SLC 5/05 controlling Powerflex 525 drives over Ethernet ???

Join Date
Dec 2008
Location
PA
Posts
16
Going back to a 15 year-old project and upgrading the drives to PowerFlex 525. SLC 5/05 was controlling three non-AB drives with analog (for speed) and digital (for start/stop). The drives run three axes of a machine (so speed of control is important). Control of the three new drives from the SLC 5/05 Ethernet port is proposed. Other items on Ethernet are one Panelview, comm to another SLC 5/05, and one serial to Ethernet module (two lasers with 10 readings per second each).
This would be easily done with Logix, but is this expecting too much of SLC 5/05 Ethernet communications?
Is there some way to analyze this and either conlude that the SLC 5/05 can easily do this or is unlikely to be able to do this over Ethernet?
Thanks in advance for your help.
 
Until the system changes to Logix control why not just leave the control of the drives as it was? This is assuming the control was satisfactory before.
 
I understand the SLC uses the same processor for program execution as well as handling the communications. As a result, it updates the comms only once per scan unless an SVC instruction is used. Adding three more devices will definitely slow things down. I don't know of a means to measure how much.

I had a system where three WonderWare stations were connected to a 5/05. I ended up adding 2-3 SVC instructions to make the pushbutton updates bearable. This creates a trade off however: no SVC instruction means the Ethernet comms will take a hit. Adding one or more SVCs mean the PLC scan time increases.

Can't say how slow is too slow for your situation. If you cannot test this somehow, I'd be inclined to stick with Bernie's suggestion.
 
Based on your description of the machine, it is unlikely that you will get suitable performance and reliability out of an Ethernet message-based control technique using an SLC-5/05 controller.

All the factors you described; HMI traffic, messaging to other devices, and low control latency requirements are also the factors that contraindicate that method.

You can use messaging to read diagnostic or monitoring parameters from the drive, or send configuration information to it, but stick with analog and discrete wiring for the actual control.
 
I’d look at two approaches but unfortunately both require spending money.
The first and probably most practical is to put a Logix PAC in place of the SLC5/05. While I like SLC5/05’s (I use/play with) them a lot, you will be limited to how fast the message instructions can execute and how many can run simultaneously. With message instructions (EtherNet/IP TCP) the 505 has to open a communications session, pass the data back and forth and then close the session before it can move onto the next one. With Produce/Consume (EtherNet/IP UDP) the connection is opened and left open so data exchange happens much faster.
The other approach that I would look at is having a dedicated PLC for the drives so that all it’s doing is controlling the drives. The main PLC could then read/write to it and deal with the other devices in the network. Because the “Drives PLC” is doing nothing but dealing with the drives (and responding to the main PLC) its messaging would be faster.
Just my two cents.
 
a year old thread but i figured i would put my two cents in.

i successfully communicated to a bank of 24 525 drives via ethernet from a 5/05 processor.

i did this by separating each drive routine into it's own ladder, attaching an incremental counter to the entire array and every scan check to make sure the message block currently being called is done. Once those conditions are met i increment the counter by 1 and go to the next drive. All reads and writes to that drive are triggered simultaneously only during the incremented scan and only 1 time. Once the entire array has been triggered i reset the counter and start again.

Doing this method i was able to scan all 24 drives, read and write, in about 250 milliseconds or so. This is by far plenty fast enough for my application and the processor scan time did NOT suffer or lag at all. We had a Panelview HMI that was hooked to the serial port too. This was bogging down a lot due to all of the comms traffic that was occurring. This was also alleviated once the counter triggering array was established. When running full speed, the counter would cycle extremely fast due to all of the ethernet traffic being manually scheduled.

Just my two cents. This site has helped me a lot and just trying to give other options to everyone.

Thanks,

beanpole_ecc
 

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