Incremental encoder with Powerflex 525

taylor1982

Member
Join Date
Aug 2011
Location
Bavaria
Posts
78
Hi,

I have a application where I must do a positioning of a conveyor belt with a PF525. The Motor of the conveyor has an incremental encoder.
So our CAD dept decided to use a 25-ENC-1 card in the PF525.

I saw that this card has no connection terminal for the zero pulse of the encoder.
So as I said I want to do a positioning with this application no speed monitoring.

Are there any hints if this is possible with that hardware? If yes a few first steps would be appreciated! Can the drive do the positioning itself or do I need the encoder value in the PLC? How do I get the encoder value to the PLC?

Thanks a lot 🍻
 
Either just parallel the encoder to the drive and the PLC, or use an encoder splitter/isolator if you have different input needs or isolation for the PLC and drive.

I use these when I have different potential inputs, but need to share an encoder between devices.
 
You can use datalinks to get the encoder value into the PLC over ethernet/IP. I have done just this on a previous project.
 
You can use datalinks to get the encoder value into the PLC over ethernet/IP. I have done just this on a previous project.

Can you show an example this? TIA

This is what I did. Double click the drive, Device Definition , Connection Format, In Input tab, select drop down Parameter, select Speed Feedback
 
Last edited:
Check the following links from the knoweldgebas:

PowerFlex 525 Drives: Reading the feedback position. Parameter 388 units traveled remains at 64,000 units
https://rockwellautomation.custhelp.com/app/answers/detail/a_id/563605

PowerFlex 525: Pulse Train Input and Encoder Use - Tach Feedback
https://rockwellautomation.custhelp.com/app/answers/detail/a_id/543119

Obtaining encoder speed feedback from the PowerFlex 525 to a Logix processor

https://rockwellautomation.custhelp.com/app/answers/detail/a_id/623572
 
tarik's last link has the details on how I did it - let me know if you need more info.

One thing I will add - as the technote says, the speed parameter is a 32-bit parameter, which chews up two of your precious four datalinks. However it need not be this way under all circumstances. In my application, the encoder was turning quite slowly, and I was able to be quite confident that unless someone decided to run the motor up to several thousand hertz, my value was never going to get so large that it couldn't be represented using only the first 15 bits. So there was no point me wasting a datalink on a parameter that was going to be zero 100% of the time, and I only used the one datalink. Depending on your application, you may be able to do the same. I *think* there may also be a parameter you can play with that effectively adjusts the resolution of your speed feedback, meaning if you did have a higher speed but didn't need the resolution/accuracy, you could get the speed in say 10's of RPMs instead of 0.01's of RPMs, and then scale it in the PLC - the would also help get you in under the 15-bit limit.

Hopefully there's enough data there to get things moving - if not let me know and I'll try to dig out my old files.
 
I've been puzzling over the topic of a tiny subset of 525 parameters I'm interested in reading being labeled "32-bit" in the manual - I think this Technote QA20639 finally clarified it:
Units Traveled H parameters [d388] is created with a signed integer data type [INT].
...
The PowerFlex 525 drive internally uses unsigned integer.
...
Other drive parameters with maximum values higher than 32767 are affected to, such as encoder speed [d378] and Speed Feedback [d376].
I have a fleshed-out 525 AOI already performing scattered reads for lots of other parameters, so I'm now sure that I can reliably parse the "32-bit" ones among them without needing to resort to dedicated single-parameter reads.
 

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