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Excellent features of Siemens which AB Control Logix Does not have

Thread Starter: Lucky123   Started: 7/8/2009 3:30 AM   Replies: 61

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  7/8/2009, 3:30 AM
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Hello Guyscool

If you have extensive experience on Allen Bradley(such as Control-Logix) Products like meblush and yougrin just started working on Siemens Products then there is a good news for youlaugh, I found some very good things about Siemens which even AB's Most popular product Control Logixtogue does not havesad.
Below is the comparisonblink
Note: I will update it as and when I will find out. Rnf:lblSmileyTooltip_xxx

COMPARISON

Features

AB-CLX 5000

S7-300/400

Remarks

Download Individual Routine/OB

NO

YES

In case of AB the complete Program Download requires much more time

Easy Symbol/Description Copy/Paste from Excel

NO

YES

In case of AB one need to export the tags in CSV file which is less convenient

Byte Structure

Yes*

YES

AB uses 32 bits minimum for creating any Tag, in case we are creating a tag of Boolean, BYTE, INT type we  waste the remaining bits of the memory

STL/Ladder/FBD Switch over

NO

YES

AB uses 4 Languages( Ladder, ST, SFC, FBD) You can't switch from one to another

Drag & Drop HW configuration

NO

YES

Less Convenient in AB.

Save HW Configuration Separately

NO

YES

Not an Option

AB Technical Support

Yes*

YES

For AB Technical Support you must have a contract in order to chat with a specialist

Full Trail Version of Software with License (14 days)

No

YES

Without license you can't Run the software.

PLC Simulation

Yes*

YES

AB PLC Simulation has very limited features. You can’t test the real program with simulator. If you need to simulate the program you would need to go through a painful procedure and still you can’t test everything. (In other words not fully supportive).

Variable Table

NO

YES

Variable Table is an Excellent Feature of Siemens.

FC’s & FB

NO

YES

AB does not have fully supportive FB & FC’s.

Online Block Monitoring

NO

YES

In Siemens what you see is what you get, though its not necessarily true in AB.

Data Block

NO

YES

Data Block Concept does not exist in AB.

Process Image

NO

YES

Process Image (buffered image of inputs and outputs) is a builtin feature of Siemens whereas in AB it must be done by via programming.




=== Edited by lalit @ 7/14/2009 6:02 PM [GMT ] ===


=== Edited by lalit @ 7/13/2009 1:12 AM [GMT ] ===


=== Edited by lalit @ 7/13/2009 12:41 AM [GMT ] ===


=== Edited by lalit @ 7/12/2009 11:25 PM [GMT ] ===


=== Edited by lalit @ 7/12/2009 11:23 PM [GMT ] ===


=== Edited by lalit @ 7/12/2009 11:22 PM [GMT ] ===


=== Edited by lalit @ 7/12/2009 11:21 PM [GMT ] ===
Please see the Fritz Notes below for explanation of the newly added points.

=== Edited by lalit @ 7/8/2009 3:37 AM [GMT ] ===


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  7/8/2009, 3:43 AM
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Hello Lalit,

Great to know that Siemens products have several good points. One point I would like to add, is FC's and FB,

AB does not have that either( not fully functional like Siemens).

Thanks
Ritu
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  7/8/2009, 3:51 AM
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Hi Ritu,

Thanks, I forgot to mention that and I also forgot to mention that in AB you can't test the actual program as AB PLC SIM does not have all the hardware. So one need to modify the complete HW configuration in order to Simulate, and thereafter also many limitiation.

Where as Siemens PLC SIM is a successful Simulation product.

Thanks
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  7/8/2009, 5:18 AM
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Hey Lalit & Ritu!

You guys deserve to be recruited as salesmen for Siemens!togue

Being a Siemens graybeard, I really appreciate your posts!grin
Keep up the good work!!gringrin

Now on a serious note, many years ago I had an opportunity of working with AB products. The thing that impressed me was their documentation. Even though I had never worked with PLC/5 before, I was able to setup a system (including software installation) and produce a working program in less than 90 minutes!

IMO, one area Siemens can improve is documentation. We have come a long way if I compare with Siemens documentation of early 80's but still some way to go...

Regards



=== Edited by Phantom75 @ 7/8/2009 5:19 AM [GMT ] ===


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  7/8/2009, 5:33 AM
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Phantom75 wrote:
Hey Lalit & Ritu!


IMO, one area Siemens can improve is documentation. We have come a long way if I compare with Siemens documentation of early 80's but still some way to go...

Regards


Hi Phantom,

Thanks for your comments,
I just started working on Siemens products and I am learner, I spend most of my time in reading the FAQ  section.

I have worked on AB, and I would agree with you on documentation part, I too remember when I started working on AB I picked up one SLC/500 and one manual, and I was all set to go. However in case of Siemens with one manual it is not possiblemad . it may need atleast 3-4, because Siemens is Different than all other PLCtogue.

I hope our Moderator will forward our feedback and direct it to Appropriate person.



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  7/8/2009, 11:14 AM
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Dear all

it's been over a decade since I last touched PLC5 and a few years since I was last "forced" to be involved in a ControlLogix project (I called this project a "downgrade" from S5 to A/B).
I believe my key "learning’s" from this experience are still valid for the latest generation ControlLogix/RSLogix but can't guarantee this though.
It would be great if someone with the latest A/B gear can verify this since I promised myself that this was definitely the last time I touch A/B gear.

Anyway, based on my experience there are two key things missing in lalit's list:

1.) Online Block monitoring


Siemens PLC:
In a Siemens PLC (dating back to S5 days) online Block monitoring displays the status of the monitored logic as it is when executed by the PLC.
Take the following examples (I need to make this point strongly, as this is THE single most important feature in a Siemens PLC as far as I'm concerned):
A Memory Bit that is used in a couple of Networks and for instance SET to "1" in NW1 but reset to "0" in NW2, will display the status correctly for both positions!!!!
A single TEMP variable that may be used a number of times in a Network for intermittent result storage of for example a mathematical calculations will nonetheless show the value that it holds correctly for each usage in all locations!!!!
I call this simply the "What you see is what you get" principle (and we all seem to take it for granted).

To do so, the CPU uses so called trigger points for online block status monitoring and needs to work a bit "harder". This is one of the reasons that S7-300 thus far allow you to monitor only one Block at any given time (to be changed soon, with the release of the latest 300's and firmware V3.0 you'll be able to monitor 2 Blocks at the same time, just like a 400 can).    

A/B PLC:
Supply of the actual status of Bits, Bytes, INT's etc.of the logic during online Block monitoring is done via simple read out of the internal data memory whenever the comms allow to do so (i.e. similar to a Variable table monitoring in an S7, except you can decide if it is updated at the start or end of the scan).
I call this the "What you see is NOT necessarily what you get" principle and I find it utterly frustrating and confusing (as a matter of fact, you will see live status of the logic even if the subroutine is currently NOT called).   

2.) Data Blocks
This concept simply doesn't exist in a ControlLogix PLC.
While you can create structures and the likes in the "flat" memory of a ControlLogix, it just doesn't cut it for me and isn't the same as being able to do what you can do with DB's.    

Anyway, that's my two cents worth.




=== Edited by fritz @ 7/10/2009 1:37 PM [GMT ] ===
Edit Data Blocks section (replaced A/B with ControlLogix) since PLC5''s were similar in memory organisation to what Db''s allow you to do in a Siemens PLC.


Cheers

fritz

The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited.
To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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  7/8/2009, 3:57 PM
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Hi Fritz,

Completely agree on 1st point, as explained in detail. but did not very well understand your second point,

Could you please elaborate in detail, it might be a good point which I am not aware of.

Thanks,
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  7/10/2009, 2:34 PM
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No worries lalit, the majority A/B fans that I’ve met in my life don’t get it either when I try to give them valid reasons for abandoning their “toys” and start programming real PLC’s (such is the power of the dark side of the force or my inability to explain things properly). 

Anyway, back onto the subject and I’ll hopefully be able to make it clearer what I mean.
Put simple, ControlLogix user data memory is just one big file (aka Tag database) in which you create your “tags” (well, one big global data file, every routine can also use local memory).
It has all the IEC compliant features such as Arrays (3 dimensional is max though), STRUCT’s, UDT’s etc.If you need a new (global) Tag (e.g. a bit, INT, REAL or whatever) you simply create a new one (as you program), give it a symbolic name and off you go.
It is indeed very similar to what you can do with the Local (TEMP) memory in an FC or FB.

Sounds too easy and great doesn’t it?
Well, here are things that rub me the wrong way about it:
In Rockwell’s own words In the RSLogix 5000 programming environment, data is set up in a tag database. Memory addresses are hidden from the programmer, which makes things easier for the programmer.”
Call me old fashioned, but I don’t get how pure symbolic addressing makes things easier compared to  being able to do either symbolic programming or address based programming (which S7 allows and you can freely switch between the two).

Secondly, a half decent size program can easily have a few thousands tags in it.
With Controllogix, the only distinguishing factor between each tag is their name (remember, no addresses anymore), or in other words, that Tag database easily becomes a gigantic mess as far as I’m concerned.
 

S7 DB functionality on the other hand allows you neatly structure your user data area in two ways (inside the DB’s AND by being able to have more than one DB).
Add to that the availability of M bits and Local (TEMP) data and even the program with the biggest data memory requirements can still be structured in a easy to identify format (e.g. if you look for Alarms you would give the “Alarm DB” the name “Alarms”, I think by now you get what I’m trying to explain). 

One last things, this thread is of course seriously Siemens biased (and so it should be, we are not really here to promote Rockwell, are we?) and there are probably features in ControlLogix 5000 that Step7 could benefit from. 



=== Edited by fritz @ 7/14/2009 3:46 PM [GMT ] ===



Cheers

fritz

The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited.
To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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  7/11/2009, 3:46 AM
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fritz wrote:

Anyway, back onto the subject and I’ll hopefully be able to make it clearer what I mean.
Put simple, ControlLogix user data memory is just one big file (aka Tag database) in which you create your “tags” (well, one big global data file, every routine can also use local memory).
It has all the IEC compliant features such as Arrays (3 dimensional is max though), STRUCT’s, UDT’s etc.If you need a new (global) Tag (e.g. a bit, INT, REAL or whatever) you simply create a new one (as you program), give it a symbolic name and off you go.
It is indeed very similar to what you can do with the Local (TEMP) memory in an FC or FB.

Sounds too easy and great doesn’t it?
Well, here are things that rub me the wrong way about it:
In Rockwell’s own words In the RSLogix 5000 programming environment, data is set up in a tag database. Memory addresses are hidden from the programmer, which makes things easier for the programmer.”
Call me old fashioned, but I don’t get how pure symbolic addressing makes things easier compared to  being able to do either symbolic programming or address based programming (which S7 allows and you can freely switch between the two).

Secondly, a half decent size program can easily have a few thousands tags in it.
With Controllogix, the only distinguishing factor between each tag is their name (remember, no addresses anymore), or in other words, that Tag database easily becomes a gigantic mess as far as I’m concerned.
 

S7 DB functionality on the other hand allows you neatly structure your user data area in two ways (inside the DB’s AND by being able to have more than one DB).
Add to that the availability of M bits and Local (TEMP) data and even the program with the biggest data memory requirements can still be structured in a easy to identify format (e.g. if you look for Alarms you would give the “Alarm DB” the name “Alarms”, I think by now you get what I’m trying to explain). 

One last things, this thread is of course seriously Siemens biased (and so it should be, we are not really here to promote Rockwell ,are we?) and there are properly features in ControlLogix 5000 that Step7 could benefit from.   

Hi Fritz, 

I think some part from the above is coming inside my mind and some part is going over my mind( because of lack of experience in having practically done the above which you mentioned). Any how I appreciate I got this information and sooner I will try to implement the way you have mentioned. 
However I appreciate you efforts for trying to explain the things as I requested. 

Last but not the least I would like to comment on the below one:

fritz wrote:
No worries lalit, the majority A/B fans that I’ve met in my life don’t get it either when I try to give them valid reasons for abandoning their “toys” and start programming real PLC’s (such is the power of the dark side of the force or my inability to explain things properly).  

I have seen several people stating the same things for either AB or Siemens. 

I would say it, people sometimes are reluctant to change though I might be wrong as I am a human being.

But let's take the example of any one if a person is working on AB PLC. If he is experienced for 20 years in AB, how positively he tries to learn any other PLC but it will take some time for him to learn Siemens and he will always try to find AB in Siemens. 
 
And vice versa is true as well. 
I know there are certain things for which you can Call A/B as "toys" but the same thing people might say about "Siemens".

Any how as well said> we are here to talk about Siemens and Certainly I have started finding new features in Siemens which other PLC's might not have.

Thanks, I hope to ask few more questions/clarification here on this forum.

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  7/11/2009, 6:17 AM
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Hi Lalit,
That was a "profound" post!grin

The reality is, each system is good (or bad)  in it's own way. But since this is a Siemens forum and since you started the thread Excellent features of Siemens... we need to bring out positive aspects of Siemens and fritz was doing just that!

My own experience with AB is extremely limited and I already stated the pros in my earlier post.
In other words I am an extremely biased pro Siemens guy who has been able to defend (and sell) Siemens to numerous Emerson, ABB, Honeywell, APACS loving customers over the years.

The most common refrain I frequently hear against Siemens is, "It's too complicated" and my answer always is, it's structured and systematic. You have to invest time and effort to understand the system, after that it's a cakewalk.

Regards
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