JETS (Customer) asked a question.
I have three devices on a Modbus RS-485-2 wire network in this configuration; the HMI (master), second device is an ABB VFD ACH550 and the L7P servo drive. The overall distance of the network is about 15 feet and operating at 9600 bps. The master has a 120-ohm termination resistor.
I have looked at the l7pcommguide.pdf and it doesn’t say where to connect AGND. I am using the APC-VSCN1T-AD (LS Electric CN1 feedthrough terminal block). Do I connect AGND to the terminal on the feedthrough block?
The L7P is the third and last device on the network so I want to use the built in RS-422-4 termination resistor(s). If I use it will the termination be 60 or 120 ohms?
I am using a T-568 B cable so in this case for RS-485-2 the wires that would be tied together would be white-green and white-blue (RS-485 +) and blue and green (RS-485 -)?
Thanks, JETS
AGND is the analog ground. Are you using the RJ-45 connectors on the drive for RS-485? Do you need to set the terminating resistor on the drive?
On the last drive in the system, set DIP switch #2 (located below the 7- segment LEDs) to ON to incorporate a 120Ω terminating resistor. Additionally, it is important to make sure grounding/common is connected between drives and controller to avoid a floating differential voltage that may affect the communication.
This is from the L7P communication quick start
In my case the digital inputs are switched to +24 and terminals 11 and 21 are tied to GND24. GND24 is common to the HMI, PLC, ABB drive and the L7P. So then I think grounding/common is covered. I haven't connected the L7P to the network yet but I will try today.
As for the 120 ohm termination the L7P is the last drive so I do need the resistor. I was just unclear if the internal resistance is two resistors because it is a RS-422 network. I will post results in a day or two.
Thanks for your help.
So I have been able to communicate with the servo and the drive over the Modbus without issues. So this will be solved then...