STEP 7 Basics

eshmx1977 · Mar 31, 2011

Hello, recently some people in our plant bought a machine with a S7 300 PLC, we are not familiar with Siemens since our standard is AB, when we have problems with this machine is painful to diagnose, even move between blocks into the program, specifically I would like to know two things, first, how to force signals in the STEP 7 program and second, how to find in the program the objects with a "#" at the begining, for example, we have a contact called #stop, but when trying to find its coil I can not because there is a message that says "can not show cross reference for this object" it is frustrating, for me, any help would be apreciated.

P.S. I can not consider a STEP 7 training due costs, so I will have to learn on the hard way.

jonnies · Mar 31, 2011

Variables beginning with a "#" are local variables declared within that block. They are declared at the top under categories like input, output, stat, temp, etc. You can't find references of these variables because they only have scope in that block.

To manually change a variable, create a variable table in the project. Open it up, type in the addresses or symbol names of variables you would like to monitor/modify, and go online by hitting the glasses icon. Then you can modify them by right-clicking on the "Modify Value" column.

L D[AR2P#0.0] · Mar 31, 2011

How much did you pay for your Step 7 licence and how much will the training cost you?

JOLTRON · Mar 31, 2011

Even tho you can't cross reference local variables (#stop) you can hight light it and use ctrl+shift+B and ctrl+shift+f to search thru the local FB or FC. (I think it is also available from the drop down list if you right click on the contact/coil) This will also find it in the declaration above.

eshmx1977 · Mar 31, 2011

Thnaks for your answer, now I have another question, if these "#" are local variables how can I know why they are not changing the state, the specific problem is:

The machine is a tube deburring machine, the brushes motors are not working and the machine does not show any malfunction of the motors, the machine can start automatically but these motors don't we went into the program an see the Q20.5 (motor 1) and Q20.6 (motor 2) never on, following the path in the same block I found the "#StrtBrush" is never changing to true and I can not find why, any other idea?

eshmx1977 · Mar 31, 2011

by the way the cost of the program was about 7000 USD and the training is about 700 USD per person, but as you may know, our company is reducing costs, and since is the unique machine we have, they believe, is not profitable...any way thanks for your help...

jonnies · Mar 31, 2011

This would be hard to say without seeing the program for myself. However I would guess that maybe #StrtBrush is an input, and to see where it turns on you have to go to the block above where you are to see what is going into that input.

L D[AR2P#0.0] · Mar 31, 2011

eshmx1977 said:
following the path in the same block I found the "#StrtBrush" is never changing to true and I can not find why, any other idea?

Post a screen shot showing what you are seeing. Better still, use Simatic manager and create new library, insert an S7 program into the library and then copy the blocks from your project to the library. Archive the library then post as an attachment. (The library does not contain the h/w config and will normally be small enough to attach to a post on this site)

eshmx1977 · Mar 31, 2011

ok, ok, Icould find where those bits come from, now the problem is on Function block it is showed in red, do you know what this could mean??

Attached is a screenshot of what I see...

KalleOlsen · Apr 1, 2011

It is probably refering a instance DB that is not up to date.
Here are some remedys.
- Right click and select update block call.
OR
- Try saving, if that doesn't work:
- Close the editor, delete the referenced DB, reopen the editor and save. You will get a question if you want to generate the DB, answer yes.

Check this: http://lmgtfy.com/?q=step7+getting+started

Kalle

eshmx1977 · Apr 1, 2011

Thanks for your help, I have an idea in how to do that, but just to be sure, I have to do this in the part of the program where the block is? I mean, right click direclty on the red block?
Sorry but as I mentioned, my experience in Siemens is zero.

L D[AR2P#0.0] · Apr 1, 2011

A successful screen shot will stop the guessing.

eshmx1977 · Apr 1, 2011

well finally we decide to overwrite the damaged block and it worked, I really need to understand how STEP 7 works, it is a very interesting and different programing eviroment, I hope to have the oportunity of learn about.

Thanks all for your help, it really oriented me.

STEP 7 Basics

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