Connectivity Options

 

How to Connect Our LED Signs To Your Computer

This information is for users who plan to use a computer and messaging software to program their LED display(s). The purpose of this document is to briefly describe the most common ways that our LED Displays can be connected to a computer using RS-232, RS-485, and wireless communications. Here are the specific sign models that this document applies to:

Advantages and disadvantages of the various connectivity options are presented.

This is a non-technical document for a non-technical reader. If you are looking for detailed technical information on connectivity options, please refer to the document, Networking Alpha® Signs. This manual describes cabling options with diagrams and includes instructions for users who are interested in making their own cables and connectors.

If you plan to program your LED display(s) with the Infrared Remote Keyboard or with the Infrared Message Loader, you do not need to read this document.

There are several cable and wireless connectivity options:

  • RS-232 Communications over RS-232 Cable.
  • RS-485 Communications over RS-485 Cable.
  • RS-232 Communications using two or more Modems.
  • RS-232 Communications and RS-485 Communications using two or more Modems.
  • RS-232 Communications using a Wireless Transmitter and Wireless Receiver or Wireless Transceivers.
  • Internet Messaging to one or more Wireless Pagers or FM Radio Receivers.
  • Ethernet Communications using an Ethernet Serial Server or a built-in Ethernet Adapter.

There are two other options that do not require the cabling or wireless solutions described above:

Many software and programming options are covered in the software pages of this web site. Click Software for detailed information on software and programming options..

RS-232 OR RS-485 OR ETHERNET?

Cable connectivity options utilize either RS-232, RS-485, or Ethernet communications. There are several significant differences between the three protocols, and your choice of protocol affects both the performance and cost of your sign messaging system. Here are the key points.

For purposes of receiving messages from a computer or other transmitting device, Alpha, AlphaVision, Alpha Premiere, and Alpha Eclipse LED Display models have two built-in communications protocols -- RS-232 and RS-485.

Notes and exceptions: Betabrite and Betabrite Big Dot models have only an RS-232 adapter. Alpha Premiere 9000 Series models may be ordered with an RS-485 adapter and an Ethernet adapter instead of RS-232 and RS-485 adapters.

There are two important differences between RS-232 and RS-485 protocols.

  1. RS-232 protocol has two limiting factors.
    1. First, there is a cable length limitation. The sign manufacturer, Adaptive Micro Systems, suggests an RS-232 cable length of 50 cable feet or less between the messaging computer and the sign. Practically speaking, we have successfully transmitted messages from a computer to an LED Display with an RS-232 cable as long as 130 feet. Some customers, however, have experienced problems transmitting messages to a sign 75 cable feet away. Reducing the transmission speed from 9600 baud to 1200 baud will sometimes extend the distance.
    2. Second, with RS-232 communications, one RS-232 cable is required for each sign. To use two or more signs, you must use a two or more RS-232 cables, and you must have as many Serial COM ports as you have signs, unless you use a switchbox to connect multiple signs and cables to one Serial COM port.

  2. RS-485 protocol allows messages to be sent up to 4,000 feet on a twisted pair cable and twice that far if a Repeater Box is used. Multiple RS-485 Network Adapters may be installed anywhere on this twisted pair cable to connect multiple displays, and messages may be sent to one display, to a group of displays, or to all displays from a single Serial COM port. Alpha, AlphaVision, and Alpha Eclipse models may be assigned a unique "address" from 0 to 255 (hexadecimal 00 to FF) for purposes of identifying each sign on the RS-485 cable.

    Note: The Betabrite LED Displays have only an RS-232 adapter, and they cannot be set with a unique "address". For these reasons, the Betabrite cannot be used in a network of signs on a single sign network cable. They can be networked if an Alpha Ethernet Adapter is ordered.

FIVE CONNECTIVITY OPTIONS

The requirements, advantages and disadvantages of five cable connectivity options and three wireless connectivity option are described in the paragraphs below. Detailed information on hardware components and configuration options are provided in Networking Alpha® Signs. Diagrams of each connectivity option with part numbers of all components are provided in this manual. Click the blue link above to download the manual.

  1. RS-232 CABLE BETWEEN COMPUTER AND SIGN

    Requirements: An RS-232 cable from up to 50 feet long and messaging software such as Alpha Messaging, Betabrite Messaging, or AlphaNet.

    Advantages: Inexpensive. Fast, reliable messaging. Error checking can be used to verify that messages are received accurately. Disadvantages:

    Distance limitation of 50 to 100 feet. Only one sign per cable.

  2. RS-485 CABLING BETWEEN COMPUTER AND SIGN(S)

    Requirements:

    1. A Converter Box Cable and a Converter Box.
    2. A length of RS-485 cable between the Converter Box and the first sign, between the first sign and the second sign, and so on.
    3. An RS-485 Modular Cable and a Modular Network Adapter for each sign.
    4. A software program, such as AlphaNet.

    Advantages:

    nexpensive. Fast, reliable messaging. Distance limitation of 4,000 feet, unless a Repeater is used. Multiple signs on one twisted pair cable on one Serial COM port. Error checking can be used to verify that messages are received accurately.

    Disadvantages:

    Connecting signs in multiple buildings together is difficult.

  3. RS-232 CABLE AND MODEMS BETWEEN COMPUTER AND ONE SIGN

    Requirements:

    1. An Internal Modem or an External Modem and Modem Cable on the sending computer.
    2. An External Modem and a Modem to Sign Cable at the sign location.
    3. An available analog modem telephone line between the two locations.
    4. A messaging software program, such as AlphaNet.

    Advantages:

    Fast, reliable messaging. Sometimes the only way to connect between two sites. No distance limitations between sites. Error checking can be used to verify that messages are received accurately.

    Disadvantages:

    Cable length limitation of 50 to 100 feet between the receiving Modem and the LED Display. Only one sign per cable. Sometimes the receiving Modem loses its Auto-Answer setup and has to be reprogrammed in the remote site. Monthly cost of dedicated phone lines at the sign location and sending location.

  4. RS-232 CABLE AND MODEM IN SENDING LOCATION; MODEM, RS-485 AND ONE OR MULTIPLE SIGNS IN RECEIVING LOCATION

    Requirements:

    1. An Internal Modem or an External Modem and Modem Cable on the sending computer.
    2. An External Modem at the sign location.
    3. A Modem to Converter Box RS-232 Cable and a Converter Box at the receiving location.
    4. An analog modem telephone line between the two locations.
    5. A length of RS-485 cable between the Converter Box and the first sign, between the first sign and the second sign, and so on.
    6. An RS-485 Modular Cable and an RS-485 Modular Network Adapter for each sign.
    7. A software program, such as AlphaNet.

    Advantages:

    Fast, reliable messaging. Sometimes the only way to connect between two sites. No distance limitations between sites. Distance limitation of 4,000 feet between the Modem and the most distant sign at the receiving location, unless a Repeater is used. Multiple signs easily attached. Error checking verifies that messages are received intact.

    Disadvantages:

    Sometimes the receiving Modem loses its Auto-Answer setup and has to be reprogrammed.

  5. WIRELESS TRANSMITTER IN SENDING LOCATION; ONE OR MORE WIRELESS RECEIVERS AND SIGNS IN RECEIVING LOCATION

    Requirements:

    1. A Wireless Transmitter in the sending location.
    2. A Wireless Receiver on each sign in the receiving location.
    3. A software program, such as AlphaNet.

    Advantages:

    Sometimes the only way to connect between two sites. Multiple signs easily attached.

    Disadvantages:

    Distance limitation of approximately two to six miles; less in some environments with thick walls or noisy equipment. Cost is considerably higher than other options. Some wireless configurations are one-way communications only with no error checking possible. Some wireless configurations use two-way communications. These systems must be used when it is important to know that the message has gotten to the receiving sign correctly.

SUMMARY

In making the decision on how to program your Alpha LED Display, you must evaluate the cost, feasibility and practicality of connecting your computer and sign(s) together either with data cable, or by modem and telephone line, or by wireless communications using a wireless transmitter and wireless receiver(s), taking into account the type of sign(s) that you have. You should strongly consider using a computer to compose and transmit your messages, if possible. If cable connectivity, connectivity by modem, or connectivity by wireless transmission are not practical, then you can use the Infrared Remote Keyboard if your sign has infrared capability, or you can use the Message Loader which works either by infrared or by serial connection.