Analysis of Similarities and Differences between Single Chip Microcomputer and PLC in Industrial Application

MCU and PLC have a wide range of applications in the industry, because their characteristics are different, so their work focus is also different, let's look at the similarities and differences between single-chip and PLC in industrial applications.

About MCU

A single-chip computer is the basic link of an electronic computer, such as a CPU (also known as a central processing unit, mainly composed of an arithmetic unit and a controller), a memory, a bus, an input/output interface, etc., integrated on a silicon substrate by using integrated circuit technology. . Because a single-chip computer is small (only finger-sized) and powerful (with a simple computer function), it is widely used in electronic devices as a controller. At present, large-scale modern weapons such as missile rocket defense, as small as TV microwave ovens, etc., use the single-chip computer as a controller without exception. Therefore, from a control point of view, we often call it a single-chip controller.

The operation of a single-chip microcontroller is inseparable from software, a well-designed program that is solidified in memory. All electronic devices with a single-chip microcontroller, its working principle is of course related to the specific device. But its most basic principle is the same, namely:

1. Receive information from the outside world from the input interface and store it in the memory.

This information mainly consists of two parts: information from sensors such as temperature and pressure;

Some manual information from manual intervention, such as switch buttons and other operations.

2. The CPU root program in the single-chip microcontroller performs high-speed arithmetic processing on the input number.

3. Send the result of the arithmetic processing to the control actuator through the output interface, such as relay, motor, bulb, etc.

The current process is repeated, that is, the microcomputer in the system constantly monitors various information and makes different processes in time to make the system run normally...

About PLC

PLC is a product built on a single-chip microcomputer. The single-chip microcomputer is a programmable integrated chip. In other words, the PLC is made up of a single-chip microcomputer plus a peripheral circuit. The development of the single-chip microcomputer is relatively troublesome. Assembly or C language such as delay using a single-chip computer to do the program, to calculate from the crystal oscillator, and PLC is not the same, a manufacturer provides a programming software, you can use ladder programming, delay only need to send a number in the time relay .

PLC is currently made up of a large number of single-chip microcomputers. It can be said that PLC is an application of single-chip microcomputer in relay control system. The ladder diagram used by PLC is similar to the relay circuit diagram, which is easy for the majority of electrical engineering technicians to accept;

In conclusion:

1. PLC is a product built on a single-chip microcomputer. The single-chip microcomputer is an integrated circuit, and the two are not comparable;

2, PLC is more suitable for industrial use in harsh environments, the use of relatively stable and single-chip work environment is higher;

3. In the programming language, the single-chip microcomputer adopts assembly language, and the PLC adopts ladder diagram language;

4, MCU can constitute a variety of application systems, from micro, small to medium, large, PLC is a special case of single-chip application system;

5, PLCs of different manufacturers have the same working principle, similar functions and indicators, have certain interchangeability, quality is guaranteed, programming software is moving towards standardization. This is the basis for the widespread use of PLCs. The single-chip application system is the Eight Immortals crossing the sea, each showing its powers, its functions vary widely, the quality is uneven, and it is difficult to learn, use and maintain.

Finally, from the engineering point of view, talk about the choice of PLC and microcontroller system:

1. For a single project or a project with few repetitions, it is a wise and quick way to adopt the PLC scheme. The success rate is high, the plasticity is good, and the hand is small, but the cost is high.

2. For large-scale supporting projects, the use of single-chip microcomputer system has the advantages of low cost and high efficiency, but it must have considerable research and development strength and industry experience to make the system stable and grounded. The best method is to embed the function of the single-chip system into the PLC, which can greatly simplify the development time of the single-chip system, the performance is guaranteed, and the benefit is guaranteed.