2 x CJ2M-CPU31 and Ethernet IP

[BobB 58]

Silly question time. I am looking at a job where I will have to use Hirschman or some other brand of switch for Ethernet IP I/O that will form a ring - they are about so that is OK - have done it before.

The other issue is that I have to have 2 x PLCs in 2 different cabinets on the network.

Each will be in the ring and the standby PLC will have a dry contact input from the duty PLC to turn the outputs off - warm standby.

They will not accept the CS1D as there is only 1 rack in 1 cabinet.

Question is can I have 2 PLCs scanning the Ethernet IP I/O at the same time?

I can see no reason why not but may be wrong.

Another issue I would have is that there is to be monitoring by a BMS system Modbus TCP. Each PLC would have an Ethernet card with the same IP address which would cause a clash on the network. Is it possible to make the Ethernet card in the standby PLC 'invisible' while in standby mode when the dry contact is on from the duty PLC and then when the dry contact turns off make it visible and make the Ethernet card in the duty PLC 'invisible'? Schneider do this internally in the M580 hot standby system.

My only other option is the very expensive Schneider M580 system.

Any help appreciated.

Edited 29 Aug 2020 by BobB

[BobB 58]

After reading some more documentation it appears that the M580 actually swaps Ethernet addresses to N and N+1. Is there a way to do this at all please?

[BobB 58]

Will rephrase - original post is all over the place like a mad woman's breakfast! Old Aussie saying.

I want to put 2 x CJ2M processors on the same Ethernet IP network - both will be scanning - they will have different IP addresses.

I will have to use a standard CJ2M and an Ethernet IP card due to the final configuration - too many drops for the onboard Ethernet IP - over 16.

Each PLC will also have an ETN card for access by a building management system via Modbus TCP - need the ETN for that as the FB uses sockets.

A dry contact to go from the duty PLC to the standby PLC to disable outputs but not disable scanning.

Also need to disable the Ethernet card as both ETN cards will have to have the same address eventually for the building management system.

When the duty PLC is in control its ETN card will have address 192.168.250.3 for example.

If the duty PLC falls over the standby PLC ETN card will also need the address 192.168.250.3 for the building management system.

It would be possible to write the address to the DMs for the IP address but the problem I see here is the rotary switch on the front of the ETN would have a different last octet number than the number written to the DMs and would cause an error.

Is it possible to turn on a bit to tell the PLC to ignore the rotary switch so there is no error?

Also is it possible to have 2 x CJ2Ms in the same Ethernet IP ring scanning all the I/O?

Eventually there will be 23 x Ethernet IP drops back to the processors.

Michael Walsh? Jay Anthony? Hi old fella from another old fella.

 

 

[panic mode 246]

unfortunately Jay Anthony passed away.

i am not doing much with PLCs these days but will try to reply.

ring topology is possible but requires Ethernet switch that can handle it (usually this is special feature for high availability networks).

EthernetIP network can have bunch of nodes. At least of of them must be a master ("Scanner"). more than one master in same Subnet are possible as long as there is no address conflict.  This means that both masters can scan same subnet.

"Device Coupling" is a feature supported by EthernetIP but this does not mean that every EthernetIP master supports that so check related Omron programming manual. One can also have both controllers check if each other is present and then (with or without negotiation) couple or connect to) slaves when other master is not using them..

Technically same slave can also have more than one master simultaneously but some masters require exclusive ownership of their slaves ("devices"). For example KRC4 controllers require exclusive ownership, not sure where CJ2M stands on this.

hope this helps, good luck

[BobB 58]

Sadly I did not know Jay had passed away. We have had discussions over a long period of time - since I joined this group actually.

I have run Ethernet switches in a ring before - no issue there.

Will have to dig further I guess.

Thanks.

 

Edited 31 Aug 2020 by BobB

[chelton 66]

How quickly are you expecting the changeover from the master to the slave? All the slaves I have dealt with only allow 1 Class 1 implicit/cyclic connection but other masters can listen if it is a multicast connection. Having a DLR (Device Level Ring) is common but this is not the same as having multiple masters for redundancy.

 

[pcmccartney1 141]

Bob, I think you mentioned early on that you are using Hirschmann switches and that's the perfect choice.  While I have not done this ring topology with Omron (granted it's all E/IP).  I have done this for DCSs with dual ring topologies.

[IO_Rack 178]

17 hours ago, panic mode said:

unfortunately Jay Anthony passed away.

Very sad news. As with BobB, we've had discussions here for a long time. Jay Anthony was a wealth of Omron knowledge and a valuable resource to members here at MrPLC, especially for the older systems. He will be missed.

Panic Mode, thank you for the information.

[Michael Walsh 268]

On 8/30/2020 at 7:00 AM, BobB said:

It would be possible to write the address to the DMs for the IP address but the problem I see here is the rotary switch on the front of the ETN would have a different last octet number than the number written to the DMs and would cause an error.

Changing the DM numbers does not work.  The IP address does not change at the point that you change the DMs and when the ETN21 is restarted, it puts the original numbers back in the DM area.  I would think that you would have use a FiNS command to do this. The error would not be a big deal for the PLC as it is a non-fatal error, but would cause issues with FINS communications on your network.  

The EIP masters can both have tag data link communications established with inputs only.  Outputs can only be assigned to one master.   You could perhaps do something with explicit messaging for the outputs.  

[BobB 58]

Thanks Michael - I think I will have to go to a dedicated PLC for this unfortunately. Schneider have the M580 and Emerson appear to have one as well. Will investigate further today.

Edited 31 Aug 2020 by BobB

[lostcontrol 23]

Bob,

Have you considered a separate network switch that is powered only when required, for the module in question?

That would allow the duplicates to be set, but only 1x be active on the network at the same time?

Edited 20 Sep 2020 by lostcontrol