Control Net vs Ethernet

Hi to All,
We are about to implement a Control Logics 5000 processor. My boss wants to use ethernet for all of the remote chassis. I think we should do it with control net. However I do not have any good arguments why we should use Control Net. He says you have to schedule the connections with C-net and not with E-net and that connection sometimes gets lost. I told him there are a lot more remote devices that accept C-net than E-net. I need some good reasons why we should use C-net...or should I just give in and do it over E-net.

Thanks
Tommy

Both will provide adequater performance if configured properly. His thinking is wrong though, as a scheduled controlnet will never lose a connection, where as a scheduled Ethernet/IP network always has the possibility to lose connections if configured imprperly. Controlnet will also be more expensive.

As a starter for properly setting up Ethernet/IP, you must make sure all the traffic is seperated from any other network. Say you are on an office network, so 10 people try to print at the same time, they could theoretically use up all the bandwidth, and then you would temporarily lose control of your remote nodes. So make sure the network is segregated and use high quality managed switches. Include your IT department in setting up these switches. Also try dedicate this network to remote IO only, do not include HMI or Datalogging on this network. Therefore, the rack containing the processor should include 2 ENxT cards.

Saying that, I always use Controlnet, due to the characteristics of the network, and it is logistically easier to maintain once it is set up

My personal opinion would be to go with ethernet. If it is well managed then it is just as reliable as controlnet, but easier to maintain and troubleshoot.
I think one of the first things I would do is check out all of the 'remote devices' that you plan to use and see if there is a significant difference in the price of the ethernet/controlnet options, also ensuring that your pereferred option is tried and tested and not a 'new' option. Some manufacturers are releasing ethernet modules but they aren't ethernet IP for example.
Of course a lot of other things should be considered, such as what is considered 'standard' comms in your particular industry, training of staff if a new system is introduced, etc, etc.

This just my opinion and I'm sure others will share their own personal preferences and experiences, but I think most people will agree that ethernet IP seems to be the way things are going.

Just my 2c worth.

My primary question is if any of the remote IO is critical or is a part of a control loop. If either of these is true, then I'd go for ControlNet.


One advanage of ControlNet vs EthernetIP is that there is no switch(s) to maintain. I prefer not to have that hardware in the mix. Keep it simple if you can.

I agree with the input above.

If the setup and requirements probably won't change, particularly if you need that deterministic update rate, go with the slower and more expensive ControlNet - it'll always be the sound engineering choice for the application you describe.

However, using Ethernet is going to be much cheaper, more flexible/expandable, and supports much higher data rates (theoretical in this application, but not so for HMI/SCADA and expansion). If your switches are properly planned, configured, and managed (this could be simply having a separate control network) then EthernetIP will perform beautifully for most applications. It is more susceptible to the idiot factor bringing the network down.

http://www.ab.com/networks/cnetfaq.html