Hi..

If i want to start stop many motor  , or scale many temlerature transmitter for showing temperature , in my OB , what do i should to do for reducing memory?  Any one can show me a example in ladder ? Thanks

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Split from multi-instance DB in step 7 basic.

There is a technique that I have seen used in the past for doing what I think you are asking for. It probably is not realistically possible for me to demonstrate it to you on a forum. You would have to understand for yourself the basis of how it works. It uses function blocks with instance datablocks, but it gives every instance the same instance name. In TIA Portal terms, that means it uses the same instance datablock for several calls to the same function. What you have to do is map all of the data for the first case into the datablock before the first call to the function, and then map all of the results out again after execution, before loading the next data for the next call. It might seem like a lot of trouble, but it does achieve what you seem to be suggesting. You have a large quantity of similar functions to do, and you can do them all with the minimum amount of PLC memory.

What is occurring to me even as I write this, is why you don’t just use an FC function? The problem with an FC function is that it has no static data, but the technique I have outlined also requires that any static data requirement is outside the function. When I saw the technique used it was not in a Siemens PLC, it was, if I remember correctly, a Mitsubishi Q series. There was some reason why the type of function with an instance name was required, but available memory was an issue, and the technique had been used to achieve the requirements within the available PLC memory. And it worked very well. So perhaps the TIA Portal equivalent would be simply to use an FC function instead of an FB function, still using multiple calls to the same FC just incrementing the block of data it works on with each call.

@KenNatton:

The attached picture is to compliment your idea with an example. It is not exactly what you described as I have taken the liberty of making some adjustment.

Hopefully it is a good enough sample to continue your conversation.

Thank you..

But , Can you show me that in simatic pcs7 300..?  I make a new FB  and on it make 'start' 'stop' 'trip' as in ,   and 'motor' as out...

And make a OB and  use my FB on OB for repeatative time...its true..?

M.Abzadeh

Thank you..

But , Can you show me that in simatic pcs7 300..?  I make a new FB  and on it make 'start' 'stop' 'trip' as in ,   and 'motor' as out...

And make a OB and  use my FB on OB for repeatative time...its true..?

attached

#dP

@KenNatton:

The attached picture is to compliment your idea with an example. It is not exactly what you described as I have taken the liberty of making some adjustment.

Hopefully it is a good enough sample to continue your conversation.

High quality contribution as ever #dP. I was a little daunted by the thought of how much effort it would take to try and demonstrate it, but you have done it very succinctly. And the other critical bit that I confess I had forgotten but remembered the moment I saw your example is that the mapping in and out of the data was done using an In/Out pin on the function. That is exactly how it was done when I saw it done by my former colleague from some years ago.

For my Fb , In "stat""  i choose what kind of data type..? Bool is true.?

And another question..

I decide to scale many Temlerature Transmitter for my project..

I build another FB for scale TT and use it on my OB...and how many DB   can i use..?