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LED SIGN BASICS

How to choose an LED sign

What you need to know about a suitable electronic for your business

What is an LED display?

An LED sign consists of a matrix of individual LED lights (LED pixels) that are individually controlled to make text, picture or video images. The LEDs are placed close together and from a short distance the individual LED colors (RGB) begin to blend together so you no longer see the individual LEDS (pixilation).

The Basics

Before selecting an LED sign you need to understand the basic parameters and why they are important to understand. These parameters are Pixel Pitch, Matrix, Viewing and Reading Angle,Viewing Distance and Viewing Time. The above parameters determine which type of sign is best suited for your business. Let's start with the general information and concepts of LED signs.

LED Pitch

The led pitch is the center-to-center spacing  of the LEDs in an LED display. A smaller led pitch means there is less space between the pixels and therefore, more pixels in a given area. More pixels results in higher resolution and higher image quality.
 
Viewing distance is the main factor in determining the pixel pitch. For indoor LED signs with short viewing distances and stationary viewing a high resolution sign is appropriate (2mm to 10mm led pitch). For outdoor signs with short viewing distances, 8mm and 10mm led pitch are recommended and for distant viewing with moving traffic 16mm and 20mm pitch signs are mostly used.

 

Display Matrix

The display matrix is the number of LEDs that make up a sign, (height x width). The display matrix
is determined the number of LEDs that will fit into a specified area. As the LED pixel size decreases, more LEDs will fit into a given area so the matrix size will increase.
 
RGB Color
Color LED Displays are made up of 3 separate color LEDs, 1 red, 1 green, and 1 blue which when viewed from a distance combine to be seen as a single color. The distance at which this occurs is referred to as the viewing distance. This distance at which the colors combine is determined by the pixel size and as the pixel size decreases, the distance at which the colors combine also decreases.

 

Viewing Angle

 
For LED Displays, viewing angle is the maximum angle at which a display can be viewed with acceptable visual performance. LED Displays are brightest when viewed straight on and become less bright and less readable as the viewer moves away from center.
 
The viewing angle is measured from side-to-side, and will be given as the maximum degree from center that the sign can be viewed. Some LEDs exhibit different behavior in horizontal and vertical axis, and manufacturers will specify maximum usable viewing angles in both directions. Usually the LEDs used for signs will have a greater horizontal viewing angle, and smaller vertical viewing angle.
 
 
 
While in most applications a wide viewing and is preferred, in some types of signs, such as traffic signage, a narrow viewing angle is used, to direct the message at the intended viewer to minimize confusion. 

 

Viewing Time and Distance

When choosing a LED sign you must consider viewing time and distance. As the distance at which the sign will be viewed increases, the character height must also increase. As a rule of thumb, for every inch of character of height, the viewing distance increases by 50 ft. If you are aiming at a stationary audience, such as traffic at a stop light or shopping center, you can choose smaller size with higher resolution (pixel pitch). If you are aiming at moving traffic, the viewing time will be less so you need a larger size display.

Viewing Time

If your sign will be viewed from a moving vehicle you must consider viewing time. As vehicle speed increases, the time the viewer has to see the sign decreases so you must increase the character or pixel size to make it readable and to have a better impact on viewer.

Pixel Size Character Size Max Viewing Distance Max Viewing Time (seconds)
20mph 30mph 36mph 60mph
inch mm Feet Meters 30km/hr 50km/hr 600km/hr 100km/hr
8mm 2.2'' 56mm 110 34m 3.8 2.5 2.1 1.3
4.4'' 112mm 220 68m 7.5 5.0 4.2 2.5
10mm 2.75'' 70mm 137 42m 4.7 3.1 2.6 1.6
5.5'' 140mm 275 84m 9.4 6.3 5.2 3.1
16mm 4.4'' 112mm 220 68m 7.5 5.0 4.2 2.5
8.8'' 224mm 450 138m 15.3 10.2 8.5 5.1
20mm 5.5'' 140mm 275 84m 9.4 6.3 5.2 3.1
11'' 280mm 550 169m 18.8 12.5 10.4 6.2
25mm 7'' 175mm 350 108m 11.9 8.0 6.6 4.0
14'' 350mm 700 215m 23.8 15.9 13.3 8.0

 

Controller Types

There are 2 types of LED Sign Controllers, Synchronous and Asynchronous

Synchronous Control

Synchronous Control requires a computer to be connected directly to the LED display and operating full time. This is type of control method is best suited for large billboards, Video backgrounds for stages, and scoreboards where you require, direct video feed, large memory capacity, real time control, or are running 3rd party software or hardware (direct video or RSS feed). Since Synchronous Controls are computer based, it is easy to upgrade the hardware and add additional software apps. The computer can be located in an office or inside the sign cabinet. When the computer is located in an office or control room, data cable is needed to connect to the sign. If mounted in the LED Display cabinet, the computer will still require a data connection (wired or wireless) and will be subjected to harsh environmental conditions (summer/winter temperature extremes), dust and humidity.

Asynchronous control

Asynchronous Controlled Displays use an Embedded Micro Controller located within the sign cabinet. They are meant for autonomous operation with all advertising data saved on internal flash memory then played back according to a programmed schedule. Asynchronous controllers are not suited for real time control and the hardware and software is not easily upgraded. The controllers are designed for harsh environments.

LED Pixel Pitch and Resolution

It is essential that you understand pixel pitch and relation between pixel pitch, resolution and viewing distance in order to make best decision according to your requirements, space and budget.

What is the pixel pitch?

The pixel pitch is the center to center distance of adjacent pixels measured in millimeters. In plain terms, pixel pitch is the spacing of the pixels in an LED display. A smaller pixel pitch means there is less space between the pixels and therefore, more pixels in a given area. More pixels results in higher resolution and higher image quality. The figure below illustrates the pixel pitch for a 16mm DIP LED module and a 8mm 3-in-1 SMD LED module. The 8m 3-in-1 SMD module has 4x the resolution as the 16mm DIP LED module.

How Pixel Pitch Effects Image Quality?

Pixel pitch determines the resolution, minimum viewing distance and best viewing distance of an LED screen. A smaller pixel pitch allows more pixels per square foot and results in a more detailed and higher quality image. If you need to show high resolution images or the display is to be viewed from a short distance, you need an LED display with a small pixel pitch. The following figure shows the pixel pitch effect on image qualitty.

16mm Pixel Pitch

10mm Pixel

8mm Pixel Pitch

How to choose the best Pixel Pitch size?

The best viewing distance is the shortest distance at which the colors blend together. A display with a large pixel pitch will have almost the same image quality as a smaller pixel, as long as the viewing distance is within the best viewing distance range for that pixel size. A smaller pixel will deliver you better image quality, but at a long distance the difference will be difficult to notice and the cost will be higher.

Take an LED sign with a pixel pitch of 10mm. The minimum viewing distance for a 10mm pixel is 30 ft (10m) and the best viewing distance is 60ft (20m) and above. So, if your audience will be viewing the display from 30ft to 160ft (10m to 50m) away, they will see an acceptable image quality with a fading level of pixilation from 30ft to 60ft (10m to 20m) and very good image quality after 60ft (20m). So while you could increase the image quality using an 8mm pixel, the benefit is marginal since the viewing distance of 30ft to 160ft (10m to 50m), is already within the recommended viewing distance for a 10mm pixel.

The following table gives the Minimum and Best Viewing Distance for different Pixel Sizes;

Pixel Pitch Minimum Viewing Distance Best Viewing Ditance
4mm 13ft (4m) ≥ 25ft (8m)
6mm 20ft (6m) ≥ 40ft (12m)
8mm 25ft (4m) ≥ 50ft (16m)
10mm 30ft (4m) ≥ 60ft (20m)
16mm 50ft (4m) ≥ 100ft (32m)
20mm 65ft (4m) ≥ 130ft (40m)
25mm 80ft (4m) ≥ 160ft (50m)

Choose the Right Resolution

Everyone's needs are different. Choose from 8mm, 10mm, 16mm, and 20mm pixel pitch

 
Pixel Pitch 6.67mm 8mm 10mm 16mm 20mm
Pixels per Sq Ft 2088 1452 929 363 232
Displayable Colors 281 Trillion 281 Trillion 281 Trillion 281 Trillion 281 Trillion
LEDs Per Pixel 1R/1G/1B 1R/1G/1B 1R/1G/1B 1R/1G/1B 1R/1G/1B
Viewing Angle 160 Degrees 160 Degrees 160 Degrees 160 Degrees 160 Degrees
Contrast Ratio 1000:1 1000:1 1000:1 1000:1 1000:1
Brightness >9000 nits >9000 nits >9000 nits >9000 nits >9000 nits
LED Life 100,000 hrs 100,000 hrs 100,000 hrs 100,000 hrs 100,000 hrs
Operating Temperature -40F to +140F
(-40C to +60C)
-40F to +140F
(-40C to +60C)
-40F to +140F
(-40C to +60C)
-40F to +140F
(-40C to +60C)
-40F to +140F
(-40C to +60C)
Graphic Capability Text, Picture, Video
(jpg, bmp, gif, swf, wmv, avi, mp4)
Text, Picture, Video
(jpg, bmp, gif, swf, wmv, avi, mp4)
Text, Picture, Video
(jpg, bmp, gif, swf, wmv, avi, mp4)
Text, Picture, Video
(jpg, bmp, gif, swf, wmv, avi, mp4)
Text, Picture, Video
(jpg, bmp, gif, swf, wmv, avi, mp4)
Control Software Options XM Player or       Pluto Manager
Windows OS
XM Player or       Pluto Manager
Windows OS
XM Player or       Pluto Manager
Windows OS
XM Player or       Pluto Manager
Windows OS
XM Player or       Pluto Manager
Windows OS
Compliance UL48-15, CSA C22.2 No. 207-15 UL48-15, CSA C22.2 No. 207-15 UL48-15, CSA C22.2 No. 207-15 UL48-15, CSA C22.2 No. 207-15 UL48-15, CSA C22.2 No. 207-15
Warranty 5 year parts / factory labor 5 year parts / factory labor 5 year parts / factory labor 5 year parts / factory labor 5 year parts / factory labor

LED Sign Communication Methods

One of the most important considerations for any electronic sign installation is how to communicate with the sign and will it be updated. There are many factors that need to be considered in determining the best communication method to use. To choosing which communication method suites your needs, you need to answer the following questions:

  • How often do you change the sign information?
  • What is the distance between your computer and the LED sign?
  • What is height of your sign and how accessible is it?
  • Can you provide data cable or Wireless Ethernet connection in the sign location?

There are many communication methods and each method has its advantages and disadvantages.

USB Flash Communication

USB Flash communication is the most basic type of communication. It requires you to export the new message data and sign settings to a USB flash drive and then go to the sign and manually upload the files from the USB drive to the sign.

USB Flash Communication for LED Signs

  

Advantage: Disadvantage:
This is the most basic type of communication. It requires no extra data cable or hardware that could fail, and is easy to repair and maintain. To use USB communication, you need to go to the sign to upload you messages which may not be convenient.

Data Cable Communication

Wired Data Cable communication uses a direct wired Ethernet connection (Cat5/6 or Fiber Optic) between the sign management computer and the LED sign. It is inexpensive, easy to install, and requires no extra hardware that may fail.

Data Cable Communication for LED Signs

  

Advantage: Disadvantage:
Wired Data Cable communication is inexpensive and is easy to install. When used outdoors, data cable is usually run underground in conduit. If there is no existing conduit, running new conduit for long distances or across sidewalks,and paved areas can be expensive.

Wireless Communication

Wireless communication has become the standard option for local communication to LED signs because it is inexpensive and easy to install. The sign management computer communicates with the LED sign directly using RS232 wireless or 2.4/5.0 GHz wireless Ethernet.

Wirelwss Communication for LED Signs

 

 

Advantage: Disadvantage:
Wireless communication is inexpensive, easy to set up and doesn’t require data cables to be run through your building or across parking lots. Wireless communication has a distance limit of 1000ft and there must be Line-of-sight between the transmitting and receiving antennas. The signal will not pass through buildings or go around corners.

Internet Communication

This communication method is best for controlling one or several electronic sign from a central location or from an off-site location. The sign management computer communicates with the LED sign through an internet connection. Each sign would would also require an internet connection either at the sign or from a near by building with a wired or wireless connection bridging the distance between the sign and building. There is no distance limitation between the controlling PC and the sign.

Internet Communication for LED Signs

  

Advantage: Disadvantage:
Can control one or several LED Signs or LED displays from any computer with the software installed and connected to internet. There is no distance limitation. Can use Secure TCP/IP. An internet connection needs to be provided both at the computer and location(s). There would be a monthly fee for the internet service.

Mobile Data - GPRS Communication

This communication method is best for controlling outdoor or mobile electronic signs from a far distance. The controlling software communicates with the LED sign through an internet connection, by uploading the message files to a Cloud Server. At the sign, the message files are downloaded from the Cloud Server using a controller that has mobile data (GPRS/3G/4G) connection.

3G/4G Communication using Cloud Server

  

Advantage: Disadvantage:
Can control one or several LED Signs from any computer with the software installed and an internet    connection. The LED Signs can be mobile or fixed.There is no distance limitation and it doesn't require any data cabling in the sign location.
Each sign would need to have its own mobile data plan, with a monthly fee.

LED Sign Cabinets

LED Sign Cabinets

One of the most important factors that is easily ignored when purchasing a sign is the sign’s cabinet structure. There are different types of cabinets and a LED sign cabinet should be carefully chosen based on the size, installation height, and accessibility.

The main concern when choosing a cabinet is maintenance. Considering the high cost of labor, lift equipment, transportation, work permits and more, a properly chosen LED sign cabinet can significantly save repair and servicing costs.

Outdoor Rear Service

Rear service cabinets have large access doors at the rear for electronic service. The cabinets need to be installed with sufficient space to allow the doors to swing open, 24” to 30” with no obstructions. Cabinets can be joined vertically and horizontally to make up any size sign. This type of LED cabinet is suitable for large signs and billboards.

Advantages:

  • Low Cost
  • Strong Body
  • No limitation for the sign height or length
  • The electronics can be serviced from a catwalk without the need for a bucket truck

Disadvantages:

  • Requires space in back for access
  • Modules still need to be removed from the front, requiring a bucket truck

Outdoor Front Open Service

Front hinged cabinets are made in two parts. The back side of the cabinet can be attached directly to a wall or structure, while the front door panel can lift up for service. This type of LED cabinet is suitable

for any application without space at the back for rear service access.

Advantages:

  • Easy Access for Repair and Service
  • With doors open all electronics are easily accessable

Disadvantages:

  • Sign height is limited 72 inches
  • Requires minimum 3” clearance top and bottom for the door panel to open.
  • Usually requires bucket truck for service

Front Removable Modules

Front Removable Modules are installed from the front and locked in place using a key. By eliminating the need for hinged doors the cabinets can be made slimmer and lighter. Cabinets can be stacked vertically and horizontally to make up any size sign. This type of LED cabinet is suitable for large signs and billboards.

  

Advantages:

  • Easy Access for Repair and Service
  • No limitation for the sign height or length
  • No mounting clearance restrictions at rear, top, or bottom
  • Suitable for High resolution LED displays

Disadvantages:

  • Requires bucket truck for service
  • May require multiple LED panels to be removed to diagnose problems