Devicenet help

[mmbte]

I have a 1769 sdn scanner on one panel and a 1769 adn i/o module on another panel, this module got burned and replaced but after replacement scanner shows code 79 and I cannot find how to fix this.

I checked all the cables, power supply, terminator resistors and nothing.

I'm also not able to see the i/o module on the network.

Am I missing something or doing something wrong?

Any help would be much appreciated.

Thanks!

 

[plvlce]

Obvious thought -- did you set the node address in the replacement?

iirc error 79 would indicate that the scanner does not see any devices on the network. Is it just the one scanner and adapter on the network, no other devices?

Could whatever burned the adapter module have damaged the scanner as well?

 

[mmbte]

yes, when the replacement was installed they set the node to 01 on the module's rotary
switches.

 

[Ken Roach]

Welcome to the PLCTalk forum community !

Error code 79 is a general network data failure error.

It means that the DeviceNet Scanner detects 24V on the red and black wires but no data traffic at all.

The 1769-ADN always uses "autobaud" to detect the data rate on the network, so if they 1769-SDN Scanner is trying to communicate with it, it should detect that and reply.

Power down the DNet and measure resistance across blue and white wires, and check for short to 24V and DC Common.

60 ohms between the CAN signal wires (blue and white) means the cable is good and both termination resistors are in place. 120 ohms means only one is in place. Any other value means there's something wrong in the cabling (or you left the DNet power on and the transceivers are affecting the meter).

 

[mmbte]

So far I've checked this. Voltage on the power supply, voltage from both CAN wires to V-, resistor with the power down and all those looked good, CAN wires to V- were 2.5 to 3 V but that means there's no communication, right? We also replaced the cable and connectors too to see if there was a bad wire but that didn't work either.

Today we ended up replacing the scanner, and after that the network showed that scanner on 2 different IP addresses for 2 different machines but one of them had a module and the other one didn't when I scanned the network both on rslinx and rsnetworx. They both showed the same scanner though. Does that mean anything?

 

[Ken Roach]

OK, so the cabling is probably good.

Obviously whatever damaged the Adapter (-ADN) could also have damaged the Scanner (-SDN). CAN transceivers are good for about +/- 40 V DC, but getting 120V or higher onto the signal lines can certainly burn them out.

That would be consistent with an error code 79, too: if the CAN transceiver is burned out, then the microcontroller isn't going to see any traffic at all, rather than seeing conflicting frames (Bus Off error 91).

I am not sure what to make of your description of the Scanner showing up under two different PLCs, or two different node numbers.... it's not clear what you were seeing.

In general, a Scanner needs to be set for its node number and data rate, and have the Scanlist loaded into its onboard memory using RSNetworx for DeviceNet. DeviceNet Scanlists are not created or stored in the ordinary PLC user program like they are for ControlNet or EtherNet/IP connections in the I/O tree.

 

[mmbte]

So if the scanner could have gotten damaged then replace the scanner and try to load the backup into the new one and go from there.
I didn't understand the whole one scanner for both modules thing either but I'm gonna look into it too, the only reason I say it is because when I replaced the scanner I didn't look at the revision number on the new one and it's a higher revisio, rsnetworx shows me there's a different device revision loaded on the network and gives me like a little light blue symbol on the scanner when I scan both devicenet networks

 

[mmbte]

Ok so I have another question, I'm looking at the network and I have 4 different devicenet slaves and scanners. 2 of them are on the devicenet network with a 1769-L35E ethernet port and the other 2 show on 1768-ENBT/A.

Could anyone explain this? What's this 1768-ENBT/A for?

 

[Ken Roach]

It would be ideal if you can describe a little more about your automation system and the role that the Compact I/O and DeviceNet play in it.

Most DeviceNet systems consist of a PLC, a slot-mounted Scanner module, and multiple sensors or I/O devices connected to the DeviceNet trunk cable.
Sometimes there is more than one Scanner per PLC controller, but each has its own DeviceNet and slave devices.

DeviceNet networks with more than one Scanner connected to the same trunkline are possible, but uncommon.

The 1769-L35E that you're seeing on an Ethernet network is a CompactLogix CPU with a built-in Ethernet port. It uses the 1769 Compact I/O bus, and therefore the DeviceNet scanner usually connected to it is the 1769-SDN.

The 1768-ENBT is an Ethernet module for another model of CompactLogix, very similar to the 1756-ENBT on the chassis-based ControlLogix platform.

The 1768-L43 and 1768-L45 were a "mid-range" controller CPU in their era, with more memory and speed than the other CompactLogix. They had a left-side data bus to connect Ethernet and ControlNet modules, and a right-side data bus for 1769-series I/O (which includes the 1769-SDN).

If you have two CPUs, each with their own 1769-SDN, connected to the same DeviceNet cable, then you might have a very unusual "hot backup" system.

 

[mmbte]

Okay so let me try to explain what I got so far, I'm not super familiar with the equipment yet because this is my second week on the job and the previous person working in control made a lot of changes without documenting anything, but as far as this system this is what I have.

we have 4 main panels (this is were we have the scanners and all that), each one of them control 2 machines, and we have 4 other slave panels where the I/O modules are located.

The schematics of the panels show that "main panel 1" connects over the ethernet switch to "main panel 2", "main panel 3" connect to "main panel 4", I don't know if that matters but that's one thing I noticed.

They all have the same PLC and scanners and I/o modules. But the PLC on the panel that I have the issue the module status and network status light indicators are off.

That's the best I can do with the information I have gathered on the past few days.

 

[Ken Roach]

But the PLC on the panel that I have the issue the module status and network status light indicators are off.

Examine the PLC closely to see if it's receiving power, and trace out the cable that connects it to the local Ethernet switch.

The network status LED should be at least illuminated and flashing green if the network port on the CompactLogix is functional.

It sounds like you've got a steep technology/product learning curve as well as a facility/process hurdle, so good luck and we'll do whatever we can to help you tear into it.

Practice cropping photos as PNG's or taking detailed notes to post as attachments to your forum posts; a picture, as they say, is worth a thousand words.