Instruction on setting up a PID

[LStewart]

Can someone give a link for instructions on how to set up a PID in a program? At least something that will point me in the correct direction. I don't have the users manual for my 1746-NIO4V

[504bloke]

User Manual for NIO4V http://literature.rockwellautomation...m005_-en-p.pdf

PID on an SLC

http://www.plctalk.net/qanda/showthr...hlight=pid+slc

[LStewart]

Thanks Bloke..looks like I have some reading to do..

[504bloke]

See this also

http://domino.automation.rockwell.co...9?OpenDocument

and here

http://domino.automation.rockwell.co...D?OpenDocument

[Ron Beaufort]

Greetings LStewart,

as you're no doubt finding out, PID is a rather large subject ... if you want to post some details about the process that you're trying to control, we'll be able to offer you a lot more help ... and if you can post your .RSS file, then we can really start nailing things down ...

besides the links that Dave mentioned above, you should also read the chapter on PID in the SLC Instruction Set Reference manual ...

[Thomas Sullens]

Hi LStewart when you finish the maual this make make more
sense. If you follow the whole thread it`s a book within itself.

http://www.plctalk.net/qanda/showthread.php?t=13459

[leitmotif]

LStewart

Ron Beaufort has posted 3 different descriptions of PID -- they are

What is I in PID
What is P in PID
What is D in PID

You can find them by using the search command. I highly recommend it - you dont get bogged down by a lot of math and he writes in a very easy to comprehend manner.

The one for P (Proportional) was the best -- only because in the version I see on my screen it has all the graphs. Made all the sense in the world with graphs.

Now if Ron could insert graphs in the text instead of word "attachment" that would be great. I assume the word attachment means the graphs were there but they have gone who knows where? It could be that my computer or me (operator error) has caused the graphs to go away in the I and D versions. IF you could email them to me Ron (and if that is easiest for YOU) that would be highly appreciated.
Dan Bentler
dan.bentler@seattle.gov

[LStewart]

Thanks for the input guys. I am converting 3 25 year old molding machines with 5TIs to slc 5/04. They are wanting the heaters to be controlled by the AB also, this I thought was no problem, I got a thermocouple input module and configured it and it worked well on the bench,after I found out the difference in N7 and #N7 makes!! and thought I would be controlling contactors which is what the print (old and hand drawn) shows, I wrote my program to. The next step is where lack of communication and homework puts me into panic mode. We have ripped out the old 5TI and the tech and I are tracing out the electrical( the prints don't include wiring just power distribution and some I/O. I dawns on me the machine is using watlow PID and either I keep what he has which is much more efficient than contactors or I add an analog out and program it..PANIC! I don't know anything about setting one up. I have 2 more machines to do, I will continue to let the watlows control heat until I have another controller set up on my bench with ALL that I need then I can play with it till its correct and just add it to the machine we are doing today later. At least they will be able to run production tomorrow. I have been in controls a little over a year now, and the more I learn, the more I find out I need to learn.

[Eric Nelson]

Originally Posted by LStewart

I am converting 3 25 year old molding machines with 5TIs to slc 5/04.

You too?...

I recently finished replacing all the controls in a second old Nissei PET blow molding machines. The preform portion of the machine is basically a standard injection molding machine. I went from Fuji to AD controls (the customer did not have an AB budget). Similar to what you're doing, this included eliminating the stand-alone barrel temperature controllers, and incorporating them into the PLC.

I used AD's 4-loop termperature controller (LINK), which made my life a WHOLE lot simpler. It runs independant of the PLC program, yet you can still control and monitor it from within the program. It also has connections for current transformers, so you can monitor heater burnout and SSR failure.

AB's 1746-BTM (LINK) seems to be the AB equivalent. You may want to consider using one of these rather then a 'roll-your-own' ladder version.



-Eric

[504bloke]

This is the BTM User Manual

http://literature.rockwellautomation...m010_-en-p.pdf

I have used 12 of these in the past and am currently on a project with 4 modules controlling 15 zones on an extruder

You communicate with them via Block Transfer which if you use a a late series C processor then this has the new BTR / BTW command

[Eric Nelson]

Thanks for the link, 504bloke. I guess the BTM is not as similar to the 4LTC as I thought. With the BTM, you still need a separate output module to control the heaters. I wonder why they didn't just stick the TPO outputs on the 5 "Do NOT Use These Connections" terminals...

It looks to me like the BTM is nothing more than a thermocouple module with a processor for the PID loops stuffed inside. Now I'm even happier that I went with the 4LTC!...



-Eric

[504bloke]

I suppose AB did it so you could use either a Digital card for TPO or an analogue card for Analogue controlled stacks

The cards not cheap here in the uk its about £800 from memory and then you have the digital or analogue to add to it !

It has some specific stuff programmed into the unit for Extruder barrels with zones adjacent to each other and has an autotune for the complete barrel or each seperate zone.

I am not conversant with AD stuff at all other than to say i just looked at their site and the prices are very goooooooooood

Does the AD stuff get over the water to the UK ?

[Eric Nelson]

Originally Posted by 504bloke

I suppose AB did it so you could use either a Digital card for TPO or an analogue card for Analogue controlled stacks

The 4LTC allows you that option as well, but ALSO has the outputs locally at the card. Download the manual from the link I provided.

Originally Posted by 504bloke

It has some specific stuff programmed into the unit for Extruder barrels with zones adjacent to each other and has an autotune for the complete barrel or each seperate zone.

Yes, I read that part with interest. I'm not sure what it does differently to accomplish this. Does it just autotune all zones concurrently? I know that the first time I used autotune with the 4LTC, I did each zone separately. This did not give good results. The nozzle kept overshooting its setpoint. Once I tried autotuning all zones at the same time, it worked great (even though the nozzle zone took much longer to finish). I was amazed to see all zones maintaining their setpoints ±1°F, even while shooting plastic!

Originally Posted by 504bloke

Does the AD stuff get over the water to the UK ?

AD lists their distributor in the UK as www.lamonde.com



-Eric

[LStewart]

There are some good links here and I appreciate it. Other than the heating, the rest of the project went exceptionally well, and I am very pleased with the results, I like it when the product engineer can't get the grin off of his face. He even wants to take pictures!! Makes me feel like I have done a good job. I know I had a headache for 2 days before the project began. This is the first phase of a 3 part project, and also my very first BIG project to conduct on my own without the senior controls eng. Whew!!

[Ron Beaufort]

for leitmotif in post #7 ...

Greetings Dan,

and thanks for the kind compliments ... the words "attachment" in the earlier posts show where I had inserted the graphics when I originally wrote the material ... now that the forum has been changed, the graphics have slid to the bottom of each post ... they should all still be there - just moved down in position ... if you check again and find that they are NOT there (not all browsers work the same) then let me know and I'll work out some type of solution ...