MicroLogix 1400, ethernet/ip over RS485

rQx

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Hello!

First a little background: My customer has received a control system developed for them. This consists of the PowerFlex 4M, ML 1400 and a PanelView plus 6 700. PowerFlex 4M is connected to the comm port 0 on ML 1400. PLC and HMI are connected through a switch. They have completed work on their software developers and put the responsibility on me. The problem is that I have not programmed AllenBradley before and have limited knowledge in the field of communication.

The problem:

My client is working on an offer where their customer requests ethernet/ip communication over RS485. I understand this is the ethernet/ip communication which Rockwell developed and this exist in the PLC. So the problem is really how I physically connects this? Is it possible to add RS485 with RJ45 directly on the switch? I' not that familiar to protocols and ways to connect them. I'm learning but there is so mush to learn.

Thanksfull for any help /Tim
 
rQx said:
...The problem is that I have not programmed AllenBradley before and have limited knowledge in the field of communication...

...The problem:

...customer requests ethernet/ip communication over RS485. I understand this is the ethernet/ip communication which Rockwell developed and this exist in the PLC. So the problem is really how I physically connects this? Is it possible to add RS485 with RJ45 directly on the switch? I' not that familiar to protocols and ways to connect them. I'm learning but there is so mush to learn.

Tim,

It sounds like you may be in a little over your head here, but I'll try to advise you the best I can.

You cannot connect an RS-485 network directly to an Ethernet switch using an RJ45 jack plug. They are electrically incompatible. Also, which ever protocol the RS-485 network is using will be incompatible with the Ethernet/IP protocol. They cannot talk to each other directly. A converter interface device would usually be used here.

If the customer's existing network is a purely Serial network, then a converter interface device, such as the Anybus Communicator Ethernet Serial Gateway from HMS, would normally be used to bridge these two types of networks.

..customer requests ethernet/ip communication over RS485

However, if your client's customer is aware of, and is already using another technology known as Ethernet-over-RS485, then you will have to look at another option.

A company called PCN Technology in the US have developed a system known as IP-485, where an existing RS-485 network can be transformed to carry both the Serial and the Ethernet protocols over the same existing Serial twisted pair media, at the same time. This option would require the customer to already have an IP-485 Server module in place on the Serial network. You then install an IP-485 Client module for the Ethernet/IP network created by your client.

You could either install the IP-485 Client module near the IP-485 Server module, and link the Client module into the serial network with a short link. Then run a CAT-5 cable to the Ethernet switch at the new system.

Or

Install the Client module near the Ethernet switch with a patch cable between them, and run an RS-485 cable from the Client module back to the Server module. The advantage of this method is that if the new system is a greater distance away from the Server than the standard 100m Ethernet limit, the RS-485 cable run, while carrying the IP data packets, can be run at a much greater distance.

The IP-485 Server handles the transport of both protocols across the single network. An IP-485 Client is installed anywhere on the Serial network that you need an Ethernet drop.

Note, if they converted their old Serial network to IP Ethernet only, using the system above, and are not using a Serial protocol across this network anymore, then they would be using a standard IP-485 Server module. If dual protocols are used then they would be using an IP-485R Server module.

You will have to ask your client to ask their customer if it's an interface/converter device they require, or have they an IP-485 Server/Client system installed.

My guess is it's a converter interface you will need, but just in case it's not, I have outlined the IP-485 system as well.

It's also useful info for others as an option.

G.
 
Yea, tell me about it. In a perfect world I would get some overlap time to learn but since when does the customer care about us right ;)

Thanks alot for the info! I have read alot on internet the past days to get a better general understanding of protocols and physical connections. I almost assumed that it wasn't possible without a anybus. This is just on the offer stage on my customers side but I got the question how mush extra it would cost so I had to dig into the problem with not so mush to go on. If or when the order comes I will have to get more info about this issue. Anyway it goes I have learned a great deal from this problem. Now I know alot more about protocols, physical layers. There is alot to learn. Thanks alot for your helpful time, I will save this topic and come back if the order will arrive.
 
Can you modify the plc program ? Because if it is just to read the local plc and drive infos over ethernet/ip, why not just using the ML1400 built in ethernet port ?
 
Yes I can modify the PLC program. Because the customer want to connect it with RS485 and not ethernet. Further more the ethernet port is connected to a switch to wish a HMI also is connected.
 
Just to further clarify the point, and make the distinction between physical media and protocols.

Physically they want to interface RS-485 wiring media with the Ethernet switch, but protocol wise they want to communicate, from the PLC, Ethernet/IP across this interface to either the Serial protocol in use on the RS-485 network, or Ethernet-over-RS-485, which does support the Ethernet/IP protocol.

Again, dependant on which method the customer is requesting.

G.
 
Because you aren't familiar with A-B products or networking technology, it is likely that you or the customer misunderstands what they actually want to implement.

It's *possible* that they really want an IP-over-485 system. But it's very unlikely.

It's like asking for a horse-drawn electric car.

See if you can get the customer to explain in more detail what they want to connect to the control system and why.
 
It sounds more and more like you might want to look at the Pf525. It has built in Ethernet and is reasonable on cost. You could keep the current bom and add a comm22-e adapter but that is significantly more expensive.
 
I'm going to get more information about the connection if or when the order comes. The question they had for me was "is it possible". To this question I have to say yes, bases on the knowledge I've gotten here. I don't know if they are getting the order but I want to be a step ahead of them and learn more about AB, protocols and diffrent types of physical connections. When or if the order comes I'm going to get more information on what they need and with my newly found knowledge about communication I can have a better dialog with them.

About the protocols and physical layers, I think I have reached a far better understanding now. From this thread and from me searching the internet.

As a matter of fact we are looking at replacing the PowerFlex 4M with a Pf525 in a project with 500V specifications. I can't see how this would help me in this case though?
 
rQx, are you sure that your customer wants you to transmit Ethernet/IP over the RS485, but not the reverse?
In fact some drives from the 4 series of PowerFlex (Or all of them, not sure), and PF525 support control of 3 devices via RS485 (DSI), from the master one, which you control via Ethernet/IP. As you describe your problem, it looks something like this.
 
I can't be sure, I only got this little info. But when the order comes I will get more information. You mean that I could connect myself to my PLC through the PowerFlex?

Anyhow since the order isn't confirmed this is just speculations on how we think they mean. I will get back to the problem when the order is finished.

It's nice to talk to someone and discuss ideas etc thanks alot for all help.
 
You connect the PLC to the first drive over EtherNet/IP. Then you connect the first drive to the other upto 3 drives daisy-chained over RS485.
From the PLC you control all 4 of them with sending messages just to the master.
Check chapter 7 of the following manual.http://literature.rockwellautomation.com/idc/groups/literature/documents/um/520com-um003_-en-e.pdf
And if you are controlling the drive from ML1400 controller, you should check some recommendations about the explicit messaging (it is not recommended) Search in the forum, there are lot of topics.
 
Well I shall just control one PowerFlex so no need for that. Ok, why isn't what recommended? We control a Pf40 today with modbus.
 
See the manual I listed.
page 62.
Here in the forum are described lot techniques to avoid that, just search for PF 40 or PF 525 and micrologix. The usually prefered way is to give the speed command (and read the feedback and so on) with MSG, but to have Start and Stop command hardwired. Just search.
 

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