PLC programmable control technology is widely used in electrical automation.
Whether it is traffic, power or industrial development, it is inseparable from PLC technology. In the process of development, PLC technology should also change with the change of technology. This technology has far exceeded the traditional control method in system adaptability, and the maturity of technology has promoted the development of electrical automation in China. However, the relevant personnel still need to understand the content of programming control technology and correctly view the current situation of PLC application, so as to help enterprises formulate correct production and management routes and promote their development. With the development of automation and computer technology, the field of electrical control plays an increasingly important role in machinery manufacturing and other industries. For the field of electrical control, the effective way to improve work efficiency is to use PLC technology to improve the functions of the system using computer software and hardware. This is a new technology with the characteristics of modern science and technology, which can open up a new side for enterprises to automate control first. In the input sampling stage, the basic information is obtained by data scanning and stored in I/O mode. After the input sampling is completed, the user program execution and output refresh are started. Because the change of input state and data can not change the data form of corresponding units in I/O image area, the width of pulse signal must be larger than one scanning period in order to be read.
2) User program execution stage. In this stage, the PLC always scans in the order of top-down, left-to-right, obtains the result of logical operation, refreshes the status of data in the image area or in the system storage, and executes the output command. 3) Output refresh stage. This stage is the completion of a complete scanning process. That is to say, the CPU completes output and refreshes all data records through the data state of the I/O image area, and can output only after the circuit drives the corresponding peripherals.
PLC programmable technology, with computer programming as its core, is widely used in electric automation control such as electric power industry production, highway transportation, intelligent central air conditioning and so on. The application of PLC in traffic system is mainly signal light control, which has strong adaptability and provides rich timer information to meet the demand of multi-intersection signal light control. This application technology is simple. Through the communication function of PLC itself, the change control of signal lamp can be realized, and the local area network can be established to realize the unified unattended management of signal lamp.
In addition, the new PLC technology adjusts the general controllers in the past, and gives corresponding controllers for different locomotives to improve the efficiency of operation and maintenance. PLC realizes intelligent and unmanned management. Supported by various decoding instructions, the data is converted into seven-segment display codes, which are eventually displayed on the large LED screen. At present, our country has begun to research and implement the track vehicle with PLC as the main engine. Its maintenance is convenient, service life and stability have been improved. It is one of the important manifestations of programmable control technology in the electrical automation control. PLC replaces the traditional relay, realizes long-term data storage, and can warn and alarm the faults. Real-time monitoring of central air-conditioning outlets, valves, solution pumps and other equipment running status, to achieve the intelligent central air-conditioning. The application of PLC technology in intelligent central air conditioning makes the performance and effect of air conditioning better.
Its core technology is online storage. Thermal power system is a typical electrical automation equipment, its main component is electromagnetic relay. The traditional thermal power system has too many relays and contact points, which lead to the decrease of safety and reliability, and increase the difficulty of wiring. Once problems arise, maintenance is difficult. PLC has changed the status of a large number of components in the past by adopting an integrated structure. For the operator, the work becomes simple and reliable.
PLC relies on the system signal to complete the work, such as failure and normal operation of the system, will light different colors of reality. PLC separates the different terminals to prevent the wrong connection of the staff. Compared with the traditional design, the number of switches is less, which can realize the centralized control of circuit breaker signal, ensure safe operation and provide convenience for system maintenance. After programmed by PLC, the signal can be output, collected and run normally, and the system status can be judged. The design of thermal power system with PLC technology as the core has powerful data processing function. Considering the operation status and anti-interference ability of the system comprehensively, it ensures simple wiring mode and convenient debugging, which is of great help to improve the reliability of the system. The peripheral circuit of PLC consists of field input signal (such as button switch, selector switch, proximity switch and some sensor output switch, analog value of relay output contact or analog-to-digital converter conversion) and field output signal (solenoid valve, relay, contactor, motor, etc.) as well as conductor and wiring terminal.
Loose wiring, component damage, mechanical failure, interference and so on can cause circuit failure. Therefore, the inspection of PLC maintenance should be careful, replaced components should choose high-quality components with reliable performance and high safety factor. Some powerful control systems use fault code tables to express faults, which brings great convenience to the analysis and elimination of faults. In addition to the multimeter, the maintenance tools sometimes use oscilloscopes or even computers. This requires the PLC maintenance personnel to have high professional skills, and have a certain foreign language and computer skills, only to complete.
Only after understanding and familiarizing with the system, can we judge and eliminate the common faults quickly, and reduce the maintenance cost as much as possible to ensure the normal and stable of the system. PLC field operation, commonly used PLC technology includes fieldbus control system and distributed control system. The former uses the combination of FCS system and PLC technology to realize intelligent operation of electrical control. This scientific and technological means, with good adaptability and bidirectional characteristics, can carry out digital communication for many communication networks and create a good network working environment. The latter is a system which combines DCS system with PLC technology. Through centralized management of electrical devices, dangerous separation and effective supervision of electrical devices can be effectively carried out. The system needs to operate in a safe and stable environment, so it is very important to do a good job in site management and production safety management. In order to prevent the instability of the line interface, the following steps must be completed during the operation of the automatic control system. Firstly, in the design stage, the type of PLC technology is clarified. To ensure the application effect of the electrical control device based on PLC technology, first of all, we need to understand the situation of the electrical control device that the system should serve. Then, through the design of the system functions, we can achieve the goal of simple operation and flexible control. Set up the application of PLC technology, analyze the complexity of the system, according to the specific analysis of the situation on the spot, to ensure that the application effect of PLC technology can meet the requirements of the system operation. In the process of realizing the PLC technology, the schematic diagram of the electrical control device is analyzed, and the design idea is embodied in the schematic diagram, and marked on the drawing. Designers can adjust the parts of the schematic diagram that do not meet the technical requirements at any time after careful analysis, including control circuit, protection device, key links of the main circuit, etc. In the design of PLC system, it must be clear that the integrity and rationality of the system have been fully considered.
The application of technology in system operation fully embodies the control of process control, production monitoring, sequence and position, realizes the communication and equipment control of the core of PLC processor, and ensures that the design of PLC system can be adapted to the function of the system. Do a good job in network design, ensure network quality, and realize the automation function of electrical control devices. Analyse the environment where the electrical devices are located, and do a good job of subnet configuration at all levels. The first step is to operate relays, wait for the delay time to reach, run the hydraulic pump motor, thermostatic element then connect the solenoid valve in the spindle operation, and operate the solenoid valve spindle reversal. At this time, the tool holder motor runs fast and all control loops stop. Stop action. According to the analysis of the control object, the software and hardware of PLC are configured and the programming software is selected. In the process of programming, the signal of PLC system is allocated, the corresponding signal name is obtained, the program graph is compiled by computer, the logic instructions and graphics are integrated into the language, and the design of the complete circuit is completed according to the logic instructions and statement tables compiled. Programmable controller (PLC) is a programmable memory, which can perform logic calculation, sequence control and other functions. Its design structure is more reasonable [1]. This kind of programmable controller was initially used in industrial industry. With the technological innovation of electric power enterprises, the application of PLC in electric automation increased. Programmable controllers and related technologies are the main trends of the development of electrical automation and intelligence.