Display Array (Rows and Columns)
An LED sign is made up of an array of dots or pixels. The array is described by the number of dots vertically and the number of dots horizontally. For example, 16 X 80 means that the sign has 16 dots vertically and 80 dots horizontally. The characters and graphics of a message are formed by turning on or activating specific patterns of pixels within the display array. A sign is defined by its display array Ė the number of rows and columns of pixels. A sign with a 7x80 display array has 560 pixels.
LED - "Light Emitting Diode"
An LED is a tiny chip of silicon made to produce light in a variety of colors including red, green, yellow, and blue.
Data Block Module
Data block modules are LED's mounted on rectangular circuit boards and epoxied into block modules that contain a specific number of rows and columns of pixels.
When a brighter pixel is needed, multiple LED's are assembled in "clusters" of LED's that together form one pixel point when they are lighted. Multiple LED's are connected to a molded cup which is then filled with clear epoxy to hold the LED's in place. Clusters may contain one color LED or in a multi-color application the cluster may contain a combination of different LED's.
To simplify the assembly of larger signs and to permit more flexibility in the design and construction of signs, we produce subassemblies that contain a specific number of rows and columns of pixels.
The size of a pixel is stated by the diameter of the pixel. A pixel can be as small as a single .1" diameter LED.
Center to Center Spacing
The distance from the center of one pixel to the center of the next adjacent pixel is called "Center to Center Spacing" or "Pitch".
The output intensity or brightness of an LED is measured in millicandela. The most common technique used in indoor displays to get the greatest range of brightness is called "multiplexing". The LED's are strobed rapidly, faster than the eye can detect, one at a time. This method limits the brightness of each pixel since the pixel is only turned on for a sequence of brief instances. When an LED is latched on, it is lighted continuously until it is turned off again. This produces brighter pixels. Data block modules can only be multiplexed; discrete clusters are usually latched.
Resolution or Density
Pixel diameter and center to center spacing define the resolution or density of the character being displayed. The closer the pixels are to each other, the higher the resolution or density of the character. Low resolution characters are designed for distance viewing.
How many pixels to form a character?
For a single stroke character, it takes 7 pixels high and 5 pixels wide, plus the spaces between characters and lines.
- Indoor - A rule of thumb is that for every inch of character height, the viewing distance increases by 50 feet. For instance, a 2" character can be read from 100 feet and a 12 inch character can be viewed from 600 feet.
- Outdoor - The size of the sign and the size of the characters are defined by the applications usage. A rule of thumb for determining how large characters must be to be easily read is to allow 50 feet of distance per readable inch or to allow 600 feet of distance per foot of readable text. Example in order to read a message on a sign 600 feet away, the characters and graphics in the message must be at least 12 inches high. The rule of thumb for messages viewed from an automobile is that an 18" character is required if traffic is moving 35 miles per hour, and a 12" character is required if traffic is stopped.
- Indoor - 2 inch and 4 inch high characters are commonly used in most interior applications. In warehouses or manufacturing environments, where signs are to be viewed from greater distances, 4" or 7" characters work best.
- Outdoor - 24 inch high characters are excellent for long distance freeway viewing. 14" characters are used on fast-paced streets and highways. On surface streets where traffic is slower and stopped near the sign, 8.5 inch and 12 inch characters are used.
Characters per Line
The number of characters on a line of a sign is determined by the number of pixels across the sign and by the size of the character. A normal character is 5 pixels wide. One pixel space is used to separate characters. Thus, an 80-column sign will display 13 characters (80/6= 13.3). As you plan out your sign requirements, write down the messages that you intend to display on the sign. Count the characters in the words that you use most often. How many words do you want to see at once? This determines the number of characters per line required by your application. If a word wonít fit on the line, the word displays, one character at a time, or it starts a new line, depending on the display mode being used.
Red or Color
For simple informational signs, red is often sufficient. Color adds interest and contrast over a monochrome red-only sign. The green and amber colors are considered softer colors and may be more appropriate for some environments. Color signs can be 3 color, (red, amber, and green), 9 colors, (additional shades of red, amber and green), 256 colors, (mixes of red and green) or 262,000 or 4,000,000 for full color displays.
Foreground and Background Color
Some signs allow you to set the color of the background or the foreground color. In a red only sign model, this would enables you to have red text on a black background or black text on a red background. In a multi-color sign, you could have a variety of text colors and a variety of background colors. Keep in mind, however, that certain colors and color combinations are more readable and visible than others. The elaborate combinations generally work better at night. In bright sunlight, bright colors on a black background are the easiest to read.
Most signs have built in computers with a certain amount of message and graphics storage capacity. Memory storage capacity ranges from 7,000 characters to 1,000,000 characters and more, depending on the sign and the application. Graphics require more storage capacity than messages do.
Most signs have battery-backed up memory and time. If the sign is turned off, unplugged or moved, the messages, graphics and time settings that were stored in the signís memory area are not lost. When the sign is plugged in again, the message, graphics and time that were in memory resume displaying.
This is the process of composing your message and graphics and specifying the display modes, fonts, colors, and location of text and graphics on the display screen.
Hand-held Remote Programming vs Computer Programming
Many signs come with their own programming keyboard. They also offer a computer programming option. As a rule, it is easier, faster and less error-prone to program a sign using a computer than it is to use the remote keyboard. The longer your messages the more tedious it is to use a remote keyboard, since the message must be edited and manipulated in the memory of the sign, rather than on the screen of the computer. Messages and graphics can also be more easily lost when the remote keyboard is used. See our document "Programming Options" for a more detailed discussion.
Programming Animations and Graphics
Some sign software provide graphics and animation design capability. Other signs accept the output of graphics design programs, such as Paint Shop Pro or Animator Pro. The sign keyboard can also be used to design dot patterns, although this is somewhat tedious and the work is vulnerable to being lost by a careless programmer or operator. It is advisable to use a computer to compose graphics. Then you can save your work in a disk file.
Most programmable signs offer a variety of message entry and exit modes or special effects. The most common display mode is the ticker tape mode made popular by stock ticker displays. Other popular display modes are hold, flash, scroll, roll, wipe, twinkle, sparkle, snow, spray, spin, starburst, turn page, shrink, explode, switch and interlock.
There are a variety of ways to connect a sign to a computer:
- Cable - The simplest connection is a cable connection between the Serial Port of the computer and the sign. There are several cable connection options. These are discussed more fully in our document, "Sign Networks."
- Modem - If cabling is difficult or impossible due to site restrictions, using a Modem is a second option. The messages and graphic programs are transmitted from the modem on the sending computer to the modem in the sign over normal telephone lines. When a message is sent, the program automatically dials the phone number of the sign modem. The telephone line can be a line provided by the phone company, or it can be an extension on your internal phone system. A modem connection is generally used when it is easier to get a phone line to the sign location than it would be to pull a cable of your own there. Modem connectivity is also used when programming needs to be done remotely.
- Ethernet - Some signs now support TCP/IP and can receive communication via a companyís Local Area Network (LAN).
Graphics vs Text
Text-only applications can be accomplished with signs with as little as one line of text. Graphics require more height to accurately display logos and animations. Graphics look best when the sign is at least 24 pixels high.
Animations vs. Graphics
A graphic is a pattern of pixels, often displayed in one position, such as a company logo or an identifiable product, such as a car or light or shoe. An animation is a sequence of graphics that have been designed to operate together to give the illusion of motion, such as a walking shoe, or a moving car, or a light turning off and on. Most signs will display both animations and graphics. Some signs have animations and graphics built in. Other signs require that you insert the animation or graphic in your message and transmit the animations and graphics to the sign when you transmit your messages. See also "Programming Animations and Graphics."
Time and Temperature
Most signs will update and display the time, if you include a Time feature in your message. Outdoor signs will also display the Fahrenheit or Celsius temperature. A temperature sensor is provided on a long cable. It is important that you position the temperature sensor out of direct sunlight and away from any heat generating sources, such as the sign itself, or building surfaces that heat up in the sunlight to avoid displaying the incorrect temperature. Signs that display temperature provide a calibration feature that allows you to correct the temperature up or down by degrees if necessary.
LEDís vs other types of Bulb Technology
LED's are significantly less expensive than incandescent lamps. LED's are also less expensive than monitors over a life of 10 years. LED's have an expected life of more than 100,000 hours or from 11 to more than 20 years. The longer life dramatically lowers maintenance expense compared to monitors or lamps. LED's need very little power and generate less heat than other light sources. Less power and heat mean less operating and maintenance costs. LED's are small and lightweight. This lowers the cost of the enclosure and installation.
Indoor vs Outdoor Brightness
An indoor sign should not be used in an outdoor application or a window application. First, the indoor sign is not bright enough to be seen in bright daylight. Outdoor signs should be at least 100 times brighter than Indoor signs. Second, the epoxy material that indoor LEDís are made of is not designed to be exposed to sunlight. UV light will turn the LED plastic dark within a relatively short time. The effect of this is to dramatically reduce the brightness of the display. If a sign must be read in daylight, it must use superbright LED technology that is designed for UV exposure. The brightness of each pixel should be at least 800 millicandela, and the brighter the better. Some of the brightest outdoor brightness signs are rated as high as 10,000 millicandela per pixel. Indoor signs usually have a brightness between 10 to 100 millicandela per pixel. Make sure that your sign is designed for an outdoor or window application.
Interior vs Exterior Enclosures
An indoor sign enclosure is not acceptable for an exterior application. The electronics of the sign must be protected against damage from heat, cold, moisture, and airborne contaminants such as dust, salt and smog components. If a sign is to be used in an exterior environment, it should have an exterior enclosure designed to withstand the weather and environmental conditions where it is being used. Donít overlook sprinkler systems and maintenance workers that use high pressure water hoses to clean windows and fixtures. Every sign should be protected against moisture.
A string file is a Protocol term used by Adaptive Micro Systems to describe a variable in a message. This variable may be updated independently of the rest of the message, and updating of the variable does not cause the sign to blink. Most Alpha and BetaBrite signs can be programmed with as many as ___ string files.
The internal instruction language used by Alpha, AlphaVision, BetaBrite, Eclipse and Solar signs.
All the following terms (and others) are being used interchangeably by various users as names for our product.
Moving Message Display
EMC (Electronic Message Center)