So many ever changing display technologies and applications, where do you start?
It is difficult to keep up with all the possibilities and options. However, there are certain foundational principles that should be generally known and applied as is appropriate to the circumstances of any digital sign project. This document attempts to share some guidelines for applying those principles.
The purpose of this document is not to assign roles to the reader. The Electronics Division will make design decisions based on their expertise with regard to matching appropriate technology to project needs. However, this document gives the reader an idea of the most common parameters that need to be taken into account before suggesting a particular solution.
Digital signage may include, but is not limited to, LED displays, LCD monitors, video walls, video processing systems, control systems, computer systems (hardware and software), computer network systems, electrical systems, audio systems (in rare cases), etc.
Research & development testing is required before vetting new technology, a new vendor, or a new integrated system for a specific project. This is done internally by Ad Art Electronics staff. Specifying a system requires understanding of the customer’s goals and intent, existing conditions, and what current technology works well together to form a system that will meet design requirements. Although calculations are involved, determining the best system is not formulaic. Accurate information must be gathered in order for human intelligence to make a sound decision. For every project, vetted technology is matched with the needs of the project.
How is information gathered? Ad Art sales and support staff is instrumental in gathering required information in order for the Electronics Division to make solid recommendations. Staff will perform a preliminary site survey, an electronics job analysis, and technology selection review before specifying a product and estimating costs.
For outdoor digital signs, sunlight is a major factor in design. What direction the sign faces has a direct bearing on how bright it needs to be in order to avoid washout from the sun. In the Northern Hemisphere, signs facing North are usually shaded all day, so brightness is not much of an issue. South facing signs are the worst case scenario because they will be exposed to sunlight all day, all year round (in summertime the sun is high in the horizon, in wintertime the sun is low in the horizon). East and West facing signs are partially exposed to the sun all year round, with varying intensities occurring as the sun rises and sets. Geographically, some areas have bright sunny days most of the year, while other areas are overcast. The environment may affect exposure to the sun as well - i.e. if the sun will be blocked by large buildings in a downtown area. To combat exposure to the sun in cases that warrant it, high brightness or high contrast LEDs may be specified, which will increase cost.
How the display is intended to be viewed is another design factor. Will the viewer be standing, walking, or driving in a car? How close will they be permitted to view the sign, at what angles, and for how long? The answers to these questions will help the Electronics Division to specify a product with an appropriate viewing angle.
In display technology parlance, viewing angle is the maximum angle at which the display can be viewed with acceptable visual performance. The image may seem garbled, poorly saturated, of poor contrast, blurry or too faint outside the stated viewing angle range; the exact mode of "failure" depends on the display type in question. The viewing angle is measured from one direction to the opposite, giving a maximum of 180° for a flat, one-sided screen. Some display devices exhibit different behavior in horizontal and vertical axes, requiring users and manufacturers to specify maximum usable viewing angles in both directions. Usually the screens are aligned and used to facilitate greater viewing angle in horizontal level, and smaller angle in the vertical level, should the two of them be different in magnitude.
With LED displays, Ad Art typically specifies either thru-hole (DIP) or surface mount (SMD) LEDs for a given project. Usually, it is the viewing angle requirement that drives the decision. SMD LEDs allow for a greater viewing angle than DIP LEDs, but are less bright when viewed directly because the light energy has to be spread over a wider angle.
The display resolution is the number of distinct pixels in each dimension that can be displayed. A “pixel” (a word invented from "picture element") is the basic unit of programmable color on a digital display or in a computer image. The physical size of a pixel depends on the design of the LED screen. “Pixel pitch” refers to the horizontal and vertical distance between each pixel in a grid formation. An LED display's “resolution” is its total number of pixels based on a combination of pixel size and pixel pitch. The more pixels there are, the more detail an image being displayed can have.
Resolution is usually quoted as width × height, with the units in pixels: for example, 1920 × 1080 means the width is 1920 pixels and the height is 1080 pixels.
Depending on the pixel pitch of the display, a greater or lesser minimum viewing distance is possible before an image becomes “pixelated.” That is to say, there is a minimum distance whereby the human eye with natural or corrected vision of 20/20 can clearly distinguish individual pixels on a particular display. A general layman’s rule of thumb says that distance is roughly 3.5x the distance in feet as the pixel pitch is in millimeters. For example, if a display was manufactured using a 5mm pixel pitch, you would clearly recognize individual pixels on the display at about 17.5 feet and closer (3.5ft x 5 = 17.5ft).
Minimum Viewing Distance Where Pixels Start to “Blend” Using Common LED Pixel Pitches
|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|
Of course, the minimum viewing distance is not the maximum viewing distance (or “Retina” viewing distance). The maximum viewing distance is where the human eye with natural or corrected vision of 20/20 can no longer discern individual pixels on a particular display. Standard visual acuity (20/20) in the US or (6/6) in the EU is the ability to discern two points separated by one arc minute. About 300 pixels per inch at 25 cm. This translates to 12 pixels/mm at 250 mm distance.
A general layman’s rule of thumb says that the maximum viewing distance of direct view LED displays is roughly 8x the distance in feet as the pixel pitch is in millimeters. For example, if a display was manufactured using a 5mm pixel pitch, you would begin to lose visual acuity at 40 feet and further. (8ft x 5 = 40ft).
Power connectivity is the responsibility of the customer. The Electronics Division needs to know how the sign electronics will connect to power in order to accurately design the system. At a minimum, we need to know what voltage, amperage, phase, and wire count is feeding the electrical panel that will feed the sign(s). If there is not enough existing power to meet the requirements of a particular digital sign proposal, then either the sign design will have to change or more power will need to be brought to the site.
Data connectivity is the responsibility of the customer. Typically, it is best practice to require the customer to house control equipment in a climate controlled room and provide a wired data connection (either fiber optic or CAT6) from wherever the control computer will be located to the sign location.
It is best to locate control equipment in a building, preferably mounted in a rack in a data-com room. The room must have a 120 VAC outlet for power and an RJ-45 network jack available that will allow the computer to be connected to the Internet. If digital signage is indoor, it is preferred to locate the control computer near the location of the display.
In order for the sign controller computer to be remotely accessed for content management and maintenance, an Internet connection is required. If the computer is attached to an existing LAN, it is the customer’s responsibility to provide connectivity to their existing network that allows the computer to access the Internet. Wired connections are best practice. If this is not feasible, then wireless Ethernet or cellular technology can be used. We only specify wireless Ethernet communications as a last resort, since that forces the control computer to be housed at the sign location. This may cause durability concerns, security concerns, and reliability concerns when the display is outdoors. Wireless is a less reliable communication method than wired, with more points of failure, and requires more maintenance.
We require a CAT6 cable to be run from the sign controller computer to the LED Display cabinet (in conduit for outdoor applications). It cannot exceed 330 feet. We highly recommend a secondary CAT 6 cable be provided to serve as a redundant backup. Sometimes, the conduit for data cable can be run in the same trench as electrical cable runs. If the distance exceeds 330 feet, then fiber optic should be used.
The principles for designing an LCD screen system are basically the same as those for designing an LED system with a few comparison amendments, such as:
The electronic display is a main part of the system, but other components are necessary to have a functioning digital sign. In order to display the right content at the right time you need (at minimum):
Ad Art has vetted 3rd party products that exceed the needs of most use cases for the above system components. In addition, Ad Art has developed proprietary computer systems that provide stable, reliable playback of content and allow for secure remote support.
Ad Art is able to specify, test, and validate any product from any vendor in order to custom design a control system. However, Ad Art has chosen standard, approved vendors because of the value their products provide. This allows Ad Art to streamline a cost effective solution for most use cases. Some supported vendors are:
Below are outline statements and some common questions that come up during various stages of a digital sign project. Although not all questions apply to all jobs, it is good to have them in mind. They serve as a mental prompt to make sure nothing is being overlooked when it comes to designing a system. The answers to some questions are required in order to specify an appropriate solution and accurately estimate the cost of a project.
It is important for the Electronics Division to understand exactly what the customer wants and needs. There may be technology out there that the Electronics Division is aware of that proves to be a better fit than what is known to sales staff. Some questions that may need answering are:
Content is a central parameter to matching technology to a project. The choice of content plays a significant role in determining the display resolution, control system capabilities, content management system, network connectivity, and other factors. Some questions that may need answering are:
In order for a digital sign project to succeed, Ad Art, its partners, and end customers all must fulfill their respective roles. These roles must be clearly defined and understood by each party and for each project. Requirements also need to be defined. Ad Art will impose certain requirements on the end customer and the customer may have requirements that Ad Art must meet in order for the project to be successful. In most cases, requirements are negotiable.
Power connectivity is the responsibility of the customer. Therefore, Ad Art will provide the customer with power requirements of a specified system when new power must be brought to the site. If there is existing power onsite already, power requirements may need to be adjusted based on availability. This could completely alter the system design. In such cases, Ad Art will need to know:
Data line runs and Internet connectivity are the responsibility of the customer. Therefore, Ad Art will provide the customer with data requirements of a typical system. Ad Art typically requires that digital control equipment and computers be housed in a building that is climate controlled with sufficient 120VAC power receptacles. When that is the case, Ad Art typically requires that the customer provide a hard wired data connection from a sign computer or controller to the display screen. The customer is also required to provide the control computer an Ethernet connection to the Internet. In some cases, these requirements cannot be met. For example, a hard line may not be not possible because the customer cannot afford to demolish an existing concrete parking lot to dig a trench, or the control equipment will need to be housed in the same enclosure as the display, or the customer may not have an Internet connection available near the digital sign. Ad Art may provide alternative design options that are not optimal, but still may allow the system to work. In such cases, Ad Art will need to know:
Oftentimes a customer will provide a “Request for proposal” document (RFP) that outlines their requirements for an upcoming sign project they wish competing companies to bid on. Even when that is not the case, customers usually impose requirements to simply satisfy the intent and purpose of the digital sign they want constructed. Below are questions that could be asked regarding customer requirements:
Typically, Ad Art provides a standard one year parts and labor warranty for all electronic display system components. Sometimes, the customer requires an extended warranty with specific terms and conditions. In such cases, Ad Art will need to know:
Existing conditions have a huge impact in regards to applying the best display technology to a project. The main purpose of a preliminary site survey is to record any and all existing conditions that will affect the choice of display(s). Some questions that may need to be answered are:
It is good to define a preliminary scope of work at this stage so as to keep focused on a system design that fits what is proposed. A scope of work summary can be derived from a consideration of the above questions and feedback from the customer.
After considering the above questions, and no doubt other factors, the Ad Art Electronics Division will recommend a display system based on their expertise that best fits the needs of the customer. However, their choice is often based on factors that follow general design patterns. The below bullet points outline some of these patterns:
We are committed to providing you with information that will help you make an informed decision. If you need further explanation or support, please feel free to contact us. We are available to assist with questions or issues not covered on our website.
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