The following is a list of commonly used terms and phrases that pertain to LED
displays and how they work. You can scroll through the list or click on a specific term to
jump to that location.
The display area of a programmable sign is composed
of rows and columns of "pixels". The term pixel is short for
"Picture Element". The characters and graphics of a message are
formed by turning on or activating specific patterns of pixels within the display array.
An LED is a tiny chip of silicon made to produce
light in a variety of colors including red, green, yellow, and blue.
Bi-color LED's are made using red and green LED's
in the same package. Most indoor programmable LED displays today use either all red LED's
or they use red and green LED's. To a lesser extent all amber is sometime
selected. It is possible to create 256 or more shades of color from red to green using
only red and green bi-color LED's. Blue LED's are the most expensive and have
the highest brightness. Adding blue LED's to the red and green will give you
over 2 million shades of color.
LED (light emitting diodes) displays are described by the number of rows by the number
of columns. Example A 7x40 display has 280 pixels.
The pixel can be one or more LED's. A
discrete LED is one individual diode. LED blocks and clusters are multiple
LED's installed as a single unit.
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.
Individual LED's are inserted one at a
time into a circuit board. The anode and cathode lead wires are then
individually soldered to the circuit board. A pixel may be composed of either
one LED or several LED's installed close together. LED's grouped together
appear as a single pixel when all LED's in the group are lighted at the same
time. A group of LED's in a single pixel may contain more than one color
LED. The various colors are produced by turning on the appropriate combination
of LED's in the pixel.
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
The distance from the center of one pixel to the
center of the next adjacent pixel is called "Center to Center Spacing" or
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.
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.
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.
Programming sets the characteristics of the characters used in the message: font, size,
color, and position; as well as any special effects.
Scroll Up or Down. Wipe Up, Down, Right, Left, In and Out. Twinkle
sparkle, Glitter, Starburst and Explode. Roll, March or Job. Snow, Spray On
and Slide Across. Switch and Interlock. Paint On and Scan On. Split
Color, Rainbow and Reverse Video. Flash and Hold. Start and Stop Time.
Date, Time of Day, Temperature and Battery Backup. Animation, Graphics and Dot