Plc-5/40 Processor Speed Control

I need some help in developing plc ladder logic to control speed controls on a servo hydraulic pump controller. The pump will produce 5000psi to a hydrostat that will increase RPM based on howe nuch flow, and what I need is to be able to control the speed of the hydrostat. Speeds will be as high as 3500rpm. I am looking for a basic plc ladder logic that can guide me in the righ direction. I need to have some kind of a PID loop to control speed. The spindle will have mag pick up attached to a 1771-VHSC and there will be an analog card that will control the servo control pump. Need help on ladder logic, thanks.
**sorry for duplicating this message**
but I'm in desperate need for help/advice.

You need help in figuring out how to use this site. This thread is about the same thing as this one and dual threads are not needed. If you are indeed desperate, you need to contact someone in your local area that can be hired to come to your shop and do some consulting work for you. That is not what this site is for. We are glad to help, but speed is not one of our strong points. Especially since we work for free and you have not provided any foundation for getting help. Expressing a need is not what you should do.

Ralph,

Your project breaks down into a few parts.

First, you need to set up the 1771-VHSC card and get a speed signal into the PLC where you can use it. The manual for the card should have some help and maybe even a sample program.

Second, you need to set up a PID instruction. The PV will be the speed signal from the VHSC card. You'll want the speed value in an integer and scaled 0-4095. (The PID instruction wants it that way.) The output of the PID instruction is also scaled 0-4095 and that should suit your analog output card if you are using a 1771-OFE.

Third, because you are using an analog output card in a PLC-5, you will have to set up block transfers to get data to the card.

That's the bare bones. There are plenty of details to cover. If this is all Greek to you, I agree with Randy, you need to hire someone. On the other hand, if you are willing to learn and you have the time and budget to do it yourself, you should find plenty of help here.

Good luck,

Mike Ellis

Greetings Ralph,

to Mike and Randy’s excellent advice, I would add the following ...

before you try to program the automatic control that you’ll eventually require, it would be a good idea to nail things down to the point where you can establish manual control ... specifically, make sure that you have all of your inputs and outputs working ... you MUST be able to go online with the PLC and monitor the input speed signal ... you MUST be able to manually alter the output setting in the PLC and insure that it does indeed control the speed of the system ... once you’ve got those features working, then give us the addresses that are involved ... for example: “my input is located at N7:54 and my output is located at N7:75” ... once you’ve got the input and output signals nailed down, THEN (and only then) will it be time to start programming in the PID function ...

as Mike said, we can help you with all of this ... but this is NOT what I’d consider a suitable project for a beginner ... so tell us ... how much experience do you have with the PLC-5 platform? ... do you already know how to handle the analog signals that Mike mentioned? ... have you ever tuned a PID loop before? ... and what is your deadline? ... please note that “as soon as possible” is NOT a valid answer ...

we can help with all of this ... but it’s going to take some time ... and one more thing: how dangerous is this system? ... specifically, is anyone (or anything) likely to be hurt in the event that your initial tuning experiments get out of hand? ...

**sorry for duplicating this message**

Click to expand...

we don’t mind ... but it’s just going to make things harder for you when some people are responding to your first thread – while other people are responding to this one ... in the future, it would be a good idea to just use one thread ... it’s easy to “bump” it up to the top of the forum - just post another message to the end ... but you need to understand that most (all?) of the people here are working for a living so it might take awhile for the responses to come in ...

and finally ... welcome to the forum ...

Thank you, Ron, Mellis and randylud for this advice. I have about 6 years experience doing plc programming and I can handle analog commands with out a problem the only thing than I will need is advice on how to tune and get the PID loop to function correctly.
This project is something that will be completed withing the next four months.

the story continues ...

Greetings Ralph,

four months? ... then we should be able to work this out ... just as a quick preview, here’s a recent post (be sure to read the whole thread) that might help give you an idea of one way to proceed with this project ...

it would be a good idea to also make sure that you’ll be able to post a trend line graph of the system’s response ... there’s an example in this post ... the example was written for RSLogix500 but the RSLogix5 software works the same way for this particular feature ... practice with this procedure ... it will help a LOT when it comes time to tune the PID loop ...

my next question is: are there already any other PID controls in this particular program? ... if so, we might want to take a look at their configuration so that we can keep things as consistent as possible ... this will make it easier on everybody working with the program in the future ...

next question: (actually a rerun of a previous question) ... what are the addresses of your input and output signals? ... and are they scaled from 0 to 4095? ... as my distinguished colleague Mike Ellis mentioned, they MUST be scaled that way to get optimum control from the PID ...

final question (at least for right now):

how dangerous is this system? ... specifically, is anyone (or anything) likely to be hurt in the event that your initial tuning experiments get out of hand? ...

Click to expand...

we really do need an answer to that one ...