CLX Scattered Param Read from 1336 via 1203CN1

Marco Baz

Member
Join Date
Mar 2019
Location
Mexico
Posts
5
Doe any one can lead my way to get some VFD 1336 paramters from Control Logix ?. I have a 1756L63, conected to a Control Net and from theres U have 2 VFD 1336 Plus; I need to gect Power, Current, speed. Cant find if explicit mesaaging does the trik?
Thanks
 
You may be able to find the drive I/O in the Controller Tags of the ControlLogix processor, which you should be able to message. Are you trying to send the parameters FROM the ControlLogix to another device? I've done this with PowerFlex 750 series drives. I'll try and get a screenshot of how I did it.
 
Under tag list of VFD these parameters are not accesible. I though maybe the way to get thes values was to mesaging as Power Flex allows, but 1336 seems to me its not possible via messaging.
 
Welcome to the PLCTalk forum community !

If you are not an A-B messaging expert, I recommend against attempting to use the Scattered Parameter Read feature.

Instead, use the ordinary Read Parameter Object service. It is relatively simple.

Each MSG instruction will address one parameter in the drive. Write a simple sequencer to fire one message at a time.

You may also be able to modify the "Data Links", but depending on your system and how much flexibility and experience you have, you may wish to simply write the MSG logic.

Please let us know exactly what interface the 1336 Plus drives use; usually it's the externally mounted 1203-CN1.
 
Ken,
Not an expert, but this far I know meesaging wil be configured as :
Service code 4b (get attribute scatered
Class 93
Instance 0
Attribute 0

And my source element should contain Par number follow of Pad WORD.
This I know because I had investigate to read also from Power Flex.

However, I have two 1336 Plus on CNet via 1203 CN (just as you mentioned). I have the need of reading Frecuency(Hz), Current(A), Speed(%) and Power(Kw). But for these 1336 on 1203 I just can´t find any information on how to do it. Would it be the same as mentioned above for Power Flex?

Any advice woul be aprecates, even on my assumptions for Power Flex.

Thanks
 
I recommend against using the Scattered Parameter Read function because you have to set it up so carefully with a payload and then parse the return. I am an expert and I seldom used it because it was harder for other programmers to understand.

It's simpler to just do a CIP Generic MSG that's set for a "Parameter Read", using the Class 0x0F Parameter Object, and execute one MSG for each parameter.

All you have to do is enter the Parameter Number in the "Instance" field.

Parameter 2 is Output Current, Parameter 3 is Output Power.

I think you can read the Output Frequency as Parameter 66, but it's generally also part of the ordinary Input connection as the "Feedback" value.

CN1_Parameter_Read.PNG
 
Ken,
Definitly I will take your advice. Would this hint may be used also with Power Flex via ethernet? and Would parameters number will remain the same?
 
Ken,
Definitly I will take your advice. Would this hint may be used also with Power Flex via ethernet? and Would parameters number will remain the same?

Forgot to ask, Destination Tag is DINT or REAL?
And just to confirm:
Current Par 2
Power Par 3
Frecuency Par 66
Speed Par ?
 
Last edited:
The Parameter Object is very well documented for each parameter in each drive, so I go to the User Manual each time I use a Parameter Read. Most parameters are integers, but some are 32-bit and some are 16-bit. The internal units of the parameters are often not the same as the plain-language or display units.

An example from the 1336 Plus II drive user manual:

https://literature.rockwellautomation.com/idc/groups/literature/documents/um/1336f-um002_-en-p.pdf

The Output Power in kilowatts is Parameter 23. While the drive displays the power in kilowatts, the "Drive Units" that you would read via a MSG instruction are described as "4096 = 100% Drive Rated KW".

So if you read that value from a 22 kw drive that was running at half power, you would get a value like (11/22 * 4096 = ) 2048.

You'll need to check through the scaling and units for each of the parameters you want to read.

In general the I/O connection always includes the Command Word and the Reference Word in the Output side, and the Status Word and the Feedback Word on the Input side, so you don't need to read the drive status or the feedback.

I used to know all this stuff by heart, but it's been a while since I work on a 1336 Plus or Plus II. The Reference and Feedback values are 0 to 32767 for the Min Frequency to the Max Frequency.

In the PowerFlex drives, there are a lot more parameters that are in engineering units (like 0.1 Hz or 0.1 RPM) than in internally-scaled drive units. It's always worth it to check the user manual.
 

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