What are the principles of PLC application design?

After understanding the basic working principle and instruction system of PLC, you can combine the design of PLC with the actual situation, the design of PLC includes two parts: hardware design and software design, and the basic principles of PLC design are: 1Give full play to the control function of PLC to meet the control requirements of the controlled production machinery or production process to the greatest extent.

2.On the premise of meeting the control requirements, we strive to make the control system economical, simple and easy to maintain. 3.

Ensure that the control system is safe and reliable. 4.Taking into account the development of production and the improvement of the process, when selecting PLC, there is appropriate leeway in the number of IO points and memory capacity.

5.Software design mainly refers to writing programs, which require clear program structure, strong readability, short programs, less memory occupation, and short scanning cycles.

Analyze the process and working characteristics of the controlled object, and determine the control plan.

Determine input and output devices (e.g., push buttons, travel switches, sensors, solenoid valves, contactors, etc.).

Select PLC, including model, capacity, IO module, power supply, etc.

Assign IO points and design PLC peripheral hardware circuits.

Programming. Online debugging.

I also studied PLC, what the hell is the principle, or I haven't learned such a profound thing.

In the design of PLC control system, the engineering design selection of PLC includes reliability, compatibility and flexibility.

1. Reliability.

PLC is the core equipment of industrial control, and its reliability is an important indicator for selection. When selecting the model, it is necessary to choose the PLC brand and model with high reliability, and consider the protection level and environmental adaptability of the equipment.

2. Compatibility.

The compatibility of the PLC with other equipment, including controllers, sensors, actuators, etc., needs to be considered when selecting the model. You need to choose an open PLC that supports a variety of communication protocols and data formats to facilitate data interaction with other devices.

3. Flexibility.

PLCs need to be able to adapt to changes in production processes and equipment, with flexible configurability and scalability. When selecting the model, it is necessary to choose a PLC with a modular structure and easy to expand, and select the appropriate module disassembly and expansion unit according to the actual needs.

Key points in the basics of getting started with PLC:

1. The basic structure of PLC.

A PLC is usually composed of a power supply, a processing unit (CPU), memory, input and output interfaces, and communication interfaces. The CPU is the control center of the PLC, the memory is used to store programs and data, the input and output interfaces are used to connect external sensors and actuators, and the communication interface is used to exchange data with other devices.

2. PLC programming language.

There are several programming languages for PLCs, the most commonly used of which is the Ladder Diagram. A ladder diagram is a graphical language similar to a circuit diagram that describes control logic by connecting individual input and output components. There are also programming languages such as statement tables and function block diagrams.

3. The program structure of PLC.

The program of a PLC consists of a main program, a subprogram, and an interrupt program. The main program is the backbone of the control process and is used to implement the basic control logic. Subroutines are reusable blocks of programs that are used to implement certain functions.

Interrupt programs are used to handle sudden control events, and can interrupt the execution of programs during the execution of the main program.

When designing the PLC control system, what are the engineering design selection principles of the PLC as follows:

The principle of PLC engineering design selection is to determine the type of control system and the selection scale of the model should be appropriate.

Knowledge expansion: PLC control system is a generation of new industrial control devices formed by introducing microelectronic technology, computer technology, automatic control technology and communication technology on the basis of the traditional sequence controller, which is used to replace relays, execution logic, timing, counting and other sequence control functions, and establish a flexible remote control system.

It has the characteristics of strong reusability, easy to use, wide adaptability, high reliability, strong anti-interference ability, and simple programming. The internal working mode of PLC is generally to adopt the cyclic scanning working mode, and the interrupt working mode is added in some large and medium-sized PLCs.

When the user debugs the user program, the program is written into the PLC memory through the programmer, and the input signal of the field and the controlled execution element are connected to the input end of the input module and the output end of the output module accordingly.

Then the PLC working mode is selected as the running working mode, and the subsequent work is completed by the PLC according to the user program, and the overview diagram is the block diagram of the PLC execution process. In the process of work, PLC mainly completes the processing of six modules.

The power supply assembly is used to provide the power required for the operation of the PLC, and the external power supply can be converted into a power supply for the PLC internal and case. The microprocessor CPU is the core device of the PLC, and the CPU is different due to the manufacturer, some use the standard chip sold in the market, and some use the special chip of the programmable controller.

The input and output components are the interface between the PLC and the industrial production site to exchange data, and the PLC is different from the ordinary computer, the working environment of the PLC is relatively poor, and the input and output components are designed for this.

Programmable logic controllers are digital computing operating electronic systems designed specifically for applications in industrial environments. It uses a programmable memory to store instructions for performing operations such as logic operations, sequence control, timing, counting, and arithmetic operations, and controls various types of mechanical equipment or production processes through digital or analog inputs and outputs.

The small one mainly depends on the number of input and output points The small one within 50 points The large one depends on your use for process control ? Data parsing and transfer? Whether it is a key station, hot standby redundancy, etc.

2. Programming. It is mainly based on the requirements of process design, and is programmed in the form of ladder diagrams, statement tables, flow charts, etc., to realize the requirements of process design.

Programming generally has two ways: offline programming and programming, the former is only carried out on the programming equipment, and then the programming is completed and then to the PLC; The latter requires the programming device to communicate with the PLC in real time, and the programmed program is immediately stored in the PLC.

3. Program debugging.

It can be divided into factory commissioning and on-site commissioning, the purpose of which is to test and verify whether the program meets the requirements of the process design.

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The following points should be considered in the selection and determination process of the PLC system scheme of this design: 1. System demand analysis: firstly, it is necessary to conduct a demand analysis on the equipment to be controlled, and determine the parameters, control logic, input and output interfaces, etc. that need to be controlled.

This step requires a good understanding of the operational characteristics and process parameters of the field equipment. <>

2. Cabinet and peripheral equipment selection: Finally, you need to select cabinets and peripheral equipment, such as power modules, communication modules, etc. This step requires determining the cabinet size and the type and number of peripherals according to the PLC model and I/O modules.

The process of selecting and determining the PLC system scheme of this design.

Dear dear, it's a pleasure to answer your <>

The selection and determination process of the PLC system scheme of this design should consider the following points: 1. System demand analysis: first, it is necessary to analyze the requirements of the equipment to be controlled, and determine the parameters, control logic, input and output interfaces, etc. that need to be controlled.

This step requires a good understanding of the operational characteristics and process parameters of the field equipment. <>

2. Cabinet and peripheral equipment selection: Finally, you need to select cabinets and peripheral equipment, such as power modules, communication modules, etc. In this step, the type and quantity of cabinet specifications and peripheral equipment need to be determined according to the PLC model and the input Chunsheng Transmission Forest.

In this step, factors such as the number of input and output points, signal type, and anti-interference capability need to be considered. 4. PLC model selection: according to the demand analysis results, combined with the actual situation of the production process, select the appropriate PLC model and specifications.

In this step, you need to consider factors such as the calculation speed, number of control points, and scalability of the PLC. <>

<>5. PLC programming design: After selecting the PLC model, PLC programming design needs to be carried out, that is, which PLC program is written according to the demand analysis. PLC programming needs to be designed according to the control logic, the program should be clear and easy to understand, the functions should be complete, and the stability and reliability of the system should be <>

<> The selection and determination of the PLC system scheme of this design needs to fully consider the equipment operation characteristics, process parameters, PLC model, PLC programming design, input and output modules, cabinets and peripheral equipment and other factors, so as to ensure the stability, sideburn reliability and efficiency of the PLC control system.

PLC programming steps.

1) Distribute according to the control requirements, 2) Design the control process according to the control requirements.

3) Draw the peripheral wiring diagram of the PLC, (electrical schematic diagram and gas circuit schematic) (4) Arrange the components; Install the trunking and fix the electrical components; Such as leakage switches, air openings, fuses, thermal relays, relays, solid state relays, stepper drivers, servo drives, inverters, temperature controllers, switching power supplies, capacitors, filters, PLCs, expansion modules, 5) press and install sensors, such as proximity switches, induction switches, photoelectric switches, micro travel switches.

6) Fix the motor; Such as speed regulating motors, brake motors, stepper motors, servo motors, single-phase motors, three-phase motors, 7) install air pressure switches, pressure sensors, pressure gauges, vacuum gauges, two-parts, pressure regulators, throttle valves, fix the solenoid valves, 8) plug the gas pipe according to the gas circuit schematic diagram.

9) Draw a good position and make a hole with an opener, and install the control panel; Such as starting, starting, emergency stop, returning to the origin, touch screen or text display, 10) connecting the IO of the PLC, 11) debugging the equipment; First manual, semi-automatic, fully automatic, step by step, debugging (12) Package the equipment; Wrap the air hose and wiring harness (sensor wire) with a wire winding tube

The program design should first understand the process requirements of the controlled object in detail, clarify the functions that the PLC should have to complete the task, determine the overall structure of the program, draw the working cycle diagram or state flow chart of the control system, clarify or select the program structure, list the IO table and the selection arrangement table of the components in the machine, and use the ladder diagram or instruction table method to complete the program design, and input it into the PLC machine for debugging and modification.