DH+ network

3 posts in this topic


I have a question regarding DH+ network for those who has really experience.


1. I has on plant 5 plc's connected   in seral by DH+ network to GW PLC. 

     I would like to de install the last one in chain . question is: while the DH+ disconnection dose all network line will be shut downed?

in case of yes how do I minimize the shutdown time?


2. in other case there is HD Remote panel connected in the middle of line . how  I can to DE install it with minimum time of shut down for the RIO's  tht installed after him in topology.









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Are you removing the cabinets that contain the hardware too? If so, you'll need to re-route the DH+ cabling. Your downtime will be however long that takes. If you're leaving the cabinets in place, you can most likely just unplug the connector from the node in the middle without any ill effect on the rest of the network. The one on the end will be a little trickier since it's supposed to have a terminating resistor that will have to be moved to the device that's now on the end.

All that said...I've found DH+ to be an extremely robust network that can withstand a LOT of mistreatment. It's supposed to be a daisy chain with cable segments connecting directly to each device in the chain with a terminating resistor at each end but I've seen some complicated messes (like drops and multiple stars mixed in with the daisy chain) work with no issues.

For comms between AB PLCs, you'd use MSG instructions. Those involving the removed nodes should be deleted/disabled. I don't know anything about GW PLCs, so you're on your own there with any necessary configuration changes to it.

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As Joe mentioned DH+ is pretty resilient to abuse.  If you are removing the last PLC in the line, you can still just unplug the PLC and leave the connector, term resistor and all until you can properly modify things.  Once you dont have to worry about things going down, you can remove the cable from the preceding device and place the termination resistor at that location.   Just as a side note, DH+ actually had a more complex installation method of station connectors and drops off of the trunk line and a very specific cable that needed to be used.  In actual practice people found that it was easily daisy chained without any problems to service.  Not having the right cable can be a problem in certain instances and not having the proper termination resistors can cause issues also, but usually people can do lots of stupid stuff and still have an operating network. 

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