P20mm Full Color LED Display

P20mm Full Color LED Display

P20mm UHD Small Pixel Pitch Outdoor LED Display 20mm pixel pitch, 2500 pixels per square meter, 16×16 pixels module resolution, 320×320mm module size. 20mm pixel pitch LED display is one of the most hot selling and popular outdoor full color LED display for during the year of 2005-2014. However,...

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P20mm UHD Small Pixel Pitch Outdoor LED Display

20mm pixel pitch, 2500 pixels per square meter, 16×16 pixels module resolution, 320×320mm module size. 20mm pixel pitch LED display is one of the most hot selling and popular outdoor full color LED display for during the year of 2005-2014. However, from the year of 2015, 20mm pixel pitch LED Displays' dominant position were taking place by smaller pixel pitch LED display, like 10mm, 8mm, 6mm, 5mm, 4mm, 3mm pixel pitch LED display due to the mature SMD technology, cost down of SMD lamps, and most customer like smaller and smaller pixel pitch LED display.

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ERALED display is a fast growing energy saving, high tech green products which taking place of the old traditional products rapidly nowadays. You can ignore the existence of the LED display. However, the LED display will never ignore you! The LED display is appearing in every corner of the world and touching with us every second. We are living and touching with the LED display every second even we don't know it is called "LED display".

LED Display is modernizing our life, our town, our city. It's so fashion that if an important events were held without the LED display. It is called "out", "failed", etc.

Every downtown, street, shop, school, church, window was also installed the giant LED display now!

LED display is the basic necessary equipment for every country's Central Television station. Even every small town's TV station has a huge LED display now!

LED display is also the basic necessary equipment for every important sports stadium. No matter NBA, or football World Cup LED display is always the necessary equipment. Even for some sports which you may never care also equipped with the LED display, for example: Badminton, Tennis, Soccer,Volleyball,Goalball,Softball,Speedball,Handball,Rugby,Aikido,Skiing,Wrestling,Archery,Beagling,Swimming,Cue sports,Dancing,Fencing,Fishing,Golf,Grappling,Gymnastics,Hockey,Hurling,Judo,Racing,Tennis,Trampolining, etc.

Even the more and more taxi tops were equipped with the LED display now!

However, what is LED display in end?

Before we know completely what LED display is, we'd better know some basic parts first. Like: What is an LED, what is LED pixel, what is LED module, what is LED module, what is LED cabinet, etc? LED display is a new display media which using LED lamps to display the content. Each LED display is composed by a certain quantity of LED cabinets in line and columns, each LED cabinet is composed by a certain quantity of LED modules in line and columns, each LED module is composed by a certain quantity of LED pixel in line and columns, each LED pixel is composed by a certain quantity of LED lamps, each LED lamps is composed by a certain quantity of LED chip.

So the most basic smallest unit of the LED display is LED chip or LED lamps. So, let's start from the very beginning: concept of the LED, LED chip and LED lamp:

1.Concept or define of the LED chip: LED chip is a semiconductor which can converts electric energy into visible light. The chemical compound used within an LED determines its color, brightness and power efficiency.

2.Concept or define of LED lamps: LED is short for 3 words: Light Emitting Diode

According to the LED chip's encapsulation type, LED lamps have several different types, like:

SMD(Surface Mountinging Device), DIP(Dual In Line package),Dot matrix, etc.

Generally speacking the LED lamps come in two basic forms:SMD and DIP.

SMD LED display is more and more popular since the Advantages of perfect: color blending capability, no color shift at extreme angles, much wider viewing angle comparing to DIP. More important reason why SMD is more popular is the resolution of SMD LED display is much higher than DIP LED display. For example, the smallest pixel for DIP LED display is 10mm. However, the smallest pixel pitch for SMD LED display is 3.2mm which means 9 times resolution higher than DIP LED displays. Furthermore, the SMD LED display is more energy saving and cost is also lower than DIP LED display

Acoording to the SMD LED's encapsulation size, SMD LED can be classified to several models, like: 0606 SMD,0808 SMD,0909 SMD,1010 SMD,1515 SMD, 2020 SMD,2121 SMD,3528 SMD,1921 SMD,2525 SMD,2727 SMD,3535 SMD,5050 SMD etc

SMD 1921, 2525, 2727, 3535, 5050 is used for outdoor waterproof models, others is used for indoor non-waterproof models.

Acoording to the SMD LED's encapsulation color:, SMD LED can be classified to Black LED lamps and white LEDs.

SMD Black LED lamps:

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SMD white LED lamps:

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Black SMD is 50% lower brightness, but can be viewed more clearly under the sunshine because the contrast ratio is higher, gray grade is higher as you can see from the below 2 SMD white LED display and SMD Black LED display's actual comparison under the sunshine condition.  Below picture to show: left is white SMD LED display, right is total black SMD LED display:

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Each SMD LED lamp contains red, green and blue LED chip, meanwhile each DIP LED lamps only contains one color LED chip of either red color LED chip, green color LED chip or blue color LED chip.

Dual In Line LED lamps

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Dual In Line LED lamps use a reflector cup and an epoxy lens package with dual legs, that is why it's called DIP. This combination as well as the type of chip used, plays a role in determining the elliptical viewing angle produced. A Dual In Line LED's reflector cup focuses the light emitted by the chip into a specific viewing area.

DIP LED display is very popular before the year of 2015, 90% of outdoor full color LED video display were made of DIP LED lamps. However, SMD LED display taking place of the DIP LED lamps rapidly after the year of 2016. Nowadays, 95% of the full color LED display is made of SMD LED lamps.

3.Concept or define of LED pixel: Pixel is short for picture elements, are points of light that illuminate to form letters, words, graphics, animations and video images. One pixel can be made up of a single LED lamp, multiple LED lamps of the same color or multiple LED lamps of different colors. They are the smallest elements of the electronic display system that can be individually controlled and turned off or on at various brightness levels. Pixel is also called dot, is also the most basic and smallest unit of resolution. For example, when we say HD, UHD resolution: normally refers to how many pixels or dots in length and how many pixels or dots in height. HD means the resolution should be 1920 pixels in length, 1080 pixels in height. UHD means the resolution should be 3840 pixels in length, 2160 pixels in height, or even 7680 pixels in length, 4320 pixels in height. LED pixel is also the basic and smallest unit of LED module since each module is composed by a certain amount of LED pixels.

4.Concept or define of pixel pitch: pixel pitch means the distance between the 2 most close neighboring pixels in line and column. For example, if the distance between the 2 closest neighboring pixels in line and column is 8mm and 3mm, then we call this LED display model: pixel pitch Indoor Rental LED display . Pixel Pitch is normally just called PH, or P. So, PH8mm equals to P8mm.

5.Concept or define of LED module: LED module is the basic unit of LED cabinet which were composed by a certain amount of LED pixels.

6.Concept or define of LED cabinet: LED cabinet is basic unit of LED display which were composed by a certain amount of LED modules.

7.Concept or define of LED display: LED display is the final product which were composed by a certain amount of LED cabinets.

8.Concept or define of LED display models: all the LED display products' model is normally classified and defined by the pixel pitch. ERALED display products' Pixel pitch typically ranges from 1.2mm up to 20mm for indoor and outdoor LED displays. Our indoor LED display model list: P1.25mm, P1.562mm, P1.667mm, P1.875mm, P1.923mm, P2.0mm, P2.5mm, P2.88mm, P2.98mm, P3mm, P3.91mm, P4mm, P4.81mm, P5mm, P5.95, P8mm,P6.25mm; Our outdoor LED display model list: P3mm, P3.2mm, P3.338mm,P3.91mm, P4mm, P4.81mm, P5mm, P5.95, P8mm,P6.25mm, P6.8mm, P6.667mm, P8mm, P10mm, P10.68mm, P12mm, P18mm, P20mm.

Pixel pitch directly correlates your display resolution and optimal viewing distance. The smaller the pixel pitch, the higher the pixel density, the higher the resolution, the more pixels used to make up the image on your display, thus improving the resolution and optimal viewing distance. What does this mean in more simple and plain terms? The smaller the pixel pitch, the closer a viewer can stand to your display and still have a very good image quality.

Theoretically speaking, the smaller pixel pitch, the better. However, we are living in the realistic world which have many limitations, especially the resources and money. The smaller pixel pitch LED display always have better image quality, but also increase the cost since the smaller the pixel pitch, the higher the pixel density, the higher the LED lamps quantity needed. Each LED lamps is not so expensive. However, when the pixel pitch is very small, like 1.25mm pixel pitch, each square meter LED display area need 640000 LED lamps which is more than half a million LED lamps. So the cost is also extremely high! So, even 1.25mm pixel pitch indoor LED display and 3.2mm pixel pitch outdoor LED display is the smallest pixel pitch LED display among all models. However, 98% customer still choose other bigger pixel pitch LED display to match their demand and balance their ROI time. For example, using 1.875-8mm pixel pitch indoor LED display and 3.91-10mm pixel pitch outdoor LED display. By having a smaller pixel pitch, you increase the number of LED pixels for your display. The more LED pixels in your display, the higher your expense. You can cut your costs and still have a fantastic display by going with a larger pixel pitch if your audience isn't too close to your screen. If your display is in a space where your target audience will be closer to the display screen, such as in a shopping mall's retail environment, a 1.2-2.5 mm pixel pitch LED display is probably better suited to your needs. If you are hanging your display higher and in turn further from your target, for a project such as airport signage, a 2.5-5mm pixel pitch LED display may be best for you.

9.Concept or define of LED display resolution? LED display resolution is defined by how many pixels or dots in length and how many pixels or dots in height on the physical area of the LED display. HD LED display means the resolution should be 1920 pixels in length, 1080 pixels in height. UHD LED display resolution means the resolution should be 3840 pixels in length, 2160 pixels in height, or even 7680 pixels in length, 4320 pixels in height. Resolution is mainly determined by pixel pitch and LED display size. The smaller the pixel pitch, the higher the resolution; the larger the LED display size, the higher the resolution. So, there's 2 ways to increase the LED display resolution: using smaller pixel pitch technology or increasing the LED display size: When the LED display pixel pitch is certain, then increasing the LED display size to increase the resolution; When the LED display size is certain, then using smaller pixel pitch LED display size to increase the resolution.

10.Concept or define of the viewing distances:Viewing distances are calculated based on the display type and the distance from the display. Each display will have a minimum and a maximum viewing distance that may vary based on application and intended use. A large character will have a longer viewing distance while a small character will have a shorter viewing distance. ERALED uses 50 feet for every one inch of character distance as a general point of reference. Character spacing, also known as pixel pitch, will vary between indoor and outdoor display applications.

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11.Concept or define of LED display viewing angle: the viewing angle is the viewing angle where the measured light intensity is 50% of its maximum value(seeing from the middle front). Measuring brightness or luminosity is done by using a spectroradiometer. Spectroradiometers typically take measurements of spectral irradiance and spectral radiance, which spectral data can be used to calculate luminosity (cd/m²). When choosing a display, consider where it will be installed and the angle at which the display will be viewed. Image quality will be at it's best within the viewing angle of the display—where your primary intended audience should be located. Readability angle or viewing angle will normally exceed the optimum viewing angle depending on site-specific circumstances and ambient light conditions.

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In Fig. 1 the Intensity (I) is shown relative to the angle, whereas 0° is perpendicular to the light source or the LED. As per definition the viewing angle is defined as the angle where the measured light intensity is 50% of its maximum value, as per the red line in Fig. 1. For this LED, which is typical for other SMD LED lamps as well, the viewing angle to 50% brightness is 60°.

Since SMD LED lamps are of symmetrical lay-out, the viewing angle is 60° in all directions, both horizontally and vertically. This means the actual viewing angle of the LED can be specified as 120° horizontally and 120° vertically.

So far, we have been talking LED intensity (or luminosity) of a single LED which is measured in candela (cd), while an LED display is an array of LED lamps and brightness is measured in candela per square meter cd/m² or NIT. This is the value always mentioned in product specifications, measured perpendicular to the display surface and the LEDs.

QUESTION Why do some product specifications mention 140° or even 160° viewing angle, while the physical LED characteristics does not exceed 120°?

This is all about measuring brightness relative to the display, and how the measuring is done.

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In order to determine the viewing angle, we have to comply with the definition. The angle relative to the display for which the luminosity is 50% of maximum perpendicular to the display.

Measuring brightness or luminosity is done by using a spectroradiometer. Spectroradiometers typically take measurements of spectral irradiance and spectral radiance, which spectral data can be used to calculate luminosity (cd/m²).

First the maximum brightness is measured in accordance with Fig. 2, perpendicular to the display surface. This represents 100% brightness.

Next the spectroradiometer is moved circular (or display is rotated) to allow for similar measuring relative to the display surface.

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As per LED specification, it is expected that 50% brightness is measured at a relative angle of 60°, as per Fig. 3.

Unfortunately, this is not the case. Look carefully, while in Fig. 2 only 4 LED lamps are covered in the measurement, in Fig. 3 8 LED lamps are covered in the measurement. This results in almost identical luminosity (8 LED lamps at 50% brightness is identical to 4 LED lamps at 100% brightness). The relative angle exceeds 60° and values of 70° or even 80° come within reach before the 50% brightness is reached. This is why sometimes 140° or 160° angles are specified for 50% brightness values.

This is however incorrect. Physically, you should not increase the number of LED lamps (or surface) that take part in the measurement. In other words, you have to rule out the side effect of the increasing display surface that is subjected to the measurement.

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Fig. 4: Directional luminance of elementary light emitting surface (source: INTEC)

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Where:

1.jpg brightness (Luminance) (cd/m² or Nit)

2.jpg Luminous intensity (cd)

3.jpg Effective surface (m²)

4.jpg Surface (m²)

5.jpg Viewin

Example:

For a display with maximum brightness of 2,000 Nits, the maximum brightness under 60° viewing angle is (measured on 1m² display surface):

g angle (°)

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The above means 50% brightness threshold on display level will never exceed individual LED specification of 60°.

Reflected on LED display example above:

Assume each LED emits 2cd. First measurement shows 8cd (100% of 4x2cd). Second measurement shows 8cd as well (50% of 8x2cd). The corrected brightness however should be 4cd (50% of 8x2cd x cos 60°). This corresponds with the theory above as well.

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Fig. 5 above shows both measured and corrected brightness under viewing angle using a spectroradiometer. In practice, between 0° and 60°, by using a spectroradiometer, brightness can even exceed the initial value if you do not apply the cos q correction.

OTHER ANGLE Alternatively, to determine the 50% brightness angle, it is better to use a measurement process that rules out the side effect of the increasing display surface subjected to the measurement from the beginning.

This can be done by measuring luminance rather than luminosity. Luminance is measured in lux by using a lux meter. Although the absolute value measured has no real meaning, you can consider the value measured similar to Fig. 2 as 100%. If you then increase the angle by following again that circle until you reach 50% of the initial value, as per Fig. 3, you will find the correct angle at which brightness is degraded to 50%. This will correspond with 60° as per original LED specification. This alternative method completely rules out the surface component or cos q in the spectroradiometer measurement.

Impact of Module mask hat or Louvers All of the above is not taking into account any side effects of shaders, masks or other front surface parameters that effect viewing angle. For indoor LED displays, with no module mask hat or Louvers influencing viewing angles, all of the above is 100% applicable.

For outdoor displays, some side notes have to be taken into account. Whilst above is true in general, vertical viewing angle is largely effected by the appearance of module mask hat or Louvers, masks, and additional protection against water. Module mask hat or Louvers are necessary to increase contrast, to block direct sunlight from reaching the LED, which reduces the light emitted by the LED, making the screen look completely washed out. The longer the louver, the better the contrast, but the earlier it will cut off light and the vertical viewing angle both up and downwards. Depending on the length of the louver this might affect vertical viewing angle. This will cause a sudden drop in brightness. Typically this is asymmetric, because normally louver design allows for greater downward viewing angle then upwards.

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The effect of module mask hat or Louvers, certainly for outdoor displays should be reflected in specification, even though this appears to be negative due to smaller viewing angle at first sight it is actually an advantage, when you consider the application. The 50% brightness in most cases have no real meaning at all, the gain in contrast however is of critical importance to most installs.

COLOR SHIFT Talking about relevance, what about color shift? We still need to meet the first advertiser or brand that prefers 50% brightness above color shift under viewing angle, although tender documents will sometimes mention other ways, brightness might affect the punch of your advertising or brand displays under extreme viewing angles, but color shift will cause your brand color to discolor into something unrecognizable.

Discoloration happens when LED lamps are (partly) blocked for various reasons. This can be module mask hat or Louvers, shaders, masks or adjacent LEDs. Viewing angle limitations are usually wider for color shift then for 50% brightness but of greater importance for advertisers and brands.

CONCLUSION  In conclusion, it can be stated that loss of brightness under viewing angle start with radiation characteristics of individual LEDs.

In most cases radiation characteristics of LED lamps show 50% brightness level at about 60°.

Brightness of displays built from LED arrays can physically not exceed radiation characteristics of individual LEDs.

In a lot of cases manufacturers/distributors manipulate the measuring method to tweak 50% brightness viewing angles towards wider angles for commercial/marketing reasons, which is actually misleading.

Correct brightness measuring should be corrected by cos q to rule out the effect of increasing surface or more LED lamps that affects the measurement. Alternatively, a measuring method could be used that is not effected by an increase surface or amount of LED lamps subjected to the measurement.

How to calculate LED display brightness?

LED display now become very popular product for the outside advertising, event, shows and so on, and there are many people don't know how to calculate the brightness, here give detail information for the calculation. Let's take P12mm outdoor 1R1G1B DIP346 for example, total pixels is 6944/m2, and scan module 1/2.

And before calculation, we need know the brightness of each LED, this can be supplied by the package companies, we take the following list for example:


Color

Red

Green

Blue

Original    brightness

1000    mcd

2100    mcd

400    mcd

Ratio

30%

60%

10%

All    with 10%

1000/3=333    mcd

2100/6=350    mcd

400/1=400    mcd


P12mm LED display with 1R1G1B, so the original brightness for each pixel is:

1x1000mcd+1x2100mcd+1x400mcd=3500mcd=3.5cd

But the original brightness is not with R:G:B=3:6:1, so it's not in white balance. And now we need to adjust the LED brightness with 3:6:1 ratio, this ratio means: red take 30% of total brightness, blue take 60%, and Blue take 10%.


Color

Red

Green

Blue

All    with 10%

1000/3=333    mcd

2100/6=350    mcd

400/1=400    mcd

Adjust    brightness

10%=333    mcd

10%=333    mcd

10%=333    mcd

White    Balance

30%=1000    mcd

60%=2000    mcd

10%=333    mcd

Pixel    brightness

One    pixel in total: 1000+2000+333=3333mcd=3.333cd

Sq.m    brightness

One    squre meter in total: 3.333×6944=23144cd

1/2    scan

23144/2=11572cd/m2

20%    loss

11572×80%=9257.6cd/m2


So we calculate based on red brightness, and cut the green and blue color, and meet the ratio:R:G:B=3:6:1. And the one pixel brightness is: 3.333cd, for P12mm with 6944 pixels each square meter, so the brightness is 23144/m2, also for P12mm LED screen, when in 1/2 scan, the brightness is also 1/2, that 11572cd/m2, and this is just theoretical value, there will be about 20% loss when use, so the final brightness is 9257.6cd/m2, or 9257.6 nit.

So, did you got how to calculate the brightness finally?

In order to ensure our LED display product quality, durability and performance, ERALED established the most comprehensive testing systems done in the lab continue to provide much needed data to our engineers. We test ERALED products more rigorously than any other manufacturer. In fact, some of our lab test equipment is similar to that used by the automobile and aerospace industries.

ERALED outdoor LED display has passed StormTest, the most rigorous test in LED display industry

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Environmental Simulator

Before product release, ERALED puts products through a variety of stress tests. Our lab technicians place entire video boards through a massive 4,500 cubic foot environmental chamber (Solar Thermal Simulation Area: 22' L x 11' H), in order to simulate extreme climate conditions, such as:

•Blistering Heat (74° C, 165° F)

•Freezing Cold (-34° C, -29° F)

•Humidity (15% to 90% RH)

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Temperature/Humidity Chamber

The Temperature/Humidity Chamber simulates worse-case environments to test component sensitivity towards humidity, corrosion and electrical property changes. This assures that product components are as tough as their displays, by undergoing:

•Chamber Transitions (5° C/min, 9° F/min)

•Humidity Testing (10% RH to 98% RH)

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Thermal Shock Chamber

This chamber ensures product durability by conducting unpowered thermal shock testing. In less than five seconds, products are transferred between hot and cold compartments.

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Highly Accelerated Life Testing (HALT)

To determine product functioning limits, the HALT chamber combines environmental variables, such as temperature shock and vibration, to stress products to the point of failure.

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Spray Test Chamber

To test how well enclosures protect components, this chamber drenches display parts with high-pressure water jets to assure performance against moisture.

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Salt Fog Chamber

To gauge a component's capacity to withstand the corrosive effects of salty coastal air, this chamber punishes ERALED products with a 5% salt solution at a sweltering 35° C (95° F).

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How to protect LED Display in Hot Weather?

Good heat dissipation is very important for LED display lifespan. For LED Display , especially the outdoor LED Display . Some countries, temperatures as high as 38 °sometimes outdoor 50 °.How to avoid high temperature affect the LED display normal work? Here are some suggestions for you.

First: excellent material

LED Display is composed of the mask, circuit boards, pan, for fire prevention moistureproof LED Display use waterproof glue is also the important component of the LED Display . All adopt the masks and pan through quality verification which has the function of flame retardant PC glass fiber materials. Circuit board is jet black anti-corrosion paint, prevent the weathering and corrosion, etc.

Second: solve the problem of heat dissipation

LED Display area is larger, the greater the use of electricity, heat, the more obvious. Combined with the summer sunshine violent, degree caused by high temperature heat dissipation is difficult. To solve the problem of heat dissipation, from LED Display appearance design and internal structure adjustment, the hollow out design, high density and high precision design circuit boards. Internal macro void design, do not produce 10 points, not cause electrical system. Without fan, reduces the LED circuit load, internal and external combined to achieve efficient heat dissipation effect.

Third: installation specification

LED Display belongs to high power electric appliances, prone to short circuit. But really qualified LED Display from the wire to the structure of short circuit phenomenon. However, during the installation process a little carelessness and negligence may cause unexpected danger. In order to ensure safety, need manufacturer to the installation guide, ensure that connect to the cathode, to ensure that the circuit connection is firm, at the same time to remove combustible surrounding the LED Display . And regularly arranged to test the LED Display , the professional and technical personnel.


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