Hello. I'm a Process Engineering student and I'm looking for the different advantages of Siemens vs. Allen Bradley PLCs and also SCADA Software from Siemens (WinCC) vs. RSViewSE (Rockwell). Maybe somebody with experience can help me?

Thank you very much,

Tiara Becerra

 

Hello,

the biggest Siemens advantage of the Siemens Simatic PLCs (against Allen-Bradley) is the flexible/modular conception of the SW system. You can devide your task into many different blocks, you can progam blocks with interface (for example: let have a few motors connected the same way to the PLC, you have to program just one block for the "motor" to start/stop it, to evaluate different states... and then you call this block more times and change the interface of the block call). With Siemens you can make the program block changes and download these changes into PLC without need to stop the PLC. Siemens offers more programing techniques (STL, FBD, LAD, SCL /Pascal like/, SFC /graphical programing/, CFC /graphical programing/).
For more specific question you can conntact me directly.
[email protected]

By,
Pavel Horak

 

Tiara

You will just open a can of worms with a question like this. Everyone will tell you their favourite. Essentially they will do the same thing in much the same way. You are best to look at more pragmatic things such as the knowlege base in the local area for programming and support/spares availability, existing systems on a site and the site's staff skills and experience.

 

We use AB and Siemens PLC lines here. They are comparable products. The difference is largely what native protocols they support. Siemens tends to support the European protocols: Profibus, ASI, and so forth. AB tends to support North American protocols natively such as ControlNet, DeviceNet, and EthernetIP. I should note that both can interface with the other's networks and both of them use published and open standards.

For most practical purposes, neither of them has an edge over the other. My personal bias is toward AB because their documentation and their products tend to take a more pragmatic approach to solving problems where Siemens tends to take a very close standards-based approach. This makes the Siemens Step 7 software a bit clunky and more difficult to use. However, that's my personal, North American opinion.

As for the issue of RSView verses WinCC, I don't have much experience with either. Frankly, both of them are based upon Microsoft Windows --and I have a poor opinion of Windows. (This is a well founded opinion --I've used and programmed in nearly every Microsoft OS since MS-DOS 1.12) I'd be more impressed if these folks would write a decent HMI for an embedded OS such as VxWorks, QNX, or perhaps even Linux.

I could rant on this subject for a long time. You'll find more than a few flames to go around on either side. The truth is that they are more similar than different. That's the way the PLC industry is these days. Ever since the '1131 standards, this industry has become more and more of a commodity.

Hope this helps...

 

Depending where you live the main difference between Siemens and Allen Bradley is the local support. They are priced about the same. A couple of other systems you might look at are Delta V from Fisher and Matrix Total Control from MTL/Standard Automation. We have used both and the installations have been succesfull.Both are form Global Companies with support Worldwide.

 

Tiara,

As many other have said, you will find both to be similar - large in size, in-flexible I/O, in-flexible rack systems, very expensive, etc. You should really consider the more compact PLCs that do as much or more than the others PLCs at about 1/3rd the cost. Some manufacturers of what I see as becomming the new PLC standard are Opto 22 (http://www.opto22.com)or WAGO (http://www.wago.com). WAGO supports more fieldbus protocols than Opto but either are a better solution than Siemens or AB.

 

This is a huge advantage, and is really the only significant difference capabilities wise. i would give ease of use in the programming software to AB as it is far more intuitive to use, although the Siemens scheme of saving all the related programs and configurations in a single location with a single backup is nice. People who have not experienced the power of user defined function
blocks (or refuse to) will never appreciate how much they can simplify your life. i wonder when AB will ever include this in the CLX. It would give them a huge advantage over Siemens, yet for some reason they just refuse to do it.

Bob Peterson

 

I would disagree with Pavel on this. A-B Logix family processors also support the use of multiple programming languages and even PLC-5's support the use of two languages (Ladder and SFC). Surprise, surprise A-B PLC's also include support for something called "subroutines" (which allow the use of reusable code).

Overall, there probably isn't much between the two. The deciding factor is probably your own experience. In a very wide sweep with a very broad brush, I would tend to think that Siemens PLC's require more of a computer programming background to even get started, whilst A-B PLC's are a lot easier for electricians (and other non programming types) to understand, program and maintain. But then I have more of an A-B background.

 

Another issue is that you should compare apples to apples. I would compare the capabilities of WinCC more properly to that of RSView32 rather than RSViewSE.

 

Compare their websites, Please belive me when I say they speak Volumes.

Siemens is a hodgepodge of where the hell am I, and I don't speak german.

Whereas AB is well organized and easy to follow.

 

Now you're confusing me, Bob. You say that Siemens present UDFB capability gives them a "huge advantage" over AB for those users willing and able to exploit it. Then you say that if AB puts this into the CLX, they will have a "huge advantage" over Siemens. How so, if Siemens already has it?

Steve Myres, PE
Automation Solutions
(480) 813-1145

 

As said previously, there is little to choose between the reliability of the hardware, the only reason I don't specify AB hardware here in England is that the hardware is hard to get, there is only ONE supplier - you do business with them or not at all!! My company, like many, buy direct from the US, saving 40% on UK prices, even after duty, etc.

--
Marc Sinclair
http://www.germainesystems.co.uk

 

Brian, sorry but I have to disagree. Could be the web pages aren't organized best way by Siemens. But you can’t say; "the web pages are bad looking and that mean the PLC is bad too".

I'm sure the Siemens program could be more difficult to understand for normal maintenance staff but not unconditionally. It is only the question how the programmer made the program. With A-B you can make unintelligible program, maybe faster than with Siemens (OK my private meaning). But I see the Siemens still better and not only because of presence lot of different languages (I prefer STL programming) I can program with. But because of program structuring possibilities. And one more, with Siemens I can program something like object /IT programming techniques/ (block with interface, internal functionality similar to methods, with internal memory, etc). And debugging functionality I find much better by Siemens.

Well, I’m European working with Siemens more than with A-B. It could be the reason why I see Siemens better.

[email protected]

 

Dear Brian,

What I noticed is that whole automation support site of siemens is in english. And it is not worse organised than AB's. You must have had bad attitude to it at least.

Regards,

Jacek Dobrowolski

BTW, I know some people speaking german who claim that AB site is lousy as they don't speak english. Think it over.

 

I have been using most PLC's over the last 20 (yes twenty!) years, but mostly A-B and Siemens.
I have Eurpoean university education, and experience but live in Australia for the past 15 years.
I have very good understanding and experience with Siemens Step5 and Step7 programming as well as Allen-Bradley PLC5, SLC and ControlLogix. A do complete system integration with Fix32, iFix, Wonderwre and Citect scada packages using anything from 300 tags to 25,000 tags.
Now, after the above introduction the fair comparision would be Siemens Step5 and A-B PLC5+SLC; and Siemens Step7 and ControlLogix.
You can achieve identical results with both systems. For years I have been working with an OEM machine manufacturer where the same machines were using Siemenes or A-B PLC's pending on customer requirements. I must say that there were no sigificant differences in performance. However, the only way to achieve good results is if you program the Siemens "the Siemens way" and the A-B in A-B way. Otherwise you end up with a mess! I have in fact seen Siemens programmers "translating" Siemens Step5 code into A-B PLC 5 - the end result was almost incomprehensible! I have also come across A-B programmers who wrote Siemens programs and the result was equally bad!

Then again, there are people who write programs which belongs in the garbage bin, regardless of the PLC brand...

I would say that the programming language itslef is not important at all! Other things are far more important, such as: The ability to create and Import/Export tags with excel to scada databases; massproduction of code; communication to third party equipment; program documentation capabilities; user friendly interface and so on. Based on these crieteria The A-B ControlLogix is better than the Siemens Step7.
The ControLogix program tree is far more user friendly that the Siemens. Also, the documentation of the Datablocks and data elements in Siemens is NOT user friendly - it simply takes much more time and effort and excel can not be used. The Step7 Pointer function is extermelly difficult to understand - probaly one of the most complicated functions in Step7. The existence of the different number formats makes it flexible (perhaps) but more time consuming to implement and monitor. Then there is one more important issue: system maintenance: The ordinary electricians who maintain the control systems will have more difficulties with a Siemens System than with an A-B system for the simle fact that the Siemens system is more "abstract". At the end of the day A-B ControlLogix wins over the Siemens Step-7.

 

Maybe I used the same adjective too many times. User defined function blocks are a substantial advantage from both a programming and testing perspective for those who actually use them. Not having them leaves a hole in its armor Siemens has not well exploited. AB could exploit such a new functionality if they chose to add it. My guess is they have it and are waiting for the marketing
mavens to decide its time to introduce it.

Bob Peterson

 

Yeah, i'll agree the STL language is better from an actual C++ Programmers Standpoint that actually Does Interpreted Languages Daily. But for 98% ("not including me") of our a.k.a > Industrial Programmers Ladder Logic is all they Know and care to know. Functions??? Procedures??? They would Blow a brain gasket to ever know any of that Stuff, they find it useless and have no idea what's it for or Does.

 

dear Brian,

no offense to any ladder programmer, but if STL is really as bad as you
state, why has it been included in IEC1131 standard?
Ladder logic is *definitely not* the only thing that "Industrial
Programmers know and care to know". It's an old, debated thread (and I'm
pretty sensitive on the subject), but the times when plain electricians
were making automation programs are over (or should be).
Functions? Procedures? Yes, that's what the software is *really* made of.
We should otherwise discuss what "Industrial Programmer" term do means.

regards
Luca Gallina

 

I'll second that thought on looking at what smaller, more nimble control vendors have to offer (acknowledging that I work for one). The March issue of Control magazine had a great article, "Second Tier, But Trying Harder", on just this subject -- link follows:

 

Joseph Voros has very neatly and accurately summarized the practical difference. Although, there is another dimension that I've found once too often overlooked by AB endorsed training and marketing programs, regarding engineering discipline, in particular with respect to life safety, environmental impact, and major economic risk. And frankly, I don't know which of these vendors today is better aligned with the needs of a consulting engineer to establish effective control of design, design verification, functional validition. In my 20 years of building both PLC and non-PLC industrial plant systems about half of the time, and dealing with more traditional hardware designs (safety related, electrical power, etc.) the other half, I find the most essential basis for using a PLC, is the structured discipline that comes with the PLC vendor's system approach including software.

I don't know of any situation in which the involvement of electricans and instrument technicians is an essential attribute of the PLC software, although many of those people are invaluable assets to implementation of minor system modifications, and critical in responding to hardware faults. One the other hand, a maintenance bargain unit that is bent on effectively sabatoging in-plant-engineering by claiming to own the plant systems and software is something I can live without even if my first priority of business is to make complicated technology understandable and workable for them and any other owner representive who is interested and paying for engineering services.

All PLC vendors appear to have evolved with increasing demand, I presume from software techies who have no understanding of genuine engineering risks, demand for dynamic control of program execution, that which makes a system resource crash or fault more threatening.

In that regard, I personally don't know to what standards AB adheres, but am willing to sputter and curse at the Siemens Step7, knowing that it reputedly adheres to some European standards developed explicitly for PLCs, and is not always as easy to mold into my designs as would be an ordinary C compiler with which I have crashed plenty of plant wide systems attempting to buffer information during a network failure, or left some other engineer wondering, what on earth was this program supposed to be about, whose design structure made all the sense in the world to me.

What I am seeing in this discussion, is that the Siemens software forces a prerequisite structure that may be an undesirable learning hump, until one is familiar with it, then finds that the programs developed by other engineers have less ability to be confusing about their structure.

So, I would guess, that those who are not engineers, who do not share information about their technical activities, who survive by secrecy rather than disclosure, would ultimately favor the AB system in the long haul, while those who survive by teamwork and standardization of design, would prefer the Siemens, but that is just a wild guess. And perhaps underlines that a really good PLC shop must be prepared for both types of customer.

[email protected]