Internet PLC Forum

Great! Thanks, I will reach out to your support team.

Ed

Guys, thanks for the info! Unfortunate, I can't seem to understand why it is happening. The program the PLC is  running is really simple. It's a Modbus master that loops through several VFD's using a sequencer to increment. I have attached the file for your review. The sequencer was initially incremented every second, now I have increased the timing to increment every 3 seconds to see if that fixes this bug.

Anything more info after your review will be greatly appreciated.

Thanks,
Ed

Hi, just to update everyone. After testing the impendence on the drive it was well above 164Ohms (34K) the transceiver was deemed blown by ABB. Next step is to change the entire board, or just use the built-in AO to read the desired analog signal. However, just because it works with the laptop, I'm researching on using an RS485 extender ie. RS485 to RS485 just to interface with the VFD to see if it works.  

Any ideas will be greatly appreciated...
Ed

The wiring is correct there's not much to it, is working on the other drives on the daisy chain. ABB suggest to check the impendence across the + and - terminal. Measurement needs to be 164ohms with +/- 5%. They also asked me to remove the shielded from the ground, and turn on the bus terminator on the drive.

I will be at the plant on Monday working on this, I will keep everyone posted.

Thanks Gary!!
Ed

Thank You Both for the input! The network is already setup as you guys mentioned, the shielded wire on each drive is connected to the AGND terminal and at the Nano is connected to the 0V. All but Drive2 is not communicating at all, with UART Errors.

My next step is to enable to built in bias terminator in the last drive (Drive4) to see if that works, if it doesn't work I will disable it and then add the 1K by the Nano and try again as you mentioned.

[---------------RS 485 Network--25' max-------------]
 ====\/=======\/======\/======\/
      [Drive1]     [Drive2]     [Drive3]     [Drive4]

I have also reached out to ABB to see if there's anything else I can do, so far still waiting....

My very last attempt to fix this id everything else doesn't work, I will try to use the Auto485 and connect it to the drive via RS232 back on the network with via 485 , I haven't try this yet... Keep you all posted.


Thanks,
Ed

Hello everyone! I have a little issue with a single drive in a 485 network. Basically I have a nano working as a modbus master polling information from each drive. My issue is that one of the drive gives me a UART error even with the nano communication turn off. Yesterday I remove that drive from the network and locally it work using an u-485 converter. But as soon as I connect one of the network wires it starts counting on UART error.

My question is, have anyone dealt with an anomaly like this? Also, what's on the U485 that's not in the nano 485.

One note, the drive in question is the 3rd node on the network at of 4 drives and the last node works fine.

Thanks, any help will be greatly appreciated...
Ed

Ok, I have not found the issue but the problem is in the PLC program that's currently running. I tested with the Ethernet Modbus sample and everything works great!

So keep everyone posted when I find the solution...

Thanks,
Ed

PS: the image was never uploaded on the previous post, it was too large...

I just changed the address from 40004 to 30004 thinking that may be causing register overflow but nothing yet. Still having the issue...

Thanks,
Ed