Need a help for FC Step 7 s7 300 LADDER logic

[TienNguyenD 0]

Excuse me.

I have got some problems for FC Step 7 s7 300 LAD,

When FC is running, ex: Q0.0 = 1;

then I break the power flow this FC, but Q0.0 still = 1.

so how can I do to turn off All components in this FC while i break it? ( its mean Q0.0 change 1 to 0 )

[TravisPedley 21]

If the FC isn't running, it can't execute code - including turning outputs off.  Not sure how this would work inside the FC.

You could add an input to the FC to act as an "Enable" and let the FC run unconditionally.  Have code inside of the FC clear what you want if the "Enable" signal goes low.

Good luck.

[TravisPedley 21]

Something like this should work.  If the enable input isn't on, it will jump to JOVR and reset Q0.1.  If the enable signal is running, if I0.0 and I0.1 are ON, Q0.1 is on, else off.

I don't have a way to test it, but it should be close.

[TienNguyenD 0]

Thanks alot :D

[TienNguyenD 0]

On 2/23/2016 at 10:33 PM, TravisPedley said:

Something like this should work.  If the enable input isn't on, it will jump to JOVR and reset Q0.1.  If the enable signal is running, if I0.0 and I0.1 are ON, Q0.1 is on, else off.

I don't have a way to test it, but it should be close.

With LADDER logic :

Someone suggested that I use : RET command

but I don't know how to use.

 

My problem is:

[TravisPedley 21]

Like I said earlier, your FC cannot process anything if it isn't running.  That means turning outputs ON or OFF.  If I0.0 is off, then the code in FC1 isn't being scanned, which means that the outputs are left in whatever state they were last in.  If you must do it in ladder, then do it like the attached picture.  will get cumbersome if you have a lot of outputs, but that's what you have to do.

 

 

[TravisPedley 21]

Or do it like this.  When you expand the code, just make sure the N.O. Enable is in the rung that fires the output.  The FC will scan nonstop assuming it is called in OB or equivalent subroutine.

This will ensure that when you want the output to be off because I0.0 is off, it will do it.

 

[TienNguyenD 0]

8 hours ago, TravisPedley said:

Like I said earlier, your FC cannot process anything if it isn't running.  That means turning outputs ON or OFF.  If I0.0 is off, then the code in FC1 isn't being scanned, which means that the outputs are left in whatever state they were last in.  If you must do it in ladder, then do it like the attached picture.  will get cumbersome if you have a lot of outputs, but that's what you have to do.

yes, i think so. Thank you

 

 

[tecnoplc 0]

Exactly:

When you switch off the FC, all the output inside the FC will remain activated if they were activated in the momento that you deactivate the FC. This is why your Q0.0 will remain activated.

You must resete the Q0.0 outside of this FC1 when you turn off the FC1.

 

--------------------------------------------------------------------------------------

www.tecnoplc.com

[pop29684 14]

I would not recommend using conditions to enable a block call. It can cause all sorts of problems, including what you have experienced. And has the potential to create some incredible troubleshooting headaches. This applies not just to outputs but any W (write) instruction, including counters, timers, bits, bytes, words, double words, M addresses, and DB addresses. Instead, I would write two additional rungs of logic and include them at the very beginning of your FC1 module. It would look something like this:

NW3 would be replaced by your existing logic in FC1.

Here's what happens:

Program scan of module code begins.

NW1 is evaluated: if input I0.0 is FALSE then Q0.0 will be reset. If input I0.0 is TRUE then Q0.0 will not be changed - regardless of what its current state might be (TRUE or FALSE).

Program scan continues to NW2 - regardless of the state of I0.0.

NW2 is evaluated: if input I0.0 is FALSE then the RET instruction is executed and the program scan of the module is immediately terminated. No additional rungs are evaluated. If input I0.0 is TRUE then the RET instruction is not executed and the program scan continues to NW3 (and any other networks that might exist).

Writing your logic in this manner allows output Q0.0 to be toggled ON or OFF from inside the same module instead of writing it ON from this module and writing it OFF from another module.

The RET instruction may be found in the overview tree:

There are other ways to achieve the same result but I think this is the easiest understood by beginners.

Edited 30 Mar 2016 by pop29684

[Sohail Riaz 0]

Hi,

I was troubleshooting a problem on Siemens CPU313C. It was showing wrong Pressure value on HMI all of a sudden. I checked the transmitter, it was oKay. Then the wires found OKay. Then I opened the logic and find the input variable and checked the raw data. It was also fine. There i saw that there was a custom FC1000 to scale the input. It was outputting the wrong value i.e showing half value of scaled. Suppose if the scaled value should be 200 then it is showing 100. When I opened the function following code is shown. Can anyone help what type of language is this and what does this mean??

[sigmadelta 5]

OK, this code is written in STL language.  Line by line:

L #INPUT - load the value of the parameter "INPUT" into ACCU1 (accumulator 1)

ITD - convert the value in ACCU1 from INT (integer) to DINT (double integer), and store in ACCU1

L L#-100 - load the value of -100 into ACCU1, the previous value in ACCU1 moves to ACCU2 (in this case #INPUT which was converted to a DINT)

>D - check if the value in ACCU2 is greater than ACCU1 (in this case #INPUT > -100)

JNB n01 - jump to label n01 if the above logic is false (#INPUT is not >  -100)

L #INPUT - load the value of the parameter "INPUT" into ACCU1

ITD - convert the value in ACCU1 from INT (integer) to DINT (double integer), and store in ACCU1

DTR - convert the value in ACCU1 from DINT (integer) to REAL (floating point), and store in ACCU1

L #MAX - load the value of #MAX into ACCU1, the previous value in ACCU1 moves to ACCU2 (in this case #INPUT which was converted to a REAL)

*R - multiply ACCU2 by ACCU1 (#INPUT * #MAX) store the result in ACCU1

L 2.7648e+004 - load the value of 27648 into ACCU1 - this happens to be the maximum integer for S7 analog input values

/R - divide ACCU2 by ACCU1 (#INPUT * MAX / 27648) store the result in ACCU1

T #output - transfer ACCU1 to the parameter #output

JU n02 - jump unconditionially to n02

n01: L 0 - label is n01, which is used for the jump statements, load the value 0 into ACCU1

T #output - transfer ACCU1 to the parameter #output

= #alarm - like a coil in LAD language the value of #alarm is based on previous logic (in this case the >D instruction - in this case #INPUT > -100)

n02: NOP 0 - label is n02, which is used for the jump statements, NOP 0 is a no operation instruction (does nothing)

I think the "= #alarm" instruction is wrong.  I would use ""SET" on one line, then S #alarm" here, and use the lines "SET" then "R #alarm" just after the "JNB n01" line.

Basically it is checking if the input is greater than 100, if it is not, it outputs a value of 0 and turns on the alarm bit.  If it is greater than -100, then output the result of INPUT * MAX / 27648.

Edited 2 Oct 2019 by sigmadelta