Hello everyone,

I'm a beginner so please bear with me.

I've to program PLCs but I never touched at PLCs. I read a lot of documentation and a lot of topics on forums but I still have some questions. 

I want to put a barometer that has a default value at 320°C. When I turn off pumps, the temperature increase. I also want to have a production counter which varies between 600 and 700 randomly. When I turn off these same pumps, the production decrease.

Unfortunately I've no idea of how to put this default value or to create a random variation. I understood that the DataBlock contains variables that are send to the other PLCs so, where am I supposed to assign a value to my variables ?

Thank you in advance for your reply.

Nathan_Cml

hi Nathan_Cml,

The Library of General Functions has Random-blocks, that could be useful for your project. Have a look to LGF_Random_Range_DInt:

Library of general functions (LGF) for SIMATIC STEP 7 (TIA Portal) and SIMATIC S7-1200 / S7-1500

hope this helps,

regards,

Thank you very much for your reply, I'm going to take a look at your documentation !

And maybe do you know how to assign a value to my variables ?

Nathan_Cml

And maybe do you know how to assign a value to my variables ?

 What programming language do you use?

in graphical languages, like LAD and FBD you can use MOVE instruction.

in STL you need to operate with LOAD and TRANSFER operations.

L #source

T #destination

 in SCL you do it with :=

#destination := #source;

I recommend you to have a look into the manual. All programming languages are described there:

Programming a PLC

 hope this helps,

Thank you very much.

However, I meant for instance : a = 5.  And then we can use "a" at several places. The only place where I find this option is in a DataBlock, but I can't use DataBlocks in HMI variable to display for instance.

Nathan_Cml

Thank you very much.

However, I meant for instance : a = 5.  And then we can use "a" at several places. The only place where I find this option is in a DataBlock, but I can't use DataBlocks in HMI variable to display for instance.

 I think I got you!

you mean constants, right?

Look here:

and the description in the manual:

Declaration of symbolic names for constants

hope this helps,

 regrards,

Dear mopS04,

Thank you for your time. I decided to change the language of my program to SCL. It looks way more easier and familiar for me. I hope everything you told me will also be helpful for this language.

The only strange thing is this : (please fin below the screen), are the variables that we define here just local ? I mean, I can't use it to create HMI tag for instance, all the variables I already define in the PLC tag tab are all useless now ?

Regards,

Nathan C

this is the block-interface of a FB or FC and yes, these are used local, inside the block. If you programm a FB, that has an Instance-DB they are stored there an can also be accessed from outside the FB(not a good programming-practice).

block interface of FB3:

calling FB3:

More infos about the Blocks in Step7 can be found in the manual:

Blocks in the user program

regards,