RS-485 Extender and Isolator

A DDNG485 should be used to connect separate RS-485 cable runs together if more than 100 devices are required on a network spur or if a single cable run may exceed its 800m limit. Segmenting the network with a DDNG485 has the added benefit of isolating faults and localising network traffic control to a smaller area.

No configuration is required when using the DDNG485 as a repeater. With the default configuration, the DDNG485 will pass all messages between its ports.

dyn ddng485 repeater topology
RS-485 repeater architecture

  • The gateway is powered from the 12 V and GND terminals on Port 1. A DDNP1501 power supply or at least one load controller is required on Port 1 to supply power to the device. The device then supplies up to 200 mA on Port 2.

  • For cable runs over 300m or baud rates over 9600, a 120 Ω end-of-line resistor must be installed across the D+ and D- terminals on the first and last device to prevent network reflections.

  • Network extension and isolation: Some projects require parts of the network to be isolated from the main network due to busy network messages from light level sensors or chase sequences that may be running on the spur. The DDNG485 can filter messages on busy networks, only allowing defined network messages through to the other network segments. The Routing editor is used to configure message routing and filtering.