migration from AB to Siemens 2

[kchap]

I work for an OEM that has used AB controls exclusively for the past ten years. We have a new customer who wants to standardize on Siemens, and we have been wrestling with them for quite some time now over the controls platform issue. They have brought in Siemens reps to woo us with all kinds of promises concerning hardware availability and support.

Is there anyone out there who has enough experience on both AB Logix5000 and Siemens to offer some guidance - especially in the motion area? I'll offer details as needed. Thanks.

 

[Ddons]

The question should be "What are you trying to accomplish?"

We use the lower line Siemens stuff with a lot of success and ease. I have found however that some of the lower line stuff can be purchased with the IDEC name on it and it seems to be an exact replacement at half the cost. An example is the Siemens LOGO which is the exact same unit as the IDEC Smart Relay. Now both these are just a smart relay with limited ability, however, for lighter controls of motion on a digital platform, they are great. Analog can be accomidated as well, but the issue is with coms as these only communicate with LONWorks or AS-International. We prefer RS485.

Don Spiker
Spike R Consulting

http://www.lewis-equipment.com

 

[controlsdude]

I have mostly did AB controls for mostly 15 years but I had to do a job using Siemens. Then also worked with brits who also used siemens on projects. I saw that the siemens plcs S7-200 was similar to the plc5, S7-300 was more integrated similar to the contrologix processors. S7 were tag based processors like the contrologix. They off the same ladder,structured text, etc as contrologix. Profibus was slower than controlnet. But you had hi speed counters for fast inputs such as motion needs.

But as far as motion goes, the brits always used the Control Techniques drives for any motion applications. I think CT beat both siemens and ab hands down. Cheap and the best product on market for motion.

Just remember their is only one way to program the siemens processors which is the german way. The problem and best thing about AB contrologix is that it is too open.

Biggest thing to remember is that AB processors are big endian and Siemens are little endian or is it the other way around.

As far as hardware goes I did not have any problems with siemens getting local and job site support. That all goes back to rep support and people relationships.

 

[FrancisL]

Many years ago I worked on a rescue project that started exactly as you describe. The OEM - the supplier of the process equipment (a polymer extruder plus the associated powder and pellet handling etc) had long been providing AB PLC systems. The client insisted that the supplier use Siemens.
A supposed expert Siemens Systems Integrator (lets call them Fred) was employed to provide the PLC's because the OEM did not want to work with Siemens.
The result was a disaster, but not really because of the Siemens/AB issue.
In the end we ditched Fred’s software and then myself and a real Siemens expert and the OEM worked together to replace the software - we completely succeeded.
Now, the issue as I said was not Siemens v AB, rather it was a combination of mostly Fred's incompetence and to a degree the inability of the OEM to specify the required functionality in a way that was independent of the actual system being used.
Siemens PLC can certainly be programmed do what your AB programs do. In general, the modularity was similar but the contents of the modules very different.
I do Not recommend taking your AB ladder and attempting to replicate it in Siemens Ladder. Take a higher level view of the software so that you have a system independent software design first (one that can apply to either Siemens or AB) then design the Siemens version.

 

[jraef]

Comments from a former AB programmer now working for Siemens;

I agree the structure of the S7 programming is very much like the Contrologix, but different from the SLC series (RSLogix). You will find a lot of similarities but you may want to get specific training from Siemens on their system because it will be different and in fact, what you did in Logix 5000 may take fewer steps in S7 (at least in my experience so far).

I never got a chance to do motion programming on AB systems personally, but from what others have told me the S7 modules for that are slightly easier to implement.

You can compare Controlnet to Profibus all day long and not come up with a decision that everyone will agree on, other than that there are good and bad things about both. Besides, no matter what we all think, the world is going Ethernet whether we like it or not IMHO.

In the Micro products as described by Ddons, ONLY the Siemens LOGO is the same as the Idec Smart Relay. Siemens makes it, Idec brand labels it. So if you paid 2x the price for the Siemens, you were not talking to the right Siemens distributor! The LOGO however is not a PLC nor is it intended to be a motion platform. It is a relay replacer with a little analog capability. If you have an intelligent drive system and just want to add some logic control for peripherals, the LOGO is OK for that, but there is no Motion control module for it.

 

[spook6869]

I work for a systems integrator and have successfully implemented both AB and Siemens. I've used PLC5, SLC5/0x and Logix. I've used Siemens S7 300.

Personally I found the Siemens very difficult to use. I didn't find the languages to be similar at all. Siemens has two different locations for data, and the syntax is different for each one and quite confusing to me (dbw.dbx5?). Everything is organized in bytes. When compared to tag-based addressing and 32-bit containers, my preference is clear. ..and what’s up with the timer syntax? :-D I fully admit that I might be biased because I “grew up” with AB, and learned the complete system in baby steps, but I find it far, far easier to use.

What I wanted to mention, however, was at least try out motion on Logix. Greatest... Thing... Ever.... I've never done motion on Siemens, but in Logix, the drives are basically extensions of the IO tree. The controller parameterizes the drive and the parameters are stored in the controller program. There is no separate drive software and no separate drive programs to write/store/maintain. There is no separate network to commission on the controller or drive end. If your customer replaces a drive in the field, the controller reparameterizes it automatically. You have all the drive data at your fingertips, and you can write code around it. Motion instructions drop right into ladder. The controller can change drive parameters on the fly!

It can be a pain to commission motion axis. Using the sample code that came with RSLogix 5000, I had my system moving in 15 minutes... I'm never going back--you can't make me go back! :-X

Even if you don't end up using it, check it out for fun.

Bottom line is the success of your project is dependent upon the skills of your engineers. Good engineers can make anything work on any platform. Bad engineers will screw up the simplest of systems. The rest is balancing system material cost with design labor...

 

[mandarvs]

easiest thing to do would be the following :
1. buy a motion control drives from siemens -- the motion control is avialable as free blocks in the drive itself.
2. controllers are freely programmable & readily available in the S7-300 series onwards. you can program these for motion control.

 

[jhprotech]

I am looking at a reverse situation at the moment

A client is looking at converting their S5 to SLC5/04 for their gas turbine generator. I was told SLC5 may not have as quick sampling time as S5 but I was failed to find any definite answer on their datasheets.

Would like to know if anyone can shine me some light...?

 

[robertjo24]

FYI...

We recently left Siemens for AB. We were a Siemens house for ever, but when they dicontinued the platform we use, we went out for an RFP for a nwe platform to migrate to.
Siemens never bothered to respond, figuring they already had the business.
Big mistake.

Just my $0.02.

 

[djs]

Hello;
I am a systems integrator, which works will all different platforms including DCS. In my opinion, the biggest difference between Siemens and AB is communications. It is much easier to get AB units to talk to one another then it is with Siemens.
So if you are designing a standalone system, with one processor, there is no real difference. However if you have a multi processor system, then AB is the choice.

 

[CanadianTaff]

True consumed tags make commes easier, but when I link Step 7 PLC's I tend to use DP couplers which makes it really easy.

There are advantages / disadvantages to both and I like both.

Some things better in Step 7 (I mean 300's and 400's here) are:

1. Ability to go on-line with a project which is not the same and compare to see the differences.

2. Ability to download small chunks of code. Which is good for preparing off-line changes and downloading without stopping the PLC.

3. Sub routines / common code.

4. Everything in one package, no need for additional software for connecting (Linx, I'm sorry is crap), comms, comparing, etc.

5. Able to mix ladder and STL to suite the functions your achieving.

These are just a couple, would be nice if Step 7 had test edits like AB.

ControlNet and Profibus are different animals so can't really be compared, DeviceNet, good god nooooo...

Both are good platforms, I believe at the moment S7 is more stable though.

 

[hillimonster]

I agree with Spook6869 (see above) as far as ease of use for Siemens. I have used AB forever and ocasionally get asked to use Seimens s7-300.
I think the addressing is confusing, especially when talking over profibus. The fact that you can only monitor one Function Block at a time. You can't monitor periferal input/output words. The endless conversion of data between byte, BCD, Floating point, etc.
Making on-line changes to function blocks that are called from from OB1, seems to generate all kinds of timestamp errors that can't be fixed. I always do everything offline and download now.
The fact that inside a function block if you have a temp tag, you can't search for it.


I do not have any motion control experience with Seimens, and frankly I wouldn't like to experience that. I think the motion implementation of AB is quite easy to use.

 

[CanadianTaff]

I think the addressing is confusing, especially when talking over profibus. - Not sure what you mean here.

The fact that you can only monitor one Function Block at a time. - Do you mean open multiple windows as in tiling, you can do that. Got to be honest can't remember if they all update or you have to click on the window.

The endless conversion of data between byte, BCD, Floating point, etc. - ?? you can look at data in whatever format you want, I don't see byte as a format, although BCD and Floating point are.

Making on-line changes to function blocks that are called from from OB1, seems to generate all kinds of timestamp errors that can't be fixed. - Never come across that, I don't place much in the way of code in OB1 though, its usually better to use OB1 as a distribution block, keep the size to a minimum.

The fact that inside a function block if you have a temp tag, you can't search for it. - The TEMP's are scratch flags, they only exist in the block in which they are created and you can search for them in the block very easily. Right click and find next.

Siemens is different from AB, its structured completely differently, both have good/bad points I don't see anything above thats particularly bad except the OB1 thing which I have not come across in 10 years.

On the other hand as someone recently becoming re-aquainted with AB, I find AB very frustrating with certain things.

At the end of the day, once I am used to its quirks and differences I'll find it better.

When there was S5 and PLC5, AB won hands down, S7 and ControlLogix, S7 wins hands down.

Only an opinion.

 

[CanadianTaff]

Nearly forgot.. frustrating not having VAT tables in AB