PLC and single chip microcomputer

1.

PLC is a relatively mature control system composed of single-chip microcomputer. It is a proct of single-chip microcomputer application system which has been debugged and stabilized. It has strong generality. The single chip microcomputer can constitute a variety of application systems, the use of a wider range

As far as single chip microcomputer is concerned, it is only a kind of integrated circuit, and it can be applied only when it is combined with other components and software

from the perspective of engineering application, for single project or project with few repetitions, PLC is fast and convenient, with high success rate, good reliability and high cost

for a large number of supporting projects, SCM system has the advantages of low cost and high efficiency, but it needs considerable R & D strength and instry experience to make the system stable

in essence, PLC is actually a set of SCM system which has been done well

expand reading:

microcontrollers is a kind of integrated circuit chip, which uses VLSI technology to integrate CPU, ram, ROM, various I / O ports and interrupt system, timer / counter and other functions with data processing ability (including display drive circuit, ram, ROM, timer / counter, etc.) Pulse width molation circuit, analog multiplexer, a / D converter and other circuits are integrated into a silicon chip to form a small and perfect microcomputer system, which is widely used in the field of instrial control. From the 1980s, from the then 4-bit, 8-bit microcontroller, to now 300m high-speed microcontroller

2.

1. Different structure

PLC is a proct based on MCU, which is an integrated circuit

2. Different uses

single chip microcomputer can constitute a variety of application systems, from micro, small to medium and large, PLC is a special case of single chip microcomputer application system

3. Different principles

different manufacturers of PLC have the same working principle, similar functions and indicators, a certain degree of interchangeability, quality assurance, programming software is moving towards standardization. This is the basis of PLC widely used

However, the quality of SCM application system is uneven, so it is difficult to learn, use and maintain

extended data:

single chip microcomputer is also known as a single-chip microcontroller. It is not a chip to complete a logic function, but to integrate a computer system into a chip

is equivalent to a micro-computer, compared with the computer, single-chip microcomputer only lacks I / O equipment

To sum up, a chip becomes a computer. It is small in size, light in weight, cheap in price, and provides convenient conditions for learning, application and development. At the same time, learning to use SCM is the best choice to understand the principle and structure of computer< br />

3. PLC is developed on the basis of single-chip microcomputer. It is mainly a proct to shorten the engineering development cycle. The most fundamental difference between PLC and single-chip microcomputer is that it is easy to use and does not need to know too much knowledge of electronic circuits
single chip microcomputer (MCU) is a complete single-chip computer system. Now MCU has superior performance and powerful functions. The core of PLC is MCU, which can complete almost all electrical control requirements. The biggest disadvantage is that it is difficult to develop, long cycle and high development cost.

4. 1. PLC is a proct based on MCU, which is a kind of integrated circuit. The two are not comparable
2. Single chip microcomputer can constitute a variety of application systems, from micro, small to medium and large, PLC is a special case of single chip microcomputer application system
3. Different manufacturers of PLC have the same working principle, similar functions and indicators, certain interchangeability, quality assurance, programming software is moving towards standardization. This is the basis for PLC to be widely used. The application system of single-chip microcomputer is
Eight Immortals crossing the sea, each shows its own magic power, the function is very different, the quality is uneven, it is very difficult to learn, use and maintain
finally, from the engineering point of view, the selection of PLC and SCM system is discussed
1. For the single project or the project with few repetitions, using PLC scheme is a wise and quick way, with high success rate, good reliability, few hands and ends, but high cost
2. For a large number of supporting projects, SCM system has the advantages of low cost and high efficiency, but it needs considerable R & D strength and instry experience to make the system stable and reliable. The best way is to embed the function of PLC in the single-chip system, which can greatly simplify the development time of the single-chip system, guarantee the performance and ensure the benefit.

5. Comparison of advantages and disadvantages:
single chip microcomputer control: advantages, economic benefits, relatively low cost; The main control board made of single-chip microcomputer is affected by the process, layout structure, device quality and other factors, resulting in poor anti-interference ability, high failure rate, difficult to expand, strong dependence on the environment, and long development cycle. It is difficult to form a real proct without a long time of practical verification for a main control board made of single chip microcomputer
PLC control: advantages: PLC is a controller that has been tested in practical application for decades, with strong anti-interference ability, low failure rate, easy equipment expansion, easy maintenance and short development cycle. Disadvantages: the cost is relatively high!

6.

Compared with single-chip microcomputer, PLC has the advantages of high reliability, strong anti-interference ability, convenient programming, convenient use and strong applicability in harsh instrial environment

PLC control system, programmable logic controller, a kind of digital operation electronic device specially designed for instrial proction, which uses a kind of programmable memory for its internal storage program, execution of logic operation, sequence control, timing, counting and arithmetic operation and other user-oriented instructions, And through digital or analog input / output control of various types of machinery or proction process. It is the core part of instrial control

since the introction of programmable logic controller (PLC) to replace the traditional relay control device in the United States in the 1960s, PLC has been developed rapidly and widely used all over the world

At the same time, the function of PLC is constantly improved. With the continuous development of computer technology, signal processing technology, control technology, network technology and the continuous improvement of user demand, PLC has added analog processing and motion control functions on the basis of switching value processing. Today's PLC is no longer limited to logic control, but also plays a very important role in motion control, process control and other fields

extended data:

PLC basic structure

PLC controller is a kind of special computer for instrial control, and its hardware structure is basically the same as microcomputer

The central processing unit (CPU) is the control center of PLC controller. According to the function given by PLC controller system program, it receives and stores user program and data input from programmer; Check the status of power supply, memory, I / O and alert timer, and diagnose syntax errors in user program

when the PLC controller is put into operation, it first receives the status and data of each input device in the field by scanning, and stores them in the I / O image area respectively, then reads the user program one by one from the user program memory, and after command interpretation, executes the logic or arithmetic operation according to the instruction, and sends the results into the I / O image area or data register

After all the user programs are executed, the output status of the I / O image area or the data in the output register are finally transmitted to the corresponding output device, and the operation is cycled until it stops

in order to further improve the reliability of PLC controller, in recent years, al CPU rendancy system or voting system with three CPUs are used for large PLC. In this way, even if a CPU fails, the whole system can still run normally

2, memory

the memory that stores system software is called system program memory. The memory where the application software is stored is called user program memory

3. Power supply of power supply

controller plays a very important role in the whole system. Without a good and reliable power supply system, it can not work normally, so PLC manufacturers also attach great importance to the design and manufacture of power supply. Generally, if the AC voltage fluctuation is within + 10 (+ 15%), the PLC controller can be directly connected to the AC power grid without other measures

The program input device is responsible for providing the operator with the functions of inputting, modifying and monitoring the program

Input / output circuit is responsible for receiving external input component signals and external output component signals

7. Single chip microcomputer can be made into PLC, which is composed of single chip microcomputer,

difference: single chip microcomputer has low cost and can be mass-proced (mass proction: for example, all kinds of electronic procts). However, single chip microcomputer has high requirements for circuit protection and weak anti-interference ability, which is easily affected by various external reasons
PLC is more expensive and stable than single-chip microcomputer. There are many kinds of moles (IO / analog / temperature control / high-speed positioning) and so on

8. It must be MCU! SCM is more powerful than PLC, control is more flexible, can form a variety of control systems, cost advantage, so the scope of application is more extensive, and PLC is also composed of SCM
it's said by people who don't know how to use SCM because SCM is not as reliable as PLC. There are many knowledge points that need to be mastered in the application of SCM, and it's really difficult to develop. It's not easy for people who have studied electronics and electricity to use it well. Because PLC programming is simple, even some factory wiring electricians can program
now the anti-interference ability of single-chip microcomputer is becoming stronger and stronger. For example, the automobile control is all controlled by single-chip microcomputer. We have never seen that the automobile is controlled by PLC, and the elevator special controller using single-chip microcomputer is also widely used. These places involving the safety of personnel can use single-chip microcomputer, so what else can prevent the single-chip microcomputer from entering
in a word, it is more reasonable to use PLC in places where the number of repetitions is small or the time is tight, and it is more economical and reasonable to use MCU in places where the number of repetitions is large and the time is relatively abundant. PLC can also be used in the early stage, and MCU can be used in the later stage to rece the cost.

9. PLC is the abbreviation of programmable logic controller, high price, relatively large volume, but rich function, can realize all kinds of complex control, reliable operation, can adapt to all kinds of bad environment, at present widely replace the traditional relay control mode, widely used in instrial proction
single chip microcomputer is the abbreviation of single chip computer, which can also realize automatic control. Compared with PLC, it is characterized by small volume and low price (you can buy one for only a dozen or even a few yuan, while PLC is often thousands or even more expensive), but it has higher requirements for the operating environment. At present, it is mainly used in the control of household appliances.

10. To put it simply:
1. The core of PLC is MCU, but it integrates the peripheral circuits (including I / O circuits), so if you use PLC, you can save the trouble of designing I / O interface and other circuits
2. In terms of programming, using single-chip microcomputer needs to be familiar with computer programming language, such as VB, while PLC programming can be programmed in a variety of ways, and the most commonly used ladder diagram programming can be programmed as long as you know the basics of electrician< But in terms of cost, SCM should be much lower than PLC. Of course, there are many domestic PLC whose price is not high.