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LED 101

What is an LED?

Light emitting diodes (LED) are special diodes that emit light when illuminated by the movement of electrons in the semi-conductor chips.


Types of LED’s

Monochrome comes from the Greek word meaning “of one color”. CPI’s monochrome series are single color LED displays usually in Amber or Red and are great for applications of streaming text, sports scoreboards, time and temperature, schools, churches, and numerous other business’s.

CPI’s tri-color or grayscale application simply means many shades of a single color. A grayscale image is an image in which the value of each pixel is a single sample, that is, it carries the full information about its intensity. For the color gray it would possess white to black and every shade in between giving you numerous shades of that color.

RGB simply means full color. Red, Green and Blue (RGB) are the three colors human eyes can perceive. By using the correct combination of red, green, and blue intensities, many colors can be represented on a display. The two most important factors for quality of RGB depend on the signal quality and the displays color processing ability. CPI’s RGB displays have a color processing ability of 16 bits of information per color giving our customers over 275 trillion gamma corrected color levels. CPI’s full color message displays are fantastic for animation imaging for that business that is really trying to leave a lasting impression for their customers.

LED Advantages

LED technology is quickly becoming tomorrow’s primary light source and have several advantages over conventional light sources:

  • LEDs are energy efficient meaning they require less energy to illuminate display’s giving you more brightness and flexibility within your advertising infrastructure.
  • LEDs are cost effective and declining in price making them affordable to all scopes of business
  • LEDs can generate billions of colors depending on the mixing scheme giving you endless options for video, text and animation
  • LEDs give you the ability to create a brand new ad every single day inspiring customers by the thousands on a daily basis
  • LEDs eliminate billboard rental costs and can be viewed 24/7

LED Terminology

Pitch is the distance from the center of a pixel to the center of an adjacent pixel. The pitch determines the resolution of the display. The higher the pitch the less pixels the display will have. Pitch is very important in determining the quality of picture for a display.

A pixel (picture element) is the smallest piece of information on an image. The more pixels used to represent an image, the higher the resolution or quality of that image is portrayed.

Matrix resolution represents the number of pixels there are on a display. A display area that has 280 (h) by 380 (w) means that it has 280 pixels from top to bottom and 380 pixels from side to side. The higher the matrix resolution is the better quality of picture or image is. By choosing a smaller pitch in a fixed area the display will emit a better and brighter quality of image.

Degradation is the loss of quality of an electronic signal. An LED diode generally loses up to 20% of it initial brightness after 2500 hours. Then the illumination of an LED diode will very slowly, unnoticeably degrade over its lifetime of up to 100,000 hours until it dies.

NIT is the calculated measurement of brightness for a LED display.
NIT = cd per pixel X pixels per M²


  • Indoor – 2 inch and 4 inch high characters are commonly used for interior applications. In warehouses or manufacturing environments, where signs are to be viewed from greater distances, 4 inch or 7 inch characters work best
  • Outdoor – 24 inch high characters are excellent for long distance freeway viewing. 14 inch 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 commonly used.


  • 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” 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 easily read is to allow 50 feet of distance per readable inch or to allow 600 feet away of distance per foot of readable text.

There are a variety of ways to connect a sign to a computer:

  • Cable – This is the simplest connection between the serial port of the computer and the sign. There are numerous cable connections available. Contact CPI Advanced Inc. for more info.
  • Modem – The messages and graphics are transmitted from the modem of the computer to the modem in the sign by way of telephone lines. When the 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 of 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 company’s Local Area Network.