ControlLogix vs Modbus IO

[Secpcb]

I searched the forum and there are posts it's possible, but no details so here goes.


I have a project in the works and the boss bought some Ethernet Remote IO, but what he bought at a discount was not RemoteIO that is Ethernet/IP like I was expecting. The are all Modbus over Ethernet that I have never encountered before to even look at another project to check into.


Other than the boss now has to buy the EN2T for "sockets" (I have the ENBT that one thread said won't work) hopefully nothing else needs bought.


Could someone please point me to a good source to learn how to do Modbus in Studio500 for a ControlLogix, I'll be using ver33 with a -L73 CPU.


If anyone has any experience they can share that will be a great help too.

 

[Puddle]

IThe are all Modbus over Ethernet

Modbus TCP is what you need to be googling. The good news is, it's much easier than Modbus RTU.

 

[Contr_Conn]

Modbus TCP Add-On instructions are available from the Rockwell Sample Code library.
However, these are targeting relatively slow update rates, that may or may not fit your application.

 

[jschulze]

A word of caution. "Modbus over Ethernet" may not mean Modbus/TCP.


There are vendors that support "Modbus over Ethernet" that is actually Modbus RTU (the serial version of Modbus that typically runs over RS-485) encapsulated in a TCP or UDP Ethernet frame.


What is the vendor and model of the Remote IO module?

 

[Contr_Conn]

There are vendors that support "Modbus over Ethernet" that is actually Modbus RTU (the serial version of Modbus that typically runs over RS-485) encapsulated in a TCP or UDP Ethernet frame.

I personally never saw these, but it's quite possible. Then AOI will not work because RTU uses CRC, while Modbus TCP relies on TCP frame CRC

 

[Secpcb]

I personally never saw these, but it's quite possible. Then AOI will not work because RTU uses CRC, while Modbus TCP relies on TCP frame CRC

That might be the tough part. One of the manuals I downloaded searching for ModbusTCP has the following line:
Modbus TCP/IP (also Modbus-TCP) is simply the Modbus RTU protocol with a TCP interface that runs on Ethernet.


And checking the sample code there is a ModbusMaster program that is all serial RTU.


jschulze,


They are OneFex modules. The 2 part numbers I have are KZ-04AL and KZ-02AL.

Also, these are not modular like RemoteIO where I could add a card or change one, these are bought as setup and not expandable.

The interesting thing is an output can be activated for a time or to come on at a certain time and even if the PLC goes offline the output will cycle. I don't know if I would ever do that for safety.

 

[jschulze]

From my experience, if the vendor uses the term "Modbus TCP", then it is very likely that the device supports the real Modbus/TCP protocol and not Modbus RTU over TCP. It's terms like "Modbus over Ethernet", "Modbus Ethernet", or "Modbus over TCP" where I question whether it is Modbus/TCP or Modbus RTU over TCP.



There's an easy way to find out if you have one of the IO modules available. You can use SimplyModbus on your PC to test communications with the module. SimplyModbus supports both Modbus/TCP and Modbus RTU over TCP.
https://www.simplymodbus.ca/TCPclient.htm

 

[Secpcb]

There's an easy way to find out if you have one of the IO modules available. You can use SimplyModbus on your PC to test communications with the module. SimplyModbus supports both Modbus/TCP and Modbus RTU over TCP.
https://www.simplymodbus.ca/TCPclient.htm

Thanks for that.


Now I just have to figure out how to do this in Studio5000. In a test program I trued to add a Modbus device under the EN2T card (that needs to be bought, the boss didn't like the cheapest one on Ebay is $1,700) but it only wanted to add one specific module made by one vendor.

 

[jschulze]

Now I just have to figure out how to do this in Studio5000. In a test program I trued to add a Modbus device under the EN2T card (that needs to be bought, the boss didn't like the cheapest one on Ebay is $1,700) but it only wanted to add one specific module made by one vendor.

One alternative solution would be to use your existing ENBT card and purchase a Modbus/TCP to Ethernet/IP gateway to bring in all the IO modules to the ControlLogix, such as ICC's ETH-1000:
http://www.iccdesigns.com/millennium-series/10-eth-1000.html

I'm not familiar with creating and configuring the Modbus AOI's needed to use the EN2T card, but I suspect that configuring the ETH-1000 to map the data is easier.

 

[Contr_Conn]

Here is Modbus TCP Add-On instruction download.
https://www.rockwellautomation.com/...%20Add-on;startIndex=0;activeTab=Sample_Code;

You can't add Modbus module under EN2TR card, you need to use sockets, and AOI will do it for you.

 

[Secpcb]

Thanks to both of you.


I think these $50 IO's are going to end up costing this place more than buying standard items in the first place.

 

[lostcontrol]

Also, modbus (any variant) will not be deterministic compared to E/IP.

I’m sure you boss considered that when he acquired them ��

 

[cardosocea]

Can you buy a Prosoft module instead of the EN2T card? I'd imagine the price to be similar.

 

[Secpcb]

I’m sure you boss considered that when he acquired them ��

Of course the guy that can't spell PLC took that into consideration