PLC as an OPC-UA client? OPC-UA vs. Ethernet/IP?

[3rady]

The company I work for sells equipment which is controlled by software running on a PC. In cases where the end-user wants to integrate our equipment with a PLC and/or HMI systems we typically use an appropriate OPC server (RSLinx, Kepware, etc.) to connect our software (which is an OPC client) to the user's system.

We are exploring options to make this integration more direct. One option I'm considering is adding OPC-UA server functionality to our software. That would allow HMI systems to connect to our system directly.

Questions: Do PLCs these days support connecting directly to OPC-UA servers? If not is this something that may happen in the future? Would making our system an OPC-UA server make any sense in terms of direct connections to PLCs?

As an alternative we are considering adding Ethernet/IP to our system. That would allow current Allen-Bradley PLCs to be able to communicate directly to our system, but I'm not sure how many HMI systems connect directly to Ethernet/IP "devices". (Note that I think integration with PLCs is more important than with HMI systems.)

Question: Would you recommend that we implement an OPC-UA server or Ethernet/IP? I'd like the widest array of PLC types to be able to connect with our system directly.

Thanks!

 

[diat150]

I have heard of some PLCs having opc servers built in, but none that act as an OPC client. But it sounds like you are dependant on what the customer has so the chance of them having a plc that supports opc client would be virtually zero if it is even available.

I would maybe look at using something like a red lion datastation that can act as a means to propagate data between devices. Modbus would be my first choice since nearly every model of plc supports modbus.

 

[Fred_Loveless]

There a a couple of hybrids out there that have OPC UA Clients embeded in them. Siemens just added support in the S7-1500 and controllers that use Codesys can be designed with the an OPC UA Server embedded on them. Though most are not currently doing that yet.

The trend I am seeing though is adding IIOT to controllers enabling them to be RST or MQTT clients and servers.

 

[AustralIan]

It depends on what industry you are in to an extent and where in the world your customers are.

The easiest to implement by a factor of 10 will be modbus tcp, and arguably lets you talk to the most amount of PLCs, with the noteable exception of many Rockwell PLCs. There are standard third party products though which can bridge this gap.

Ethernet IP can win you a lot of customers though, particularly for the reason that modbus TCP is sometimes not an option for some Rockwell PLCs. On the otherhand, It will lose you some customers if this is your only option, as Siemens and others cannot talk Ethernet IP easily.

OPC UA is probably not going to be well used for direct communication to PLCs, partly due to the processing overhead and partly due to the extra trust issue steps.

The best people to ask would be your existing clients, as different equipment types and different industries will have different preferences. Often they will know of other installations similar to theirs and know what protocols are common.