STep programming in S7, a question of a method

[Combo]

Hi,

I have to start-up a project from someone else. He makes steps like this:

http://www.plctalk.net/qanda/uploads/steppie_1.jpg

"DB aanvoer1".toestemming is needed for start-up in step/step. My question is, how does this work what you can see here. When "DB aanvoer1".toestemming is low, then we jump over the actions (to M051 in this case). When we dont run automatically but in step/step, then "DB scherm".stapknop is high. So I think that, each time we push the start button, "DB aanvoer1".toestemming is high until AN "P303+" is done, because scherm".stapknop is high, aanvoer1".toestemming will be resetted, and we then jump again over the actioncode.

Okay, I think I'm on the right road. When scherm".stapknop is low, and we press start auto, then "DB aanvoer1".toestemming is high and we run through everything, because the JC will not jump.


BUT

Now see this:

http://www.plctalk.net/qanda/uploads/steppie_2.jpg

Here you can see that no action code is programmed, so this is more a wait step I guess ?



Little question, how do you guys see this, is there a better method to do the same, have automatic mode and step/step possibillity ?

[Marshy]

Using S7 Graph if you have Step7 Pro is most probably the easiest route.

[Combo]

S7 Graph, and there is one other, SFC or something ?

But wich one is best, and how much does it costs ?

Do u have a link for the siemens site about this ?

[Marshy]

S7 Graph, and there is one other, SFC or something ?

But wich one is best, and how much does it costs ?

Do u have a link for the siemens site about this ?

I've only ever used S7 Graph which is SFC (Sequential Function Chart) according to IEC 61131-3.

I think there is a package called Hi-graph not sure if it's similar or something completly different.

http://www2.sea.siemens.com/Products/Automation/Engineering-Software/?languagecode=en

I'm also not sure of the cost.

[Marshy]

I've just had a quick search and found a better link:
http://www.automation.siemens.com/simatic/industriesoftware/html_76/produkte/software-cfc.htm

[JesperMP]

The difference between Graph and HiGraph are like this (according to my most superficial investigation):

Graph is most suitable for linear step sequences. In other words there should only be one path in the steps. It IS possible to configure branching paths, but Siemens warns against too complex step networks. Alledgedly the generated code will become very big and inefficient.

HiGraph is suitable for more complex step sequences - like sequences you would map with a "state diagram". Alledgedly the generated code will stay efficient even for relatively complex state sequences. Also the graphical tool looks exactly like state diagrams and is therefore easier to interpret visually. I would like to experiment with it, but the price of 1000 Euro is a bit intimidating for such an option.

[RMA]

Siemens warns against too complex step networks. Alledgedly the generated code will become very big and inefficient.






Good job I didn't know this while I was working on the Rossendorf project! The heart of that project were nine (if I remember correctly) Graph7 FBs, three of which were so big that I had to break them into two parts because they had reached the maximum size (number of steps must be < 255 because the whole thing is based on JL commands). These all included several parts with 21 parallel paths.

Although the FBs concerned were pretty huge - 40 - 50+ kB, there was no apparent impact on performance. If I remember correctly the cycle times were around the 15 ms mark (on a 317-2 DP).

PS: it's a long time ago now, but I worked on a PCS7 project back in 2001 - 2002 and I seem to remember that part of the PCS7 package was an SFC program that was also called by that name. It was certainly a completely different animal to Graph7.

[Combo]

So there is graph and there is SFC, can you show or explain the difference ?


Another question is, if we have to continue in STL, then we should use Jump Label (JL) I think, I've red this in an other post of me. When using JL, I can say in a MB100 for example which step is needed. This MB100 can be monitorred, zo I don't need to send the value to anywhere for showing on screen, I can see this in MB100. That's good.

2 questions about JUMP LABEL:

- Is BE needed in every Step ? otherwise it keeps on running through the rest of the code behind this step.

- What about parallel steps ? In the method that I've shown when opneing this topic, there we use an array of bits to make steps. We can Set more then One step active... how van I do this when using JL



Good job I didn't know this while I was working on the Rossendorf project! The heart of that project were nine (if I remember correctly) Graph7 FBs, three of which were so big that I had to break them into two parts because they had reached the maximum size (number of steps must be < 255 because the whole thing is based on JL commands). These all included several parts with 21 parallel paths.

Although the FBs concerned were pretty huge - 40 - 50+ kB, there was no apparent impact on performance. If I remember correctly the cycle times were around the 15 ms mark (on a 317-2 DP).

PS: it's a long time ago now, but I worked on a PCS7 project back in 2001 - 2002 and I seem to remember that part of the PCS7 package was an SFC program that was also called by that name. It was certainly a completely different animal to Graph7.

[JesperMP]

Siemens "Graph" = IEC 61131-3 "SFC".

[RMA]

As Jesper says Graph is an IEC compliant version of SFC. The SFC program I worked with from PCS7 may or may not have been IEC compliant, it was probably a few years older, so it may not have been. I have no idea whether or not it is still part of PCS7, because I haven't worked with this since then.

As far as your question about building an SFC in STL, yes you will need a BE in each step, for the reason you mention. I have no idea how you would build parallel paths in an STL SFC though. I think this is the point at which you need to dish out the extra money for Graph7 - I can vouch for the fact that it's well worth it if you do need multiple parallel paths as I did. The graphical view makes monitoring paralalel paths very comfortable as well.

[dchartier]

Hello guys;

Just fr your information, engineering of the control system in PCS7 is done in combination of 2 programming codes: CFC charts, (something like FBD, but slightly more complex) built in SCL code, to establish direct process controls, and SFC sequences to call the different CFC structures and organise the process flow.

The SFC used in the PCS7 comntrol system is built on the original Grafcet standard (designed by the french AFCET in the 1980's); it also incorporates a variation of the original standard know as GEMMA (Gestion des Modes de Marche-Arret: Management of Start-Stop Modes) , a type of uber-SFC that analyses and maintains the different states the whole SFC can use: auto, manual, emergency stop, semi-auto, step by step modes...

So it is not compliant to IEC61131-3, and requires some getting used to when starting to use PCS7.

For those who could be interested, here is a link to the Siemens PCS7 portal; technical and prigramming manuals are available through this webpage:

https://pcs.khe.siemens.com/index.aspx?nr=1075
Hope this helps,
Daniel Chartier