The Facts About Electronic Message Centers


Introduction

The dynamic capabilities of electronic message centers using light emitting diode (LED) technology continues to attract more and more customers. Schools, fire districts, and churches use this affordable, reliable and flexible medium to advertise events, circulate information and reach out to communities with public service announcements.

A number of suppliers manufacturing LED systems have emerged in response to this rising market demand. How can the quality of the displays they offer be evaluated? This portion of our website provides you some critical points to consider when assessing an LED electronic message center:

LIGHT EMITTING DIODES (LEDs)
Critical characteristics

LED DISPLAY LIFETIME
What affects LED display lifetime

LED COLORS & INTENSITIES
Requirements of different LED colors

LED DISPLAY CONTRAST
Effects of good and poor contrast

LED DISPLAY DIMMING
Suitable dimming for readability in all conditions

LED DISPLAY COLOR DEPTH
Determining available colors

VIDEO
What constitutes a video-capable display

ELECTRONIC MESSAGE CENTER INDUSTRY
Characteristics of a reliable supplier

QUESTIONS TO ASK A POTENTIAL SUPPLIER
About their ELECTRONIC message centers

 

 

LIGHT EMITTING DIODE (LED)

"LED" is an abbreviation for "light emitting diode". An LED is a solid-state electronic device that emits light when energized by applying power. The LED die is mounted to a lead frame which is encapsulated in an epoxy lens. The epoxy lens directs the emitted light and protects the LED die from physical damage. A lead frame provides the electrical connections, the physical mounting and a thermal heat sink to remove the heat generated within the LED. A display manufacturer must have an in-depth understanding of LEDs and their properties, as well as use high-quality components in order to develop effective designs that stand the test of time.

WHAT WE DO:

• Daktronics uses LEDs from the industry’s leading suppliers and only from suppliers capable of meeting our specifications for brightness, longevity, and color standards.
   
• Toth’s Sports utilizes LEDs from Daktronics. Daktronics uses more LEDs than any other display manufacturer.*
   
• Daktronics has excellent relationships with the top LED manufacturers in the world.
   
• Daktronics contributes to the research and development efforts of our LED suppliers, spending significant time at their facilities reviewing processes, communication market needs and discussing development paths.

*"Daktronics is the #1 user of NICHIA light emitting diodes in the LED display market in America" --Hideki Kaneguchi, Manager at Nichia Corporation

"Daktronics is an AVAGO (formerly Agilent) Premier Partner. Premier partners are long-term, high-volume Avago customers." --Jovani Torres, Regional Manager at Avago Technologies



LED DISPLAY LIFETIME

The operational lifetime of an LED display is determined by the lifetime of the LEDs. LED manufacturers estimate the LED lifetime to be 100,000 hours under certain operating conditions. LED display end of lifetime is when the frontal brightness has decreased to 50% of original brightness.

Three primary factors determine LED lifetime:
--Manufacturing process of the LED
--Driving (powering) method of the LED
--Temperatures present at the LED die during operation

LED thermal management is vitally important to maintaining LED lifetime. Increasing the power through an LED increases brightness but reduces its lifetime due to increased heat generation. Increased exposure to higher temperature also shortens the lifetime. LED thermal management can only be done through the LED lead frame by conducting heat to a Printed Circuit Board (PCB) and by allowing airflow to cool the LED lead frame.


Led display components must be designed to handle a wide range of outdoor environmental factors, such as temperature and humidity. All components must be coated to protect from possible corrosion.


WHAT DAKTRONICS DOES-- Toth’s Sports utilizes Daktronics LED modules.

• Daktronics designs and manufactures its own LED modules to ensure the consistency and quality of the manufacturing process.
  --Some display manufacturers purchase LED modules from low-cost manufacturers, who many times have sacrificed quality to ensure lower cost.
   
• Our LEDs are mounted directly to a Printed Circuit Board (PCB) that is installed as part of the cabinet construction. This allows ventilated air to cool the PCB and lead frame, thereby cooling the LED die and providing thermal management of the heat to maintain LED lifetime as recommended by the LED manufacturers.
  --Some manufacturers encapsulate the entire LED lead frame in a pixel separate from the cabinet, not allowing the LED to cool through the lead frame.
   
• Our display modules are manufactured using a module-coating process that protects the displays to lengthen their lifetimes.
  --Some manufacturers skip this process to cut costs.

 

LED COLORS AND INTENSITIES

The color and brightness emitted by an LED are determined by the chemical composition and construction. Single-color (monochrome) displays are made up of one color of LEDs, whereas full-color displays contain LEDs that emit red, green and blue light. The color efficiency of the human eye has different sensitivity to different colors, and therefore perceives the brightness of each color differently.

The number of LEDs alone does not determine the brightness. The design, quality, brightness, lens, and viewing angle of the LEDs, as well as the drive method and contrast of the module, determine the overall brightness of a display. In fact, using more LEDs per unit area creates more heat and therefore requires more cooling.


WHAT WE DO:

• Our electronic message centers are designed for proper color efficiency matching which provides a red, amber, or full-color display with uniform intensities.
  --Some manufacturers design displays for the same brightness for all colors, which creates red displays that are too bright and amber displays that are not bright enough.
   
• Our electronic display LEDs are powered according to manufacturers’ specification and use the optimal number of LEDs required for the application.
  --Some manufacturers suggest that more LEDs create a brighter and therefore better display, but as noted above, this may not always be the case.

 

LED DISPLAY CONTRAST

Along with the proper brightness, a display must have high contrast for good readability. Contrast is the difference between the background’s "off state" (blank display area) versus the "onstate" (illuminated display area). High contrast increases the readability of a message, much like white text on a black background, causing readers to focus on what needs to be seen. The highest contrast appears in a display with a dark border and a consistent dark black background across the entire display with minimal sunlight reflection. A louver system provides shading and black, non-reflective materials ensure the least amount of reflection. Polycarbonate or acrylic face material may provide sufficient contrast, although with a potential for glare, but does not provide as high a contrast as flat black paint or a black potting encapsulant.


WHAT WE DO:

• Our LED modules feature a full-length, seamless black louver system across the entire module, providing a consistent contrast across the complete display face.
  --Some display manufacturers use individual louvers over each pixel or LED, which produces a pixilated effect and adversely affect uniform contrast.
   
• We offer different display products with carefully selected face materials, each having a preferred application and quality of image.
  --Some manufacturers offer customers a limited selection of face materials.

 

LED DISPLAY DIMMING

For maximum effectiveness, an electronic message center must have the capability to adjust brightness levels for correct intensity and high contrast according to ambient light conditions during any time of the day. At night, during lower light conditions, an electronic message center that is too bright due to inadequate adjustment may be worse than a display that is too dim. An overly bright display can be distracting and difficult to read, which can damage market appearance and result in stricter sign codes.

A good electronic message center control system should have multiple dimming control methods including: automatic dimming as determined by ambient light conditions, scheduled dimming that can be preset to adjust at scheduled times and manual dimming that instantly adjusts the brightness. Scheduled dimming is required when an auto dimming system must be overridden to meet certain conditions or as sign codes require.


WHAT WE DO:

• To ensure effective dimming, our electronic message centers feature these capabilities: automatic dimming through a light sensor, scheduled or manual dimming through software control.
  --Not all manufacturers have options for automatic dimming or scheduled dimming, resulting in an overly-bright display that will be difficult to read.
   
• Our electronic message centers dim to an optimal level according to current ambient light conditions using many levels of dimming to provide superior readability and maximum effectiveness of the display.
  --Many other manufacturers’ displays don’t dim low enough in dark conditions, or don’t provide multiple levels that allow a wide range of dimming, resulting in unclear content and diminished effectiveness.

 

LED DISPLAY COLOR DEPTH

"Dimming" and "shading" refer to entirely different functions and the terms should not be interchanged. The word "dimming" refers to a uniform brightness adjustment across the entire display to correct intensity for ease of reading during different ambient light conditions. "Shading", or color depth, affects the light output variations of each red, green, and blue LED to create images within the display.


COLOR DEPTH CHART

Each individual red, green, and blue LED can be in one of two states, either on or off. This example uses a color data processing of 5 bits for each color. So, each color is 2 to the 5th power and multiplying each color’s depth provides the overall color depth of 32, 768 colors.

Although "dimming" and "shading" have different meanings, some manufacturers will combine greyscale shading values with dimming values to create color specification that appears more impressive on paper than it is capable of producing in the field. Combining shading values with overall values is a deceiving and misleading practice.

WHAT WE DO:

• Our electronic message centers are available in no shading monochrome, 64 shades monochrome, 32,768 colors RGB or 68 billion and 4.4 trillion colors for video displays.
  --Many other manufacturers will combine shading and dimming values to create a more impressive number. This practice can be deceiving.

 

VIDEO

Video can be described as displaying a moving image, which is made up of many individual frames played at a fast rate. Good video is played at 30 frames per second or higher. Slower rates can begin to look choppy and affect the presentation quality.

Video content can be "live", such as from camera feed, or "pre-produced", such as previously recorded live feeds, or previously created content. The LED display industry generally defines fully capable video displays as being capable of both live feeds and pre-produced, or stored content, whereas graphic messaging displays are only capable of pre-produced, or stored content. Many LED display applications do not require the live feed capability or complexity of these systems. The higher the level of expectation, the higher the required display capability.

Video graphical frames require high pixel counts and color depth to provide good definition for highly detailed, accurate and recognizable images. Video clips can be run on small displays with minimal color depth, but the image will look pixilated and will lack definition; however, the results may be acceptable for certain applications. Color depth, or levels, is the amount of color available to portray the image. Most digital video content in 16.7 million colors, but more levels of color depth are recommended to provide proper color matching to the original image. Video purists suggest a minimum of 1 billion colors for the best video images.


LED MESSAGE CENTER INDUSTRY

Since the advent of high-brightness red, green, and blue light emitting diodes in the mid-1990’s, many firms have entered the LED display manufacturing industry, and many have failed. To be successful in the industry, a company must provide dependable displays capable of showing high-quality imagery, control systems that offer creation and management of content appropriate for the needs of each particular customer and ongoing support for many years.


WHY WE CHOOSE TO USE DAKTRONICS BRAND ELECTRONIC MESSAGE CENTER COMPONENTS

• Dedicated to the electronic display industry since 1968.
   
• Since 2001, independent market research firm iSuppli Corp. lists Daktronics as the world’s leading provider of LED displays.
   
• Daktronics LED displays are constructed in Brookings, S.D., United States, on one of the largest manufacturing floors devoted to building LED displays in the industry. Manufacturing space expands as needed, in response to changing market needs.
   
• Daktronics is committed to continued investment in research and product development to expand the market.
   
• Daktronics is a financially stable, publicly traded company that will be around for years to come to support your Daktronics display systems.
   
• Daktronics offers a comprehensive set of service options and maintenance agreements to keep customers’ display systems operating at maximum impact.