S7-300 Equivalent to RS5000 Scale and Limit Blocks

[WilsonNC]

I am looking to see if anyone has any blocks that are the equivalent the RS-Logix 5000 scale and limit blocks, or if the S-7 library has blocks to do these functions. Also any working examples with comments.

I will have to scale some analog inputs, and write to analog outputs.

 

[KalleOlsen]

From this thread: http://www.plctalk.net/qanda/showthread.php?t=60011

In S7 manager:
Open + Library + TI-S7 Converting Blocks
You will find the treasure FC106 UNSCALE.

and also FC105 SCALE.

And a free library with lots of different functions here: www.oscat.de

Kalle

 

[JRW]

Look under "downloads"
Theres some libraries there
Under the Siemens folder

 

[WilsonNC]

What about a Limit block? A/B LIM

 

[JRW]

Its very easy to build one
Are you familiar with FB's and FC's?

 

[KalleOlsen]

While waiting for the potatoes to cook I made this limiter example, real values (not tested).

Kalle

 

[bara_hence]

Why do we keep reinventing the wheel???

Look in standard library IEC functions there is a LIMIT, MIN, MAX and such blocks there ready to go..

 

[L D[AR2P#0.0]]

While waiting for the potatoes to cook

...that's given me an idea for this years Xmas puzzle

 

[KalleOlsen]

Why do we keep reinventing the wheel???

And why do we keep cooking potatoes?

I'm sorry if my piece of reinvented ladder has offended some of you. I will eat raw potatoes with my next dinner.


Kalle

 

[L D[AR2P#0.0]]

Keep on rollin' baby, you know what time it is....

 

[geniusintraining]

And why do we keep cooking potatoes?

Just finished cooking mine also... (made clam chowder ummm)

 

[Tharon]

And why do we keep cooking potatoes?

I'm sorry if my piece of reinvented ladder has offended some of you. I will eat raw potatoes with my next dinner.


Kalle

Because raw potatoes are technically poisonous?

Reinventing the wheel is a good way to learn how the wheel works though. So it's not always a bad thing to do.

 

[KalleOlsen]

@LD:
Nice wheels, but as I'm living among the wild, raw potatoes in the bush, these would be more my style:

http://www.youtube.com/watch?v=mi8SlYGt0YM&feature=related

 

[ELake20]

FC105 doesn't handle negative numbers so I developed this solution:

FUNCTION_BLOCK SCALE

VAR_INPUT

RAW : INT; //Enter value to be scaled
rInput_Min : REAL; //Enter input value @ rest (real)
rInput_Max : REAL; //Enter input value @ max (real)
rScaled_Min : REAL; //Enter minimum engineering units (real)
rScaled_Max : REAL; //Enter maximum engineering units (real)
Gen_Alarm : BOOL;

END_VAR

VAR_OUTPUT

iScaled_Out : INT;
rScaled_Out : REAL;

END_VAR

VAR

rRAW : REAL;
Rate : REAL;
Offset : REAL;

END_VAR


BEGIN

rRAW:=INT_TO_REAL(RAW); //Convert incoming integer to REAL



IF Gen_Alarm = FALSE THEN //If General Alarm isn't present

Rate := (rScaled_Max - rScaled_Min) / (rInput_Max - rInput_Min); //solve for X
Offset := rScaled_Min - (rInput_Min * Rate); //solve for B

rScaled_Out:= (rRAW * Rate) + Offset; // solve Y=MX+B where M = RAW, X = Rate B = Offset
iScaled_Out:=REAL_TO_INT(rScaled_Out);

ELSE

rScaled_Out := 0; // GenAlarm Alarm is true, output 0
iScaled_Out := 0;

END_IF;

END_FUNCTION_BLOCK

 

[WilsonNC]

Although these are some good examples, they dont address the equivalent of the AB LIM block. It has a high and low setpoint, then if the input is between those two values, the output (boolean) is true.