PID FB42 not working??

hey guys, i'm testing the FB42 from siemens simatic manager,
i'm wondering why FB42 is not working accordingly?
when i put values on PV_IN and SP_INT, the PID does not run.
ive tried diagnostic everything according the block diagram still cant find the problems...

so far i've covered:
pvper_ON - checked switch to '0'
LMNR_ON - checked switch to '0'
LMNR_HS - checked switch to '0'
LMNR_LS - checked switch to '0'
Cycle - checked T#100MS

The function is called in a function block of fb10 with the instance db10.
then the function will be called in OB35 where the cyclic interrupt is 100ms

This is the archive file of simatic manager.
https://www.dropbox.com/s/40rappswf79zcdc/pid_test.zip

Edited:
I'm using SIMATIC manager S7 V5.5 + SP3. Revision Level K5.5.3.0
hope this info is useful..

Hi

I am not sure how you are setting your values, but it seems to me that you are not actually setting anything to the PI block. (there is no D action in the 3 point step)

I would use a FC to call the FB42, or call it directly.

Do you pass values into the controller at all? PV, SP, Gain, Ti and Deadband being the most important next to the ones you mentioned.

Hi, yeah i did. I directly test it with my PLC, i create variable table which pass the parameters directly into the Instance DB for the block maybe i should try to use it in FC.
do you have any suggestion to test it out?? Or method to troubleshoot this problem?

boneless said:

Hi

I am not sure how you are setting your values, but it seems to me that you are not actually setting anything to the PI block. (there is no D action in the 3 point step)

I would use a FC to call the FB42, or call it directly.

Do you pass values into the controller at all? PV, SP, Gain, Ti and Deadband being the most important next to the ones you mentioned.

Click to expand...

Do you know about the initialization steps for FB42?
i found out that we need to reset the FB42 when the start up of the PLC using OB100, and synchronize the FB42 with the cyclic interrupt of OB35, i have tired the possible method to initialize this, but still cant make the PID part operational instead of the disturbance by pass value can be manupulated.

Not sure what you are doing wrong, If you are calling in OB35 at 100ms then that has to be the value entered in the CYCLE Param. Not sure you did that but just checking. The only other thing i would tell you is to drop the FB42 directly in OB35, create a DI for it and populate the params as you had done before. Make sure OB35 is set to 100ms in the HW Config.

If that works, then you may want to blow away the current DI used for FB42 and regenerate a new one. Hope that works for you.

GHammer said:

Not sure what you are doing wrong, If you are calling in OB35 at 100ms then that has to be the value entered in the CYCLE Param. Not sure you did that but just checking. The only other thing i would tell you is to drop the FB42 directly in OB35, create a DI for it and populate the params as you had done before. Make sure OB35 is set to 100ms in the HW Config.

Click to expand...

Hi GHammer,
Sorry for late reply, I've been working on other project for this 3 days.
i will go through your suggestions..
i will share the information once the problem is solved.
Thanks,

Hi GHammer,

I have gone through with your suggestions and checked, i'm also doing the same way as you suggested.


There is some consideration from my side, which the PLC is shared among us to do testing for our program. Is there any possibility that the FB42 block having interference with other blocks or db? Because at the first time the FB42 is working fine, and suddenly the PID for FB42 not functional since then. Or the settings had been changed by my colleague?

Thanks,

Sounds like you need to do a complete Clear/Reset and Load before you start with your testing. Yes, if you are sharing the PLC you could definitely have problems.

Ic, i try again by wiped all other unnecessary blocks inside the PLC then.

Thanks