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Mitsubishi QJ71C24N “Modbus RTU” FR-E720 VFD Tutorial

Written by plc247.com

Hello friends!
In previous posts, plc247.com has written instructions for you to use the Mitsubishi QJ71C24N Module to connect and control different temperature controllers, today I will guide you to control the FR-E700 Series inverters as well over Modbus-RTU Communication Protocol.

Mitsubishi inverter FR-E700 Series (or D700 Series) has built-in RS485 Comm. Port. so we can easily connect to Module QJ71C24N.

Mitsubishi QJ71C24N & FR-E720 “Wiring Diagram”

Below is the Modbus-RTU RS485 communication diagram between the QJ71C24N Module and the Mitsubishi FR-E720 Inverter.

Mitsubishi FR-E720 Modbus Parameters Setting

We need to set the following communication parameters so that the FR-E700 Series inverter can be controlled and monitored using Modbus-RTU protocol:

  • Pr117 = 1 (Slave Address)
  • Pr118 = 3 (Baudrate 9600)
  • Pr119 = 0 (8bit, stop bit = 1)
  • Pr120 = 2 (Even)
  • Pr121 = 9999
  • Pr122 = 9999
  • Pr123 = 9999
  • Pr124 = 1
  • Pr340 = 1
  • Pr549 = 1
  • Pr79 = 2 (Last Setting)
Mitsubishi FR-E720 Modbus Registers Address
Note: Control Address = Starting register address (decimal) – 40001

>>> vfd Control Address = 40009 – 40001 = 8 (dec) = 8 (hexa)

  • Set Word 8(hexa) = 0000 0000 0000 0010 = 2 >>> Forward Run
  • Set Word 8(hexa) = 0000 0000 0000 0100 = 4 >>> Reverse Run
  • Set Word 8(hexa) = 0000 0000 0000 0000 = 0 >>> Stop

>>> Frequency Setting Address = 40014 – 40001 = 13 (dec) = D (hex)

>>> Output Frequency Address = 40201 – 40001 = 200 (dec) = C8 (hex)

Module QJ71C24N “Modbus RTU” Configuration

Please configure the QJ71C24N Module according to the following steps:

+ Step 1: Create Project folow your PLC

+ Step 2: I/O Assignment

+ Step 3: Channel.2 (RS422/485 Port.) Parameters Setting

+ Step 4: Sent Parameters to PLC

+ Step 5: Disable “Echoback”

  • Echoback references to the function in which data transmitted by RS-485 (2-wire) is returned about the local station’s “RDA and RDB”.
  • Echoback references to the function in which data transmitted by RS-485 (2 wires) is returned about the local station’s “RDA and RDB”.

>>> Set G450 = 1 (Disable Echoback) / = 0 (Enable Echoback)

QJ71C24N & FR-E720 VFD “Modbus Registers Configuration”

+ Go to Tool “Serial Communication Module…”

+ Protocol Configuration

Registers Address Config.

>>> Protocol No.1: Func = 06 / Write Single Registers

  • Slave Address = D100
  • Register Adress = D101
  • Register Value = D110
  • “Error Code” = D300

>>> Protocol No.2: Func = 03 / Read Holding Registers

  • Slave Address = D200
  • Starting Address = D201
  • Quantity of Registers = D202
  • Registers Value Response = D210 “From D210…D335 depending on the number of Registers (D202) to read”
  • “Error Code” = D300

Important: Need to set “Receive Wait Time”, if Set = 0, then when Modbus Command gives error, Module will wait for infinity time and need to Reset PLC

PLC Programming

+ Disable “Echoback” & Error Reset

+ Communication Distribution

+ Frequency Setting Command

+ VFD Control Command

+ Data Response Monitoring

+ HMI Address Mapping

Detailed Instruction Video

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Related Software and Documents
+ Download Mitsubishi GX-Works.2 Software Free
+ PLC Q-Series & HMI Weintek Connection Tutorial
+ Download Mitsubishi FR-E720 Manual PDF

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