led backlit tft lcd free sample

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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.

The next example is controlling an RGB LED using these three RGB sliders. For example if we start to slide the blue slider, the LED will light up in blue and increase the light as we would go to the maximum value. So the sliders can move from 0 to 255 and with their combination we can set any color to the RGB LED,  but just keep in mind that the LED cannot represent the colors that much accurate.

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 already used by the TFT Screen I will use the pin number 13 as VCC, by setting it right away high in the setup section of code.

I will use the UTFT and URTouch libraries made by Henning Karlsen. Here I would like to say thanks to him for the incredible work he has done. The libraries enable really easy use of the TFT Screens, and they work with many different TFT screens sizes, shields and controllers. You can download these libraries from his website, RinkyDinkElectronics.com and also find a lot of demo examples and detailed documentation of how to use them.

After we include the libraries we need to create UTFT and URTouch objects. The parameters of these objects depends on the model of the TFT Screen and Shield and these details can be also found in the documentation of the libraries.

Next we need to define the fonts that are coming with the libraries and also define some variables needed for the program. In the setup section we need to initiate the screen and the touch, define the pin modes for the connected sensor, the led and the button, and initially call the drawHomeSreen() custom function, which will draw the home screen of the program.

So now I will explain how we can make the home screen of the program. With the setBackColor() function we need to set the background color of the text, black one in our case. Then we need to set the color to white, set the big font and using the print() function, we will print the string “Arduino TFT Tutorial” at the center of the screen and 10 pixels  down the Y – Axis of the screen. Next we will set the color to red and draw the red line below the text. After that we need to set the color back to white, and print the two other strings, “by HowToMechatronics.com” using the small font and “Select Example” using the big font.

drawDistanceSensor(); // It is called only once, because in the next iteration of the loop, this above if statement will be false so this funtion won"t be called. This function will draw the graphics of the first example.

getDistance(); // Gets distance from the sensor and this function is repeatedly called while we are at the first example in order to print the lasest results from the distance sensor

So the drawDistanceSensor() custom function needs to be called only once when the button is pressed in order to draw all the graphics of this example in similar way as we described for the home screen. However, the getDistance() custom function needs to be called repeatedly in order to print the latest results of the distance measured by the sensor.

Ok next is the RGB LED Control example. If we press the second button, the drawLedControl() custom function will be called only once for drawing the graphic of that example and the setLedColor() custom function will be repeatedly called. In this function we use the touch screen to set the values of the 3 sliders from 0 to 255. With the if statements we confine the area of each slider and get the X value of the slider. So the values of the X coordinate of each slider are from 38 to 310 pixels and we need to map these values into values from 0 to 255 which will be used as a PWM signal for lighting up the LED. If you need more details how the RGB LED works you can check my particular tutorialfor that. The rest of the code in this custom function is for drawing the sliders. Back in the loop section we only have the back button which also turns off the LED when pressed.

drawDistanceSensor(); // It is called only once, because in the next iteration of the loop, this above if statement will be false so this funtion won"t be called. This function will draw the graphics of the first example.

getDistance(); // Gets distance from the sensor and this function is repeatedly called while we are at the first example in order to print the lasest results from the distance sensor

FocusLCDs.com sent me a free sample of a 4x3” TFT LCD (P/N: E43RG34827LW2M300-R) to try out. This is a color active matrix TFT (Thin Film Transistor) LCD (liquid crystal display) that uses amorphous silicon TFT as a switching device. This model is composed of a Transmissive type TFT-LCD Panel, driver circuit, backlight unit. The resolution of a 4.3” TFT-LCD contains 480x272 pixels, and can display up to 16.7M colors.

For this project, you would need the RA8875 driver board (available at AdaFruit for US$35) to interface the TFT display to the Arduino. It comes with a header which you can solder on as needed.

As an option, you can order this TFT pre-assembled onto a breakout/carrier board. The board allows easy prototyping through its 0.1" headers. You can also include the carrier board in your end product to simplify construction and assembly.

This kit consists of a CFAF320240F-035T a 320x240 3.5" Full Color TFT LCD module mounted on a carrier board (CFA-10074). The carrier board supports a current driver for the LED backlight of the display.

This TFT LCD display module is perfect for the designer who"s looking to have a graphic and audio processor already embedded in the display unit. Powered by an FTDI/BridgeTek FT810 Embedded Video Engine (EVE) graphics accelerator chip, simply send over a few commands via SPI or I2C and the EVE will put your stored image up on the display. Need to draw a line, create dials/knobs/buttons, or rotate an image? Send a handful of bytes and the EVE will take care of it.

With our rich experience and considerate services, we have been recognized as a reliable supplier for many international buyers for Portable Lcd Screen, Custom Touch Lcd Displays, Tft Lcd Backlight, Welcome all nice buyers communicate details of products and ideas with us!!

Our eternal pursuits are the attitude of "regard the market, regard the custom, regard the science" plus the theory of "quality the basic, have faith in the main and management the advanced" for Factory Free sample Monitor Lcd Panel - 3.2/3.5/3.97 inch Standard Color TFT LCD Display for interpreter device – DISEN , The product will supply to all over the world, such as: Ghana, Nepal, Namibia, Our solutions are produced with the best raw materials. Every moment, we constantly improve the production programme. In order to ensure better quality and service, we now have been focusing on the production process. We have got high praise by partner. We are looking forward to establishing business relationship with you.

As a TFT LCD manufacturer, we import mother glass from brands including BOE, INNOLUX, and HANSTAR, Century etc., then cut into small size in house, to assemble with in house produced LCD backlight by semi-automatic and fully-automatic equipment. Those processes contain COF(chip-on-glass), FOG(Flex on Glass) assembling, Backlight design and production, FPC design and production. So our experienced engineers have ability to custom the characters of the TFT LCD screen according to customer demands, LCD panel shape also can custom if you can pay glass mask fee, we can custom high brightness TFT LCD, Flex cable, Interface, with touch and control board are all available.

TFT LCD image retention we also call it "Burn-in". In CRT displays, this caused the phosphorus to be worn and the patterns to be burnt in to the display. But the term "burn in" is a bit misleading in LCD screen. There is no actual burning or heat involved. When you meet TFT LCD burn in problem, how do you solve it?

When driving the TFT LCD display pixels Continously, the slightly unbalanced AC will attract free ions to the pixels internal surface. Those ions act like an addition DC with the AC driving voltage.

Those burn-in fixers, screen fixer software may help. Once the Image Retention happened on a TFT, it may easy to appear again. So we need to take preventive actions to avoid burn in reappearing.

For normal white TFT LCD, white area presenting minimal drive, black area presenting maximum drive. Free ions inside the TFT may are attracted towards the black area (maximum drive area)

LCD displays don’t emit light by themselves. They need a light source, and LED backlights are now dominating the market. In this article, Orient Display’s Bill Cheung provides a complete overview of LED backlight technology, discussing different types, driver technologies, color deviation, brightness options and more.

LCD (liquid crystal display) has long been the dominant technology in the display world. Certainly, there are some emerging competing display technologies—such as OLED (Organic Light Emitting Diode) [1] and micro-LED—that have the potential to threaten LCD’s position in the market. But both are currently only used for niche and high-end markets.

An LCD display can’t emit light by itself. In order to have an LCD display [2] used in a dim environment, a backlight has to be used as the light source. There are a few different technologies that are able to produce backlight ranging from EL (electroluminescent), CCFL (cold cathode fluorescent lamps) and LED (light emitting diode). However, a breakthrough in blue LED technology by Shuji Nakamura [3] led to LED backlights dominating the market.

One of the greatest benefits of LED backlighting is its long lifetime. Normally, LED lifetime can be measured with half-life when the original brightness decreases by 50%. With different LED chip manufacturing materials, technologies and environment used, the LED life can vary from 20,000 hours to well over 100,000 hours.

LED backlights have low power consumption and produce much less heat than other backlight technologies, which extends the durability and performance of the other display components. Furthermore, this reduces the risk of fire and explosion. LED backlights are also driven with DC (direct current) and low voltage (can be as low as 1.5V), which are good for battery drive and emit no interference to the circuitry. With the development of LED technology, the LED chips become small. So, it is possible to produce very thin backlight (0.5mm thick or thinner).

Although white LED is the most popular color, LED backlight can be made into different single colors, bi-colors and tri-colors [4] (Figure 1) (Figure 2). With RGB LED backlight color mixing, normal 8 color LED backlight can be produced (Figure 3).

LED backlight can be classified as bottom (array) lit and side (edge) lit backlights, and each have their plusses and minuses. The advantages of the bottom lit (array) backlight are that it is uniform and bright. Its disadvantage is high current draw, thickness, heat dissipation and cost. Meanwhile, the advantages of the side lit backlight are its thinness, flexibility in design, low current and lower cost. The main disadvantage of the side lit backlight is its non-uniformity—hot spots can be seen from most of the side lit backlight from certain angle. Figure 4 compares the bottom lit and side (edge) lit backlight LCD types.

Now let’s look at LED backlight structures. An LED backlight can be simplified into layers starting with a LED chip, light guide, diffusor and reflector (Figure 5). This is the lowest cost structure. Except for some very low current efficiency LCD displays—such as utility meters, battery-powered clock, watch, GPS and so on—most LCD displays need backlights to be visible in the dim lighting. Most often the backlight is actually at the back of the LCD. In rare cases, this light can be done as front light. The traditional LCD structure with LED backlight shown in Figure 6.

Direct current driving: This is the simple and low-cost way to drive a LED backlight, however, be mindful of the current limit otherwise the LED life can deteriorate quickly. The solution is simply to add a current limiting resistor in the circuit. Current limitation resistors value calculation formula: R = (V0– Vf)/If.Also be mindful of reverse drive, otherwise, the LED chip can break down easily.

LED driver with constant current: The advantage of constant current LED driver is that it will be the best option to use when building your own fixture or working with high powered LED because they avoid violating the maximum current specified for the LEDs, therefore avoiding burnout/thermal runaway. They are easier for designers to control applications, and help create a more consistent bright light.

LED driver with constant voltage: Using a constant voltage LED driver makes sense when using an LED or array that has been specified to take a certain voltage. This is helpful because constant voltage is a much more familiar technology for design and installation engineers. Moreover, the cost of these systems can be lower, especially in larger scale applications.

There are a variety of ways to connect a backlight and LCD module electrically. It can be done with wires that are soldered on the LCD or LCD module. It can be connected using pins, which can be soldered onto the LCD or LCD module. A third way is to use a FPC (flexible printed circuit), which can be soldered or plugged in a ZIF (zero insertion force) connector. And finally, there is the connector method. With this method you use connectors which can be plugged into mating connectors.

As the LED is manufactured via the semiconductor process, there are some color deviations that can be a quality control issue. One way to solve the issue is through a process of selection and sorting after manufacturing the LEDs. The LEDs are sorted into different categories or bins. How this sorting is done and what each bin actually contains is defined differently by each LED manufacturer. The backlight manufacturer can choose from which bin they take the LEDs for backlight color hue.

Some customers might request very fine binning by the LED manufacturer, which can be very expensive since only a very small percentage of the LEDs manufactured would meet the requirements for a specific bin. Figure 7 shows an example of the bin selection from Nichia, the most renowned LED manufacturer in the world. Figure 8 shows the 1931 CIE chromaticity diagram. And Figure 9 shows the color deviations (bin definition) by Cree for a qualified production lot.

In actual LED backlight production, most customers will accept the LED color for two big categories: white with yellowish (warm) and white with bluish (cold). Of course, the LED brightness will also need to be defined. For general application, most customers will accept a brightness tolerance of 70 percent.

It is extremely hard to estimate the LED backlight lifetime or MTBF (mean time between failures) because there are so many variable factors. However, the most important is the temperature on the LED chip. The factors that can affect the LED chip temperature include: surrounding temperature, humidity, driving current, voltage, backlight design (how many LED chips to be used, how close to each other, heatsink design), backlight manufacturing process (type and thickness of adhesive), quality of the LED chip and so forth.

To test the LED life is also very time consuming, requiring at least 1,000 hours. That’s the reason why no LED manufacturers can guarantee LED backlight life and most backlight manufacturers also are reluctant to provide lifespan data. As for LCD manufacturers, they need to discuss it with the customer to understand the applications and provide suggestions. It is normal that the LCD datasheet lists the typical life time and avoids providing a minimum lifetime. From Figure 10, we can see that over room temperature, the current needs to decrease as the temperature increases. At over 85°C, the LED is not usable.

To estimate LED backlight lifetime, you can use ballpark estimation or theoretical calculation. Let’s first examine the ballpark method. To take white LED as example, the nominal biasing current is 20mA. If we use a safe lifetime estimation, we can estimate using Table 1.

Now let’s use the theoretical calculation approach. As we previously mentioned, LED life is affected by a lot of factors: surrounding temperature, humidity, driving current, voltage, backlight design (how many LED chips to be used, how close to each other, heatsink designed), backlight manufacturing process (type and thickness of adhesive), quality of the LED chip and so on. LED chip manufacturers are not willing to give absolute values of LED chip lifetimes, but there is a theoretical calculation that we can use.

Temperature is the determination factor for LED chip life, while LED chip manufacturers use LED junction temperature to predict LED chip life more accurately. An example is:

Finally, let’s look at ways to increase LED backlight brightness. There are many ways to increase LED backlight brightness, but all these measures are balanced with performance and cost. Here are some of the methods:

For the LCD module side, using better aperture opening ratio, anti-reflection coating on surface, optical bonding. This results in higher cost. Actually, this measure is not to increase LED backlight brightness directly but to increase to the visibility to users.

Bill Cheung is an engineering lead and marketing manager at Orient Display, an LCD and display technology provider with over two decades of industry experience in delivering cutting edge display solutions. You can browse Orient Display"s knowledge base [7] to learn more about LCDs.