Modbus TCP communications with Micrologix 1400

I have 6 lift stations through out a plant. Will be looking at 4-20 feedback from levels and controlling pumps. My plan is to use universal remote i/o modules as slaves and run a Micrologix 1400 as the master. My question is will this actually work with the modules only supporting Modbus TCP? The Micrologix 1400 series B, to my understanding has the capabilities but i'm still unsure of it. Normally I would have several processors out and just MSG/multi-hop to each back and forth. Any ideas or suggestions on using the Micrologix 1400 Master setup? Unfortunately the company isn't ready to move up to compact or control logix just yet. Thanks all

yes it should work, but like anything else you need to prepare for what happens if the comms goes down. I am sure you would not want the pump to continue to run if the comms is lost.

a better option may be to put a plc at each site and communicate back and forth.

diat150 said:

yes it should work, but like anything else you need to prepare for what happens if the comms goes down.

Click to expand...

He really means "when" comms go down, not if

diat150 said:

yes it should work, but like anything else you need to prepare for what happens if the comms goes down. I am sure you would not want the pump to continue to run if the comms is lost.

a better option may be to put a plc at each site and communicate back and forth.

Click to expand...

^ I'd agree here. The cost of say, 6 addt ML1100 with an addt analog card if you need better resolution may be higher than the modules you want. But rather simplier to manage.

Hi,

As stated in the comments above, comms can simplify many things, but...can also introduce lots of 'what if' sorts of problems!! That said, i currently have a Micrologix 1400 acting as a temporary ICSS for simulation during testing. It's set as the Modbus TCP Client (or Master in RTU land) and i have 10 Compactlogix processors with Prosoft cards as Modbus TCP servers (or Slaves). Works surprisingly well and was reasonably straightforward to configure. Just use the standard MSG instruction, pick your Function code and give it the IP address of the particular server you want to communicate with...that's it!

Hope this helps.

Rob

Is some limitations about how many slaves can be addressed if the 1400 is a MB TCP master, but think you should be OK with 6...

As said above, If the potential is a mess if the pumps don't operate, seems a local PLC for each pump may be a better option.. Don't know about pricing of the "universal remote i/o modules", but an 1100 or micro820 are both pretty affordable...

I recommend strongly against using the MicroLogix 1400 with remote Modbus/TCP modules as a "poor man's distributed I/O" system.

While it's technically possible to write Message instruction code to move data between I/O modules and a MicroLogix reliably, it's just not what the MicroLogix is built to do.

In ControlLogix and CompactLogix systems, the Ethernet daughtercard takes care of making connections and handling timeouts and recording faults and dividing up resources for I/O versus HMI and online programming.

With the MicroLogix, all that programming is up to you.

One thing that always irritates me about MicroLogix messaging is that you can't edit a rung containing a MSG instruction online. If you are trying to troubleshoot or tune or develop logic that relies strongly on MSG instructions, you're going to have to take the controller offline and download every time you want to change one of those rungs.

I agree that MicroLogix 1100 controllers that can make their own logic decisions when the network goes down are a good choice.