Compact Logix - Barcode Scanner via Ethernet

[Plastic]

We are going to use (5) bar-code scanners connected to a 1768 Compact-Logix processor via ethernet. Each scanner will have a unique (static) IP address.

What (ladder / function block) instructions are used to accept the incoming data that the bar-code scanner is going to broadcast? (Scanners will be set up to broadcast one data string on a successful read)

We can trigger the barcode scanner in three optional methods:
1. Continous scanning - and broadcast one burst of data on read success

2. Digitally triggered read scan via PLC output and discrete wiring.

3. Commanded to trigger a read scan via the PLC program over established ethernet connection. (Desired method)

What (ladder / function block) instrucion would be used to send the "read" command to the scanner at a fixed IP?


Lasty, any caveats using Ethernet to scan bar codes?
5 scanners, each scanner would need to read about once every 30 seconds.

Thank You

Plastic

 

[bernie_carlton]

I would look first to the barcode scanner manufacturer for program examples.

 

[rdrast]

Are these Ethernet/IP scanners? What model?
What protocol do they use? Just pure broadcast UDP?
The CompactLogix isn't all that good as a generic Ethernet communications device...

 

[TheStarr]

"What (ladder / function block) instrucion would be used to send the "read" command to the scanner at a fixed IP?"

When using ethernet comms with the PLC you will load the scanner as a "new module" to the network device (under I/O configuration at the bottom of the tree on the left)

Once it is loaded, usually as a "Generic Ethernet Device", it will show up in your controller tag list.

Then you can directly reference the data.

As Bernie said, most manufacturers have examples of how to setup this connection to each of the major PLC manufacturers.

If you can't find anything, maybe we can help.

 

[bernie_carlton]

Saying they are connected via Ethernet is barely one step up from saying that they are connected "by a wire". A lot more information, beginning with exact manufacturer/model, before any even halfway accurat responses can be made.

 

[TheStarr]

No doubt Bernie. I was just giving a heads up on how the PLC side of things may work.

One other important note about having 5 scanners....

When you start to have many ethernet devices on a single network, the RPI becomes important.

RPI stands for Requested Packet Interval. This basically means how often the PLC and the scanner are going to link up their memory tables.

For mission critical items you may want an RPI of 1ms. But for something like a scanner, an RPI of 100ms is probably fine.

If everything on the network has an RPI of 1ms, there will be so much traffic that you start to get excessive collisions which slow down your entire network.

 

[rdrast]

"What (ladder / function block) instrucion would be used to send the "read" command to the scanner at a fixed IP?"

When using ethernet comms with the PLC you will load the scanner as a "new module" to the network device (under I/O configuration at the bottom of the tree on the left)

Once it is loaded, usually as a "Generic Ethernet Device", it will show up in your controller tag list.

Then you can directly reference the data.

As Bernie said, most manufacturers have examples of how to setup this connection to each of the major PLC manufacturers.

If you can't find anything, maybe we can help.

Well, couple problems. A barcode scanner that spits out a line of data when the trigger is pulled isn't likely to a) have an EDS file, or b) want to play nice with scheduled packet CIP communications.

The best bet, honestly, as long as the scanners have some sort of ID (if you need to distinguish them) would be to run them into an Ethernet switch, then to an Ethernet to Serial converter, and poll the serial port on the CompactLogix processor.

 

[Plastic]

Saying they are connected via Ethernet is barely one step up from saying that they are connected "by a wire". A lot more information, beginning with exact manufacturer/model, before any even halfway accurat responses can be made.

Thank you TheStarr, you have me started. I have added one scanner as a generic ethernet modulue under the network. (And the hint for adjust the RPI up from default.


Bernie, I have contacted the manufacturer of the barcode scanner and am waiting for reply. The scanner is a MICROSCAN QX-830, I have read the manual front-to-back, and there are no examples of proper configuration for use with Compact Logix.

I am under no time constraint, We are develping this for an upcoming project.

Thanks again gentlemen for the "jumping off" point.

Plastic

 

[TheStarr]

Ok, here is the total hook up, you can thank me later.

Go to http://www.microscan.com/en-us/Products/ProductCategory/ProductDetails.aspx?id=2379

(or just search microscan.com for the QX-830)

On the right side you will see a link for QX Ethernet IP to PLC

You have to setup a free account to download.

The file contains exact instructions on how to load the scanner into your PLC and even has the Allen Bradley ".eds" files.

Everything you could ever need!

 

[Plastic]

Ok, here is the total hook up, you can thank me later.

Go to http://www.microscan.com/en-us/Products/ProductCategory/ProductDetails.aspx?id=2379

(or just search microscan.com for the QX-830)

On the right side you will see a link for QX Ethernet IP to PLC

You have to setup a free account to download.

The file contains exact instructions on how to load the scanner into your PLC and even has the Allen Bradley ".eds" files.

Everything you could ever need!

TheStarr,
I love you man!
Thanks a bajillion!

 

[TheStarr]

No problem, glad I could help.

 

[widelto]

What about if you try to make an inventory based on what you read from the scanner, and all the boxes have the same bar code. An additional photocell would be needed in order to be sure that a new box is under scanner range, or is there a better idea ?

 

[TheStarr]

When you read through ethernet, each scanner is it's own "ethenet module", so identity should not be a problem.

They show up in the tag list the same way that you would see different remote I/O modules.

Therefore you can trigger a specific scanner and analyze the input data.

Does that make sense?

 

[widelto]

When you read through ethernet, each scanner is it's own "ethenet module", so identity should not be a problem.

They show up in the tag list the same way that you would see different remote I/O modules.

Therefore you can trigger a specific scanner and analyze the input data.

Does that make sense?

No, let´s say that you're using just one line and obviously reading from just one scanner, and all the boxes in that line have the same bar code. In this case data read from the scanner is always the same or is there some kind of trigger when a new box is under scanner´s range ?

 

[bernie_carlton]

There's usually one of two ways. Either the barcode scanner has a local sensor which must make an OFF-To-ON transition off the object to start a new read or it accepts a 'new read' command from the controlling PLC, possibly by the Ethernet link. So as long as there is some way to recognise that "this object" has left now here's a "new object" then the confusion usually doesn't exist. Obviously it's different for each situation.