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Member
Johnnykoo
Posts: 37
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How can I connect SP to PID block when there is no AI block ?

Hi, I just started using NI-FBUS (NI USB-8486 with NI configurator 4.1) 

 

for my device setup there are only AO, TB, RB and PID block. 

 

Question 1. 

Can I manually set SP in the configurator ? if so, can you please tell me how ? 

 

 

Questino 2. 

I tried to follow the tutorial in the manual but I don't have AI block.. then how can I 

wire up my desired SP to PID block ? 

 

 

Very much appreciated, 

 

Thanks, 

Member
Chris.W
Posts: 82
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Re: How can I connect SP to PID block when there is no AI block ?

Hi,

 

You could just modify the value of SP in Configurator.

And click the button of Write Changes.

 

set SP.JPG

 

But the thing is that if you don't have the AI block, you might not be able to set the PID block to Auto or to create a PID schedule.

Have a try.

 

Thanks.

Chris

Member
Johnnykoo
Posts: 37
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Re: How can I connect SP to PID block when there is no AI block ?

[ Edited ]

Thanks for the quick response, 

 

can you please see my attachment ? 

 

I only have PID and AO block in my FB application and scheduling, 

 

From my understanding, I should not have RB and TB in my FB application and scheduling ,..is it correct ? 

 

and i think I did change the pid to auto mode.. 

 

but it's not working ..  I have a valve positioner connected to it

Member
Chris.W
Posts: 82
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Re: How can I connect SP to PID block when there is no AI block ?

What do you want to do by creating this schedule?

 

If you want to do a PID control, you must have an AI block. That is the Input, not SP (short for Set Point).

 

Please refer to the FBAP Templates -> PID Feedback Control.

 

Even it is under Auto, there is no effect either.

Member
Johnnykoo
Posts: 37
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Re: How can I connect SP to PID block when there is no AI block ?

thank you, 

I'm trying to give input as 0-100% and see if it controls the position of the actuator. 

unfortunately, I do not have the AI block... Is there certainly no way to use PID control ? 

 

Do I leave RB and TB outside of the application ?

 

 

Member
Chris.W
Posts: 82
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Re: How can I connect SP to PID block when there is no AI block ?

Yes, you have to have AI.

 

RB and TB are not within the loop.

Member
Johnnykoo
Posts: 37
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Re: How can I connect SP to PID block when there is no AI block ?

Hello, Chris, 

 

I've been working on the same issue and I have more questions for you. 

 

please see the attached picture. it shows our device block setup. 

 

We're not using a transmitter, so are not PID function for now, 

 

so we just would like to change the value of CAS_IN of AO block to control our device. 

 

I've spent time to change the value in the configurator.. but it's not working, 

 

Can you please give me some advices ? 

 

Thanks, 

 

Sincerely

 

Johnny

Member
Chris.W
Posts: 82
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Re: How can I connect SP to PID block when there is no AI block ?

Hi Johnny,

 

We have real-time data monitoring function in the FBAP view by clicking on the Eye button.

Then you could see how the data flow is.

 

PS: sometimes you probably need to download the schedule first to monitor the data.

 

Hope this will help somehow.

Thanks.

 

Chris

Member
Johnnykoo
Posts: 37
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Re: How can I connect SP to PID block when there is no AI block ?

Thank you for your help, Chris, 

 

I have another question for you.. 

 

perhaps i'm not understanding how to make this loop work ......

 

please see the attachment, it's simple PID FBAP

 

I'm trying to see if this loop works ok, 

 

I've done changing the final value parameter in TB manually 

 

and confirmed my positioner works fine. 

 

Now, I want to see if the FBAP loop works and see the change. 

 

However, How do i change the desired input in PC ? 

 

Do I just have to change the parameters in blocks manuallly ??? 

 

I tried to change the OUT value in teh AI block, but it's not responding at all. 

 

Can I get some advices ?? 

Thx, 

 

 

Member
Chris.W
Posts: 82
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Re: How can I connect SP to PID block when there is no AI block ?

Hi,

 

AI 's OUT value should follow the change in TB after the setting. But you couldn't modify it manually.

 

Here I have prepared a PPT regarding how to create PID loop.

 

FYI.

Good luck.