ControlLogix and Profibus

[dlogger]

I would like to know if anyone can help me with a question that I have with Profibus running on a ControlLogix PLC.

We are looking into installing a Profibus network in our facility, running on a ControlLogix PLC. I have heard of the SST-PFB-CLX-RLL card and I know that there is also a card from ProSoft.

My question is this:
After the initial installation of the Profibus system, our process will run 24x7x364 days a year (we only go down one day a year). We do not get shutdown times to add devices to the Profibus network very often. We could be adding Profibus DP or PA devices as time goes on. Can devices be added to Profibus on the fly without interrupting the communications to existing devices? I don't have the luxury of putting the PLC into Program Mode when a device is added. This is a big issue for us. In the old days, you just wired the device to an I/O card, and away you go. But I need to understand how a Profibus Master functions.

Can anyone get me some specifics on these moudules?

Thanks,

Dlogger

 

[RPax]

Hi dlogger, just doing a job similiar to the description below. I'am using a Contrologix with a Prosoft Card installed on the rack with most of my Profibus slaves being flex I\O.

On your question, when adding additional slave in the future to a Profibus network you will need to configure it in the Master software and download. During the download the currently attached slaves will go down for the few seconds during the download but should recover thenselves when download completed.

The biggest issue is when adding slaves in the future is breaking into the wired Profibus network. If this is the case it will be unavoidable but to bring some slaves down unless your slaves are added to the end of your network.

If you forsee your self adding slaves at certain parts in your plant you could wire for them and leave spare connectors. If your very well organised and forsee the type of Slave you will attached then you could insert into your configuration software during commissioning and when the time comes you could plug them in and away you go. Although this can depend on the slave etc

Hope this helps - Rpax

 

[dlogger]

RPax,

Thanks for the reply.
I was hoping that the Profibus Card could have a selection that would be able to hold the slave inputs/outputs while the download was in progress. But from what you are saying, they will go down. That's going to be a problem for our process.

As for adding devices in the future, I knew about breaking the network issue. We would have to add them to the end of the line, or as you said, install spare connectors. That would take some planning.

I may be trying to implement something that won't work for us.

Thanks again,

Dlogger

 

[bkottaras]

Not sure if this can be of any help but with step7 hardware configuration and CPs you can add slave placeholders (dummies) to your network for future use.
Yes, you have to physically do the install and initialize but that is almost unavoidable.
I know you are using ControlLogix so not sure if such a setup even exists in CLX or the Prosoft module itself.

 

[RPax]

Hi Dlogger, some slaves have the option of Holding the last I\O state when a fault occurs etc (an example of this is the Flex I/O modules). A fault will also include a download however this might not suite if a real fault occured in the network.

You can design the I\O list for each slave so that the items you need to go to Zero are attached to some slaves configured this way and the ones to hold state attached to the other slave etc. Although this method might not be possible due to plant layout and cost etc

With the Prosoft card you can download the configuration software from there website and start adding your slaves. When adding the slaves you require you'll see what options are available on the slaves that you choose. Might give you a foresight on pitfalls!

Rpax

 

[dlogger]

bkottaras,

ControlLogix doesn't have that kind of setup. They rely on the Profibus vendors to perform that task.

Thanks for your reply.


RPax,

I'm not a fan of Holding the I/O state on a fault. Just as you said, a processor fault is where we would need to have the devices go to their fail-safe state.

Dlogger