Siemens OPC/UA or ?

I'm trying to figure out which I should use.

My VB.NET 2012 application needs to talk to a S7-1500.

I think I have figured out 2 options

1. Siemens Scout OPC/UA

2. http://www.plccom.net/ There product seems to be pretty good, easy to use, no configuration to make.

Does anyone have any experience recently making a .NET application for an HMI linked to a S7 processor using Ethernet?

Right now the biggest chunk of data to be read by the .NET application is a DB that has following:

73630 Bytes Load Memory
72188 Bytes Work Memory

I'm just giving this 1 bump.

Has anyone used an S7 talking to a PC with Tcp/Ip?

rblunt said:

I'm just giving this 1 bump.

Has anyone used an S7 talking to a PC with Tcp/Ip?

Click to expand...

I have done s7 over tcp/ip (trend blocks). Note that one send command can only handle 64kB, if I recall.

I've never personally done the programming on the OPC UA client, but OPC is a very popular option.

Never tried plccom.

How often do you need that data from the PLC? I think siemens publishes some performance benchmarks on what to expect, but I think that transfer would be at least a second via OPC.

What about libnodave or snap7?

So i need to send in total 3,600 REAL values, preferably in 1 or 2 seconds every 3 or 4 seconds ideally.

It was my impression OPC is not meant to transfer a large volume of data?


I'm just looking at Snap7 right now, and I'll look at libnodave closer. My fear is that these 2 besides maybe not being any faster, are 3rd party not really supported by a company. I'm not sure that really matters though in this case.

rblunt said:

So i need to send in total 3,600 REAL values, preferably in 1 or 2 seconds every 3 or 4 seconds ideally.

It was my impression OPC is not meant to transfer a large volume of data?


I'm just looking at Snap7 right now, and I'll look at libnodave closer. My fear is that these 2 besides maybe not being any faster, are 3rd party not really supported by a company. I'm not sure that really matters though in this case.

Click to expand...

I can't comment on the ease of implementation, as I've never tried to use any of these before. I can say that it seems like it would be easier to use a library like snap7 or libnodave, instead of writing an OPC client to match up to an external OPC server.

On the technical capabilities, my guess is that most of these options will be similar. Snap7, libnodave, and most OPC servers all use S7 connections to get the data out of the PLC. I would expect that the PLC would process the requests from the different programs with similar bandwidth. Different tools may have different amounts of overhead on the PC end, or have a limit for how much data they support.

Snap 7 and libnodave were both written for the S7-300. There is a new version of the S7 protocol that is used in the 1200/1500. an S7-300 comm driver will be able to get data from standard DBs, but not Optimized DBs. My guess is most OPC servers (Kepware, etc) have a similar limitation, except for the Simatic Net OPC server from Siemens. I think Siemens is holding the new protocol pretty close.

TCP/IP, using blocks in the PLC, might be different than that. Not sure if it would be faster or slower.