Automation Direct SVA-2300 Modbus Comms

FYI, if you’re connecting up to the AD servo product (I assume they all have same issue) please note, it will save you a lot of time.
I have connected a Epic with the 4 port Opto serial card to a “SureServo” model SVA-2300. They have a newer model called SureServo2, but I suspect that might all have this same issue.
The issue at hand is it is not possible to get the serial card connected to their serial port directly without using a convert or isolator. I have tried every possible config, 232/485 slow baud, fast baud, no way no how. I even ran Modbus Poll on the SVA and Modbus Slave on the Opto serial card port, both passed with flying colors at 115,200.
However, I happened to have a B&B Model 232USB09M converter, so I connected it up and no problem, comm was perfect at any baud.
I ordered a new RS485 cable for the SVA and tried every possible combo to the Opto serial card, including using a different port, different term and bias combos, no success.
My conclusion is the UART drivers on these 2 machines have a problem electrically.
My next experiment is to use a 485 Isolator from B&B. I want to use the serial card, but I may have to resort to a USB to 485 connection.

Is it possible that the rs485 chip on the Automation Direct drive does not pull low to a zero state when the line is not active. Did you try to use the bias setting on the CSERI module. This would bias the line low when there is no active driver on the RS485 line and may solve the issue without the external converter.

As a note, I have noticed in using Codesys with the CSERI module that the module settings made in codesys do not change the settings on the card. You can verify this by logging in to the controller and looking at the module settings through the configuration website. I have just made the changes needed for serial communication on the configuration website page.

Yah, that what I was thinking, however, the drive doesn’t have any options for setting bias up or termination, so I tried all those settings on the CSERI module and nothing made a difference.
I wasn’t going to bother with setting up a scope to figure it all out, so I figured I would try an opto isolator type 485 repeater. That hasn’t come in yet, and since I had a working solution with the RS232 USB module, I have been moving forward on the project.

As I was trying all these different combinations, I kept checking the actual config in CSERI and I don’t remember if I saw that problem. I’ll look again next time I revisit this issue.

I have to say that the AD Sure Servo 1 is kind of crude and is pretty awkward to set up and use. I hope they’re newer version Sure Servo 2 is better than this…you can’t even set drive to work in counts across multiple turns. You have to do everything in revs and counts combined. Also, turns out that if I set the absolute position to say 250 degrees of a 10:1 gear head output shaft (6 turns and 9444 counts), on the next move the drive runs in reverse to get to the next position, even though the drive direction is set to fwd…this means i have to add an intermediate position less than 180 degs to make it go fwd.

Unfortunately, this was a job left over by someone else, as usual…it was totally messed up. Even the servo was end of life’d.

Can’t wait to get back to a project with Kolmorgen, there is just no comparison.

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