Led displays explained
- 1. What is a LED Screen? A LED screen is a video display which uses light-emitting diodes. An LED panel is a small display, or a component of a larger display or screen. They are typically used outdoors in store signs and billboards, and in recent years have also become commonly used in destination signs on public transport vehicles. LED panels are sometimes used as form of lighting, for the purpose of general illumination, task lighting, or even stage lighting rather than display. Types of LED Screens There are two types of LED panels: conventional (using discrete LEDs) and surface-mounted device (SMD) panels. Most outdoor screens and some indoor screens are built around discrete LEDs, also known as individually mounted LEDs. A cluster of red, green, and blue diodes is driven together to form a full-color pixel, usually square in shape. These pixels are spaced evenly apart and are measured from center to center for absolute pixel resolution. The largest LED display in the world is over 1,500 foot (457.2 m) long and is located in Las Vegas, Nevada covering the Fremont Street Experience. The largest LED television in the world, the Center Hung Video Display at Cowboys Stadium, is 160 by 72 feet (49 by 22 m), 11,520-square-foot (1,070 m2). Most indoor screens on the market are built using SMD technology—a trend that is now extending to the outdoor market. An SMD pixel consists of red, green, and blue diodes mounted on a chipset, which is then mounted on the driver PC board. The individual diodes are smaller than a pinhead and are set very close together. The difference is that the maximum viewing distance is reduced by 25% from the discrete diode screen with the same resolution. Indoor use generally requires a screen that is based on SMD technology and has a minimum brightness of 600 candelas per square meter (cd/m², sometimes informally called nits). This will usually be more than sufficient for corporate and retail applications, but under high ambient-brightness conditions, higher brightness may be required for visibility. Fashion and auto shows are two examples of high-brightness stage lighting that may require higher LED brightness. Conversely, when a screen may appear in a shot on a television studio set, the requirement will often be for lower brightness levels with lower color temperatures (common displays have a white point of 6500 to 9000 K, which is much bluer than the common lighting on a television production set). For outdoor use, at least 2,000 cd/m² is required for most situations, whereas higher- brightness types of up to 5,000 cd/m² cope even better with direct sunlight on the screen. (The brightness of LED panels can be reduced from the designed maximum, if required.) Suitable locations for large display panels are identified by factors such as line of sight, local authority planning requirements (if the installation is to become semi-permanent), vehicular access (trucks carrying the screen, truck-mounted screens, or cranes), cable runs for power and video (accounting for both distance and health and safety requirements), power, suitability of the ground for the location of the screen (if there are no pipes, shallow drains, caves, or tunnels that may not be able to support heavy loads), and overhead obstructions.
- 2. Decoding the LED Signal to LED Screen. How does it work? A jumbo TV that is 60 feet (20 meters) high has to do the same thing that a normal television set does -- it has to take a video signal and convert it into points of light. If you have read How Television Works, then you know how a television that uses a cathode ray tube (CRT) does this. Here is a quick summary of how a black-and-white TV works: The electron beam in a CRT paints across the screen one line at a time. As it moves across the screen, the beam energizes small dots of phosphor, which then produce light that we can see. The video signal tells the CRT beam what its intensity should be as it moves across the screen. You can see in the following figure the way that the video signal carries the intensity information. The initial five-microsecond pulse at zero volts (the horizontal retrace signal) tells the electron beam that it is time to start a new line. The beam starts painting on the left side of the screen, and zips across the screen in 42 microseconds. The varying voltage following the horizontal retrace signal adjusts the electron beam to be bright or dark as it shoots across. The electron beam paints lines down the face of the CRT, and then receives a vertical retrace signal telling it to start again at the upper right-hand corner. A color screen does the same thing, but uses 3 separate electron beams and 3 dots of phosphor (red, green and blue) for each pixel on the screen. A separate color signal indicates the color of each pixel as the electron beam moves across the display. As the electron beam paints across the screen, it is hitting the phosphor on the screen with electrons. The electrons in the electron beam excite a small dot of phosphor and the screen lights up. By rapidly painting 480 lines on the screen at a rate of 30 frames per second, the TV screen allows the eye to integrate everything into a smooth moving image. CRT technology works great indoors, but as soon as you put a CRT-based TV set outside in bright sunlight, you cannot see the display anymore. The phosphor on the CRT simply is not bright enough to compete with sunlight. Also, CRT displays are limited to about a 36-inch screen. You need a different technology to create a large, outdoor screen that is bright enough to compete with sunlight. LEDs may be little, but new high-brightness models are producing a considerable amount of light. First used as status and indicator lamps, and more recently in under-shelf illumination, accent lighting, and directional marking applications, high-brightness LEDs have emerged within the last six years. But only recently have they been seriously looked upon as a feasible option in general purpose lighting applications. Before you recommend or install this type of lighting system, you should understand the basic technology upon which these devices are based. Light-emitting diodes (LEDs) are solid-state devices that convert electric energy directly into light of a single color. Because they employ “cold” light generation technology, in which
- 3. most of the energy is delivered in the visible spectrum, LEDs don't waste energy in the form of non-light producing heat. In comparison, most of the energy in an incandescent lamp is in the infrared (or non-visible) portion of the spectrum. As a result, both fluorescent and HID lamps produce a great deal of heat. In addition to producing cold light, LEDs: Can be powered from a portable battery pack or even a solar array. Can be integrated into a control system. Are small in size and resistant to vibration and shock. Have a very fast “on-time” (60 nsec vs 10 msec for an incandescent lamp). Have good color resolution and present low, or no, shock hazard. The centerpiece of a typical LED is a diode that is chip-mounted in a reflector cup and held in place by a mild steel lead frame connected to a pair of electrical wires. The entire arrangement is then encapsulated in epoxy. The diode chip is generally about 0.25 mm square. When current flows across the junction of two different materials, light is produced from within the solid crystal chip. The shape, or width, of the emitted light beam is determined by a variety of factors: the shape of the reflector cup, the size of the LED chip, the shape of the epoxy lens and the distance between the LED chip and the epoxy lens. The composition of the materials determines the wavelength and color of light. In addition to visible wavelengths, LEDs are also available in infrared wavelengths, from 830 nm to 940 nm. The definition of “life” varies from industry to industry. The useful life for a semiconductor is defined as the calculated time for the light level to decline to 50% of its original value. For the lighting industry, the average life of a particular lamp type is the point where 50% of the lamps in a representative group have burned out. The life of an LED depends on its packaging configuration, drive current, and operating environment. A high ambient temperature greatly shortens an LED's life. Additionally, LEDs now cover the entire light spectrum, including red, orange, yellow, green, blue, and white. Although colored light is useful for more creative installations, white light remains the holy grail of LED technology. Until a true white is possible, researchers have developed three ways to deliver it: Blend the beams. This technique involves mixing the light from multiple single-color devices. (Typically red, blue, and green.) Adjusting the beams' relative intensity yields the desired color. Provide a phosphor coating. When energized photons from a blue LED strike a phosphor coating, it will emit light as a mixture of wavelengths to produce a white color. Create a light sandwich. Blue light from one LED device elicits orange light from an adjacent layer of a different material. The complementary colors mix to produce white. Of the three methods, the phosphor approach appears to be the most promising technology. Another shortcoming of early LED designs was light output, so researchers have been working on several methods for increasing lumens per watt. A new “doping” technique increases light output several times over compared to earlier generations of LEDs. Other methods under development include:
- 4. Producing larger semiconductors. Passing larger currents with better heat extraction. Designing a different shape for the device. Improving light conversion efficiency. Packaging several LEDs within a single epoxy dome. One family of LEDs may already be closer to improved light output. Devices with enlarged chips produce more light while maintaining proper heat and current management. These advances allow the units to generate 10 times to 20 times more light than standard indicator lights, making them a practical illumination source for lighting fixtures. Before LEDs can enter the general illumination market, designers and advocates of the technology must overcome several problems, including the usual obstacles to mainstream market adoption: Industry-accepted standards must be developed and costs must be reduced. But more specific issues remain. Things like lumen-per-watt efficacy and color consistency must be improved, and reliability and lumen maintenance should be addressed. Nevertheless, LEDs are well on their way to becoming a viable lighting alternative. There are two big differences between a jumbo TV screen that you see at a stadium and the TV in your home: Obviously, it is gigantic compared to your TV. It might be 60 feet (20 meters) high instead of 18 inches (0.5 meters) high. It is incredibly bright so that people can see it in sunlight. To accomplish these feats, almost all large-screen outdoor displays use light emitting diodes (LEDs) to create the image. LEDs are, essentially, little colored light bulbs. Modern LEDs are small, extremely bright and use relatively little power for the light that they produce. Other places you now see LEDs used outdoors are on traffic lights and automobile brake lights. On a color CRT television set, all of the colors are produced using red, green and blue phosphor dots for each pixel on the screen: In a jumbo TV, red, green and blue LEDs are used instead of phosphor. A "pixel" on a jumbo TV is a small module that can have as few as three or four LEDs in it (one red, one green and one blue). In the biggest jumbo TVs, each pixel module could have dozens of LEDs. Pixel modules typically range from 4 mm to 4 cm (about 0.2 to 1.5 inches) in size. To build a jumbo TV, you take thousands of these LED modules and arrange them in a rectangular grid. For example, the grid might contain 640 by 480 LED modules, or 307,200 modules. The size of the ultimate screen depends on the size of the LED modules:
- 5. Full Color Integrated 3in1 SMD LED Screens The full color integrated 3in1 SMD LED screens by Vegas LED Screens is a revolutionary development in the LED industry. It features higher definition and a super wide viewing angle in comparison to the ordinary led screens. Each panel is made by custom quantities of modules with an 8x8 or 4x4 configurations. Every 3-in-1 pixel in a reflect cavity is comprised by three LED chips: Red, Green, and Blue. A dot matrix LED screen is a LED display device used to display information on machines, clocks, railway departure indicators and many and other devices requiring a simple display device of limited resolution. The display consists of a matrix of lights or mechanical indicators arranged in a rectangular configuration (other shapes are also possible, although not common) such that by switching on or off selected lights, text or graphics can be displayed. A dot matrix controller converts instructions from a processor into signals which turns on or off lights in the matrix so that the required display is produced. Usual Resolutions for Dot Matrix LED Screens Common sizes of dot matrix displays: 128×16 (Two lined) 128×32 (Four lined) 192×64 (Eight lined) Usual Character Resolutions for Dot Matrix LED Screens A common size for a character is 5×7 pixels, either separated with blank lines with no dots (in most text-only displays), or with lines of blank pixels (making the real size 6x8). This is seen on most graphic calculators, such as CASIO calculators or TI-82 and superior. A smaller size is 3×5 (or 4x6 when separated with blank pixels). This is seen on the TI-80 calculator as a "pure", fixed-size 3×5 font, or on most 7×5 calculators as a proportional (1×5 to 5×5) font. The disadvantage of the 7×5 matrix and smaller is that lower case characters with descenders are not practical. A matrix of 11×9 is often used to give far superior resolution. Dot matrix displays of sufficient resolution can be programmed to emulate the customary seven-segment numeral patterns.
- 6. Difference Between Real and Virtual Pixels LED Screens What is the difference between real pixel LED screens and virtual pixel LED screens? With the virtual pixel technology, the LED display will appear a more clear vision. Theoretically the resolution will be 4 times of a real pixel technology LED display.The difference of a real a virtual pixel LED screen of LED display can be seen in the next pictures. Virtual Pixel LED Screen Real Pixel LED Screen How do virtual LED screens work? Below you can clearly see how the virtual pixels are made, we surely recommend you a virtual display, even so our new technology of Dot Matrix it’s still better than virtual pixels, because the three colors RGB are in the same dot or pixel, just like the SMD technology and also the Dot Matrix have a horizontal viewing angle of over 160 degrees. The virtual pixel LED screens have a horizontal viewing angle of upto 130 degrees.
- 7. Do I need a wide LED screen to play 16:9 movies? Playing Videos on LED Screens To play videos on a LED screen a video file will be loaded into the LED screen software if the format is in AVI or MPEG. Another option is that the video(s) or publicity spot(s) is placed on a DVD and can be loaded with the LED screen software directly from the DVD. But the question will be: "In what aspect ratio I have to produce my video?". The answer is very simple and will be explained in this article! Wide Screen and Letterbox Mode for LED Screens A DVD-player or blu-ray can be connected to any LED screen, but with a Widescreen LED screen you will get the most viewing enjoyment. DVD-Video supports multiple aspect ratios. Video stored on a DVD in 16:9 format is horizontally squeezed to a 4:3 (standard TV) ratio. On Wide-screen LED screens, the squeezed image is enlarged by the LED screen to an aspect ratio of 16:9. DVD video players and video files output widescreen video on LED screens in three different ways 1. Letterbox (for 4:3 LED screens) 2. Pan & scan (for 4:3 screens) 3. Anamorphic or unchanged (for wide LED screens) In widescreen or letterbox mode, if a movie is wider than 16:9 (and most are), additional thin black bars will be added to the top and bottom at production time or the sides will be cropped. Video stored in 4:3 format is not changed by the player. It will appear normally on a 4:3 screen. Widescreen systems will either stretch it horizontally or add black bars to the sides. Advanced Live Video Processor for LED Screens With our advanced live video processor, the image can be adjusted horizontally and vertically to make the image or video fit the screen. Another option is to produce the video in the right aspect ration of the screen, due to the fact that some screens do have odd sizes which makes the aspect ratio wider or longer. Conclusion Aspect Ratio LED Screens It is not necesary to have a wide screen LED screen to play different kind of movies, video clips and pictures and animations. A LED screen can play any kind of aspect ratio, although it might be possible that the image will be cropped leaving a black line at the top, bottom, left or right of the image. But with the advanced live video processor it can be eliminated
- 8. although the image will deform a bit depending on the aspect ratio. Prices LED Screens, LED Displays and Electronic Billboards How much does a LED screen or LED display cost? The price or cost of a LED screen, LED display or electronic billboard depends on two variables. Those two variables are the total size of the LED screen, and the total resolution of the LED screen. 1. The total size of the LED screen: The bigger or larger the LED screen the higher the cost. The prices are based on USD/sqm, which means that if the total size is 24sqm, the price will be 24 multiplied by the cost per sqm. 2. The total resolution of the screen: The more pixels, or the more number of LED´s, the screen has the higher the cost will be. For example if a screen is 12sqm and has 49,000 pixels, it will be cheaper if the LED screen is 12sqm with 120,000 pixels. This is because more LED lamps will be placed onto the screen which is a higher cost. But on the other hand the more LED´s the screen has, the higher the detail will be of the videos and images that the LED screen will be publishing. Why LED screens have different costs and prices? Everything depends on the customers´ needs. Some customers want the public to see their LED screen from a distance of 10 meters and further, and others from 20 meters and further. The more resolution/sqm a screen has the closer will be the viewing distance without loosing detail looking at the screen from closeby. For that we always need the client to answer us several questions to determine the right LED screen size and resolution and come with the right proposal. Nothing is predetermined, but based on the needs of the client. If you want to know what are our prices per square meter please let us know and give us a call, or contact us by writing an email or online chat. We can send you our prices and you can figure out what will be the right size and right resolution for your LED screen that fits your budget. LED Screens and Refresh Rate What is the refresh rate for LED screens? The refresh rate of a LED screen is the number of times in a second that the LED screen hardware draws the data. This is distinct from the measure of frame rate in that the refresh rate for LED screens includes the repeated drawing of identical frames, while frame rate measures how often a video source can feed an entire frame of new data to a display. For example, most movie projectors advance from one frame to the next one 24 times each
- 9. second. But each frame is illuminated two or three times before the next frame is projected using a shutter in front of its lamp. As a result, the movie projector runs at 24 frames per second, but has a 48 or 72 Hz refresh rate. Increase refresh rate for decreasing LED screen flickering On LED screens, increasing the refresh rate decreases flickering, thereby reducing eye strain. However, if a refresh rate is specified that is beyond what is recommended for the LED screen, damage to the display can occur. Normally our LED screens of Vegas LED Screens have a refresh rate of over 300Hz, which is more than 5 times the refresh rate of a normal cathode television which is 50Hz (PAL and SECAM) or 60Hz (NTSC). For football stadiums (stadium LED screens and perimeter LED screens) our LED screens can reach a refresh rate of over 800Hz, which means that they won´t show any flickering when recorded with a video camera and broadcasted live on television. Life Time of our LED Screens What is the life time for our LED screens? The life time for our LED screens is over 100,000 hours, but it depends how the client is taking care of his LED screen and how it is used. When a LED Screens´ life time will get to 100,000 hours, it means that the brightness of the LED´s of the LED screen is about 50% of it´s original brightness, depending on several factors that will enlarge a LED screen´s life time or reach 100,000 hours. The most important factors are, which are: LED Screen Maintenance LED Screen Temperature LED Screen Power Protection LED Chip Packaging LED Screen Maintenance Maintenance is a very important factor, dusty environments require more often maintenance to the LED screen than clean environments. The soldering of the LED chips can dry out and break which require changing often pieces like LED modules and receiving cards. LED Screen Temperature The temperature of the LED screen is very important to keep it cool. In hot environments it is wise to install a cooling system inside the LED screen to avoid overheating.
- 10. LED Screen Power Protection Electrical peaks can put more force on the electrical components which will decrease life time. It is wise to install a protection that can control the peaks. LED Chip Packaging The LED chip packaging material is also a very important variable that will determine the lifetime of a LED screen. For example iron has less life than cuprum LED packages. Besides iron is more corrosive than cuprum. Vegas LED Screens Quality Explanation and Comparison Vegas LED Screens Quality Explanation and Comparison Below you can find the comparison of the main components we use for our LED screens compared to other LED screen companies and factories. There are many ways to lower the cost using cheaper materials like LED lamps with iron leg or low quality power supplies. We are usinghighqualitymaterials&partsto ensure the reliabilityof ourLED Screensfrom the verybeginning; Full automaticproductionlineswithourstate-of-the artmanufacturingfacilities; Rigorousqualitycontrol fromthe raw materials& partsinspectiontofinal inspectionwith advancedtestingequipment; Our expertiseandknow-howonLED displays; Experience gainedfrommanyinstalledsystemsworldwide. Item Components Vegas LED Screens' Choice Other Factory's Choice LED Lamp LightningChip 1. LED manufacturerand packagerby Nichia 2. LED manufacturerand packagerby Cree 3. Top grade Silanwithbigger chips (highbrightnessandless powerconsumption) Fake lampsor unprofessional encapsulation Lamp Leg Onlyuse Name brand Copperlegs Use copperlegsor ironlegs withunknownbrands
- 11. Encapsulation Glue Onlyuse Name brandfrom Taiwan DomesticBrand Lamp Board & Driving Board PCB Board Name brand;Grade A material Domesticbrand,normal Grade B material Connector Copperplatedwithgold Copperplatedwithnickel DrivingIC Original TaiwanMacro Block Domesticunknownbrand Resistance Tolerance ± 1% Tolerance ± 5% Capacitance Hightemperature resistance,upto 150 degree Celsius Not-high-temperature- resistance,only 90degree Celsius FasteningScrew Stainlesssteel withplating Iron withplating Anti-Water Glue Name Brand DomesticBrand Louver Louver 1. PC + fiberglass(good weatherproofed)- regular screen 2. Softsiliconrubber- for perimeterLEDscreen - Grade A material 1. ABS or recycle PC 2. Grade B material Anti-water plasticglue Low-temperatureresistance silicon Normal Silicon Cabinet & Assemble Components Cabinet material:highqualitycoldrolled steel (1.5mmstandard) or Aluminum metal sheet5052 (2.0mm standard) ThinnerMaterial Rust Proof Electrostaticspraying StovingVarnish Wires& Cables Certifiedproduct; Real coppercore withstandard diameter Non-certificatesand standardcore and core diameter CoolingFan Name brandand certifiedproducts Non-certificates
- 12. Screw& Fixed Pole Stainlesssteel Iron withZinc/ nickel plating Power Supply PowerSupply Brand Names: 1. TDK - Lamda (Japanese Brand) 2. Meanwell Meanwell orotherbrands like mingwell Facts about Parts used for building LED Screens Below you can find some very important facts about parts that are used for to build LED screens for to improve lifetime and picture quality. Name Brand:Meanwell orTDK-Lamda powersupplies We are using name brand power supply for all our LED screen projects. Meanwell and TDK - Lamda power supplies for LED screens are lightweight high-efficient power supplies switched by high-speed semi conductors. ExtraprotectionforLED Screensfromlouver The louver itself will protect the LED screen from direct exposure of sunshine; our louver is made of fiber-glass reinforced PC (except the sports stadium screens), which is strong in both compressive loading and sensible strength by combining the two materials PC plastics and glass fiber. It has much better performance against high temperature, erosion and UV radiation, in comparison to ABS. For sports stadium LED displays, we are using louver made of soft silicon rubber, which are both protection for players from getting hurt if pumping on LED displays, and seemly protect LED displays itself from being damaging if a ball hits the LED displays at high speed. LED lamp BrandsforLED Screens We purchase Cree LED lamps and Nichia LED lamps encapsulated by their own factory; for Silan lamp, we also use a professional packager. Also our output of LED displays could be very high per month, this means we have quite large purchasing volume of LED lamps at one time, which could ensure our good bin selection of LED lamp i.e. large volume LED lamp under the same lot and grade. Hence it could ensure the consistence of a single LED display (even in large size like hundreds sqm) using the same lot and grade lamp. This is one of key factors on the consistence of LED display. What do the IP protection grades for LED screens mean?
- 13. LED screens must be able to work 24 hours a day and 7 days a week and withstand extremely stormy or sandy storm weather. For manufacturers it is required that the LED screens meet the criterion for outdoor LED screens IP65, and for indoor LED screens IP20. So what do these criterion mean? And what does IP65 and IP20 stand for? The IP code (or International Protection Rating, sometimes also interpreted as Ingress Protection Rating) consists of the letters IP followed by two digits and an optional letter. As defined in international standard IEC 60529, it classifies the degrees of protection provided against the intrusion of solid objects (including body parts like hands and fingers), dust, accidental contact, and water in electrical enclosures of the LED display screens. The standard aims to provide users more detailed information than vague marketing terms such as waterproof. International Protection Rating Of Vegas LED Screens for Outdoor LED Display It's the technical introduction by reading which you will command all the conception in details. But here as a company dedicated in LED display screens, we'd like to be short to avoid any unnecessary mistake. Front OutdoorLED Screens:IP67 The first digit indicates the protection against dust. And "6" means Dust Tight, which means no ingress of dust and complete protection against contact. The second digit indicates the protection against liquids. And "7" means ingress of water in harmful quantity shall not be possible when the enclosure is immersed in water under defined conditions of pressure and time (up to 1 m of submersion). BackOutdoorLED Screens:IP55 The 2 digits indicate the same parameter with above. But the letters are different. And the first "5" means Dust Protected: Ingress of dust is not entirely prevented, but it must not enter in sufficient quantity to interfere with the satisfactory operation of the equipment; complete protection against contact. The second "5" means: Water projected by a nozzle against enclosure from any direction shall have no harmful effects. According to the "The General Criterion For LED Displays": Indoor LED displays should be IP20+, Outdoor LED displays should be IP33+ So with IP67 for the front side, and IP55 for the rear side, we ensure the led display working well in all the outdoor environment and weather conditions. Clarify On the IP65 LED Screens Sometimes clients are misled by non-professional suppliers who aim only selling out the led screens. As the reliable partner, we think it's necessary to make clear each confusing point, and be honest with true result. For the front side, it's no difficult to reach "IP65". But for the
- 14. rear side, as long as there's air inlet and outlet, the protection against dust can't reach "6" - totally prevent the dust. In another words, as long as the heat dissipation design based on fans, the air inlet and outlet is necessary. As a result, the ingress protection can't reach "6". Vegas LED Screens LED Display Test Method of "IP_5" 1. The inside diameterof waterjet:6.3mm 2. Distance betweenthe displayandwaterjet:2.5-3m 3. Flowvelocity:12.5L/min±5% 4. TestTime:3 min/m2 5. TestCondition:Everyfeasible anglejetontothe testsample cabinets. Relationship between pixel pitch distance and viewing distance According to the working environment, LED displays can be divided into indoor led screens, outdoor led screens and semi-outdoor led screens. There are some data in theory which can reflect the relationship between the pixel pitch and the best viewing distance. The relationship between pixel pitch distance and the best viewing distance Pixel Pitch P5 P6 P7.62 P8 P10 P12 P16 P20 P25 Viewing Distance (m) 11 14 17 18 23.5 28.2 35.5 46.99 56.4 Viewing Distance (ft) 36 46 56 59 77 92.5 116.5 154.16 185 In the actual application, because of the limitation of led display installation environment and identify ability, led display’s smallest viewing distance is mean the shortest distance that can identify the text and picture showing. The shortest viewing distance and led specification are on below: The smallest viewing distance and led display specification Viewing Distance (m) 3 ~ 5 5 ~ 8 8 ~ 10 10 ~ 12 12 ~ 16 16 ~ 20 20 ~ 25 > 25 Viewing Distance (ft) 10 ~ 16 16 ~ 26 26 ~ 33 33 ~ 39 39 ~ 52 39 ~ 66 66 ~ 82 > 82 Pixel Pitch P3 P4 P4.75 P4.75 P5 P6 P7.62 P7.62 P8 P10 P10 P12 P12 P14 P16 P16 P20 P20 P25 P25 P31.25 The Effective Control Distance Of LED Displays and LED Screens In this article, we will explain the effective control distance of full color LED displays and LED screens signals transferred with a normal network cable. Generally, the signal cable of a
- 15. LED display is RJ45 which is a standard network cable. The control distance can reach up to 100m, which is enough for most clients needS. A LED screen will be installed with a structure, the function of which is not only to back up the LED display and decoration, but also, there will be a small control room inside the LED screen structure or nearby the LED screen structure where a PC will be placed to control the LED screen. Economic LED Screen Controlling The most economic way for controlling a LED screen is using the basic RJ45 signal cable. But for some special clients, they will not place the control PC nearby the LED display, because it's not convenient for them to edit and program the content nearby the LED display. Those clients will request for a longer control distance. In this condition, a fibre-optic solution will be chosen. And in this way, the control distance from the LED screen to control room where the controlling computer is placed can reach up to 10Km, or even more. This will bring a relative high cost which won't make it an economic solution. Usually for LED screens and LED displays that will be controlled over a long distance, an internet connection can be choosen too. This only applies if an internet connection is available for both locations to control the LED display and to control the PC. We recomment to control the LED screen remotely by the internet of course. LED Displays Controlling Remotely For most application, the signal from the controlling PC to the LED display screen is transferred via a RJ45 cable. The distance of 100m is normally far than enough for most clients enough for most clients' requirements and most economic way. But some clients would like to control the display in a further distance than 100m, or even thousands of Km. For these cases the remote control by internet will be chosen. For to realize controlling remotely the LED screen by internet you need the following: The internet connection ror both locations, for the LED screen as well as for the controlling PC; Two PC's, one for to place at the LED screen and the other one to control the LED screen remotely. At last, we will introduce the signal transfer in a simple way. For most people it's not strange to know that one PC can control another PC through internet. And the essential of LED display remote control is the same. But our software will combine and set the control in a convenient method. And the operator will easily control the display from quite a far distance. For the detailed information please ask our sales for the manual of control system. Wireless GPRS Solution for LED Display Screens The usage of LED display screens is getting wider, such as advertising LED screens, traffic LED screens, etc. However, users have to do a lot of work to update the LED displays contents due to numerous numbers and widely distribution. In order to solve this problem,
- 16. our company has successfully researched and developed LED display screens control systems based on GPRS. As long as users can access the internet and find the control card which connects with GPRS, they can control display contents and achieve off-site control. In this way, users can solve problems by transmitting over a long distance and with one PC it controls multiple LED display screens. GPRS Traits for LED Display Screens 1. Making efficiencyreliable TransmissionControl Protocol (TCP)based onfeaturesof GPRS communicationsoasto adjustpacketstransferrates(Mbps) and use GPRS bandwidth effectively,average ratescouldreachto15kbps. 2. SupportingTransmitDataSearchingandDocumentResuming.Itjusttransmitsthe amendmentparteverytime soasto reduce GPRS trafficandsave costsfor customers. 3. GPRS not onlycan transmitsimple textsmessage butalsopicturesandvideos. 4. ProgrammingSoftware willprocessvideosandpicturesaccordingtothe screen’ssize then transmitthroughharmless compressionandstorage,makingastorage cell can perform informationasmuchas possible. LED Screen GPRS System Structure 1. Connectingusers’PCwithADSLrouterbyLAN line,insertingADSLrouterintoInternetby
- 17. telephonelineorinotherways. 2. Connectingcontrol cardwithGPRS modulesbyserial port232. 3. Connectingcontrol cardwithdisplayscreenbynormal adapterplate andflatcables. Compositions of LED Screen GPRS Main Hardware and Software LED ScreenGPRS Hardware 1. ADSL router(recommendedtypes:TP-LINK,TD-W89541G) 2. LED displayscreencontrol card(ourcompany’sM-seriescontrol cards) 3. Normal adapterplate (HUB: usedforconnectingdisplayscreenwithcontrol card) 4. LED displayscreen 5. Users’PC that can control LED displayscreen(needtoinstall LEDEditorSoftware) LED ScreenGPRS Software 1. Name of LED displayscreencontrol card:LED Editor 2. WirelessM-GPRS.exe software 3. Interface screenshotof LEDEditorSoftware as showninimage 1 below 4. Interface screenshotof M-GPRSwirelessSoftware asshowninimage 2 below
- 18. LED Screen Power Consumption Explained One of the most asked questions is how to calculate the maximal power consumption of a LED screen. Well first of all, you should know the input current and the voltage of the LEDs on the LED screen. Theoretically, in a labratory environment the greatest input current of the LEDs on a LED screen is 20mA, and the voltage for the LEDs for the LED screens is 5V. But in reality, the current of the LEDs of a LED screen can't reach 20mA. So the power consumption of a LED is 20mA x 5V = 0.1W. So it is very simple how to calculate the power consumption of one LED on a LED display. Pixel Configuration of LED Displays And secondly, what you should know is the pixel configuration of the LED display and the resolution per square meter of the LED display. When you get this data you will know how many LEDs are available on the LED display. For example, let's take a LED display with a pixel pitch of P16mm, the pixel configuration is 2R1G1B, which means that each pixel consists of 2 red LED's, 1 green LED and 1 blue LED. So this means that every pixel has 4 LED's. And the resolution per square meter of pitch 16mm LED display is 3906 pixels, which means there are totally 3906 pixels in one square meter. According to the previous data the calculation will be as folows: 4 x 3906 = 15,624 total LED's per square meter for this LED display. Maximal Power Consumption for LED displays There are two types of driving methods for LED displays, which is the constant static driving method and the scan driving method. First let's explain how to calculate the maximal power consumption and average power consumption of a pitch 16mm LED display using constant static current driving. ConstantStatic CurrentDrivingMethod The maximal power consumption of a pitch 16mm LED display is 15624 x 0.1W = 1.56Kw pero square meter. The average power consumption of a pitch 16mm LED display is 1.56Kw / 2 = 780W. This calculation way is for static constant current driving LED displays. ScanDrivingMethod For scan driving LED displays, you must notice that it has a 1/4 driving, 1/8 driving or 1/2 driving. Taking a pitch 6mm indoor LED display as an example, the usual driving method is 1/8, so if you calculate according to above way, the maximal power consumption of a pitch 6mm indoor LED display will be extremely high and gives us more than 8Kw per square meter. But in reality it is not correct, the reason is that you need to make the total calculation result divided by 8 because the driving method is 1 over 8 (1/8), and like that you get a maximal power consumption of 1.1Kw per square meter.
- 19. The Relationship between LED Screen Brightness and Viewing Angle What is the difference between a LED screens' brightness and viewing angle. Well depending on the environment (indoor or outdoor) where a LED screen is installed, the requested brightness of a LED screens is different according to the environmental contrast ratio. Difference between Indoor LED Screens and Outdoor LED Screens Brightness and Viewing Angle Indoor LED screens request a lower brightness but request a high viewing angle. On the other hand outdoor LED screens' request a higher brightness, and also a much better better grey grade. Therefore the outdoor LED screens' viewing angle request is not as high as an indoor LED screen, generally between ± 35--± 50 degrees. Relationship between LED Screens' Brightness and Viewing Angle If the viewing angle of the LED screen becomes lower, the LED screen brightness will be higher, or vice versa. If the contrast ratio between LED screens' brightness and environmental brightness is higher, the led screens' showing performance will be more colorful. However, if the brightness of the LED screen is too high, it is bad for the human eye, and much more power consumption will be wasted. Also much more heat will be produced, and then the temperature becomes much higher. For that the led chip's brightness decreases much faster, and of course, its lifespan will become shorter. Conclusion Hereby, LED screens brightness and viewing angle should be applied to the LED screens' environment. What LED brand to choose when buying a LED screen The LED's are surely the most important quality criteria when it comes to LED video displays. They determine the image quality of the display and are decisive in determining how the image quality is retained over time. The quality characteristics for LED's are very diverse, and, here too, the maxim applies: the most expensive choice is not always the best choice. To highlight an example from the automobile industry: You are sure to be able to spontaneously list a
- 20. variety of luxury sedans, though you may not generally consider these when selecting a new vehicle. Price and purpose play major roles in the decision of which model to choose. And also, luxury sedans differ in many ways, although they often all meet the highest quality standards. The quality of an LED is determined primarily by the chip used. It determines the service life of the LED and how the lighting behavior of the LED changes over time. The mayor Chip manufacturers of LED's are: Nichia (Japan) Cree (USA) AXT (USA) Epistar (Taiwan) Silan (China) The prevailing opinion on the market today is that LED's made by Nichia are the best for use in LED video displays. However, they are also undeniably the most expensive LED's on the market by a wide margin. The price of LED's varies on average from less than one cent per LED to up to 15 cents and more, depending on the type of LED (RGB LED's with three chips in one housing are often more expensive). An extensive price difference can arise in manufacturing, depending on the LED's used. The most important factor for purchasing a LED screen and determining which LED's to choose are: Brightness: The brightness of the LED's is measured in mcd (milli-candela). The higher the brightness, the better. You can run the display at a lower brightness, thus increasing the service life or increasing visibility during the day when the sun is shining. Electrostatic Discharge(ESD): The LED chips produced by various manufacturers differentiate themselves through a varying sensitivity to the effects of electrostatic discharge (for example due to contact). Display failures caused by electrostatic discharges can be prevented by implementing safeguarding measures against ESD in the production process. The following LED chips listed are indicating the voltages that the LED's can withstand in case of electrostatic discharges: o Cree: 2000V o Nichia: 1000V o Taiwanese LED Chips: 800V o Chinese LED Chips: 200~800V Sensitivity to Temperature Variations: Poor LED
- 21. chips can fade faster, i.e. their service life can shorten, if they are exposed to high temperature variations. Depending on the country, temperatures can become extremely hot or cold during the summer or winter months, respectively. As a result, a poor LED quality could cause premature fading of the overall, expensive LED display. General Service Life: The general service life of the LED's often lies between 50,000 and 100,000 hours. (100,000 hours equates to 10 years of continuous display operation at full white, if no other factors exist which reduce the service life; such as increased heat in the display housing, or operating the LED's at overvoltage in order to balance brightness reduction. Brightness Reduction due Aging: Below is a table indicating the lighting reductions which arise within the first 10,000 hours: LED brightness reduction after the first 10,000 hours, sorted by manufacturer: Nichia (Japan) Cree (USA) AXT (USA) Silan (China) Epistar (Taiwan) Red LED 2.5% Unknown Unknown Unknown 28% Green LED 2,50% 26% 8% 7% 28% Blue LED 2,50% 45% 8% 7% 28% For the advertising screens we recommend always Silan LED’s, or the Cree LED’s which are a little more expensive than the Silan LED’s. Nichia LED’s, which are at least twice as expensive than Silan LED’s, for LED screens is mostly used for the professional industry like on stages or for television programs where quality is of high importance due to the high brightness and longer lifetime, and professionals invest a higher amount to have the screen performance and quality optimal at all times if not they are out of business and glamour is important in those industries. For advertising screens which are placed outside that quality is not necessary to be as optimal as the professional industry like stages or television programs because the screen is seen as an investment to shorten the ROI to less than 1 year and using the screen for advertising for over a period of at least 5 years to 8 years and gain 5 to 7 years from advertising. If investing in Silan LED’s the initial investment is about
- 22. 25%(Cree) to 50%(Nichia) lower than investing in Cree and Nichia LED’s. So for that Silan LED’s will have an ROI of around 1 year depending on the portfolio of clients that the screen owner has, the place where it is placed and price of the advertisements. When advertisers want to publish their products on the screen, of course quality is important but in practical terms the selling price of the commercial space on the screen will be the same if used Nichia or Silan or Cree LED’s because they don’t care about the lifetime and differences of brightness between Nichia, Silan or Cree LED's, they just want to be seen and promote their products and or services on the screen. What is important for the publicity clients is the resolution, if it doesn’t look pixelated they do see that as a plus and will attract more advertisers because the better the resolution the higher the impact of the advertisement and the higher the company’s goodwill of the product announced. Also for Nichia and Cree LED’s the ROI is one and a half to twice the time in comparison to Silan LED’s which is two years at least. Normally Silan and Cree LED’s need 100,000 hours to reach around 40% of its total original brightness, Nichia will need 100,000 hours to reach 60% of its total original brightness. This is because the materials used are much more expensive for the Nichia LED’s than for the Cree and Silan LED’s and are better conductors. Besides Nichia uses around 50% of the energy used to burn the LED’s in comparison to the Silan and Cree LED’s. For example 1sqm of 16mm pixel pitch Silan and Cree LED’s consumes around 1200W/m2 and Nichia 575w/m2 which is less than 50% to get the same amount of brightness. Many of the quality factors for LED's play a role in how they behave over time. Nichia LED's are the only ones for which it is generally known that they thoroughly meet the required criteria, positively setting themselves apart from other LED's on the market. The long-term values for some of the other manufacturers were not available. Many developments in the LED field are so new that long-term values over five, ten, or more years don't exist yet. If price and performance should be balanced, we recommend LED's with Silan chips. In terms of overall service life, Silan LED's are 1/3 weaker than Nichia LED's but they cost significantly less. With the service life of Silan LED's, you can run your display for 6 years of continuous operation at full white, although running the screen at full white is never done in reality. In displaying average video image content, the effective service life increases by two to four times as much, that is, 14 to 28 years, depending on the image content. In contrast to the still very expensive Cree LED's, Silan LED's age more evenly and also
- 23. don't have as much lighting reduction after 10,000 hours. This proves particularly lucrative when exchanging individual pixel cards, since the calibration requirement is lower. Color Depth (Gray Scale) of LED Displays The LED display color depth, or gray scale, indicates the process depth of the colors showed by a LED display. When looking at the technical specifications of a LED display given by LED display suppliers you can always find values like "12-bit, 14-bit, 16-bit". Many clients and even sales executives don't know what this value means. For that this article will explain what the color depth, or gray scale, means. 1-bit color (21 = 2 colors): often black and white 2-bit color (22 = 4 colors) 3-bit color (23 = 8 colors) 4-bit color (24 = 16 colors) 5-bit color (25 = 32 colors) 6-bit color (26 = 64 colors) 8-bit color (28 = 256 colors) 12-bit color (212 = 4096 colors) 14-bit color (214 = 16384 colors) 16-bit color (216 = 65536 colors) So from above table, it's not difficult to find the color depth actually shows how many colors can be shown on the LED display. As well-known, LED display is RGB color model, and each pixel consists of red, green, and blue color LEDs. And here we will explain further about it in below table: 12-bit: there are 4 bits (16 possible levels) for each of the RG,B LEDs. So it would show totally 16x16x16=4096 kinds colors. 14-bit: In 14-bit process depth, there's a little difference from 12-bit. For the reason that human eyes are not so sensitive to blue, than red or green. So it is assigned one bit less than the others. So for red and green, there are 32 possible levels, and for blue, there's 16 possible levels. So totally it can show 32x32x16=16384 colors. 16-bit: It is very similar with above. But this time it's due to the green color are most sensitive to human eyes. So it's assigned one bit more than the others. So for red and blue, there're 32 possible levels. And for green, there are 64 possible levels. So it can show totally 32x32x64=65536 colors. Within the LED display industry many LED screen suppliers do not pay that much attention wen making the LED displays' technical specifications accurate. And the technology homogenization is currently very serious. The true situation is, for the widely-adopted technology, the highest color depth is actually 14 bits. It is not arbitrarily speaking because
- 24. it's limited by the hardware part. If adopting higher level IC and system, it wont be any problem to realize the 16-bit color depth or gray scales. But with nowadays tech, it must lose the virtual pixel technology. And actually the 14-bit color depth or gray scale doesnt make any big difference from 16-bit color depth for the human eye.