PID help

hey guys - I'm a novice PLC enthusiast, so this may be a simple one. I'm running a PID on a Micrologix 1200 PLC and I want to change the Gain for the PID without having to connect to the PLC and open the Setup screen.

Is there a way to simply use a MOV instruction to accomplish this?

I'd like to use an HMI button to activate different MOV instructions to change the PIDs gain. Any help would be great!

Mr. Ro Bot,
I think you could do MOV different values into the gain value for your PID, but you'd need to put that instruction in the logic of your plc and that would require connecting to the plc.

To MOV a new gain Value of 1.5 into your PID:

MOV 15 to PDx:x.KC

Good Luck
Byron

Hello and welcome...

In short yes, in the screen shot below, your HMI would write to N7.1 a value and then do a MOV from N7.1 to PD9.0.KC, my PID is in PD9

If you use the method above I would check the value from the HMI for limits before moving it to the PID . Use a "LIM" (limit instruction) before the "MOV" instruction.

You may be able to directly address PD9:0.KC from the HMI. Can limit the entry at the HMI input and/or also limit it one rung before the PID instruction.

mixed messages...

First let me say THANKS! for the help.

When I try the MOV it doesn't transfer correctly. It gives a scrambled number.

Examples: MOV
Source
N7:1
1111

Dest.
PD9:0.KC
-8192

or
Source
N7:1
333

Dest.
PD9.0.KC
-32768

the values seem to be all over the place.

If you can post your program, Its .RSS file (zip it first)

Is N7.1 being used anywhere else in the program?

File

Here's a download link to the test file I made. I'm trying to locate my Winzip, but I think it's on my other laptop.

https://ln2.sync.com/dl/748d23c30/zmuqa27f-qifmhrug-bpnxcjzh-ybkxpcdh

I'm pretty sure I'm doing something wrong that's elementary...

Thanks!

Should be able to enter data to an N7:x or F8:x from the hmi, Then just an always open move instruction to PD9:0.KC, or set your limits as conditions of the move with compairitive instructions greater than and less than.

Looking at the manual, it might be converting it for you, as KC is 0 to 327.67 for /RG=1

Try a mov less than 320, or with a float less than 320.0, or a copy

https://literature.rockwellautomati...ure/documents/rm/1762-rm001_-en-p.pdf#page255

fun with numbers...

I did note a pattern in the numbers that I put in N7 when they are moved.

It's almost like the numbers are scaled, but the higher you go the lower the change.

N7:0 PD9:0.kc
257 -32768
258 0
259 -32768
260 0
261 -32768

1344 0
1345 8192
1346 16384
1347 24576
1348 -32768
1349 -24576
1350 -16384
1351 -8192
1352 0

32000 0
32001 512
32002 1024
32003 1536
32004 2048
32005 2560
32006 3072
32007 3584
32008 4096


So technically, the MOV is working, it's just changing it when it's moved. I also noticed it seems to affect Ti moving and filling that field with another number that changes as you change the N7. However, it's much lower incrementally, and only seems to change on the numbers, not the zeros. Almost like it's counting every full cycle of the KC numbers, as the rate of change on the .TI slows the higher the N7 goes. It appears to only change the TI number 0.1 every full cycle back to zero on the .kc

For example:
N7:0 PD9:0.TI
257 1728.0
258 1728.1
259 1728.1
260 1728.2
261 1728.2

So they should be in tenths... if N7x = 257 then your Gain should be 25.7

yes. However, if I set N7:0 = 257 it changes my Gain PD9:0.kc = -32768

Lower your scaled set point, you have it set at 20000.... try watching this video https://www.youtube.com/watch?v=UzvJnFtyoIM

Its a sales video I made for our PID trainer but it covers the basics of setting it up and getting it going

I dont know what device you are controlling but 20k looks on the high side