Siemens PLC-SIM simulation

[spaderkung]

Hello,

I would like to use PLC-SIM together with some PC-software, for instance VB, and have my PLC-program connected to a PC-based plant model (fancy words for having S7 read from cells in XL).

With InTouch and Dassidirect I can pretty much accomplish this, but it still requires a physical PLC. I assume there's a price attached to the software option sas well, but it will not take up any physical space.

Regards
Jon

 

[Bratt]

You can use the S7ProSim COM Object with vb6 and vb.net its included with plcsim. Detailed information can be found in the manual XX\Siemens\Plcsim\s7manual\s7wsi\s7wspscb.pdf

 

[spaderkung]

Thanks, will check. Is this something you have experience with?

 

[spaderkung]

Couldn't find the edit, so here's a new post with update.

Got the ProSim working; wrote a VB app that scans, pauses, read/write DB and so on. However, some of the events are not triggered from PLC-Sim but only from the VB app. (PauseStateChanged triggers for instance only when "pause" is pressed in my app).

Next step is to decode the German logic behind the floating-point format so I can handle more than bools and signed integers.

 

[jvdcande]

There is no 'German logic' behind the floating-point numbers used in S7. Step 7 simply uses the 32 bit implementation of the IEEE 754 standard, which can be reviewed here.

Kind regards,

 

[spaderkung]

Of course. Reviewed. Verified. (Glad to find no byteswapping as in DWORD).

 

[Arun]

Hi Jean

Good Information on the Link.
Thank you refreshing my knowledge

 

[spaderkung]

After writing conversion functions to and from "readable" format and IEEE.Single, i realize that there's no need. The interface will handle real(!) signals and anlogue signals are not fp, but words (PQW, PIW).

 

[tel]

Hi, I am doing the same thing...

I build a block in step7 and want to test it. But i have no PLC.
I am using Prosim to simulate it.

I want it to read input from an excel file and write the output to another excel file. I am new to VB. Could you share what you did to do that?

Please. Really appreciate any help

 

[tel]

there's another thing..I can't get it to read floating point numbers. any idea to work around it?

 

[spaderkung]

I have neglected this project. The way I do it is like this: ProSim talks to VB. VB handles file I/O and I use a .txt file. The idea is that VB acts as an interpreter between any third party simulation software capable of writing/reading .txt and ProSim.

Help on VB... Use VB.net or any other "new" version. I have found the help on M$ www surprisingly useful. As many others I learned VB from VBA in XL over a period of many years. Copy&Paste from existing programs is a good method.

Please bump the thread and elaborate on your fp problem if you still have it.

 

[tel]

hey thanks for the reply...

I am now slowly progressing.. my block works..

now the problem is at floating point.
'***** Read 2 DoubleWords at the starting address Q 50.0 *****
DataType = S7DoubleWord 'Read type DoubleWord
lStartIndex = 50 'Start at addresse Q 50.0
lElementsToRead = 2 'Read 2 Elements (DoubleWords)
errReadOutputImage = S7ProSim1.ReadOuputImage(lStartIndex, _
lElementsToRead, DataType, vData)
If errReadOutputImage = S_OK Then
D = CLng(vData(0))
Else
ShowError errReadOutputImage
End If


It works fine in the loop, siemens S7 reads it just as i want it.

But when I print it out in a text it is all Long numbers.

i tried Cdbl(D) but it still doesn't print as a double nor floating point.

I need to in decimal form so that i can then manipulate it in Matlab.

 

[spaderkung]

The PQWs are (read as) integer values. Then you need to convert it to a useful fp value. If you read 12345 as a control signal from ProsSim you would prob want to scale it either in VB or ML to 45%. Why not let ML read the long nbr and do the manipulation in there?

 

[tel]

Yes, it's either one of the option. I would like to do it in matlab as it is more straightfoward number calculations but
What do you mean by 45%? I don't know the formula for scaling

1058918147 to it's fp value of 0.61644 nor 1058918147

1060002323 into 0.681062. It's not a direct multiplication.

I have been searching for the formula but couldn't find it anywhere yet.

Anyone has an idea?

1058918147

 

[spaderkung]

Sorry. I assumed that you read your PQW from VB, and that you the use the default scale in S7 0..27648. If this is the control signal to a valve/pump/whatever then 12345 would mean 45% of the full scale. As I recall the ReadOutputImage did not work for me, so I used ReadOutputPoint and a for loop.