Specific Applications of PLC Controllers

With the advancement of technology, PLC (Programmable Logic Controller) systems have evolved into standardized, modular, and modular products available in various sizes, including large, medium, and small models. They are equipped with a comprehensive selection of hardware components, allowing users to flexibly configure systems to achieve different performance and scales. PLC installation and wiring is straightforward, usually involving external wire terminal connections. These controllers have strong load-carrying capabilities, allowing them to directly drive devices such as solenoid valves and AC switches. They are suitable for different industrial control environments.

Technological advances have greatly reduced the cost of PLCs, while the microprocessors used in PLCs have seen significant improvements in performance. To further improve processing speed, manufacturers have developed special point processing chips, resulting in major changes in PLC software and hardware capabilities.

Applications of PLCs

At present, PLCs are widely used in industries around the world, such as steel, petroleum, chemicals, energy, construction materials, machinery manufacturing, automobiles, textiles, transportation, environmental protection and entertainment. Their applications can be broadly classified as follows:

1. Logical Control of Switching Signals

Logical control of switching signals is a basic and widely accepted application of PLCs. They replace traditional relay circuits, realizing logical and sequential control.

• Use Cases: It is suitable for controlling individual equipment or multiple machines in automated production lines, such as injection molding machines, printing machines, gluing machines, assembly machine tools, mills, packaging lines, and electroplating lines.

2. Analog Signal Control

Many industrial processes involve variable analog signals, such as temperature, flow, fluid level, pressure, and speed. PLCs handle analog signals through Analog-to-Digital (A/D) and Digital-to-Analog (D/A) conversion.

• Implementation: Manufacturers provide A/D and D/A modules so that PLCs can process analog signals effectively.

3. Motion Control

PLCs can perform both circular and linear motion controls.

• Applications: It is widely used in machines, machine tools, robots, elevators, and similar systems.

4. Process Control

Process control involves closed-loop control of analog parameters.

• To do: PLCs use A/D and D/A modules to convert the signal and apply PID control to variables such as temperature, pressure, and flow. PID algorithms calculate the appropriate output to adjust the controlled variable back to its setpoints when a deviation occurs.

5. Data Processing

Modern PLCs support advanced functions such as arithmetic operations, data transfer, conversion, sorting, table lookup, and bit manipulation.

• Skills: These features enable data collection, analysis, and processing. Data can be compared with reference values ​​stored in memory to perform control actions, transferred to smart devices, or printed in a report.
• Use Cases: It is usually found in large systems such as unmanned flexible manufacturing systems or in industrial process control systems such as paper, metallurgy, and food processing.

6. Communication and Communication

PLC communication includes communication with computers, communication between PLCs, and communication with other intelligent devices.

• Applications: PLCs form distributed control systems that consist of centralized management and decentralized control.
• Central Processing Unit (CPU): The core of the system, responsible for control and communication.
• Memory Unit: Stores programs and performance data.
• Input/Output: Field device communication interface.
• Power supply: It ensures stable performance.
• Editing device: It is used for programming and debugging.

The CPU, as a control center, performs the following important functions:

1. Receiving and storing user programs and data from the programming device.
2. Diagnose power supply, internal circuit errors, and syntax errors in programs.
3. Collecting real-time data or status from the input is detected and stored in the input image registers or data registers.
4. Step-by-step user programming, interpreting and processing instructions.
5. Updates flags, output graphics registers, and driver interfaces to control devices.