Control.com - Nerds in Control

Any thoughts on the two systems? Give me the good and the bad of both.

Well, S7 PLCs and the ControlLogix platform could be compared, and lead to long and convoluted discussions (it has already happened a couple of times, on this forum and others).

I would dare say that the question for you would be: how complex is your process, and what experience do you have with these 2 platforms? If you say none, the ;learning curve will be similar on both, and the deciding factor should be the quality of local support and training for your project.

However PCS7 is a totally different beast. It is based on S7-400 PLCs, true, but is is a complete distributed control system, incorporating SCADA tools, databases and communications, with a large library of specific functions and dedicated programming tools. It is used mostly in large and complex processes, and is built to those specifications. We have used it in aluminium smelters and power generator plants for example. It is much more than S7-400 PLC + WinCC SCADA software. It truly approaches the level of a DCS (for those skeptics who still will not give it the title).

So look for PCS7 where it is most applicable; it will depend on what the process you want to control presents itself.

This link will bring you to the PCS7 portal, for system descriptions and solutions:
https://www.automation.siemens.com/simatic/portal/html_7 6/product-navigation-pcs7.htm

This link will take you to much technical documentation on PCS7:
https://www.automation.siemens.com/simatic/portal/html_76/tec hdok_simatic/pcs7_701_techdoku.htm?HTTPS=REDIR

Hope this helps,
Daniel Chartier

ControlLogix is just a line of controllers, PCS7 is a complete hybrid DCS with both control hardware and HMI integrated. For the sake of comparison, I am considering ControlLogix with AB's RSViewSE HMI.

Hardware: Both are good platforms with a wide selection of I/O. AB uses EthernetIP and ControlNet for I/O, while Siemens uses Profibus-DP. I would consider this a wash.

Controller programming: Both platforms offer ladder, function block diagram, structured text and sequential function charts. Siemens also offers instruction list. I have found that with the exception of ladder, Siemens' programming software is much more mature and easier to use. One important point to make is for PCS7, programming is almost exclusively done in continuous function charts, with custom function blocks written in other languages. On the note of custom function blocks, AB has only had this capability since v16, which they released last year. Siemens has been doing this for much, much longer. The negative part of PCS7 is it can be more complicated to configure, especially if you do not have experience with Siemens' PLCs before. (For example, in the US, AB PLCs are much more common, and thus just about every integrator knows how to program them. Siemens PLCs are much more object oriented, and are programmed differently, so training may be an issue. If you are in Eur
ope, then this is probably less of a problem. You may also want to consider support. Depending on where you are, one platform may have a more engineers with experience who can support your installation.

HMI: To be fair, I have little experience with RSViewSE. From what I have seen, though, it seems to be a good product. The HMI used in PCS7 (WinCC) includes faceplates and a graphic library which is tightly integrated to the PCS7 function block library. (I'm not sure if this is the case with AB or not.)

Hopefully this was helpful. I would be interested in reading what other people who have used both platforms think.

Good assessment. I'm just coming off some Rockwell training, so I'm full of the latest info on how they approach this. Take it for what it's worth.

Rockwell Automation (AB) is beginning to show up in DCS applications using their ControlLogix as a multi-functional controller. They also claim that Ethernet IP and Devicenet are truly open (along with Modbus TCP/IP). I've read on this forum that users who wish to use a Profibus network should hard-spec which rev they desire V1/V2.

As you stated V16 made some HUGER leaps that brought Rockwell into the game. The FactoryTalk View is comparable to the WinCC... but I think they are really trying to take out Wonderware. The Add-On Instructions (AOI) are a new feature that created some buzz... predefined screens that hook directly into function blocks.

Anyway, I'm always interested in seeing how the top end controllers are compared. It seems that the market interest is shifting to lo-end controllers that mimic top-end functionality. It's critical for engineers to discern where that line is drawn.

In reply to TJ: With regards to Ethernet/IP being open, there was a previous discussion earlier this spring on that subject here (COMM: Ethernet/IP Communication http://www.control.com/thread/1026244726#1026245100).

To sum up that extensive discussion, the specifications for Ethernet/IP are available at a price "for evaluation purposes only". However, you are not allowed to implement them unless you are an ODVA member. To implement it (without being sued) you have to sign a contract, be accepted as a "member", give up various legal rights, jump through a lot of hoops, pay an annual fee, etc., and even then they might decide not to approve you. In other words, Ethernet/IP is a typical proprietary protocol with a "technology licensing program".

On the other hand, you can download the specs for Modbus/TCP and implement it and use it without getting permission from anyone or even telling them you are doing it. This is what most people would recognise as "open". Vendors know that customers want openness and an end to vendor lock-in, so they like to plaster the word "open" all over their products. Few actually deliver on it though.

With regards to "open" versus "proprietary", there doesn't seem to be any difference that I can see between Ethernet/IP and ProfiNet. Both are licensed to "partners" in pretty much the same manner. AB has ODVA, and Siemens has PI. In other words, neither Ethernet/IP nor ProfiNet can really be considered to be open.