System overview
December 10, 2007
Front Access Full Matrix LED Sign Maintenance Manual (pn 1507610501 rev. A)
9
System overview
This section contains the LED Variable Message Sign (VMS) systems description and a general explanation of
how each system operates.
Introduction
The Adaptive LED family of Variable Message Signs is considered to be one of the highest visibility sign
systems available. Utilizing the latest generation of light emitting diode (LED) technology has allowed us to
construct a high-reliability, variable message sign display system.
The LED Variable Message Signs discussed in this manual consist of front access types with a 28 x 96 display
board at 1.07-inch, 1.35-inch, and 1.75-inch pitch. The signs are designed for use as outdoor highway
information signs. The signs utilize a corrosion-resistant front access housing with enclosed control circuitry
within. The only connections necessary are AC power and Communications Input/Output between the sign
housings and the ground cabinets.
General system
The entire sign system can be broken down into four basic subsystems:
•
VMS control system
•
LED brightness control system
•
Environmental control
•
Electrical system
In the following sections, we explain each of the above-mentioned systems in general terms for ease of
understanding. Referring to the drawings throughout this manual should help you to gain a general
understanding of the LED Variable Message Sign system.
What is an LED?
LED-based signs are one of the most versatile and visible display systems available. We use a cluster of four
LEDs to form a single pixel. The pixels are arranged in various matrices to form alphanumeric characters.
These characters are then linked together to form an LED display line. The display line format used in the signs
discussed in this manual is full matrix, which allows for the display of any alphanumeric character, including
punctuation marks, as well as simple graphics characters.
VMS control system
The VMS control system utilized in the Variable Message Sign consists of the following components:
•
IDI 1320 controller
•
IDI 1321 controller
•
LED display board/driver board
General operation
The controllers interface with the “Host” computer system, and communicate with the Host through a CAT5
Ethernet cable or an RS232 Input/Output (I/O) port. Using this network connection or I/O port, the host issues
commands to, and requests status information from, the LED VMS equipment. The controllers monitor and
control the entire LED VMS system. Communication by the controllers to and from the host and the VMS is
accomplished using industry standard 10/100 Ethernet or RS232 communications circuitry and NTCIP
protocol.
