Crash course in SIemens programming

[electrical_geek]

Hello.

In my last post I wished everyone good bye. I planned to retire and spend time with my hobbies. Ha ha!! It is difficult to make forecasts, especially about the future!
I was headhunted to a Volvo-project in China. This is an offer you cant refuse!
So, to make a long story short. I am supposed to spend some months with Siemens programming, using Step7. A program I have limited knowledge about.
My major concern is the relation between OB1, OB2, ------ OBx.
And the same for FC1, FC2, ------ FCx and FB1, FB2, ------ FBx.

Where can I find information about this?

Peter

 

[L D[AR2P#0.0]]

Which Step 7 programming software/hardware will you be using?

 

[dahnuguy]

General information

Hello.

In my last post I wished everyone good bye. I planned to retire and spend time with my hobbies. Ha ha!! It is difficult to make forecasts, especially about the future!
I was headhunted to a Volvo-project in China. This is an offer you cant refuse!
So, to make a long story short. I am supposed to spend some months with Siemens programming, using Step7. A program I have limited knowledge about.
My major concern is the relation between OB1, OB2, ------ OBx.
And the same for FC1, FC2, ------ FCx and FB1, FB2, ------ FBx.

Where can I find information about this?

Peter

http://www.amazon.com/STEP-Steps-Implementing-Programmable-Controllers/dp/1889101036

http://www.plcdev.com/siemens_simatic_step_7_programmers_handbook

Not sure why it would matter which hardware you are using , Step7 is Step7.

Not understanding the association between OB1,OB2 etc and the FC FB relationship is the same.

The basic PLCs are different due to hardware limits and use a different software.

TIA portal is different, but the blocks work similarly.


A real basic explanation to your general questions:

OB1 is the "main" part of the program. And is called every scan.

The other OBs are called under certain conditions, all this is in the help.

Some OBs are called on a cycle every X milliseconds, other OBs are called if there is a hardware fault. What ever code is in the OB is only run when that OB's condition is met.

FCs are functions like in C. They can have an interface and accept parameters. They have no internal memory.

FBs are similar to FCs but an FB has internal memory and some of the rules of the interface are different. The exceptions in Step 7 make up a long list.

The FB / FC could be thought of as a subroutine.

Note, the number of the FC is only to identify it. It is not sacred. You can rename FC4 to FC12 and it is still the same.

SFCs are System Function Blocks. You don't edit those.

If you write an FB3 and use it again, it will require a new number to differentiate the instance of one from the other as they have maintain separate memory (instance DB)

The DBs are very interesting and useful in Step7.

They are like an excel spreadsheet with only one column, but they are still useful.

2D data blocks would be so nice.

 

[wimpiesplc]

It is difficult to make forecasts, especially about the future!

Well, I always thought that forecasts were about nothing *but* the future...

 

[jcr]

Hello.

In my last post I wished everyone good bye. I planned to retire and spend time with my hobbies. Ha ha!! It is difficult to make forecasts, especially about the future!
I was headhunted to a Volvo-project in China. This is an offer you cant refuse!
So, to make a long story short. I am supposed to spend some months with Siemens programming, using Step7. A program I have limited knowledge about.
My major concern is the relation between OB1, OB2, ------ OBx.
And the same for FC1, FC2, ------ FCx and FB1, FB2, ------ FBx.

Where can I find information about this?

Peter

Need any help in China? I love it over there and love the people!

 

[electrical_geek]

dahnuguy!!

http://www.plcdev.com/siemens_simati...mmers_handbook

This link was a goldmine of information.
Many thanks for this.