Reading data on multiple Allen Bradley Controllogix PLC

[Chronik]

OK, but what about if i go in OPC and i delete the tags, is this going to delete the values in OPC only or it will affect the PLC? Could i just delete everything and have only 1 variable, (read only), and thats all? If so, I can create tags in OPC, should i create de tag called "SPEED" to read the machine's tag "GE01_Mop.ActualSpeed" ?

Setting all the variables to read only will take forever.

Thanks a lot!

[Drew_T]

Chronik,

I'm not sure how you got all the tags in your OPC Server to begin with.  Can you enlighten me as to this?  I am not aware of any mass add or auto add features of the product, so either you had to add them all manually yourself, or they were already added by someone else.  If you added them, then deleting them should be no problem.  If someone else added them, I would doublecheck with them to make sure they are not using the tags.

Either way, deleting tags in your OPC Server should not affect the tags on your PLC.  It is simply an interface to view and update the tags present on the PLC.  However, as above, if someone else is using these tags to update values on the PLC, deleting the tags will stop the updates.  

[Chronik]

Thanks for your time and help.

Here are some screenshots of what i am talking about.

Should i just ignore the tag and database creation and create my own variable that will be bounded/linked to an existing tag that i want to read. (And setting this variable to READ)?

[Chronik]

one more picture showing the icon to force database/tags creation.

[Drew_T]

Chronik,

This is a great feature of the Controllogix PLC that I was unaware of.  However, in your case, I think it would be better, as you suggested, to simply manually create the tags you need and set them to read.  Thanks for taking the time to show me in screenshots what you were referring to.

[Chronik]

Thanks for your time and help on this.

I hope i will have time to test it this week. I will let you know how it goes.

Thanks again.

[Chronik]

Hi,

i finaly had a little time to work on this project.

I encountered a couple of problems.

I managed to read the values on the PLC and use in it my VI, but as soon as i added another device that was on the same gateway (same machine, different PLC but all linked together ie : 192.168.16.113 MAIN and 192.168.16.114 secondary), it seems that the tags would update randomly, if ever...

I tried many things to make it work, and i finaly gave up and tried doing it as multiple channels. (at first i had 1 channel for the whole machine, with all its PLCs listed as devices) So now i have 3 channels for the 3 PLCs i try to monitor, even though they are on the same gateway and (from what i read and saw) should work under 1 channel..

Can anyone enlighten me on this ?

THanks

[Chronik]

Picture of the current "seems to be working" setup in OPC

all 3 are Controllogix PLCs, 192.168.16.X

[Chronik]

The two following pictures shows a configuration that does not work, and i'm trying to understand why.

1 channel, 3 devices. the 3 devices were auto-promoted on connection... and they remained "connected" ... (normally if it lose connection it will auto demote within couple of seconds)

in quick OPC client, some of the values get an update... once or twice and that is it.  The connection says it is "good", but they should refresh at 250 ms (or on value change) and they dont, ever.... (and yes the values that i am monitoring do change every 100 ms or so, so i should see it. I see it when doing the OPC setup with 3 channels and 1 device per channel..)

Thanks for your help.

[Drew_T]

Chronik,

What devices are these?

What do the system tags indicate?  There should be at least 4 (error, no error, enable, simulated).

You can try to force an update by going to Tools » Items and trying out Sychronous Read, or Asynchronous Read / Refresh.

Try checking if the server connection is running by going to Edit » Properties with the server selected.  Then check the Server State field.  Also, double check the active state of the group by going to Edit » Properties with a group selected and check the Active State checkbox.  Do the same for the tags.  I realize that the visual indicators show that these things are true, but I want to double check the back end.

Do you have multiple network cards in your computer?  Make sure the channel is looking at the right connection.