Best solution to read Modbus RTU with a compactlogix CPU

[Jeff23spl]

Thanks all

Using ML1100 is sond like a good idea, the price tag for me is close to a gateway module and will probably be more easy to use than a gateway.

By the way, i have to read 3 Modbus RTU device that are only 485 (not 232 compatible) But ML seem to have both choice possibility...

 

[antoniomrc]

Hi, are you sure we can do it? Also with the cheapest 820 ?
Antonio

 

[5618]

The Micro 820 and some other Micro 800 models can be used well to get Modbus RTU to Compact/ControlLogix. I have Micro 820 and 850 running the Modbus communication on-board then being read by MSGs over Ethernet from other controllers. The Click is another small controller I would consider for that. It can do the same, plus it could also be added to the Rockwell system as an IO adapter so MSG management is not needed.

Since OP of this thread mentioned CompactLogix, if using a newer 5380 controller or a remote 5069 rack, I really like the 5069-SERIAL module for Modbus communication. ProSoft is another go-to for Modbus and Rockwell. Anybus is also well liked, but I haven’t used them yet.

I have not used the 1769-SM2, but I’m sure others here have. In the 1769 chassis, my first Prosoft from scratch project used MVI69E-MBS. The ProSoft was a bit confusing at first to set up with the IO table fully open and nothing defined. Once I figured out a clean logical layout of the data and status from the commands, I really liked the module.

If you have specific questions, starting a new thread will be best for getting some help. Let us know the specific hardware you're using, what you have tried so far, and the results you’re seeing. More details is better.

 

[TheWaterboy]

Spectrum Controls makes a $400 gateway that works very well for these instances and is dead simple to set up.

Caveat: In the case where the Modbus target device goes offline for a long time (like when a device is taken offline for a couple weeks) these gateways seem to just die and become unresponsive, requiring nothing more than a power cycle to start up again.

If the Modbus comms doesn't get interrupted, they work forever. I think the failure is because their log file fills up with the comm error messages but I can't get them to duplicate (and therefor fix) it.