Chapter 1 - LED Sign Terms & LED Sign Components



LED Sign Terms

LED - Light Emitting Diode.  The electronic circuit that produces light when power is applied.

Sign / Display / Panel - These terms are used interchangeably to refer to the rectangular case that displays the messages via the LED's.

Display Area - The actual X * Y area that the LED's take up to generate the text messages.

Tri-Color - LED's that are capable of displaying multiple colors, usually red, green and yellow.  Black is created by the absence of any color. Blue and white are relatively new colors and allow for the creation of true color (red, green, blue) LED displays.

PC - Personal Computer, usually with a Windows operating system.

Viewing Distance - The longest distance that a person can read an LED sign from.

LED Sign Components

Display - The display is what shows the stationary or scrolling text via LED's. The most important aspects of the display are the height and width of the Display Area, the brightness of the LED's, and the viewing angle.  The vertical height will determine the minimum and maximum viewing distances that the LED sign can be read from.  See Chapter 6 for a chart showing the min / max viewing distances for various LED sign character heights.

The horizontal width will determine how much of a message can be displayed at one time.  For displays that will be scrolling text right-to-left, there is no need to go beyond 15-20 characters in width for a one-line display.  The human mind can only read a couple of words at a time, so there is no need to show more than 3-5 words scrolling at a time.  Your message can be 50 words long, but you only need to have visible 3-5 words at a time for people to read your message.

If you are going to display a stationary text message, you may want a display area that is wider than 15-20 characters.  Another option is to get a multi-line display, to show more text at a time.

For outdoor applications you need brighter LED's.  LED signs with wider viewing angles such as 140 degrees, can be read by more people, for a longer time, then an LED sign with a narrow angle of view, such as 30 degrees.


Keypad - Keypads let the LED sign user enter and change messages on the display, without the aid of any other device, such as a computer.  Most keypads are wireless, and most wireless keypads use infrared technology.  Infrared keypads require that the user hold and point the keypad at an infrared sensor on the display (usually on the front) to enter and change the messages.  No objects can be in the line-of-sight from the keypad to the display, or the infrared light beam will not reach the infrared sensor.  Most infrared keypads will work from 5 to 50 feet away from the display.

A more expensive radio frequency wireless keypad, eliminates this line-of-sight issue, but for most LED sign uses, an infrared keypad works fine.

When changing messages frequently, or when entering a lot of text, a keypad will quickly become cumbersome since a keypad is not laid out like a PC keyboard for two hand typing.  Using a PC keyboard on a PC via a computer interface speeds up volume text entry.  For 20 messages of 50 to 100 characters, where they might change once a month, a keypad will work fine.

Computer Interface - Some LED signs have computer interfaces which enable a user to control the LED sign and it's messages from a computer software program.  The advantages include . . .

1)   Easy to type in and program long message sequences.
2)   Message editing is faster since you can see the whole message on the PC display, and change just one word.
3)   You can save your messages in a file for quick retrieval and for back up purposes.
4)   You can display computer generated information and change it in real time.

The disadvantages of using a computer interface include . . .

1)   You must have a computer or network close enough to connect to the display.
2)   You must have software on the computer to communicate with the display.
3)   A display connected to a network can be hacked.

Some LED signs have a serial RS232 port to communicate with a PC.  With the serial port, you will need a serial cable to connect your PC to the LED sign.  Many newer LED signs come with a USB port or a network enabled Ethernet connection, requiring a CAT5 network cable. 

Power Adapter - Most LED signs use a power adapter.  The only issue with the power adapters is usually where do you place it?  Extension cords can be used to extend the reach of the power adapter so that it can be out of sight, yet still reach the display.


Click for . . .     Chapter 2 - LED Sign Feature Tradeoffs


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