GE Serial vs Ethernet for Remote I/O

Hello Everyone,
I have a new project that I am working on. I am not doing the actual PLC work. It is being done by the customer using a GE RX3i processor in the main rack with 2 remote I/O Racks.

My experience with GE PLC is nada so that is why I am here asking questions. The customer is planning on using a serial Protocol from the PLC to the RIO. I assume it is Profibus. To me that seems a little "outdated" why wouldn't they want to use Profinet instead? Is there a good reason why that you can think of? I have recommended Profinet but just wanted to get a sanity check from you guys. Would you also recommend Profinet over Profibus?

Thanks for the help

I would agree with you about Profinet, especially since that is the horse that GE has said they're going to ride into the future. However, if the customer already has an installed base using some other network protocol I can understand them wanting to stay with that. As long as the other option can be expected to remain viable.

Steve Bailey said:

I would agree with you about Profinet, especially since that is the horse that GE has said they're going to ride into the future. However, if the customer already has an installed base using some other network protocol I can understand them wanting to stay with that. As long as the other option can be expected to remain viable.

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My response was going to be exactly that. If the customer has a strong desire to expand an existing network, that can make sense. Otherwise, I'd recommend Profinet.

Steve Bailey said:

I would agree with you about Profinet, especially since that is the horse that GE has said they're going to ride into the future. However, if the customer already has an installed base using some other network protocol I can understand them wanting to stay with that. As long as the other option can be expected to remain viable.

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I respect this answer but I disagree that just because that's what we did last time it's right for today too.

It's the sort of attitude that prevents growth and improvement.

Profinet is so much better in all respects to any of the older 'serial' based protocols that it is worth the very small learning curve. Not even taking into consideration the much less expensive installation and start up.

Now if the remote racks are using the GE standard 'Remote Rack' system which uses a proprietary high-speed multiplexing serial protocol up to 750' IIRC, that would be different. In this case it would just be another 3 rack PLC system spread out a bit.

I even did an expansion system a while back using a Profibus to Profinet Gateway and the customer is very happy that they went this route.

GE standard 'Remote Rack' system which uses a proprietary high-speed multiplexing serial protocol up to 750'

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Russ what is that protocol called? I couldn't find it on the GE website. I know customer has spec'd out a very high dollar cable for this communication. The guy I am working with has been very "koy" when I ask for details so that is why I am asking you guys

When you originally mentioned serial communications I pictured something like DeviceNet, Profibus or even GE's Genius network. What Russ is talking about is the way GE ties together multiple baseplates populated with I/O modules using the IC695LRE001 expansion module in each rack. Its what you would expect to see if you had a system with two or more racks in the same cabinet, but the remote racks can be up to 700 feet away from the CPU rack. The protocol is proprietary.
Can you get a bill of materials for the PLC? That will allow us to make more informed comments about the architecture.

Steve Bailey said:

When you originally mentioned serial communications I pictured something like DeviceNet, Profibus or even GE's Genius network. What Russ is talking about is the way GE ties together multiple baseplates populated with I/O modules using the IC695LRE001 expansion module in each rack. Its what you would expect to see if you had a system with two or more racks in the same cabinet, but the remote racks can be up to 700 feet away from the CPU rack. The protocol is proprietary.
Can you get a bill of materials for the PLC? That will allow us to make more informed comments about the architecture.

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This is correct except only the CPU rack or 'Main' Rack-0 gets an IC695LRE001 in an RX3i system.
The expansion racks are IC694CHSxxx there are 2 styles and 2 sizes of each style, 5 or 10 slot, the 'Expansion' Racks go up to 50' from rack-0 and the 'Remote' racks up to either 450' or 750' I don't recall right now. (That's another story from my past.)
IIRC, the cable is a 10 Twisted pair with DB-25 at each end and you must follow directions to get the proper pairs twisted.

Thanks for all the help everyone!!

That is exactly what they are doing. The distance from the PLC to the RIO is about 200' so I guess it will work. I am just surprised they are going this way as the cable is about $15 per foot and there isn't a tray rated version so we will have to run conduit. With the tray already there and Cat 6 being cheap seems the Profinet would be the "bang for the buck".

Bullzi said:

Thanks for all the help everyone!!

That is exactly what they are doing. The distance from the PLC to the RIO is about 200' so I guess it will work. I am just surprised they are going this way as the cable is about $15 per foot and there isn't a tray rated version so we will have to run conduit. With the tray already there and Cat 6 being cheap seems the Profinet would be the "bang for the buck".

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You are correct if they are using Profinet already, likely a wash if it would be used only for one remote drop, but still more efficient for future expansion.

I would look into splitting the communication between two cables that were tray rated before running conduit. What do you pay for 8 wire tray rated CAT5e shielded cable?
But... so long as they are willing to pay the price???