What is the recommended WWVDS RS485 wiring toplogy?

This article discusses the WWVDS RS485 wiring topology.

Please see the information below for recommended wiring topology.

Maximum Recommended Cable Length:

2,900 ft total for all cable legs combined when using the recommended twisted-pair cable.

Recommended Cable:

  • DRS485DBBK — preferred cable, or equivalent
    • 1 Pair, 22 AWG
    • Shielded RS-485 CM
    • Outdoor Direct Burial
  • Twisted-pair, shielded cable

Daisy-Chain — Preferred Method:

The GovComm Wrong Way Vehicle Detection System (WWVDS) uses RS485 communication over twisted-pair cable to transmit sign activation signals and communicate with GovComm Wrong Way Signs.

For the most reliable and stable communication, GovComm recommends using a daisy-chain topology with the RS485 devices connected sequentially along the communication path.

The RS485 communication segment should be properly terminated at both physical ends of the network. Proper termination helps minimize signal reflections and provides the most reliable communication, particularly over long cable runs.

Star Wiring — Alternative Method:

Although not the preferred wiring method, the GovComm WWVDS can operate using a star topology under certain installation conditions.

The WWVDS primarily uses RS485 communication to send one-way activation commands to the Wrong Way Signs to trigger the signs to flash.

However, some extended system functions that require two-way communication between the WWVDS controller and the Wrong Way Signs may experience communication issues or may not operate properly when a star topology is used.

Whenever possible, the activation network should be installed using the recommended daisy-chain topology.

The GovComm WWVDS RS485 network is designed to communicate only between GovComm equipment supplied as part of the project.

Do not connect third-party devices or other non-GovComm equipment to the RS485 communication bus.

Adding additional devices to the RS485 network may affect communication performance and can result in unreliable sign activation or other system functions.

If your installation requires star wiring or you have concerns about communication reliability, please contact GovComm Technical Support. Our support specialists can evaluate your installation and provide recommendations, including converting the activation network to a daisy-chain topology if necessary.