Arne

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About Arne

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  • Location Stavanger, Norway
  • Interests Automation, Linux, computer security, traveling.
  1. Hello ! I think that quite many of those books I have found for learning to program Siemens Siemens Step 7 start out with the methods of building and using moduls, OB's, FC's, FB's, DB's etc before you learn almost anything else. For personell with background in programming and doing object oriented things like C++ it might be obvious what these things can be used for. For maintenance personell not used to these methods it might be not so familiar and possibly a bit confusing. It can be rather difficult to explain the use of FC's and FB's as the foirst step in the process of learning PLC programming. I think it is a good idea to start to learn and undertstand the more general terms and the use of each block before you extend these basic methods using a more structured aproach. In this way, from the point of view as I see it, the existing Allen Bradley book could be a great Step 7 book if it just got an amendment (or something like that) with the Step 7 implementations on the program codes and a rather easy and short amendment "how to expand this basic to also include more stuctured elements a la IEC 61131". Just some ideas .. Best reg Arne G.
  2. Hello ! Procedure as described above tested at Siemens Step 7. Works as described and expected. By the way, I think the book is great in the way it explaines the theory behind flow chart and state based design. Thats a thing I think I really has missed, a book that explain these things. There is really some books that explain syntax and not much more. When students ask "but how do you really think to make a PLC program" I think I have used to answer something like: "Well you have to know a lot of syntax and a lot of exaples and use these in a creative way". This book is much more methodical so it's very interesting to work trough the theory and the examples, and actually the theory and the methods is so "general", so I believe they can be used on allmost any PLC. (Even though adjusting some minor syntax details to make it work.) Of cource there is "an other story" about more specific Siemens and IEC 61131-3 related things like OB's, FC's, FB and DB's, program modularisation and things like that. My personal point of view is that some more Simens spesific books does to much out of this programming elements, explaining to much syntax and syntax oportunities, without any really good explanation of how to use this syntax. My personal point of view is that it might be a good idea to just let Siemens Step 7 ba as easy and classical as it can be, If you want it to be like that, and then rather to add on the more Siemens spesific things, on al later stage, "on top of that". ...Just some general reflections about the more general and the more specific related to PLC programming... Best reg Arne.
  3. Wheather you release B or C first, you will allways end up in St3. After the flickering and the alternating between ST2 and St3 you will allwaus end up in St3. It is locked in St3 and it can not come out of it. I tried to set in a positive flange detector, but even with that it was still stuck in St3. To come back to St2 "as is", and to avoyd jumping back to St3, you will have to releace B and C in the same fraction of a milisecond. Because of this it will be neccessary to build in some "tracking mechanism" to keep track om "where it came from", as long as input B ans C are used like they are. Using some other inputs as criteria for the transactions would also clear out the situation. The problem is actually rather interesting, because the boolean equatations is describing a logical situation with no "time factor" and no "sequences". The real life situation contanis a "time factor" and things that happen as a "sequence". Best reg Arne.
  4. Yes, thats right. The 12-36 program produced loops and "flickering". Because of this I tried to change it to SR flip flops. (To avoid the problems.) The 12-36 proram did not work for me "as-is" and I think there is som indications on logical faults in that program that is in the book, but of course I could be wrong (and I have never tried to program an Allan Bradley.) The problems experienced with the 12-36 program is explained in the link to the modified program with the SR flip flops (As far as I have tested it, I believe that the SR flip flop variant does not have the same problem. On the other side I belive it is not according to the Boolean equatation after the modification.
  5. Program 12-37 (rev 5) seems to be working without a problem. (Unchanged, near identical code seems to working on Allen Bradley and on Siemens step 7. I guess that the problems in 12-36 is just because of a "misprint" and that it was not the intention that 12.36 should be so much more difficult than 12.37 ? http://arne.dyndns.dk/plcbook/Chapter-12/p...c-states-12-37/
  6. By the way .. the problem in 12.36 prog 4 is only due to the use of inpu B and C more than one time. If it were like 12.37 prog 5, there would be no problem at all. here it is used 6 different inpust, A, B, C, D, E, F I think this should work easy at any PLC, allmost unchanged. Will give it a try ..
  7. I run into an interesting problem in page "plc states - 12.36", Rev 5 of the book. I chosed this problem because it looked "so easy", but actually it apeared to be "so difficult". Does this progran code really run on Allen Bradley PLC ? (It might be something that I have not understood, but for me it looks like it is "something" with the logic in this program". Woluld be happy for any ideas or suggestions. http://arne.dyndns.dk/plcbook/Chapter-12/p...c-states-12-36/ Best reg Arne.
  8. Hello ! Think I start to understand what "delayed update" means .. Thought ST1X were just "another bit" but it actually keeps its value for one aditional "turn" of the program execution ?! (On the Allen Bradley.) Could not find such a function for the Step-7 and don't know if it exist at all, but I belive I got the same functionality running using set and reset on the outout (?!) http://arne.dyndns.dk/plcbook/Chapter-12/Figure-12-24/ By the way .. is it any progress with the Omron/Telemechanique etc .. translation ?? (I think such translations for diferent brands and program systems could lead to som "average program code" that can be used for nearly any PLC.) By the way, thanks for the comments because it's booring to work on things just alone. Best reg Arne.
  9. Hello ! I think I havn't done that yet. "delayed update and state transition equations" Sounds interesting. Do you have a reference to a certain page ? (I will try to test it out if I know exactely wich page or program.) Best reg Arne
  10. The state based programs in chapter 12 seems to be easy to implement to the Step 7. (Or any other modern PLC I believe.) I hope that there is some people with the rifgt equipment that makes translation to the other brands and program systems as well. http://arne.dyndns.dk/plcbook/
  11. http://arne.dyndns.dk/plcbook/Chapter-11/P...rogram-11.16-1/
  12. I think this programming of the first flowchart in Ch 11 is an easy one. I belive it can be implemented for most PLC's: http://arne.dyndns.dk/plcbook/Chapter-11/P...m-1-simplified/
  13. I think my first program example works, but it might not be to good. Will try to come up with a bether design. I hope that we can develop program soulutions for some of the major brands, so that the free book can be used by "all of us" not only those who have a Allen Bradley. I think that those prinsiples and methods that is in the book actually can be adapted to allmost any new PLS.
  14. Simulator for CX ?

    I have some experience programming Omron PLC via Syswin. One thing that I am missing in Syswin sis that there is no simulator so you allways will need a PLC to check out your program. Does the new CX program contain a simulator or is it possible to buy such a simulator as an "ad on" ? Best reg Arne.
  15. Step 7 first scan bit ?

    I do agree that my impression of Omron is that it is a lot easier to get started with. One thing about Siemens, I think, is also that things are explained in a more difficult way than it had to be, trough manuals, books, etc. Siemens can also be easy if explained (My opinion). Have tried Omron with Syswin, but never the new CX. Does it contain a simulator, so you can train programming on your laptop without the PLC ? Best reg Arne.