7/8/2009 3:43 AM | |
Posts: 22 Rating: (18) |
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 | |
Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236) |
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 | |
Posts: 2661 Rating: (279) |
Hey Lalit & Ritu! You guys deserve to be recruited as salesmen for Siemens! Being a Siemens graybeard, I really appreciate your posts! Keep up the good work!! 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 programin less than90 minutes! IMO, one area Siemens can improve is documentation. We have come a long way if I compare with Siemens documentationof early 80's but stillsome way to go... Regards |
Last edited by: Phantom75 at: 7/8/2009 5:19 AM |
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7/8/2009 5:33 AM | |
Posts: 22 Rating: (18) |
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 possible . it may need atleast 3-4, because Siemens is Different than all other PLC. I hope our Moderator will forward our feedback and direct it to Appropriate person. |
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7/8/2009 11:14 AM | |
Joined: 10/7/2005 Last visit: 9/24/2024 Posts: 3022 Rating: (1054) |
Dear all |
Last edited by: fritz at: 7/10/2009 1:37 PMEdit 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 |
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7/8/2009 3:57 PM | |
Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236) |
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, |
7/10/2009 2:34 PM | |
Joined: 10/7/2005 Last visit: 9/24/2024 Posts: 3022 Rating: (1054) |
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 tagis 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. |
Last edited by: fritz at: 7/14/2009 3:46 PMCheers |
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7/11/2009 3:46 AM | |
Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236) |
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:
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. |
7/11/2009 6:17 AM | |
Posts: 2661 Rating: (279) |
Hi Lalit, That was a "profound" post! The reality is, each system is good (or bad)in it's own way. But since this isa 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 inmy 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 Ifrequently 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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7/12/2009 2:30 PM | |
Joined: 10/7/2005 Last visit: 9/24/2024 Posts: 3022 Rating: (1054) |
Excellent point Phantom75 and the same can be said for the following words from lalit:
Let's also not forget that people tend to like what they know (or have experience with). A/B PLC’s and their programming software are perceived by A/B fans to be “easier”, “more powerful” and more “user friendly” than Siemens PLC’s and I can see where this (WRONG) perception comes from. For one, ControlLogix PLC’s have a wealth of inbuilt instructions (e.g. Array (file) shift/compare/search/sort instructions, FIFO buffer handling, the hideous “compute” instruction etc.etc.) which far exceeds what you’ll find in the “normal” Step7 instruction set. There is of course a wealth of SFC’s/SFB’s available to begin with and a considerable amount of IEC blocks, knowing that they exist can of course be a challenge. I don’t mean to be sarcastic here and its good that these questions are asked, but even in this forum we have questions like “Is there a way to set all values to zero in a DB”, the simple answer is of course “Yes, have a look at SFC21”, but people simple aren't "naturally" aware of these. And you can of course always develop your own blocks to do what you want to do and neatly put them into libraries (or use blocks created by others such as www.oscat.de). Secondly, programming of a ControlLogix PLC takes a lot of the thinking effort away from you. For example, essentially all math and compare instructions exist only as one instruction, whereas Step7 has as set of INT, DINT and REAL for these. And yes, you can compare an INT with a REAL via the A/B compare instruction (you can even compare STRINGS with the same instruction!). The compiler will in runtime convert and match the data types and spit out the result. You can also for example add an INT with a DINT and have the result delivered as a REAL (in one common ADD instruction). People (who don’t know better) like this nonsense, it does however lead to “sloppy” programming techniques and can cause unforeseen results (note that even the manual actually states that every instruction has so called “optimal” data types which makes the instruction execute faster and requires less memory and these are typically DINT or REAL. There is additionally a long section at the end in the instruction set manual that describes what rules govern the conversion of one data type to another if mixed data types are used). Anyway, I’ve seen a colleague during commissioning scratching his head why his comparison didn’t deliver the results he thought it should, until he realised that he fell prey to the usage of mixed data types. To sum this yet again way to drawn out entry up: Siemens PLC’s are more logical, more strictand don’t hide anything from you. Human nature unfortunately favors being a bit lazy and being able to quickly program something without the need to fully understand what you are doing and in this case (and this case alone)A/B programming wins against Siemens programming (and for the record, A/B PLC’s are Toys, I am after all entitled to my narrow-minded point of view). Lastely dear lalit, there are twomore points to add to your main list, which are: 1.)Controllogix PLC's don't have a process image available. If you want to ensure that Inputs stay the same throughout the scan you need to create an input buffer via programming. 2.) NO STL available in A/B PLC's (and if this not the clear winner than I don't know what is, I can't belive I didn't think of this straight away) Keep up the good work guys |
Last edited by: fritz at: 7/12/2009 2:54 PMLast edited by: fritz at: 7/12/2009 2:38 PMLast edited by: fritz at: 7/12/2009 2:37 PMCheers |
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7/12/2009 11:30 PM | |
Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236) |
Hi Fritz & Phantom, Its nice to have you guys on the forum, as you explained the things nicely, I have added the points mentioned by you on the features page. I will keep it updated as and when I will find something. Thanks. |
7/13/2009 7:33 AM | |
Posts: 118 Rating: (4) |
Hello All, In AB we have "TAG DATA MONITOR TOOL", its same as Variable Table. but when we compare both, Variable table is the best one. Just to share. |
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7/13/2009 5:14 PM | |
Posts: 2661 Rating: (279) |
How true! Fritz, I believe you have hit the nail on the head! Regards |
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7/14/2009 7:40 AM | |
Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236) |
Hi Fritz, I can't stop myself from keep giving you 5 Star rating for the efforts you have done to explain this thing so much clearly. Fritz> It is really the people like you and Phantom who makes the things different. You guys are the real expert on this forum, I hope our moderator will recoginze your efforts to keep this forum so lively, so interesting, so much knowledgeable and so much active. Keep it up Guys! And Fritz the below word is absolutely from you. Cheers! |
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8/12/2009 3:21 PM | |
Posts: 487 Rating: (45) |
I think this comes from the way American PLC Market (or for that matter any product) is. In US the first and most important requirement is user friendliness, not the power and feature of product. In most of the rest of the world engineers program PLC. In US, mostly technicians program PLCs, and the background of these technicians can be mechanical or whatever. They may not have gone to any technical school. I have met people in plants who started in plant as an machine operator or something and later became maintenance technicians. For such people, it is difficult to get the concept of accumulator/Boolean operation etc. So they love AB because that's what they can work with. (I think this may be the reason Siemens has less market share in US) I always believed Siemens is an engineer's PLC. (That is how a PLC should be). It has excellent features, very flexible, very structured and more over extremely powerful. I have not seen any other PLC that has so many module spectrums. I think this is one point that was missed in this discussion. You can find a module for almost every application. Another area where Siemens wins hands down is communication. First of all the TIA concept makes it so easy to configure communication. (I have to confess, inS5 days, communications was difficult to configure/program for many). Profibus is miles ahead of ControlNet and DeviceNet. Though, Ethernet/IP is easier that other A/B supported networks, it has been proved by Univ. of Michigan that Profinet is far more reliable communication for I/O. I still rememberthe days we changed PLCproduct usedby the biggest Tobacco Company inthecountry I worked then from AB to Siemens just by comparing Profibus& ASiVS ControlNet & DeviceNet. Being an Ex-Siemens guy and a fan of Siemens products, I suream biased, butthere are few things I like about ControlLogix. And I have to sayRSLogix ladder editor (being their bread and butter language) is much easier than Siemens. Drag and drop and drawing "rungs"is much easier. I guess I had to say something good about AB. After all, being in USA now, sometimes I am forced to work with AB. |
Last edited by: JMJ at: 8/12/2009 3:27 PMLast edited by: JMJ at: 8/12/2009 3:23 PM |
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9/17/2009 3:39 AM | |
Posts: 37 Rating: (0) |
One thing that always strikes me about Siemens is that the documentation is huge. Sometimes you download a manual to look for something in what you expect to be a basic search and understand, you open the pdf and it is a 400+ page manual. It puts you off reading them sometimes and this is why this forum is a great help. |
9/23/2009 6:52 PM | |
Posts: 261 Rating: (42) |
You are absolutely right. It seems like a big family and we all are the members. One word I want to share that, it’s one of the best ways to learn and gather Knowledge. With best regards ddg |
10/30/2009 9:08 PM | |
Posts: 3 Rating: (1) |
Lucky123 (and others), Pardon me here because I'm a *** on this site. I have worked with A-B for years and now have a job where I will be working with Siemens exclusively. I have been using Siemens for a little over six months now and, sorry, I can't let Lucky's comments go unanswered. To be fair, Siemens has some good points. In response: - "Download Individual Routine/OB" You can make edits to individual routines in A-B then commit the changes, so yes A-B does this. A-B also lets you test the edits before you commit them, which is an advantage over Siemens and something Siemens can't do. Being able to download an individual block is actually a disadvantage as it too easily allows situations to happen where two or more people have the latest code for certain blocks, but no one person has the complete program. This is why A-B is like this. You can also have to or more people editing A-B at the same time and the edits will transfer to the other's PC. Siemens can't do that. - "Easy Symbol/Description Copy/Paste from Excel" so it takes about 30 seconds to convert the file. Big deal. The .csv file also lets you do plain text editing and also lets you exclude unnecessary columns. - "Byte Structure" This is no big deal. Just group the bools together in UDTs. Siemens does the same thing, except with bytes and with a few megs of memory, it is superfluous. - "STL/Ladder/FBD Switch over" since all of Siemen's code in the processor is primitive, assembly-like STL, all it is doing is making the code easier to understand. A-B actually downloads in ladder or ST. I do understand this point and can somewhat agree, though. - "Variable Table" A-B does have these, they are just called something else (I don't have a PC w/A-B software to confirm). A-B also has a feature where you can record tag values like a scope. Siemens has this as a separate package. - "FC’s & FB" A-B v17 has this. They have had this since the inception of ControlLogix, but you have not been able to monitor individual instances. - "Online Block Monitoring" Siemens will actually read the value of the tags at the point in the logic that you are viewing, which is somewhat of an advantage, however, if the logic is not being executed because of a jump, it will never read it. A-B just reads the value of the tag. I have found Siemens monitoring to be buggy. For instance, tags below a certain point on the screen will not refresh in the logic editor or the VAT table (pain in the rear!). So I have to scroll just to see a tag's value! Also, Siemens CANNOT monitor more than one FC or FB at the same time. If you want to monitor another block, you have to stop monitoring the previous block at the same time. Also, to have more than one person trying to monitoring a PLC at the same time almost cannot be done because you get a "resource event trigger" error or something. With A-B, youCAN monitor as many routines at a time as you like and CAN have more than one person monitoring the same PLC. - "Data Block" A-B does not have data blocks. It just has tags. Why do you need data blocks? They are an archaic throwback to the S5, like STL, OBs and a lot of other S7 items (A-B actually started with a clean slate when they designed ControlLogix). There is no advantage to data blocks over tags. These tags are addresses-less. So you don't EVER have to worry about tag addressing! It has UDTs that are WAY easier to create than Siemens. You create a UDT, then you can create a tag with a datatype of that UDT. The documentation you place in the UDT then goes with every tag of that UDT so you only have to document once. With Siemens, the UDTs are antiquated with the byte, word and double-word addressing, etc. If you need to add some interface stuff to A-B for a sub-routine, you just add it. You don't have to worry about addressing and the size of the interface. With Siemens, you have to always remember to go to the calling routines (good luck finding them all) and click "File", then "Check and Update Accesses" and all the other crap so that it doesn't crash the PLC. If you need to update a UDT in A-B, just update it and it does the error-checking, etc. - "Process Image" this is because A-B CLX does not have the traditional scan cycle (read inputs, scan logic, write outputs) like traditional PLCs. Instead it can have multiple programs, each running either continuously or at specified intervals. It takes a few minutes to write a routine to buffer the inputs; a small trade-off for the flexibility. With that said, let me make my oen list of things A-B can do that Siemens can't: - Search: this is a BIG FEATURE that Siemens CAN'T do! In a routine in A-B, I just press CTRL-F and I can find ANY text ANYwhere in the program! It will find that text in tags, comments orinstructions ANYWHERE in the PLC program or in that routine only. Siemens doesn't do that. Siemens CAN'T find comments. Want to find a tag that may be addressed as either DB100.DBX10.1 or as "MyDB".mybit? Good luck because the search for the address for one will not find the symbol and vice versa. - Indexing: in Siemens, you can't do array indexing in ladder. In A-B, it is as easy as MyArray[myinex].mytag. In Siemens, you CAN'T do this. You have to use the primitive, archaic, antiquated, difficult STL language to create a pointer. This is almost no better than an S5. - Single file save: A-B saves the program as an .ACD file. With Siemens, if you want to give someone the latest program, you have to archive it then they have to retrieve it. What a pain. -- A-B also save as .L5K, a text-based xml-like file that can be manipulated by programs like Excel using script to rapidly create PLC programs. - The reason Siemens has so many programming options like C, etc. is because, unlike A-B, you can't do everything in ladder. I have done some pretty complicated stuff in A-B and it can all easilybe done in ladder. If you want to program using 4 or 5 different languages, then compile them, then write FCs to call and interface them and glue them together and crash the PLC when it lets you download separate FBs and FCs that are mismatched, then try to find out why it crashed, be my guest. - Monitor multiple routines: you CAN'T monitor more than one FC or FB in Siemens. A-B - no problem; monitor as many as you like! - Monitoring by multiple people: you CAN'T have more than one person monitoring a PLC at a time. A-B no problem! - Automatically update from changes made by another person: if two people are online making changes at a time in A-B, the changes made by one person will be uploaded automatically by the other person's software. Siemens CAN'T do that! Also, good luck making sure you have the complete latest code in this case with Siemens! - There's more, but I am tired of typing! |
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10/30/2009 9:59 PM | |
Posts: 3 Rating: (1) |
Sorry, Lucky, a few more points to reply to: "2.) NO STL available in A/B PLC's (and if this not the clear winner than I don't know what is, I can't belive I didn't think of this straight away)" To say that a PLC has to have something like STL is to say that Microsoft Visual C# needs to have a direct assembly language programming tool. STL is akin to assembly language (I believe that's what it actually is). The reason that A-B does not have STL is that this is the 21st century! Languages are moving to a higher level. Why would anyone, except out of old-fashioned codger stubborness or nostalgia, want to spend time converting datatypes from bytes to int to real when they can just have one instruction that takes it and just does it? It is much quicker and, with the faster CPUs, the extra CPU overheaddoesn't really matter. The point here is, the A-B PLC is simple enough that a beginner can sit down and write a sloppy program and get a machine running without knowing STL, LAD, SCL, etc. But once they learn and want to create a structured program, they can start using DINTs and other tricks to get the scan time lower for more complicated things. "the hideous “compute” instruction" this instruction is here to make things easier. Yes it has some overhead, but if you just want to play with a formula or algorithm, it is there to just enter a formula, not spend hours trying to get the PLC to properly do acalculation in STL. That's what it's about - convenience. If someone is trying to get a calculation right to control a process, they want to work on the formula and NOT worry about the PLC language. Then, when they are sure about their formula, they can break the instruction down to something more efficient if scan time is a factor. The point here is to save time. If I spend a few hours struggling with converting INTs to DINTs, loading and transferring accumulators and having to make pointers to arrays in STL, that time is money. Programs are faster to write in A-B because it is a higher level language and you don't have to think about every detail. "Secondly, a half decent size program can easily have a few thousands tags in it. With Controllogix, the only distinguishing factor between each tagis their name (remember, no addresses anymore), or in other words, that Tag database easily becomes a gigantic mess as far as I’m concerned." (from fritz) With A-B, if you have a group of tags that you want to keep in a group, you can just create a UDT for them. If you have a conveyor that has a motor, sensors, timers, counters, etc, you can group all these into a UDT and then make a tag, tags or or an array of that UDT, as many as you like with the UDT for a template. This is a very easy way to keep it structured and provides a great deal of flexibility in the way you can structure it. You can even nest UDTs. If you have 50 conveyors and each conveyor has one, two or more motors, you can make a UDT for the motors, then nest the motor UDT in the conveyor UDT. I have written dozens of PLC programs in A-B CLX and there has never been a problem with too many tags. You say that A-B takes a lot of thought away, but it just lets you put the thought where it belongs - in thinking about the structure of the PLC program. All of the PLC programs I have written have been structured, but it takes less time to write them. "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." If you really want something like a DB, then just create a UDT. The A-B UDT is more flexible than the DB. |
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11/30/2009 9:35 PM | |
Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236) |
Hi AB Guy, Thanks for your comments, however you mentioned a lot about ADD on Instructions, however there are Anamolies, till date all the Anamolies have not been resolved by Rockwell. The fully tested version without having any Anamolies is expected to Release by Dec 2011, which is far away. Moreover in this competetive Era there is a word Fully tested and working for years which means Siemens. Where As under test and modificiations a Revesion every 6 months which is Rockwell. Let the Software establish itself for years any version, without any anamolies then you can realize an End user prospective. An End user is not a developer who pays for a continous modificiaction, an End User is the customer who pays for his machine to perform the same for quite few years without any anamolies. Thanks for your nice comments about RW. I agree with some of it however here we talk more about Siemens. |
2/25/2010 6:50 PM | |
Posts: 42 Rating: (3) |
Shall we compare software preformance? Siemens: Runs slow on even a high-end laptop giving you an excuse on why your boss needs to buy you that shiny new laptop. This also has a side effect of encouraging multi-tasking while waiting on that much beloved hourglass. Rockwell, Omron, really any other automation software package: Runs on any decent computer forcing you to keep your old laptop longer. Wulfgar |
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4/2/2010 8:36 PM | |
Posts: 8 Rating: (2) |
I recently wrote an article explaining some of the practical differences between Siemens and Allen Bradley (AB), especially focused on function blocks. Check it out here: Siemens vs Allen-Bradley: Function BlocksHope this is informative. |
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6/29/2010 3:34 PM | |
Posts: 1 Rating: (0) |
Compare a Logix with a s7 is like comparing an iPod with a mp3 player from the Lidll it has same features but its not the same thing. |
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6/29/2010 3:55 PM | |
Posts: 42 Rating: (3) |
High Speed Trace/Graph Function: Siemens: NO! Omron, AB, most modern PLC/PAC Yes Even the old DOS based Yaskawa had a trace function |
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6/29/2010 8:29 PM | |
Joined: 3/21/2006 Last visit: 9/10/2024 Posts: 10228 Rating: (1181) |
Hello guys, One question - Why all software from other companies have drivers or support Simenes hardware? I am not familiar with Yaskawa, but probably I could use its trace functions with Siemens hardware. From other side, why Siemens supports only its hardware. OK, at the moment this is not exactly true, but... Best regards, Hristo Mihalev |
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8/3/2010 4:08 PM | |
Posts: 4 Rating: (1) |
AB_Guy, I so agree. I have been programming A/B PLC2-ControlLogix, Modicon, Telemecanique, Omron, Mitsubishi, S5, and now S7 for 20 years. I have been using just the S7 for the last year or so. I STILL hate the "Structure" and how anyone can claim S7 is superior to a ControlLogix is beyond me. The "Power" of the FB is highly over rated. There is nothing there that cannot be done using a UDT and a JSR. But the real problem I have is trying to do an indirect array. Things that I can do in 5 simple ladder rungs takes me hours to figure out if it will work at all in the S7. Don |
Last edited by: Don Sigman at: 8/3/2010 4:10 PM |
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8/3/2010 4:16 PM | |
Posts: 8946 Rating: (999) |
Hi Don, it is easy to do with SCL - language! |
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3/14/2011 3:41 AM | |
Joined: 10/17/2008 Last visit: 3/10/2021 Posts: 4 Rating: (6) |
I have used S7 for 2 years. I understand most of it. The first year was pure torture. My list of advantages. Siemens: Nearly impossible to learn in less than 3 months. I did it, it wasn't fun. I still find gotchas all over the place. Any A/B platform: I learned them all in a week or two with one book. Yes ONE easy to find manual. Two if you download the separate instruction list only book. Read that again S7 guys. A/B has a manual with every instruction listed WITH a clear example of its use AND its FREEEEEE!!! Show me a list of instructions for S7 from Siemens. Please, I still can't find the instruction I need without a search. Siemens documentation: I had a stack of printed manuals over 3 feet high from Siemens. I bought the three books from Hans Burger for 100 USD EACH!!!!!! and I still have questions. I have never seen so many words used to say so little, and do it in such an unclear manner. I even found that some issues I understood were made so unclear I began to wonder if I understood any of it. I also bought "Step 7 in 7 steps" and this was the only useful book in the bunch. Of course it is written surprisingly like an A/B manual by an American. A/B instruction list: Look at the top of the page, open the group, select the function. Use arrow key over for more groups. Groups are logical and easy to find. S7: Libraries are a mix of functions with no discernible pattern. If you don't know where it is already prepare for a 5 to 20 minute search. 40% of the functions are not named in a way that describes the function very well. So you have to look them up in the help file. Good luck with the help file. Sometimes all you get is a sentence or two with very few examples. Hope your Germanic English is good. Siemens: You can address any piece of the memory any way you want, even if the parts overlap. There is no warning, no limit, but there is a memory map you can use to check after you find out where it is. Go ahead use M2.2 and MW2 and MWD1 no problem. And go ahead do some math with some memory. Is that a word or an Integer? A/B: in versions before Logix 5000, the memory area is addressed by the data type. N3 is the third integer. Period. You want to use the second bit of that INT for something? N3.2. Want to use the same memory for a real, sorry can't do that. Might cause a problem. You want to use a bool? Go get the next one not used. Oh the mem map is right there beside the program window. See all the memory addresses right there? Not enough, need more INTs? Extend the array of INTs in the memory. Never overwrites anything or steps on any other memory. Want to use the same area for a word , a double word and a real? Sorry, that's insane. Can't do it. Hardware config? Siemens: define each piece of hardware manualy. And you better get it right. A/B: Go online with the processor. Select auto config. Confirm. Save. Done. You can also do it yourself if you like or edit it after auto config. Using an instruction block. A/B: Pick a group, timers/ counters, bools, math, move instructions, conversions......select group, drop down list of available instructions. Select one. Drag or double click. Place variables. Go to next rung. Siemens: Look through list of instuctions beside programming window which has most of the instructions. Most are easy to find if they are in this list. If what you want is not there, like a linear scaling function. Look down at the libraries. Yes there is more than one, yes you can even make your own. And you will need to if you want to find anything with reasonable results. Place instruction from library on network. Input variables. Wonder why it doesn't work. The input says it needs an INT. MW5 contains the variable 9. It is an INT!!! no no, you have to go to the symbol table and declare it to be an INT and NOT a word, which is the default. Or try using a constant. Go ahead. I want to enter "9" as an INT constant. In A/B, its a "9" type it in the blank and hit enter. In S7, you need a suffix. OK fine. True /False is a bool. B#16#0 to B#16#FF is a byte Word 16 bits : Binary number 2#0 to 2#1111_1111_1111_1111 <2 prefix Hexadecimal number W#16#0 to W#16#FFFF <W#16# HEX prefix BCD C#0 to C#999 <C# prefix Decimal number unsigned B#(0,0) to B#(255,255) < B# prefix DINT (Double integer) 32 Decimal number signed L#-2147483648 to L#2147483647 <notice the "L"? Keep that in mind. L is prefix. REAL (Floating-point number) 32 IEEE Floating-point number Upper limit +/-3.402823e+38 Now pay attention..........INT (Integer) 16 Decimal number signed -32768 to 32767 <hey look no prefix! OK so INT must be the default right? NO! ok so if I just type in "9" S7 knows I want an INT right? NOOOOOOOO! Have fun with that one. There is a prefix for every number entry except INT and INT is NOT recognized as the default. Read some one else's code. A/B: online or offline, everyone uses standard blocks and instructions. Some people go about the big picture differently, but if you want to do a specific function, it is done with this one instruction and everyone knows what it does or can look it up in a very nice and complete help file or manual. Siemens: If it is written in LAD, most of it is fairly easy to follow until the DB indirect addressing starts. Then a custom function is written in STL because the processor will do it, but there is no instruction in LAD to use the function. SO even LAD programs have to use STL. Now if the whole program is in STL, Just hope it works. STL can and will do anything in such convoluted methods it is easier to re-write the whole program than try to follow something someone else wrote. If the programmer was a German from S5, good luck. Be careful if you edit anything, who knows what is moving around in the loops and indirect addressing. Now you want to see something online and troubleshoot? Well you can open an FC in S7 and see some variables, but after the first network none of it is even close to right. Do they mention any of this in the manual? Not that I found. You will find new odd bits about S7 for as long as you use it. None of it is straight forward. I have learned over 12 PLC languages, S7 is the most counter intuitive of them all. Of course since everyone hates S7 around here, I have good job security. Few I know will even touch Siemens. It's just not worth the hassle. Will they ever update S7 or make it better? I have not seen the new version yet V10. Maybe it is better. But I would not bet on it. Probably just cosmetic changes and more insane gotchas. Even if it is better, I doubt I will see it for 10 years. No one is going to buy the new one for another 5 thousand dollars, just because it is better. The boss doesn't have to use everyday. Can S7 do things A/B can't? yes. Do you need those things? I never did. You do enjoy more flexibility with S7, and you need it. A/B is so easy to use, it makes me feel funny, like I'm not really working. I spend most of the time thinking about what needs to happen, and then 10% of the time entering code that works. S7, without the PLC SIM, I can't even guess whether a new function I just wrote will work or not. I spend 80% of my time online searching for information and reading through non help files trying decrypt the purpose of the standard functions. It is easier to write my own many times than to even try to use the standard blocks. Good thing I have that flexibility. And Data blocks are just one dimensional arrays, not sure why everyone thinks they are so great. Give me a 2 dimensional table with a row of data. Each column is a different data type and I can search one column and then look over at the corresponding data in that row from a different column. Nope, can't do that. Excel does it. Everyone thinks this way. Whats the big deal about a spreadsheet with one column? Excel users would freak out if they could have one column. If you really want to open this debate, use the different PLCs for a year , then look back on the experience. Only S7 programmers have trouble seeing how other PLCs work. And only S7 is a problem for programmers of any other brand. That alone should tell you something. Go ahead and try to twist the argument in your favor. But you know the truth. |
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3/14/2011 3:52 AM | |
Joined: 10/17/2008 Last visit: 3/10/2021 Posts: 4 Rating: (6) |
"But the real problem I have is trying to do an indirect array. No no, the basic package does not include SCL. Do indirect addressing with Ladder. Oops, have to do that in STL. And it looks and feels like your hacking a PC to make it work. There is no function block that does this. You have to manipulate the accumulators and go through several hard to follow steps to make this work. And figure out how pointers work and the whole data type thing. It is ugly. Everything written in S7 can be infinitely variable, no 2 programmers do the same thing the same way. Nice to have the flexibility, not so nice to require the end user to do most of the work Siemens should have done in the first place. |
Last edited by: dahnuguy at: 3/14/2011 3:54 AM |
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3/14/2011 8:08 AM | |
Joined: 3/21/2006 Last visit: 9/10/2024 Posts: 10228 Rating: (1181) |
Ooouuu dahnuguy, to be a little OFFTOPIC, I could say your comparing betwen S7 and AB is amazing. Thank you for sharing with us your expirience. |
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3/14/2011 1:10 PM | |
Posts: 4 Rating: (1) |
I have now been using the S7 exclusively for a year now on the same program. IF I was given the option to scrap it and start over in a Control Logix I would in a heart beat. There is nothing friendly and intuitive about S7. It amazes me the hoops and contortions it takes to do indirect array addresses. I do not know how anyone can hate the Compute instruction. It is a marvelous feature. S7 is so antiquated you can't even do a drag and drop. Heck you can barely do a cut and paste. I will be so happy when I am through with this job and go back to ANY other processor. |
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3/15/2011 1:12 AM | |
Joined: 10/7/2005 Last visit: 9/24/2024 Posts: 3022 Rating: (1054) |
Dear all |
Last edited by: fritz at: 3/18/2011 1:55 PMfixed up broken dark side of the force link Cheers |
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6/3/2011 9:03 PM | |
Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236) |
After working on Siemens PLC for last few years, I can see why people find it hard to work on Siemens.Based upon my experience, It may take you a while to understand it. Moreover, if for a while if you switch away from it, then it makes you work harder to make yourself efficient on Siemens. Where as developing an application on AB or any other PLC might be comparatively easier. Though, I strongly agree that Siemens makes a better and Robust Product, even the software. Support and Customer Care is Awesome. Only thing is you just need to work on it for a longer period of time to understand it better. |
6/3/2011 10:09 PM | |
Joined: 1/28/2009 Last visit: 9/10/2024 Posts: 6849 Rating: (1365) |
I am using SIMENS PLCs for a long time and , for me it is much easier to find solution for automation tasks.AB is much easier to start from zero but you have flexible and powerful tools in SIEMENS programming tools. As I compare , the rate of module failure in much higher than SIEMENS products.AB is really fragile in harsh environment. This is only a feedback. regards |
6/3/2011 10:26 PM | |
Posts: 4 Rating: (1) |
Really??? I can program any level of complexity faster and more straight forward in AB then in Siemens. Try a multi indirect address array in S7 and you will see what I mean. |
Last edited by: Don Sigman at: 6/3/2011 10:51 PM |
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6/3/2011 10:47 PM | |
Joined: 1/28/2009 Last visit: 9/10/2024 Posts: 6849 Rating: (1365) |
What I mentioned is not the scientific fact, this is matter of preference and experience. Of course, AB is also one of the leading brands in the international market. Regards |
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6/6/2011 8:39 PM | |
Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236) |
Yes, I completely agree with you, you can make many things faster and straight, may be for smaller or medium sized applications. But you do not have SCL in AB, which can simplify hell lot of things when you have to deal with bigger plants and several other bigger complicated algorithams.
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Last edited by: Lucky123 at: 6/6/2011 8:40 PM |
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6/6/2011 10:00 PM | |
Joined: 1/28/2009 Last visit: 9/10/2024 Posts: 6849 Rating: (1365) |
I accept that 2 company have 2 different approaches to do same task or they may followed some standards in their products.As a person who have worked with SIEMENS , it is really difficult to handle AB products. As an example, Data archiving and trends in WINCC is activated by a simple wizard, tag selection and a check mark in start up of the project.But I had a big trouble writing codes to activate the trends in RSVIEW and also trend control is not available like we have in WINCC. I did the job, but I quit further working with RSVIEW . regards |
6/7/2011 5:07 PM | |
Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236) |
There is no comparison of RSView with WINCC. I have never seen anyone who likes to work with RSView.
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6/7/2011 6:17 PM | |
Joined: 1/28/2009 Last visit: 9/10/2024 Posts: 6849 Rating: (1365) |
RSView,frequent change of properties and also name of product to be afraid of encountering new interfaces in each revision.But in WINCC, you can work with it , if you have basic knowledge. There are also some important point which bother a SIMATIC user: 1-In rslogix5000, the description or help of a function is not available by selecting the function and presing <F1> 2-All project I have checked,they just used some routines which may return a value.It is a big mystry till now ,for me , how to create a FC or FB like in STEP7. regards |
6/7/2011 6:35 PM | |
Posts: 8 Rating: (2) |
hdhosseini, take a look at previous posting in this thread that discusses modular programming in RSLogix 5000. AOIs are the closest thing to FBs in the Rockwell world. In my experience, very few Rockwell programmers have adopted this powerful tool. Siemens programmers who are more familiar with Function Blocks, however, should be able to easily adopt and capitalize on this feature. -Nick
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6/8/2011 5:19 AM | |
Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236) |
Your Comparison seems awesome. I think you should elaborate little more on it(emphasising for beginners of siemens). As it will give a better idea to the people who know AB and trying to learn Siemens. It would be nice if you could use this forum for elaborating it more, I am sure people would like it. Keep it up!
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11/14/2011 6:15 PM | |
Posts: 18 Rating: (0) |
I think Don Sigman's post is exact right. AB tops S7 as far as being easy to use. |
11/14/2011 6:43 PM | |
Joined: 3/21/2006 Last visit: 9/10/2024 Posts: 10228 Rating: (1181) |
OFFTOPIC I am sure that almost in all big companies (more then 1000 employers) the contracts for revamps, installing and improving a new equipments with the newer control units have been signed the people (managers) which "didn't care about CPU's excellent features...So, if you are lucky OK but there is not possibility to make a choice. OK fully agree in case of small projects. Best regards, Hristo Mihalev |
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11/15/2011 4:59 PM | |
Posts: 18 Rating: (0) |
It's not just 'small projects' where people like me think that "workability" is much more important than "features", it's also the larger projects (like SCADA systems and multiple PLC networks). Just look at the 2011 Control Magazine Readers Awards results pollinghundreds ofprofessionals in our industry: Rockwell tops Siemens in all categories. http://www.controlglobal.com/Media/2011/1101/Cg1101_CovTable1.pdf I think it is a shame that someone starts a thread like this on this support website asa "sales gimick"so that Siemens employees/distributors can post their biased opinions posing as controls engineers like me with real world experience. And I'm not a Rockwell employee, just one knows what works best for most companies in the automation world(less workable PLC/HMIs= more engineering development time = less profit). I think the moderater should delete this thread, it serves no constructive purpose. |
Last edited by: garf123 at: 11/15/2011 5:13 PM |
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11/16/2011 12:40 AM | |
Joined: 10/7/2005 Last visit: 9/24/2024 Posts: 3022 Rating: (1054) |
Hello garf123
While it is hosted and moderated by Siemens and falls under the Umbrella oftheir Service & Support offering, it is still a Forum where everyone is invited to express their opinion.
Guilty as charged . Then again, aren't we all biased in one way or another?
I fear you are fighting fire with fire here as far as being biased is concerned. Control Magazineis published by Putman Media which is based in the USAbut at leastcredibleenough to admitthat thesurvey results are biased bystating the following (see HERE for more): "This year's awards represent the collective opinion of over 1000 automation professionals. The results still reflect a North American bias. However, each year we see more responses from automation professionals from outside the United States."
It serves the purpose of people openly voicing their opinions which is a key function of any forum (call it "freedom of speech" if you like and I think this is something we can all agree on to be a good thing). |
Cheers |
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2/3/2012 6:40 AM | |
Posts: 79 Rating: (7) |
Its nice, but what ever the features, COST MATTERS A LOT.......!!!!! Just compare cost of both, then you will see why people prefers allen-bradley......!!! In cost of S7 300-400, you cant get onboard Ethernet, DB-8 & DB-9 pin com ports, onboard analog I/Os in cost of Micrologix or Controllogix from AB. I wite this coz i have already worked in both make's PLC, SCADA, HMI..... |
2/28/2012 11:42 PM | |
Posts: 8 Rating: (0) |
Just like to add as a former AB user and now using Siemens for 2 years I will never use AB by choice again. Too many things to list why I prefer it over AB gav s |
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4/20/2012 3:09 PM | |
Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236) |
Please compare Apple to Apple and Orange to Orange. What cost analysis you are talking about is not exactly in line with the hardware. A micrologix can not be compared with even S7200 PLC, leave S7300/400 aside. You can not get the cheapest model of Control Logix CPU with S7 300 CPU series. With S7300 series PN/DP port comes along with CPU, which is not the case with CLX. You will have to buy seperate ETH module with AB unlike SIemens. So here again Siemens is cost effective. |
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