Devicenet Problem

[Kballard122]

I am having an interesting devicenet problem that I can't seem to diagnose.  I am fairly new to devicenet and have never used it prior to this application so it is likely that I am doing something wrong and not the robot.

My problem is that I have no problem seeing outputs FROM my robots on the PLC, but when I try to send an output from the PLC, back to the robot I am not seeing any of the universal outputs that should be switching.  I admit that I am not entirely sure which set of outputs I should be sending to the robot using the PLC so I have been trying trial and error so far.  Has anybody ever seen an issue like this before?

I have a small fleet of 3 MH-50's with DX-100 controllers.  Each robot is equipped with a 2-channel SST-DN3-PCU-2 Devicenet card.  I am only utilizing channel A of each card.  I have the three robots daisy-chained with an AB CompactLogix PLC as the master and power supply.  This PLC is placed as close to the middle of the network as possible.

I have no problem seeing all three robots with the PLC.  I have ensured that I have put the right EDS file for the number of bits (12) assigned to each robot.  I have also inserted a resistor into each end of the network. 

Because the network is fairly short I have not utilized any repeaters, end-caps or nodes.  I would be surprised to ever see a need to add more devices to the network than we already have so I didn't really design in much of that functionality.  I was told that I didn't really need any of the extra equipment or to set up a trunk-line system, so I did not.

[tony gast]

Don't look Univeral.....look at ex inputs this will tell you where the PLC outputs are coming into the robot

[Kballard122]

Tried looking at Ex-inputs in the past.  I didn't see anything switching on and off there either. 

I also looked at several other input groups.

The robot is supposed to be set up from the factory to map the I/O for the devicenet card to universal inputs and outputs upon setup.  The Universal outputs are functioning correctly for all 96 outgoing signals on all 3 robots.  The universal inputs don't seem to be working that way.

One thing I did find interesting was the fact that I left a few outputs on the DN scanner in the PLC on over the weekend and when I booted the first robot up today it looked like there were a few Universal Inputs on that corresponded with where I would expect to see them coming from the PLC.  I switched them off on the PLC and they went off on the robot.  I have since lost that capability and am unable to get the inputs to flash on and off on the robot when I toggle the outputs of the PLC.  I have not made any changes that should have affected the operation there. This has baffled me.  I may try changing the baud rate of the entire network and seeing if that can help.  I figured I would just leave it down at 125kps since that seemed to cause the least number of problems with the wiring and communications. 

[tony gast]

If your ex out to plc are say 30060 first bit you ex in to robot should be 20060

[Kballard122]

Its starting to look a lot more like a PLC problem than an issue with the robot.  I am going to call support at AB and see what they've got to say. 

[tony gast]

turn on say 2words in the plc.....I have seen plc offset..... had to do remapping ....I was 2 words offset from where i should have been

[Kballard122]

I just ended up needing to turn on the device net output on the PLC.  Apparently AB requires you to enable a scanning bit in order to use DN.  After figuring that out, DN is a pretty simple system to work with!