Heartbeat for PowerFlex

I'm doing a lot of Ethernet based control of PowerFlex drives these days and currently don't have a method to verify that the signals I see from the drive are currently valid. Sure, I will eventually get a fault once the PLC recognizes a disconnected device in the I/O Configuration, but that can take a while.

Has anybody got a heartbeat monitoring method for devices like this? I'm thinking maybe a MSG command and a timer looking the DN bit. I'm pretty sure that would work, but does someone have anything better?

Steve

Steve,

What I've done in the past is use spare data links. I send an integer heartbeat signal from the PLC to an input data link and assign it to an innocuous parameter (like a speed setpoint I'm not using). I setup an output data link to read that same parameter, thus reading the heartbeat back to the PLC.

If the heartbeat I'm reading back from the drive into the PLC is changing, I know my comms are good. I've found this to be a cheap & easy solution. Hope it works for you.

RonJohn

Isn't a GSV to the Module Object's EntryStatus fast enough ?

The EntryStatus changes immediately after the connection breaks. If you need to know about a drive disconnection as fast as possible, run the GSV every scan.

Are we talking RSLogix 5000 and implicit control here?

Or are we talking RSLogix 500 and explicit messaging?

If the former, Ken's GSV suggestion is spot on and see here...

44910 - PowerFlex drive. How can I verify it is still connected on EtherNet/IP ?
Access Level: Everyone

If the latter, have a look here...

52205 - PowerFlex Drives: Controlling via EtherNet/IP from MicroLogix, SLC or PLC5
Access Level: Everyone

It uses a MSG to monitor the 22-COMM-E's built-in timeout, which can be set between 5-20 seconds.

Explicit will be nowhere near as fast as implicit at detecting a communications loss.

Regards,
George

10-4 on the GSV. We do the same.

I concur regarding the GSV with a Logix based processor. The application I mentioned earlier used a SoftLogix 5800 PLC, so GSV instruction was not an option.

Kudos, George for the links above.

Very cool. This GSV method is exactly what I was looking for but could not find. It seems it's all about asking your questions using the right words. Thanks guys.

Steve

I do something similar in a Periotic Task to just monitor if a 525 drive is online.

Me Three, the GSV of EntryStatus method is a life-saver! We use it on every drive we have, as well as every EthernetIP module we have. Tried a million different homemade heartbeat methods before finding this technique, and none work as well or are as simple to implement.
I've also used it on a system where I had one controllogix plc talking to a few dozen other logix PLC's on a periodic cycle. If one or two of the satellite PLC's went offline, it would bog down the MSG instructions to the other PLC's. Checking EntryStatus prior to each MSG solved that problem very nicely.