Drives Inverters Guides PLC Guides

Siemens S7 1200 “Modbus RTU” Danfoss FC51 Tutorial

Written by

Hello, Siemens PLC S7-1200 and Danfoss-FC302 inverter are two devices commonly used in many machines around the world, especially standalone machines.

Today will guide you to use PLC S7-1200 to connect and control Danfoss FC302 via Modbus RTU (RS485).

Siemens S7-1200 & Danfoss FC51 “Wiring Diagram”

With S7-1200 we need to use more RS485 Module: S7-1200 CB1241 (or S7-1200 CM1241), and with Danfoss FC51 inverter, it has a built-in RS485 Port.

Danfoss FC51 Modbus RTU Configuration

To be able to control Danfoss FC51 with Modbus RTU, we need to configure the following parameters

Danfoss FC51 Registers for Control

Note: S7-1200 Modbus Address
= “VFD Address (dec) + 400001”

>>> VFD Control Address = 49999 + 400001 = 450000

  • Set Register 450000 = 1148 (dec) >>> Run Forward
    = 33916 (dec) >>> Run Reverse
  • Set Register 450000 = 1084 (dec) >>> Stop
  • Set Register 450000 = 1212 (dec) >>> VFD Reset

>>> VFD Frequency Setting Address = 50009 + 400001 = 450010

  • Speed Reference = 0 to 16384(dec) ~ (0 to 100%)
Danfoss FC51 Registers for Monitoring
  • Output Voltage Address = 416120 (dec)
  • Output Frequency Address = 416130 (dec)
  • Output Current Address = 416140 (dec)

Siemens S7-1200 Modbus RTU Setting

We need to set the communication parameters of S7-1200 the same as Danfoss FC51

+ S7-1200 RS485 Parameters Setting

+ Data Block Create

S7-1200 Modbus RTU Example

+ Read and Write Distribution

+ VFD Frequency Setting

+ VFD Control Command

+ Read Ouput Voltage

+ Read Output Frequency

+ Read Output Current

Project Video Tutorial


Related Software and Documents

+ Download Siemens S7-1200 Programming Software

+ Danfoss FC51 Manual PDF Download

Password Extract:

If in the process of connecting S7-1200 with Danfoss FC51 you have any questions, please comment below the article, will answer you as soon as I read the comments.

Best Regards!

About the author


Leave a Comment Protection Status