ControlNet - only 1 remote node

[GAJimbo]

With only one remote Flex I/O node communicating to a 1756-CNB, will only one segment terminated at both ends work? Or do I have to add an intermediate tap with a dummy load to create two segments?

 

[dmargineau]

You might be able to get by without a T-Tap + Dummy Load, depending of the trunk coax run length and the eventual scheduling requirements or at least I have seen similar setups running with a 20ms RPIs within non -scheduled topologies.
However, http://literature.rockwellautomation.com/idc/groups/literature/documents/in/cnet-in002_-en-p.pdf Page 2-7 states that 75Ω terminating resisors are a must.
T-Taps and Dummy Loads are pretty inexpensive and you should try using the recommended installation hardware components for future expansion and proper functionality; why would you run the trunk coax directly into the comms adapter other than while within an "emergency"?

Dummy Load 1786-XT $9.93 List
T-Tap 1786-TPS $121.00 List

 

[GAJimbo]

Not sure what you mean by "emergency", but I do intend to connect terminating resistors on each end of the link. I guess the question could be re-stated as...in a non-redundant ControlNet network, what is the minimum number of nodes? 2? or 3?

 

[dmargineau]

2.
Installing a Dummy Load T-Tap will not create a new segment.
Install as many taps as required nodes.

 

[Ken Roach]

Make sure you aren't confusing the physical T-taps or Y-taps with the logical 'Nodes', which are the actual automation devices.

Understand also that devices with two BNC connectors, like the 1794-ACNR15 adapter, have two separate channels (A and B). The signal doesn't pass from one channel to another in a daisy-chain.

A ControlNet network with one 1756-CNB and one 1794-ACN(R)15 adapter must physically have two Taps, two Terminators, and a trunk cable.

 

[GAJimbo]

Thanks to all!