Answer 1: A PLC is an electronic device designed to perform digital operations in an industrial environment.
It employs a memory that can be programmed and used to store instructions within it for performing operations such as logical operations, sequential operations, timing, counting, and arithmetic operations, and is capable of controlling various types of machinery or production processes by means of digital or analog inputs and outputs.The PLC and its related peripherals should be designed according to the principles of being easy to form an integral whole with the industrial control system and easy to expand its functions. "
First, the characteristics of PLC
1, high reliability, strong anti-interference ability
High reliability is the key performance of electrical control equipment. PLC due to the use of modern large-scale integrated circuit technology, the use of strict production process manufacturing, internal circuitry to take the advanced anti-interference technology, has a high degree of reliability. PLC with hardware failure self-detection function, failure can be issued in a timely manner when the alarm message. In the application software, the applicant can also be programmed into the peripheral device failure self-diagnostic program, so that the system in addition to the PLC other than the circuit and equipment to obtain failure self-diagnostic protection. In this way, the whole system has a very high reliability is not surprising.
2, supporting complete, functional and adaptable
PLC development to date, has formed a large, medium and small series of products of various sizes. Can be used for various scales of industrial control occasions. In addition to logic processing functions, most of the modern PLC has perfect data computing capabilities, can be used in a variety of digital control areas. In recent years, a large number of PLC function units have emerged, making PLC penetrate into various industrial controls such as position control, temperature control, and CNC. Coupled with the enhancement of PLC communication capabilities and the development of human-machine interface technology, the use of PLC to form a variety of control systems has become very easy.
3, easy to learn and easy to use, welcomed by engineers and technicians
PLC as a general industrial control computer, industrial control equipment for industrial and mining enterprises. It is easy to interface, programming language is easy for engineers and technicians to accept. Ladder diagram language graphic symbols and expressions and relay circuit diagrams are quite close, only a small number of switching logic control instructions with PLC can easily realize the function of the relay circuit. Not familiar with electronic circuits, do not understand the principles of computers and assembly language for people using computers to engage in industrial control opens the door to convenience.
4, the design of the system, build a small workload, easy maintenance, easy to transform
PLC with storage logic instead of wiring logic, greatly reducing the wiring of the external control equipment, so that the control system design and construction of the cycle has been greatly reduced, while maintenance has become easier. What's more, it makes it possible to change the production process of the same equipment by changing the program. This is very suitable for multi-species, small batch production occasions.
5, small size, light weight, low energy consumption
Ultra-compact PLC, for example, the newly produced varieties of the bottom size of less than 100mm, weight less than 150g, power consumption of only a few watts. Due to the small size is easy to fit inside the machinery, is the realization of the ideal control equipment for mechatronics.
Second, the application of PLC
At present, PLC has been widely used at home and abroad in iron and steel, petroleum, chemical, electric power, building materials, machinery manufacturing, automotive, textile, transportation, environmental protection and culture and entertainment industries, the use of which can be broadly summarized in the following categories:
1, switching logic control
This is the most basic, the most extensive application of PLC, which replaces the traditional relay circuit to achieve logic control, sequence control, can be used for the control of a single piece of equipment, can also be used for multi-machine group control and automated assembly lines. Such as injection molding machines, printing machines, stapling machines, combined machine tools, grinding machines, packaging production lines, plating lines and so on.
2, analog control
In the industrial production process, there are many continuously changing quantities, such as temperature, pressure, flow, level and speed are analog. In order to make the programmable controller to deal with analog, must realize the analog (Analog) and digital (Digital) between the A/D conversion and D/A conversion. PLC manufacturers have produced supporting A/D and D/A conversion module, so that the programmable controller for analog control.
3, motion control
PLC can be used for circular motion or linear motion control. From the control mechanism configuration, early directly for switching I / O module connected to the position sensor and actuator, and now generally use a dedicated motion control module. Such as single-axis or multi-axis position control modules that can drive stepper motors or servo motors. The products of the world's major PLC manufacturers almost all have motion control functions, widely used in a variety of machinery, machine tools, robots, elevators and other occasions.
4, process control
Process control refers to the closed-loop control of temperature, pressure, flow and other analog quantities. As an industrial control computer, PLC can program a variety of control algorithms to complete the closed-loop control, PID regulation is generally used in the closed-loop control system more regulation. Large and medium-sized PLC have PID function.
Answer 2: PLC = Programmable Logic Controller, an electronic system of digital arithmetic operations designed for applications in industrial environments.
It employs a class of programmable memories for storing programs internally, executing user-oriented instructions such as logical operations, sequential control, timing, counting and arithmetic operations, and controlling various types of machinery or production processes through digital or analog inputs/outputs. It is the core part of industrial control. At present, PLC has been widely used at home and abroad in various industries such as steel, petroleum, chemical, electric power, building materials, machinery manufacturing, automotive, textile, transportation, environmental protection, water treatment and culture and entertainment, the use of which can be broadly summarized as follows.
1, switching logic control which is the most basic, the most extensive application of PLC, which replaces the traditional relay circuit to achieve logic control, sequence control, can be used for the control of a single piece of equipment, can also be used for multi-machine group control and automated assembly lines. Such as injection molding
2, analog control in the industrial production process, there are many continuously changing quantities, such as temperature, pressure, flow, level and speed are analog. In order to enable programmable controllers to deal with analog, analog (Analog) and digital (Digital) between the A/D conversion and D/A conversion. PLC manufacturers are producing supporting A/D and D/A conversion modules, so that programmable controllers for analog control.
3, motion control PLC can be used for circular or linear motion control. From the control mechanism configuration, early directly for switching I / O module connected to the position sensor and actuator, and now generally use a dedicated motion control module. Such as single-axis or multi-axis position control modules that can drive stepper motors or servo motors. The products of the world's major PLC manufacturers almost all have motion control functions, widely used in a variety of machinery, machine tools, robots, elevators and other occasions.
4, process control process control refers to the temperature, pressure, flow and other analog closed-loop control. As an industrial control computer, PLC can program a variety of control algorithms to complete the closed-loop control, PID regulation is a general closed-loop control system used more regulation. Large and medium-sized PLC have PID module, many small PLC also has this function module.PID processing is generally run a special PID subroutine. Process control in metallurgy, chemical industry, heat treatment, boiler control and other occasions have a very wide range of applications.
5, data processing modern PLC with mathematical operations (including matrix operations, function operations, logical operations), data transfer, data conversion, sorting, table lookup, bit operation and other functions, can complete the data acquisition, analysis and processing. These data can be compared with the reference value stored in the memory to accomplish certain control operations, and can also be transmitted to other intelligent devices using the communication function, or they can be printed and tabulated. Data processing is generally used for large-scale control systems, such as unmanned flexible manufacturing systems; can also be used for process control systems, such as paper, metallurgy, food industry in some large-scale control systems.
6, communication and networking PLC communication including PLC communication and PLC communication with other intelligent devices. With the development of computer control, factory automation network development is very fast, the PLC manufacturers attach great importance to the communication function of the PLC, have introduced their own network system. Newly produced PLCs have communication interfaces, communication is very convenient.
Answer 3: plc is a controller, the main role is to realize the control of the control object according to the control steps you want or control requirements!
In fact, this question for the PLC has not been used or do not know much about the people, it is difficult to explain clearly! However, such as elevator control, some families of smart home systems, or traffic lights at intersections, or washing machines, or music fountain control, these slightly common things, will also use PLC, of course, do not use PLC with other controllers can be achieved. ---The problem with these instructions is that PLCs are used in a wide range of applications because the interface types are rich, and the internal timing counters, mathematical operations, communications and other commands are also powerful, so they are widely used in all walks of life!
PLC is evolved from the original relay control circuit, of course, now its performance has far beyond the initial function, but its programming method and circuit diagram design of the same idea, so for those who have the foundation of electrical circuitry for the introduction and programming is relatively simple, which is also it can be widely used in a major feature!
To put it in another way, you buy a calculator can realize the function, PLC can realize, PLC is also like a very powerful computer with CPU, and then with the upper computer monitoring software, you can through the screen way to monitor and control, you want to control the object, these controlled objects are usually electric motors, fans, pumps, lights, switches, valves, etc., PLC can also be accessed to the button switch, temperature, pressure, and other signals. PLC can also access the button switch, temperature, pressure and other signals.
Simply say so much, the main role of the PLC is to realize the automation you want to control these signals or devices, the organic combination, and in accordance with your ideas so that these signals and devices to achieve some automatic correlation, such as automatic open or close automatically and so on! If there is a touch screen and other display devices, you can more intuitively monitor the switching state of the equipment and parameters, such as indoor temperature and humidity!
Answer 4: PLC is only the implementation of a single program of industrial computers.
The main role is to change the peripheral modules to form a new device. Through the combination of modules to achieve functional changes, to achieve rapid development and formation of productivity, reduce the time of development and various types of testing risks.
In the last century, it was proposed in 1968, and the first one appeared in 69. In the era of great industrial development, on the one hand, the language engineers are not enough, and at the same time there is a need for someone to be able to quickly change the function of the equipment in the field with the operation of the maintenance. It is not possible to rely on engineers to take the burner to the scene to deal with directly, there will be no laptop, only to return the equipment to the manufacturer to deal with, so the need for a kind of industrial computer that can be operated by workers is proposed. At that time, burning the program requires UV light Eprom a few hours.
Modern PLC has long been upgraded to a very powerful degree, the operator requirements have also increased, but the site modification, easy to operate the mechanic is still the dominant mode. So the main role of the PLC is to quickly combine, easy to operate, easy to maintain.
Answer 5: PLC is a controller, the main role is based on the control steps you want or control requirements, to achieve the control of the control object!
In fact, this question for the PLC has not been used or not much understanding of the people, it is difficult to explain clearly! However, such as elevator control, some families of smart home systems, or traffic lights at intersections, or washing machines, or music fountain control, these slightly common things, will also use PLC, of course, do not use PLC with other controllers can be achieved. ---The problem with these instructions is that PLCs are used in a wide range of applications because the interface types are rich, and the internal timing counters, mathematical operations, communications and other commands are also powerful, so they are widely used in all walks of life!
PLC is evolved from the original relay control circuit, of course, now its performance has far beyond the initial function, but its programming method and circuit diagram design of the same idea, so for those who have the foundation of electrical circuitry for the introduction and programming is relatively simple, which is also it can be widely used in a major feature!
To put it in another way, you buy a calculator can realize the function, PLC can realize, PLC is also like a very powerful computer with CPU, and then with the upper computer monitoring software, you can through the screen way to monitor and control, you want to control the object, these controlled objects are usually electric motors, fans, pumps, lights, switches, valves, etc., PLC can also be accessed to the button switch, temperature, pressure, and other signals. PLC can also access the button switch, temperature, pressure and other signals.
Simply say so much, the main role of the PLC is to realize the automation you want to control these signals or devices, the organic combination, and in accordance with your ideas so that these signals and devices to achieve some automatic correlation, such as automatic open or close automatically and so on! If there is a touch screen and other display devices, you can more intuitively monitor the switching state of the equipment and parameters, such as indoor temperature and humidity!
Answer 6: PLC basic knowledge
Programmable Logic Controller (Programmable Logic Controuer, PLC) is in the continuous development of microelectronics technology and computer technology, based on the rapid growth of a new type of industrial control equipment.
PLC because of its own advantages and characteristics, at home and abroad has been widely used in various fields of industrial automation control, gradually replaced the original relay control of industrial control methods, and become the pillar of industrial production automation products.
Definition of PLC
The traditional relay control system is connected to the electrical components through hard wires to form a logic control system, there are many wires, wiring complexity, poor adaptability to changes in the production process, large size, low reliability, difficult to find faults and other shortcomings. 1968, the United States' largest automobile manufacturer General Motors (GM) is trying to find a new type of industrial control methods to adapt to the automobile model of the constant updating, minimizing the need to rewrite the car. Continuous updating, as far as possible to reduce the redesign and replacement of relay control system hardware and wiring workload, thereby reducing costs. Thus, General Motors envisioned a new type of control device suitable for industrial control by combining the computer's functional completeness, flexibility and proximity with the relay control system's simplicity, ease of operation and low price. In the same year, the company's public tender. 1969, the United States Digital Equipment Corporation (IDEC) according to the requirements of the tender, developed the world's first programmable controller, and in the General Motors automated assembly line on a successful trial. Early programmable controller is to replace the relay control circuit, the use of stored program instructions, to complete the sequential control and design, mainly for logic operations, timing, counting and sequential operations and other switching logic control, so it is usually called programmable logic controller (ProgrammableLogic Conroller, PIC).
Into the 1970s, with the development of microelectronics technology, the emergence of microprocessors and microcomputers, and was applied to the PLC, so that the PLC not only has the logic control function, but also increased the data operation, transmission and processing functions, so it is called a computer function of the industrial control device. 1980, the United States Electrical Manufacturers Association formally named the programmable controller ( PogrammableController, PIC). PogrammableController, PC), but because it is easy to personal computer (PersonalComputer, PC) confused, people are still accustomed to use PIC as a programmable controller abbreviation.
In 1987, the International Electrotechnical Commission (nternational Electrical Commite, LECc Gu cloth PLC standard draft of the PIC made the following definition: "PLC is a specially designed for the application of the industrial environment and the operation of digital computing electronic devices. It can be programmed using the memory, in its internal storage to perform logical operations, sequential operations, timing, counting and arithmetic operations and other operations of the instructions, and can be digital or analog inputs and outputs, control of various types of mechanical processes, PIC and its peripherals should be easy to form a whole with the industrial control system, easy to expand the function of the principle of design. "
▲The characteristics of PLC
PLC as a new type of industrial control device, the reason for the widespread application and development of its own characteristics.
1, high reliability, anti-interference ability, it is one of the most prominent features of PLC.
PLC due to the use of modern large-scale integrated circuit technology, strict manufacturing process, the internal circuitry to take the advanced anti-interference technology, so it has a high degree of reliability. In addition, PLC with hardware failure self-detection function, failure can be issued in a timely manner when the alarm information. In the application software, can also be embedded in the peripheral device failure self-diagnostic program, so that the system in addition to the PIC device outside the circuit and equipment to obtain self-diagnostic fault protection.
2, complete hardware, functionality, applicability
PLC development to date, has formed a large, medium and small scale series of products, and has been standardized, serialized, modular, equipped with a full range of hardware devices for the user to choose from, the user can flexibly and conveniently configure the system, composed of different functions, different sizes of the system PLC installation and wiring is also very easy to connect the external wiring with the general terminals. With more load capacity, can directly drive the general solenoid valve and AC contactor, can also be used for various scales of industrial control places.
Due to technological enhancement, the price of PLC has fallen dramatically, making various types of PLC microprocessors used by the performance of the general improvement. In order to further improve the processing speed of PLC, the manufacturers have also developed a special logic processing chip, making the PLC hardware and software functions have changed dramatically.
Application of PLC
At present, PLC has been widely used at home and abroad in iron and steel, petroleum, chemical, electric power, building materials, machinery manufacturing, automotive, textile, transportation, environmental protection and cultural and entertainment industries, its application can be roughly summarized in the following categories.
1, switching logic control
Switching logic control is the most basic, the most extensive application of PLC, which replaces the traditional relay circuit, the realization of the logic control, sequence control. It can be used for single device control, can also be used for multi-machine group control and automation lines, such as injection molding machines, printing machines, stapling machines, combined machine tools, grinding machines, packaging lines, plating lines and so on.
2, analog control
In the industrial production process, there are many continuously changing analog quantities, such as temperature, flow, level, pressure and speed. In order to make the programmable controller to deal with analog, must realize the analog (Analog) and digital (Digital) between the A/D conversion and D/A conversion. PLC manufacturers are producing supporting A/D and D/A conversion module, so that the programmable controller for analog control.
3, motion control
PLC can be used for circular or linear motion control. Widely used in a variety of machinery, machine tools, robots, elevators and other occasions.
4, process control
Process control generally refers to the closed-loop control of the controlled analog parameters.
PLC through the analog 1 / 0 module to achieve analog and digital A/D, D / A conversion can be achieved on the temperature, pressure, flow and other continuously changing analog PID control. When a variable in the process control deviation, the PID control algorithm will calculate the correct output, so that the controlled analog quantity in accordance with the design requirements of the control law changes back to the set value.
5, data processing
Modern PLC has mathematical operations, data transfer, data conversion, sorting, table lookup, bit operation and other functions, can complete the data acquisition, analysis and processing. This data can be stored in the memory with the reference value comparison, to complete certain control operations, but also can be transmitted to other intelligent devices using the communication function, or print them tab. Data processing is generally used for large-scale control systems, such as unmanned flexible manufacturing system; can also be used for process control systems, such as paper, metallurgy, food industry in some large-scale control systems.
6, communication and networking
PLC communication mainly includes PLC and computer communication, PLC communication and PLC communication with other intelligent devices known communication. PLC and other intelligent devices can be composed of "centralized management, decentralized control" of the distributed control system.
▲ PLC is essentially a microprocessor as the core of the computer dedicated to industrial control, but it is more than the general computer has a stronger interface with the industrial field for information exchange, as well as directly adapt to the control requirements of the programming language.
From the hardware organization, PLC is mainly composed of central processing unit (CPU), storage unit, input/output unit, power supply and programmer and other parts.
Central processing unit is the core part of the PLC, is the control center of the system, plays the role of the commander-in-chief. In the PLC, the CPU according to the system program to give the function, command PLC to work in an orderly manner, summarized in the following functions.
1) Receive, store the user program and data input from the programmer.
2) Diagnose power supply, PLC internal circuit faults and programming syntax errors.
3) Receive the status or data from the field through the input interface and store them in the input image register or data register.
4) Read the user program from the memory line by line, after the interpretation of the execution.
5) According to the results of the implementation, update the status of the relevant flag bits and the contents of the output image descent memory, through the output unit to achieve output control. Some PLC also has a tabular printing or data communication functions.
At present, small PLC for a single-CPU system, and large and medium-sized PLCs are mostly dual-CPU system, and even some PLCs up to 8 CPUs. for the dual-CPU system, generally a word processor, 8-bit or 16-bit processor; the other for the bit processor, the use of manufacturers to design and manufacture of special chips. Word processor is the main processor, used to perform the programmer interface functions, monitor the internal timer, monitor the scan time, processing byte instructions and the system bus and bit processor control. Bit processor for the slave processor, mainly used for processing bit operation instructions and the realization of the PLC programming language.
Answer 7: To say that the role of PLC has to say it in the field of industrial control.
As we all know, PLC was born at the beginning of the industrial production line is applied to, after nearly fifty years of development, PLC in the field of industrial control plays an increasingly important role.
We start from the industrial simple logic control, wherever the modernization of the relay control line are inevitably used to PLC; then in the modern industrial integrated control system PLC is also one of the main core control devices, such as in the flexible manufacturing system (FMS) PLC plays a role in the received peripheral signals for conversion, calculation and output and then control the role of various loads; With the modern PLC technology is more and more perfect, many brands of PLC are reserved for a variety of communication interfaces, PLC and PLC, PLC and peripherals (such as inverters, touch screens, etc.) for long-distance communication between the realization of remote control provides a possibility; in addition, in the modern intelligent manufacturing, industrial robots work on the production line, industrial robots to obtain a variety of information should be processed through the PLC and provided to the industrial robot. PLC processing and provide to the industrial robot.
It can be seen, PLC whether in the simple logic control or in the modern industrial intelligent integrated system PLC's role is unshakeable!
PLC is not only in the industrial field has a great role in other areas are also very common, such as in a variety of high-rise buildings in the elevator control circuits; directing traffic used in traffic light control circuits; life in the music fountain control circuits, advertising lights control and so on can be seen in the application of PLC!
Answer 8: What is the main role of PLC?
Glad to answer this question, PLC full programmable logic controller, in industrial equipment is equivalent to the human brain, according to the input signal and the program written, you can control solenoid valves, contactors, intermediate relays, lights, buzzers, digital display tubes and so on.
The previous complex logic wiring transplanted to the software wiring, such as a button and three intermediate relays to control a single button start / stop, to connect a lot of wires, with the PLC as long as the connection of a button, programmed to save a lot of wiring work, and hardware wiring failures are very difficult to repair, with the PLC is simple and convenient.
With the continuous development of science and technology, PLC inputs can be connected to analog signals, high-speed counting inputs, etc., and other equipment through 232, 422, network communication with each other, the output can also be analog signals, high-speed pulse output, PWM outputs, you can control servo amplifiers, multi-axis linkage and so on.
PLC is now inexpensive, a variety of equipment can not be separated from the electrical cabinet PLC, to tell a joke if the equipment does not have the electronic control of PLC, that would appear to be no grade.
PLC is based on the development of relay sequence control to the microprocessor as the core of the general automatic control device.
PLC to microprocessor-based, integrated computer technology, automatic control technology and communications technology, with the control process-oriented, user-oriented programming language, to provide a simple and easy to understand, easy to operate, high reliability of a new generation of general-purpose industrial control devices.
PLC has been widely used in machinery manufacturing, transportation, electric power, industrial production and other industries, the actual application of the following six types:
01 PLC for switching control
PLC switching control to replace the traditional relay circuit, the control of the number of inbound and outbound points, less than a dozen points, dozens of points, more than a few hundred, thousands, or even tens of thousands of points. Through networking, the number of points is almost unlimited.
PLC can be controlled by the logic of the combination of issues, timing, immediate, delayed, do not need to count, need to count, fixed order, random work, etc., which is unmatched by other controllers.
PLC's hardware structure is variable, and can be used for single device control, multi-machine group control or automated assembly line. Its software program is also programmable, if necessary, can be written in multiple sets or groups of programs, as needed to call.
02 PLC for analog control
PLC can be used to control analog quantities, such as temperature, pressure, flow, level and speed, which are continuously changing analog quantities, by using conversion modules (A/D, D/A conversion) between analog and digital quantities.
Along with analog control, switching control is also possible. Other controllers are not available, and control realization is not as convenient as PLC.
- The A/D unit (analog-to-digital conversion) converts the analog quantity from the external circuit into a digital quantity and sends it to the PLC;
-D/A unit (digital, analog conversion), the PLC's digital volume into analog, and then sent to the external circuit;
A/D and D/A have single and multiple circuits. Medium and large PLC can not only carry out digital addition, subtraction, multiplication, division, but also square, interpolation and floating-point operations, and some have PID instructions, which can be deviated from the amount of proportional, differential and integral operations, which in turn produce the corresponding output.
03 PLC for motion control
PLC can control the switching quantity, analog quantity, but also can control the motion quantity. For example, the control of circular motion or linear motion of machine parts (the motion quantity is also expressed as a digital quantity).
Early PLCs directly connect position sensors and actuators with switching modules, but nowadays they generally use motion control modules, which can drive single-axis or multi-axis position control modules for stepper motors or servo motors.
-PLCs can receive counting pulses in several ways and in multiple ways, at frequencies of up to a few k to tens of k Hz;
-Some PLCs also have a pulse output function, and the pulse frequency can also be up to tens of k;
These two functions, coupled with the PLC has the data processing and arithmetic capabilities, and then equipped with the appropriate sensors (such as rotary encoder) or pulse servo device, in accordance with the principles of digital control technology to achieve a variety of control, such as: the realization of the point control, curve interpolation, curved motion and so on.
04 PLC for data processing
With the development of PLC technology, mathematical operations (including matrix operations, function operations, logical operations), data transfer, data conversion, sorting, table and bit operations and other functions used in PLC, and PLC data storage area is getting bigger and bigger, you can complete the data acquisition, analysis and processing.
PLC can use the communication function to transfer to other intelligent devices (such as computers), and then process these data, or print them through a printer to tabulate.
05 PLC for signal monitoring
PLC self-test signals are many, and there are many internal devices, which can be used to monitor the work of the PLC itself, or to monitor the control object. This can reduce system failures (faults or find), can improve the cumulative average trouble-free operation time, reduce the fault repair time, improve system reliability.
06 PLC for networking, communication
PLC networking, communication capabilities are very strong, can be connected with a personal computer, communication, computer programming and control of PLC management. And there are constantly new networking structure launched.
A computer can control and manage multiple PLCs, up to 32.
-A PLC can connect and communicate with many computers to realize the monitoring of PLC control system by many devices;
-PLC and PLC can communicate with each other, either one-to-one or many-to-many, as many as dozens or hundreds;
-PLC can connect and communicate with intelligent meters and intelligent execution devices (such as frequency converters), etc., which can form a remote control system.
PLC is today's computer-integrated manufacturing systems and intelligent factory development needs.
PLC makes industrial control from the point, to the line, and then to the surface, so that the equipment level control, production line control, factory management control into a whole, which in turn can create higher economic benefits.