[RS485 RTU MODBUS communication Setup]

On 1/7/2020 at 9:35 AM, wynn.c.ni@gmail.com said:

Thank you both

I ended up getting the drive to function with the I/O pins of the PLC, and using a different configuration setting for the VFD

I avoided using RS485 but might need to use it in the future. I'll keep in mind to use equipment from the same suppliers in the future.

I see, so address 43 is frequency, which controls the speed of the motor

and 34 is the address for Stop/Run

I was a bit confused by the syntax, but I see that uni stream subtracts 400001 from the MODBUS address to read from

Best Regards

Wynn Ni

 

 

[RS485 RTU MODBUS communication Setup]

Thank you Joe!

I am new to the protocol and implantation so my terminology  is off when I made the post above.

I got off the phone with a Siemens Technician and sort of tried to convey the issue to the best of my understanding.

I think "echo" means to write from the PLC to the VFD

 

I would like to read speed of the VFD and read the status of the motor (whether it is on/off).

I would like to write to the VFD to ramp the speed of the motor to a certain value when the program begins and hold the speed constant

Just something simple to demonstrate motion and that communication is successful.

 

Much gratitude, 

Wynn Ni

 

[RS485 RTU MODBUS communication Setup]

Hi,

I'm new to the RS485 communication protocol.

I am trying to communicate with a Siemens SINAMICS V20 VFD with the Unitronics Unistream PLC ( USP-070-B10)

The VFD leads to a 3 phase motor

I set up the baud rate to 9600, data bit to 8, parity list to none, and stop bit to 1

In addition I set up a remote slave in COM1 of Masters drop down, in MODBUS

In the slave configuration I made a coil named "motor" that writes to address 40 every 100 ms

I spoke with a Siemens Technician about the driver settings, and could not find a setting to "ECHO" bits to the driver

I was told I need to set a transmit telegram

The is there an FC03 for "read holding register" or a way to "Echo" data to 40,100 (MODBUS)?

Any sort of references or suggestions for setting up communication?

Thank you,

Wynn Ni