What are the basics of getting started with PLC?

The basics of getting started with PLC are:

1. From the perspective of the composition of PLC, in addition to CPU, memory and communication interfaces, what other interfaces are directly related to the industrial site? And explain its main functions.

1) Input interface: Accept the signal of the controlled equipment, and drive the internal circuit to be turned on or off through the optocoupler device and the input circuit.

2) Output interface: The execution result of the program is output through the optocoupler device and output components (relays, thyristors, transistors) of the output interface, and the external load is switched on or off to be controlled.

2. What are the basic components of PLC? What role does each play?

1) The CPU :p the core component of the LC, directing the PLC to carry out various tasks. Such as accepting user programs and data, diagnosing, executing programs, etc.;

2) Memory: Programs and data that store the system and users;

3) IO interface: the connecting part between the PLC and the controlled object at the industrial production site, which is used to receive the signal of the controlled equipment and the execution result of the output program;

4) Communication interface: exchange information with monitors, printers and other equipment through communication interfaces;

5) Power supply. 3. What are the types of PLC switching output interfaces? What are the characteristics of each?

Thyristor output type: under normal circumstances, it can only carry AC load, with fast response speed and high action frequency;

Transistor output type: under normal circumstances, it can only carry DC load, with fast response speed and high action frequency;

Relay output type: Under normal circumstances, it can carry AC and DC loads, but its response time is long and the action frequency is low.

4. According to the structural type, what are the types of PLC? What are the characteristics of each?

1) Integral: CPU, power supply, and IO components are all concentrated in a chassis, with compact structure and low structure, and this structure is generally used for small PLCs;

2) Modular: each part of the PLC is divided into a number of individual modules, and different modules can be selected to form a system according to the needs, which has the characteristics of flexible configuration, convenient expansion and maintenance, and generally adopts this structure for medium and large PLC. The modular PLC consists of a frame or substrate and various modules, and the modules are mounted on the sockets of the frame or substrate.

3) Stacked type: Combining the characteristics of integral and modular type, the CPU, power supply, and IO interface of the stacked PLC are also independent modules, but they are connected by cables, making the system not only flexible in configuration but also small in size.

5. What is the scanning cycle of PLC? What is it mainly affected by?

The scanning process of PLC consists of five stages: internal processing, communication services, input processing, program execution, and output processing, and the time required for one scan in these five stages is called the scanning cycle.

The scan cycle is related to the CPU running speed, PLC hardware configuration, and the length of the user program.

6. What is the way in which the PLC executes the user program? What are the stages of the user program execution process?

The PLC executes the user program in a cyclic scanning mode, and the execution process of the user program includes the input sampling stage, the program execution stage and the output refresh stage.

1. Have basic hardware knowledge.

Before programming, you need to understand some basic hardware knowledge, it is best to start with the selection and drawing of hardware, and wait for the type of input and output, the selection of analog quantities, etc., and then start programming will be simpler.

If you are familiar with the basic hardware circuits, you will find that the original ladder diagram and these hardware circuits can be well corresponded.

PLC2, reading some excellent programs, is very helpful to improve your programming habits and programming concepts. If not, then it is necessary to get practice from the limited cases in the textbook, such as marquee, traffic light, assembly line, etc.

3. Practice. Do-it-yourself wiring, writing programs and debugging, being able to debug these functions by yourself, and then combine some sensors to realize the function of analog input and output, basically the foundation is laid.

Now the PLC software design is very good, if there is a hardware with better cooperation, if not, install a software, install a simulator, the basic operation is familiar, and then observe the input and output changes of the PLC.

The basics of PLC are as follows:1. It is necessary to master a certain electrical foundation: master the use of commonly used devices such as sensors, proximity switches, encoders and the working principle of contactors.

2. Master the basic knowledge of computer: familiar with the installation of various software and the setting of network communication.

3. Counters and timers should be assigned before use.

4. The expression of the logic function diagram basically follows the logic language of the "and", "or" and "not" gate circuits of the digital logic circuit, and is represented in the form of a logic block diagram.

5. The logical function diagram is used to describe the program, which is easy to describe the more complex control function, the expression is intuitive, and it is easy to check the error.

First of all, it is necessary to understand the knowledge of electricians, understand the control of electrical appliances, understand various actuators, and then understand the working mode of PLC, input and output circuits, and finally understand the corresponding process.

1, learn PLC first of all to choose a good learning of which manufacturer's PLC, the Japanese PLC internal software integration is high application simple early OMRON, Mitsubishi application more, now due to the first and international cooperation between the application of Siemens PLC, Rockwell a little more, (although it is said that a brand is profound, others will soon get started, but people's energy is limited, must be used in the most widely used, potential, development of a direction, However, for each brand of PLC have some understanding, including imported, domestic, these have a corresponding understanding, for the characteristics of each PLC, advantages and disadvantages, these have a better understanding, then will be a rare talent in the market in the future. ）

2. PLC is not a single programming technology, it is a system professional course. A PLC can be broadly considered a highly reliable PC with an operating system embedded in the back. First of all, you need to be proficient in the programming language ladder diagram and sentence table language of the PLC itself.

At this level, you can only read the programmed programs and design some of the programs needed for the project. In this industry, it is also necessary to apply VB and VC to realize serial port communication and distributed control system. Knowledge of databases is also required in some large programs.

PLC is quick to get started, but you have to keep making an effort. ）

3. PLC is a discipline that focuses on the application direction. So a little more practice. Don't look down on small projects, where you can summarize the logical thinking method for designing programs.

Keep making progress in the summary. For example, every time you go to the site to debug, call the program on the site to view, from which to understand the structure of the program, and other programs are different and characteristics, then the progress will be faster, good luck!

Language, there are spring change scum many people pure Chinese instructions, instruction manuals, etc. can not be understood.

Some operations are often used in mathematics and PLC programs. I've met Ph.D. students who don't even know what the remainder is and how to calculate it.

Physics, sometimes some physical formulas are used, such as ui=p, vt=s.

Computer basics, such as binary, decimal sails, etc.

Electrical foundation, PLC itself is electrical, direct current, AC flash electricity, contactors, motors and the like still need to know what it is. The most outrageous thing I encountered was when someone took a photoelectric switch and asked me what kind of motor it was.

English, is dispensable, sometimes there is no Chinese information, you need to read some English information, I can't understand, but now the translation software is so powerful, direct photo translation is over. If you are good at English, it will be more convenient.

Hope...