Data Logging: Where do I start?

[Squirrell]

Here's what I am trying to do:

We have a large automated piece of equipment at our plant.  Basically, it processes spooled tubing in a variety of ways, but the final station is for flow testing.  All of the components are controlled through an Allen Bradley PLC unit.  I have the PLC connected to this computer and RSLinx is being utilitzed for data transfer.

There are four tags that I need to have logged in an Excel spreadsheet (Actually, any speadsheet will do).  These four tags/variables are the four test results from the flow test stage:  Four pieces of processed tubing are tested for flow rates and compared to customer-supplied references.  The result is returned as a ratio of Processed Piece Flow to Reference Piece Flow.  So, a perfect piece registers as a 1.000 and a bad piece is anything < .9600 and > 1.0400 for a ratio.

Unfortunately, the cycle times differ from job to job.  They range from 21 seconds to 46 seconds per cycle.

I can see the tags I want to log in LabView, but I am VERY confused as to how I can log them.  That's all I want to do.  I don't need a computer-based interface for the PLC since we have a touch-screen panel (PanelView Plus 1000 by AB) for that.  Here's an example of a variable location:

opc://localhost/RSLinx OPC Server/[PLC NAME]TEST_RESULT_A

Obviously, PLC NAME is the name of the PLC in brackets:  I'm not including it because of company policy.

Again, I only want to log these four variables.  That's it.  I want to log them ONCE per cycle. So, I found a variable that changes twice per cycle:  From 0 to 1 and 1 to 0.  This is done when a robot lifts the four pieces to be tested.  When the robot finishes testing, the variable switches to 1.  I want to log the four test-result variables when the end_test variable switches to 1. 

First off, is this possible?

Secondly, I can't get Measurement + Automation Explorer to work, so is this something that I can do without it?

Any help would be appreciated.

Thanks in advance,

Chris

[andre.buurman@carya]

First of all you don't need MAX (Measurement and Automation Explorer).

Second:

Yes, its possible to do what you want.

As file format I would suggest a Tab-delimited file, since most of the spreadsheet apps can deal with them and its standard.

The "Write to text file.vi" example that comes with LV shows you have to create a tab-delimited file. At least in LV 8.2.

Regards,

André

[Squirrell]

Thanks!  I'll try that right now. 

I was worried that not having MAX would affect things, but apparently not.  I downloaded the driver CD yesterday and installed everything as well.

I'll let you know how it turns out!

[Squirrell]

Wow, I didn't realize that the process was so complicated...

In which terminal can I specifiy what tag to pull from the PLC?

[andre.buurman@carya]

I'm sorry.

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@Squirrell wrote:

Wow, I didn't realize that the process was so complicated...

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Which part of the process to you mean? (Getting the values, writing to file or both)

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@Squirrell wrote:

In which terminal can I specifiy what tag to pull from the PLC?

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I thought you already knew how to get the values of the PLC variables in LV. Which VI are planning to use to get the values?

Regards,

André

[Squirrell]

Hahaha it's no problem that it's complicated...  It's a good way to learn, right?

My dilemma is that I have the address for the variables in LV.  I used Browse to OPC item/server and found the variables I needed.

What is my next step to get LV to even SEE these variables?

Thanks for your help, by the way.

[andre.buurman@carya]

In version 8 and up you are able to read OPC variables by binding them to a Shared Variable.

Add a new variable to you project and bind it to a network variable, the OPC items should turn up in the list.

Regards,

André

[Squirrell]

Ok, I'm doing that now.  I didn't see the OPC items in the list, so I just copied in the tag location I received from "Browse OPC Item" back on the main page...

I hope that works...

That, and I'm not very familiar with the heirarchy of things in LV.  I mean, there's VIs, LLB, LVProj, etc etc and I think I'm getting way in over my head here. 

Still, thanks for your help, and I'll keep trying at this until I get it working!!

[Squirrell]

Ok, so here's where I am now:

I created a variable.  Unfortunately, the OPC server does not appear in the "browse" option for binding the variable to a OPC tag.  So, I copied that path from the "Browse to OPC item.VI" example.  I can easily find the tag in there, but nowhere else.  I copied the tag path into the bind path.  I tried running this JUST to view the current value and it did not work.

Any ideas?

[Squirrell]

The OPC items did not show up in the browse list.  I added a new variable called "TEST_RESULT_A" which is also the same name as the tag I want to monitor.

I went to the variable's properties and selected "Bind to Source."  I clicked browse and only my computer showed up as a directory (Network Item).

What should I do?