Mitsubishi PLC and computer communication connection - Database & Sql Blog Articles

Due to its high performance and reliability, PLCs have become widely used in industrial control systems. Over time, they have evolved from simple logic controllers into multi-functional devices that integrate logic control, process control, servo control, data processing, and network communication. However, since a PLC itself does not have a display function, it is crucial to implement internal data display, which has become one of the key challenges in designing a PLC-based control system.

In a PLC control system, the main data to be displayed include timer values, counter values, and data register values. There are generally two basic methods for data display: one is through the PLC’s communication interface, such as RS-232 or RS-485/422. The display device must also support these interfaces, allowing data transmission and display via communication protocols.

Communication-Based Data Display Technology

Using a data communication interface is an effective way to display PLC data. Most modern PLCs come with standard RS-232 or RS-485/422 interfaces, or can be expanded with modules to add such capabilities. For example, Mitsubishi FX2N series supports communication modules like 232ADP, 232BD, 485BD, and 485ADP, which serve as data interfaces.

The display devices can be either dedicated intelligent screens or general-purpose computers (PCs). Choosing a screen or touch panel compatible with the PLC allows centralized display of multiple internal data points. With editing software, users can customize the display interface, improving clarity and usability. For instance, the FX series can use F93000T-BWD, F940GOT-LWD, or F940GOT-SWD models. These intelligent displays read PLC registers via the communication interface, achieving efficient data display and simplifying system design.

However, due to the higher cost of large displays, this method is more suitable for compact PLC systems. As computer performance and reliability continue to improve, the "PC + PLC" control mode has become popular in industrial applications. PCs offer rich software and hardware resources, enabling real-time monitoring of PLCs and displaying a large amount of internal data. They can graphically present dynamic process flows and data trends, making the human-machine interface more intuitive and user-friendly.

PLC and Group Taiwang Communication Connection

- 1:1 single station, distance less than 15 meters, driven by programming port

- Communication via programming port (no need for PLC programming)

- 1:N multiple stations (up to 16 stations), distance between 15m and 50m, driven by FX485

- 1:N multiple stations (up to 16 stations), distance between 50m and 500m, driven by FX485

- 1:N multiple stations (up to 16 stations), distance between 500m and 1200m, driven by FX485 with 485 relay

RS485 connections can use one or two pairs of wires. Based on the application requirements, this design uses two pairs of wires for better signal integrity.

To establish communication between the PLC and Group Taiwang, the communication address and parameters can be set in the "PLC/Serial Port Settings" menu of the PLC programming software, or directly programmed using MOV instructions. For RS485 configuration:

- Baud rate: 9600 bit/s

- Data bits: 7 bits

- Start bit: 1 bit

- Stop bit: 2 bits

- Parity: Even

- Protocol: 1

Set the communication address in D8121 using the programming software.