphics in grayscale, enabling you to show images and elements of your UI (user interface) with more depth and definition.

Established in 2010, Topfoison has devoted itself to the manufacturing and development of high-quality products for the Wearable device, Smart Watch, VR, Medical device, Industrial LCD display including Color LCD modules/OLED/LCD display/Round lcd screen/Round AMOLED/ Square transflective lcd screen/ IPS full wide display/ 1080p fhd AMOLED and 2K 1440p lcd. Topfoison focus on1.22-7.0 inch small size displays, all the products produced in our company enjoys the most advanced production craft and technology as well as the strictly ISO quality management system.

The ST7789 TFT module contains a display controller with the same name: ST7789. It’s a color display that uses SPI interface protocol and requires 3, 4 or 5 control pins, it’s low cost and easy to use. This display is an IPS display, it comes in different sizes (1.3″, 1.54″ …) but all of them should have the same resolution of 240×240 pixel, this means it has 57600 pixels. This module works with 3.3V only and it doesn’t support 5V (not 5V tolerant).

As mentioned above, the ST7789 TFT display controller works with 3.3V only (power supply and control lines). The display module is supplied with 3.3V (between VCC and GND) which comes from the Arduino board.

The first library is a driver for the ST7789 TFT display which can be installed from Arduino IDE library manager (Sketch —> Include Library —> Manage Libraries …, in the search box write “st7789” and install the one from Adafruit).

The TFT LCD screen display, for the general masses, is no longer a difficult noun. And it is another after semiconductor could create a large number of emerging technology products of the business turnover, more because of its features, thin so it than using the application scope of the cathode ray tube (CRT, cathode ray tube) display made by wider. Today, I’m going to talk about how the TFT LCD Touch Screen Display Works.

As I mentioned earlier, liquid-crystal displays (LCDs) refer to a bunch produced by using the TFT screen LCD display. Now for LCD displays the name is directed mostly used in notebook computers, or desktop computer applications display. Is the thin film transistor TFT LCD display. Abbreviation of TFT LCD. This kind of display form has two main characteristics, one is a thin film transistor, the other is TFT LCD itself. Let’s talk about the TFT screen itself.

This type of TFT LCD screen was first discovered, had been spent more than one hundred years ago. In 1888 AD, the Austrian botanist Friedrich Reinitzer, found in the observation from the plant refined out of benzoic acid cholesterol (cholesteryl benzoate) found that when the melting behavior of the compound heated to 145.5 ℃, Solid can melt, presents a kind of solid phase and liquid phase between the half gonorrhea melt flow of the liquid. This situation will always maintain ℃ temperature rise to 178.5 degrees, to form a clear isotropic liquid (isotropic liquid).

The next year, in 1889, the study of thermodynamic equilibrium and the phase transfer German physicist O.L Ehmann, compounds for a more detailed analysis of this. He found that under the polarizing microscope, half of the viscous liquid gonorrhea liquid compounds with different parts peculiar to the crystal birefringence (birefringence) of the optical properties, namely, optical interphase (optically anisotropic). It will be a name to this as the liquid crystal. Since then, scientists will be the nature of this new discovery, known as the fourth state material – LCD (liquid crystal). It at a specific temperature range can have the characteristics of the liquid and solid at the same time.

Its structure is composed of TFT LCD molecules stick together, forming a layer structure. It’s every layer of the molecular long axis direction parallel to each other. And the long axis direction for each layer plane is vertical or a tilt Angle. Due to its structure is very similar to crystals, so they are called phase. The order parameter S (the order parameter) tend to be 1. Type in layered crystal layer and interlayer bonding can fracture because of temperature, so the layer and interlayer sliding more easily. But each layer within the molecular bonding is stronger, so it is not easy to be interrupted. Therefore in the context of the monolayer, Its arranged orderly and viscosity is bigger. If we use the macroscopic phenomenon to describe the physical properties of liquid crystal, we can make a group of regional average points as the liquid crystal molecules are pointing in the direction of the arrow (director), which is the direction of a group of liquid crystal molecules regional average. And with lamellar liquid crystal, because of its structure, the TFT LCD molecules will cambium-like so can point to a vector of different classification of the different lamellar liquid crystal again. When the long axis of the liquid crystal molecules are vertical stand, Call it “Sematic A phase.” if stand long axis direction of the TFT LCD molecules have some Angle of tilt (tilt), call it “Sematic C phase”. In A, C and other letters to name, which was discovered in accordance with the order to address, and so on, there should be A “Semantic phase B is.” but later found A deformation phase B is C phase, And the liquid crystal molecules in the structure layer by layer, in addition to each layer of TFT LCD molecules have tilt Angle, the tilt Angle between layer by layer will form a helical structure.

Nematic is a Greek word, the word mean in the thread is the same as in English. Mainly because with the naked eye to observe the liquid crystal, it looks like a silk pattern. The LCD screen molecules on the space of the regular arrangement of one dimension, all rod long axis of the liquid crystal molecules will choose a particular direction (that is, pointing vector) as the main shaft and arranged parallel to each other. And don’t like lamellar liquid crystal has a layered structure. Compared with the layer column type liquid crystal alignment is no order, That is to say, its order parameter S is smaller than the lamellar liquid crystal, and its viscosity is smaller, so it is easier to flow (its flow mainly comes from the free movement of molecules in the long axis direction). Linear liquid crystal is the common TFT LCD display screen TN(Twisted nematic) type liquid crystal.

Most of the sources of the name, because are generated by the derivative of the cholesterol. But some without cholesterol structure of LCD screen with this liquid crystal phase. This kind of liquid crystal as shown in figure 5, if it is a layer of a layer to separate, would very much like a linear LCD screen. But look at the Z-axis, may find it pointing in the direction of the arrow will with layers and layers of different distribution, like a spiraling when the pointing vector rotate 360 degrees for molecular layer thickness is called a pitch. Because of its every layer like linear LCD, so also known as Chiral nematic phase. In terms of cholesterol crystal, and pointing in the direction vector of the vertical distribution of LCD screen molecules, due to the different point to vector, will have the different optical or electrical differences, thus has produced different features.

If we are according to the molecular weight of high and low points can be divided into liquid crystal polymer (polymer liquid crystal, the polymer in many of the liquid crystal molecules) and low molecular liquid crystal. This kind of classification of TFT LCD belongs to the application of the low molecular liquid crystal. If the reasons for the formation of liquid crystal state, because it can be divided into type temperature formation of liquid crystal state to a liquid crystal (thermotropic), and because of the concentration and the formation of a liquid crystal state type lyotropic liquid crystal (lyotropic).

The solution so types lyotropic TFT screen molecules in the appropriate solvents reaches a certain critical concentration, the formation of liquid crystal state. Type lyotropic liquid crystal is one of the best examples that is soap. When soap bubbles in the water will not be at once into a liquid, and the bubble in the water for a long time, after the formation of white matter, is its liquid crystal state.

Our dielectric coefficient can be separated into two directions respectively is epsilon / / (and point to parallel component) and epsilon coming (a component perpendicular to the pointing vector). When the epsilon / / > epsilon coming then called the dielectric coefficient of different parts of LCD, can be used in parallel coordination. And epsilon / / < epsilon is called the dielectric coefficient of the different part coming negative type of TFT screen, only can be used in vertical coordination will need the photoelectric effect. When the applied electric field, the liquid crystal molecules will vary with dielectric coefficient is positive or negative, To determine whether the orientation of the liquid crystal molecules is parallel or perpendicular to the electric field, to determine whether the light penetrates. Now on most commonly used type TN LCD TFT LCD that belongs to the dielectric coefficient are type liquid crystal. When the dielectric coefficient of square difference Δ epsilon (= epsilon / / – epsilon) comes, the greater the LCD of the critical voltage (threshold voltage) will be smaller. So the LCD can be in the low voltage operation.

In accordance with the described above, the lamellar liquid crystal, linear liquid crystal, and LCD screen for cholesterol levels, because of its long liquid crystal molecules like a stick, so point to the direction of the vector and the molecular long axis parallel. To be defined with reference to the refraction coefficient of a single optical axis crystal, it will have two refractive indexes, respectively is perpendicular to the direction of the long axis of the liquid crystal n coming (= ne) and parallel to the long axis of the liquid crystal direction n / / (= no), so when the incident light liquid crystal, will be affected by two refractive indexes, cause in the vertical long axis of the liquid crystal and LCD long axis parallel to the direction of the speed of light will be different.

If with the molecular long axis parallel to the direction of light speed, when less than perpendicular to the speed of the molecular long axis direction, which means that parallel the molecular long axis direction of refractive index is greater than the vertical direction of the refractive index (because the refractive index is inversely proportional to the speed of light), is the one – no > 0. So the birefringence Δ n > 0, we think that it is called optics is a type of LCD, and lamellar liquid crystal and LCD are all belong to the optical is almost linear LCD. If the light of the parallel to the direction of the long axis was faster, On behalf of the flat to the governor of the axis of the refractive index is less than the vertical direction, so the birefringence Δ n < 0. We call it is the optical negative type of LCD. The cholesterol liquid crystal optical negative type of LCD.

For example, the elastic constant (kappa 11, kappa 22, kappa 33) contains the three most important constants: kappa 11 is the elastic constant at splay, kappa 22 is the elastic constant at the twist. Kappa 33 refers to predominating the elastic constants of bending (bend). The other as the coefficient of viscosity (viscosity coefficients and eta), will affect the rotational speed of the liquid crystal molecules with reaction time (response time), its value as small as possible. But this feature is affected by temperature is the largest. In addition to magnetic susceptibility (magnetic susceptibility), but also because of liquid crystals of different sex, Divided into c / / c coming. And the difference of magnetic susceptibility is defined as Δ c = c / / – c coming. In addition to the conductance coefficient (conductivity), and so on the photoelectric properties. Liquid crystal properties of the most important are the dielectric coefficient and refractive index of liquid crystal. The dielectric coefficient is determined liquid crystal under the influence of the electric field to the characteristics of the liquid crystal molecules, while the refractive index is liquid crystal in the light of its important parameters influencing the light path. The LCD is in using the liquid crystal itself of these features, the appropriate use of voltage, to control the rotation of the TFT LCD molecules, in turn, affect the direction of the light, to form different grayscale, a tool for displaying images. Of course, LCD itself is not alone as the monitor, also need other materials to help, Below, we will introduce the composition of various materials and operating principle of TFT LCD display.

The upper and lower two layers of glass are mainly to grip the LCD with. Below the glass layer with Thin film transistor (thin film transistor, TFT screen), while the layer above the glass with a Color filter (Color filter). If you notice (see figure 3), these two pieces of glass are in contact with the side of the LCD screen, not smooth, but with jagged grooves. The main purpose of the groove with the hope of a long rod, liquid crystal molecules will line up along the grooves. In this way, Liquid crystal molecules are arranged neatly. Because if it is smooth and flat, the arrangement of the liquid crystal molecules will not neat, causing light scattering, forming a light-leaking phenomenon. In fact, this is just a theory that told us to put the glass and LCD interface, complete processing so that the arrangement of liquid crystal has a certain order. But in the actual manufacturing process, and can not be with such a groove, the distribution of glass is made usually in glass coating on the surface layer of the PI (polyimide), and then a cloth to do the action of friction (rubbing), In order to make the surface molecules of PI no longer be scattered and arranged in a fixed and uniform direction, this layer of PI is called the coordination membrane, and its function is just like the grooves in the glass in FIG. 3, which provides the interface conditions for the uniform arrangement of liquid crystal molecules and allows the liquid crystals to be arranged in a predetermined order.

We can know from figure 10, when there is no applied voltage between the upper and lower two pieces of glass, the arrangement of LCD will be in accordance with the match to the membrane of the upper and lower two pieces of glass. For TN type of LCD, and match to the film’s point of view of the poor to 90 degrees. (see figure 9) so the liquid crystal molecules are arranged by the up and down automatically rotate 90 degrees when the incident light passes through the upper polarizing film, the polarization of light waves will only order direction. Through the liquid crystal molecules, the liquid crystal molecules rotate for 90 degrees, so when the waves reach the lower polarizing film, the polarization direction of the light just turned 90 degrees. The polarizing film of the lower and upper polarizing film, 90 – degree Angle is just the differences. (see figure 9) so can smoothly through the light, but if we applied voltage between the upper and lower two pieces of glass, because the type TN LCD for the dielectric coefficient of different sex more positive type of LCD (epsilon / / > epsilon coming, represent the parallel direction of the dielectric coefficient is larger than the dielectric coefficient of the vertical direction, so when the liquid crystal molecules are influenced by an electric field, will tend to be parallel to the orientation of the electric field direction.), so we can see from figure 10, At this time, the polarized light wave passing through the upper polarizer will not change the polarization direction when passing through the liquid crystal molecule, so it cannot pass through the lower polarizer.

The so-called NW (Normally white), is to point to when we don’t apply voltage on the LCD screen panel, we can see the panel is pervious to light, also is bright, so-called Normally white. But on the other hand, when we don’t apply voltage on the LCD panel if the panel is not pervious to light, the look is black, it’s called NB (Normally black). We have just mentioned in figure 9 and figure 10 all belongs to the configuration of NW, also we can know from figure 11, For type TN LCD, located in the upper and lower glass is perpendicular to the membrane, and the difference between NB and NW just lies in the relative position of the polarizing film is different. For NB, the fluctuation of the polarizing film polarity is parallel to each other. So when the NB no applied voltage, the light will be because the polarity of the LCD to rotate 90 degrees to be pervious to light. Why there are NW and NB these two kinds of a different configuration of the polarizing film? Mainly for different applications. Commonly used in a desktop computer or notebook computer, most of the NW configuration. That’s because, if you notice, generally the use of computer software environment, you will find that most of the entire screen is a bright spot, that is to say, computer software for the application of white background and black text. Since on the point of the majority, using NW is more convenient, of course. Also because the NW window does not need to add the voltage, the average will compare to save electricity. In turn, said that the application of the NB environment mostly belongs to the screen for the application of black.

The STN LCD and TN LCD are very similar in structure, the main difference between TN LCD, the arrangement of the liquid crystal molecules, the rotation angle from top to bottom. A total of 90 degrees and type the STN LCD liquid crystal molecules are arranged, the rotation angle will be greater than 180 degrees, usually is 270 degrees. (see figure 12) because of its rotation Angle is different, its characteristics different. We from figure 13 TN type and type the STN LCD voltage of the transmittance curve can know, when the voltage is low, the light penetration rate is very high. With a high voltage, the light of the penetration rate is very low. So they belong to the Normal White polaroids configuration. When the voltage in the middle position, the change of type TN LCD curve is flat, and the change of the STN LCD type curve is steep. So in TN type LCD, when transmittance change from 90% to 10%, corresponding to the voltage difference is larger than the STN LCD. We mentioned before, in the liquid crystal display, The different characteristics of TN and STN will result in TN type LCD, which has more grayscale changes than STN type LCD, so generally TN type LCD has 6~8 bits of changes. It is 64 ~ 256 gray-scale changes. Type the STN LCD for a maximum of 4 bits are only 16 orders of gray-scale changes. In addition, the STN type and TN LCD has a different place is the reaction time (response time) general type the STN LCD it’s response time to type in more than 100 ms and TN LCD its response time is 30 ~ 50 ms as shown in the image change quickly for the STN LCD type ghosting effect phenomenon is easy to happen.

TFT LCD Chinese translation of the name is called a thin film transistor liquid crystal display, from the beginning, we mentioned LCD voltage control is needed to produce gray. And the use of a thin-film transistor to generate the voltage, to control the transition of liquid crystal display, is called a TFT LCD. From the point of the cross-section structure of figure 8, between upper and lower two layers of glass, with LCD, will form a parallel plate capacitor, we call it the CLC (capacitor of liquid crystal). Its size is about 0.1 m3, But on the practical application, the capacitance and unable to keep the voltage to the next time to update the data in the picture.

That is to say, when TFT is good to the capacitor charging power, it is impossible to maintain voltage, until the next TFT this point charge again. (in general of 60 Hz screen update frequency, need time to keep about 16 ms.) as a result, there were changes in voltage, displayed gray scale is not correct. Therefore generally on the design of the panel, we will add a storage capacitor CS (storage capacitor is about 0.5 pF). So charged electric voltage can keep until the next update screen. But the right, long on the glass TFT itself, just use a transistor to make the switch. Its main work is to determine the LCD source voltage on the driver whether to charge to this point. As for this point more charge to high voltage, so as to show how the gray-scale. It is outside of the LCD source driver.

If you have a chance, take a magnifying glass, close to the LCD screen. You will find that as shown in figure 9 shows. We know that red, blue and green, are the so-called primary colors. That is to say, using the three kinds of color, can produce a variety of different colors. In a lot of flat-panel displays, this principle is used to show the color. We put the RGB 3 kinds of color, is divided into independent three points, each has different gray-scale changes, then the three neighboring RGB display point, as the basic unit of a display, Pixel is that this a pixel, and can have different color changes. Then for a need for a 1024 * 768 resolution display screen, we just let the composition of the flat panel display with 1024 * 768 pixels, can show a picture of the right. In figure 9, each point between the Black part of RGB is called the Black matrix. We can find that looking back on it in figure 8Black matrix is mainly used to cover do not intend to previous to light part. Such as some ITOs walk the line, or Cr/Al walk the line or are part of a TFT. This is why we in figure 9, the highlight of each RGB, it seems, is not a rectangle, and also on the top left corner is a piece of black matrix cover part, this part of a black missing Angle is the location of the TFT.

Figure 9 shows the common arrangement of color filters. Stripe is most commonly used in OA products, such as laptops, desktop computers, etc. Why is stripe used in this application? More often than not, the reason is now software is the Windows interface. That is to say, we can see the screen content, is composed of a pile of boxes of various sizes. The strips, just can make the edge of the box, look more straight, and there won’t be a straight line, look have the feeling of burrs or serrated. But if it is applied in the AV products, just not the same. Probably because the TV signal is a character, the character of the line is not straight, the contour is a mostly irregular curve. So in the beginning, the Use Mosaic arrangement used in AV products is (Mosaic, or called arranged diagonally). But the latest AV products, more have been improved to use triangle arrangement (triangle, or known as the delta). In addition to the above arrangement, still have a kind of arrangement, which is called a square arrangement. It is not the same as the first few, it is not three-point to as a pixel, but with four points as a pixel. And just four points are combined to form a square.

The CRT screen, it is using a high-speed electron gun that emits electrons, hits the phosphors on the silver screen, so as to produce the light, to show the picture. LCD itself, however, can only control the brightness of the light through, no glowing function itself. Therefore, a liquid crystal display must be combined with a backplate, to provide high brightness, brightness, and uniform distribution of the light source. We can see in figure 14, of the backplate of the main parts are CCFL (cold cathode tube), reflex plate, guide plate, prism sheet, Diffuser plate, and so on. Tubes are the main light-emitting parts, by a light guide, everywhere. The light distribution and baffle will be limited only to the TFT LCD light direction. Finally, by prism sheet and help diffuser, the light evenly distributed to all areas, provide TFT LCD a bright light. While TFT LCD is borrowed by the rotation of the voltage-controlled liquid crystal, control through the brightness of the light, so as to form different grayscale.

Another box in figure 14 glue and spacer structure of two kinds of ingredients. The box adhesive USES is to make the LCD panel in the upper and lower two layers of glass, to be able to stick close and to provide a panel of LCD screen molecules, cut off from the outside world, so the box plastic as its name suggests, is around and around in the panel to the liquid crystal molecules box limited to within a panel. The spacer is mainly provided two-layer glass support, it must be distributed evenly on the glass, or a part but uneven distribution cause spacer gathered together, it will block the light, It is also unable to maintain the appropriate gap between the upper and lower glass, which will lead to uneven distribution of electric field and affect the performance of the crystal grayscale.

A very important specification of LCD is brightness, and the most important factor to determine the brightness is the opening rate. What is the opening rate? Is simple light can pass through the effective area proportion. 17, let’s look at the picture to the left of figure 17 is an LCD display from directly above or below the past structure. When the light is emitted through the backplate, not all of the light can be through the panel, like for LCD source driver chip and the gate driver chip signal line, and TFT itself, the stored voltage is the use of storage capacity, etc. These places besides incomplete pervious to light, but also because the light through these places is not under voltage control, to display the correct gray-scale, so have to use the black matrix to cover, in order to avoid interference to other correct brightness of the light area. So the effective area of the previous to light, it’s just like figure 17 shows area on the right. This piece of the effective area of the previous to light and the ratio of the total area is called the opening rate.

When the light is emitted from the backlight plate, it will pass through the polarizer, glass, LCD screen, color filter, etc. It is assumed that the penetration rate of each part is as follows:

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Hi guys, welcome to today’s tutorial. Today, we will look on how to use the 1.8″ ST7735  colored TFT display with Arduino. The past few tutorials have been focused on how to use the Nokia 5110 LCD display extensively but there will be a time when we will need to use a colored display or something bigger with additional features, that’s where the 1.8″ ST7735 TFT display comes in.

The ST7735 TFT display is a 1.8″ display with a resolution of 128×160 pixels and can display a wide range of colors ( full 18-bit color, 262,144 shades!). The display uses the SPI protocol for communication and has its own pixel-addressable frame buffer which means it can be used with all kinds of microcontroller and you only need 4 i/o pins. To complement the display, it also comes with an SD card slot on which colored bitmaps can be loaded and easily displayed on the screen.

Due to variation in display pin out from different manufacturers and for clarity, the pin connection between the Arduino and the TFT display is mapped out below:

We will use two libraries from Adafruit to help us easily communicate with the LCD. The libraries include the Adafruit GFX library which can be downloaded here and the Adafruit ST7735 Library which can be downloaded here.

We will use two example sketches to demonstrate the use of the ST7735 TFT display. The first example is the lightweight TFT Display text example sketch from the Adafruit TFT examples. It can be accessed by going to examples -> TFT -> Arduino -> TFTDisplaytext. This example displays the analog value of pin A0 on the display. It is one of the easiest examples that can be used to demonstrate the ability of this display.

The first thing, as usual, is to include the libraries to be used after which we declare the pins on the Arduino to which our LCD pins are connected to. We also make a slight change to the code setting reset pin as pin 8 and DC pin as pin 9 to match our schematics.

Next, we create an object of the library with the pins to which the LCD is connected on the Arduino as parameters. There are two options for this, feel free to choose the most preferred.

Next, we move to the void setup function where we initialize the screen and call different test functions to display certain texts or images.  These functions can be edited to display what you want based on your project needs.

In this Arduino touch screen tutorial we will learn how to use TFT LCD Touch Screen with Arduino. You can watch the following video or read the written tutorial below.

For this tutorial I composed three examples. The first example is distance measurement using ultrasonic sensor. The output from the sensor, or the distance is printed on the screen and using the touch screen we can select the units, either centimeters or inches.

The third example is a game. Actually it’s a replica of the popular Flappy Bird game for smartphones. We can play the game using the push button or even using the touch screen itself.

As an example I am using a 3.2” TFT Touch Screen in a combination with a TFT LCD Arduino Mega Shield. We need a shield because the TFT Touch screen works at 3.3V and the Arduino Mega outputs are 5 V. For the first example I have the HC-SR04 ultrasonic sensor, then for the second example an RGB LED with three resistors and a push button for the game example. Also I had to make a custom made pin header like this, by soldering pin headers and bend on of them so I could insert them in between the Arduino Board and the TFT Shield.

Here’s the circuit schematic. We will use the GND pin, the digital pins from 8 to 13, as well as the pin number 14. As the 5V pins are