May 31, 2011

Delta PLC Modbus Communication With Delta Drive

PLC to Drive Communication through RS 485 is a very good way to establish a communication network when we have more drives in the Network.In this article we will see the Communication Parameter Set up in Drive and PLC and also the PLC Program for Delta PLC to communicate through RS 485 port.

Delta PLC RS 485 Communication with Delta VFD-E :-

First of all we need to have the proper Communication cable , its very simple for this all we need is a RJ 45 jack and connect the the PLC with VFD. Just use the Pin 3 SG- and Pin 4 SG+. After the communication cable is ready we need to configure the VFD i.e delta VFD-E , we have to set up the following parameters.

VFD-E parameters for RS485 Communication:-
Parameter Number -------------------Name---------------------------------Value
2.00-------------------------Source of First Master Frequency Command-----3
2.01-------------------------Source of First Operation Command------------3(RS-485 )
9.00-------------------------Communication Address------------------------2
9.01-------------------------Transmission Speed---------------------------3(Baud rate 38400bps)
9.04-------------------------Communication Protocol-----------------------0(7,N,2 (ModbusASCII)

Now after setting these parameters in the Drive ,we have to make a appropriate PLC Program. As we all know that in Modbus Slave device needs to be issue command and it respond accordingly. All the Communication in Modbus is in the form of Queries , a Master device always Send Query to Slave Device and Slave Device respond accordingly.

PLC Program for Delta Modbus / RS 485 Communication :-

First of all we have to decide the communication Protocol settings , in this case we are using
7, N, 2, 38400, ASCII. To send a frame in delta plc we use MODWR Instruction and we have to trigger the bit M1122 to send the frame.
Also we need to read some data from Drive , for example then we have to use the MODRD instruction. We have made a sample program for this. All the comments are written in the program and you can understand it easily. The slave address we have used in the plc logic is 2.

Delta PLC Program for Modbus Communication.

Also to understand the Basics of MODBUS and modbus communication of Omron PLC with Drive and HMI, you can check our MODBUS Section.

UPDATE:- Delta VFD Modbus Parameters Read/Write

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