[SIEMENS] SIMATIC S7-300 FB41 PID bloc issue.

[intertarik]

hello,
I'm new in automatics, and i'm working on a speed control project for a hydraulic turbine.

i'm using FB41 pid bloc, but the LMN give me 0 to 100 input.
the SP is 1000 RPM and the PV is calculated from an inductif sensor.

how can i get bipolar LMN -100% ... +100%
if the speed >1000 rpm, then LMN give négative value to reduce the speed.
and if speed < 1000 rpm, the LMN give ^positive value to increase the speed.

thx a lot

 

[userxyz]

Hey,

Try this:

Set the follwing parameters on the FB41 pins or inside the instance DB:

LMN_HLM: 100.0
LMN_LLM= -100.0

Kind regards,
C

 

[intertarik]

Thanks

thanks a lot that's exactly what i need
one more question...
I have this little network:

and i want to execute it one time

exemple:
when md10<950 E0.0=1
when md10>950 E0.0 = 0

and even if md10<950 again, E0.0 = 0

i hope you understand.

 

[KalleOlsen]

thanks a lot that's exactly what i need
one more question...
I have this little network:

and i want to execute it one time

exemple:
when md10<950 E0.0=1
when md10>950 E0.0 = 0

and even if md10<950 again, E0.0 = 0

i hope you understand.

You describe a very simple problem here.
Set an M-bit to remember that the MD10 > 9.5e2 and use that M in your logic.

AND! to manipulate an input (E0.0) like this is normally considered bad practice.

Kalle