MicroLogix to Powerflex 525 via Ethernet

lam2363

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Aug 2013
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Hello All,

I am using the on-board PID on a PowerFlex 525 to run a conveyor that will maintain a loop using a distance laser. The laser is hooked up to a MicroLogix 1100 and is communicating via Ethernet. The way the hardware has been built will require setpoint and feedback to be routed through Ethernet from the MicroLogix 1100 to the PowerFlex 525.
I am having difficulty finding any information beyond an appendix in the back of the user manual to describe how to access the parameters other than the command, status, feedback, and reference words.
Before anyone tells me, so I already know this is not the less than ideal way to use a 525 but the decision was made without my input and I am now stuck with this now, need to make it work, and in need of assistance. Any and all would be greatly appreciated.
In a nut shell, I would like to know is how to write to the PID feedback (Parameter: 464) and setpoint (Parameter: ???) parameters on the 525 parameters and that's it.

Thanks,

Lucas
 
Hello,

As far as I know, there's no way to access parameters directly in the 525 using messaging from a MicroLogix. In this case, I think it would be best to do all of the PID logic in the MicroLogix and simply send the 525 the speed reference that the MicroLogix calculates from the PID.
 
Hi

Or upgrade to a compact logix like the l16
I find that the extra spend over the micrologix is saved in programming time alone

Donnchadh
 
Thanks everyone that's what I was figuring I was going to have to do but I wanted to be thorough. I would love to convert to a CompactLogix.

Thanks again
 
The PowerFlex 525 evidently didn't implement the PCCC object quite as thoroughly as some other drives. You can read and write the I/O assembly objects as though they were SLC/MicroLogix data table elements, but not the other parameters.

You're aware that doing so makes the baby Jesus cry, so we'll set that issue aside.

What might work to read and write individual parameters is to use the CIP Generic MSG in the MicroLogix 1100.

This will allow you to use the PowerFlex 525's Parameter Object to read and write any Parameter. Configure the MSG for CIP Generic, then select Read Parameter or Write Parameter as the Service code, and put in the parameter number as the Instance value.
 
If we take a step back, though, I see the fundamental problem of attempting to use the drive's onboard PID loop when the feedback instrument isn't actually connected to the drive.

The PowerFlex 525 onboard PID can be configured to use a Feedback signal from several different sources. The most common ones are the actual analog feedback terminals on the drive.

You could set Parameter 460 (PID1 Feedback Select) to a value of 6 to configure the PID1 loop to use the "EtherNet/IP" as its Feedback.

But... heck, I don't know what part of the EtherNet/IP connection will serve as the Feedback when you make that setting.

I agree that it would be significantly easier to do the PID control in the MicroLogix and use that to trim or control the PowerFlex itself. It would certainly be easier to troubleshoot.
 
I'm obligated to re-tell the silly old story about the customer who thoroughly soured drive control over MSG instructions for me.

They were in a situation similar to this one: they had an SLC-5/05 connected over Ethernet to three PowerFlex 700 drives. There were no available slots in the SLC chassis and the system was onsite with an impatient customer waiting for it to start up.

So I gathered up three PowerFlex drives and an SLC-5/05 and wrote a well-tested, solid, easy-to-troubleshoot ladder logic routine that integrated well with their pump control logic. Pulled an all-nighter on a Saturday to get it done. Integrator was thrilled, customer was satisfied, Allen-Bradley support was worth the money again.

When the programmer returned from the startup I asked for a meeting with him, because I'd done a "lunch and learn" for them just a few months previous in which I had explained in detail how ControlLogix premier integration worked, and that you couldn't do the same thing with SLC-5/05 or MicroLogix.

The designer admitted that he knew that it would be harder to program, slower, and less reliable, but that the (at the time) lower cost of the SLC-5/05 made him choose that platform. He thanked me for bailing them out of a pinch and promised he would use analog or SCANPort modules for future SLC-5/05 controlled drives.

A few months later he called back and asked for help configuring a 20-COMM-E on a PowerFlex 700.

Had something gone wrong with the system we'd commissioned ? I worked so hard testing the error recovery !

No, he admitted, it was a new system. "Your program worked so well, it's our new standard."
 
Hey, the Knowledgebase came through !

KB Article ID # 627551, Access Level = Everyone.

Because you need to access both the Command word and the DataLinks, you will need to use the Assembly Object.

You'll have to read and write to the Assembly Object with Generic CIP messages, and also set the Timeout attribute (page 128 of the Embedded Ethernet Adapter user manual).
 

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