PLC ladder design thinking training method - Database & Sql Blog Articles

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Manufacturing equipment. At present, there is a large demand for talents who are proficient in the industrial control technology. In order to adapt to the market, plc has become a professional technical course that must be mastered by professional students in vocational schools, but the difficulty in learning this technical course lies in Ladder diagram design, because PLC programming language is a lot, the most commonly used is the ladder language, but every time the student gets the PLC ladder design problem, "the tiger eats nowhere and has no claws."

I think the key to solving this problem lies in the teacher's cultivation of the student's PLC ladder design thinking in the teaching process. PLC ladder design thinking refers to how the programmer uses the given preconditions and process requirements to analyze, synthesize, judge, reason, etc. the process of compiling the PLC ladder diagram. In order to meet the needs of skilled operation of enterprises, it is necessary to cultivate a habit of thinking and form a proficient mode of thinking. The following aspects should be emphasized.

First, the establishment method of PLC ladder diagram design thinking

1. Imitation method:
After the students have learned the principle of PLC, they have not fully grasped the basics and imitated some kind of ready-made ladder mode to learn to do. For example, 24h timing ladder design, students can imitate the 1h timing ladder design method to practice writing 24h timing program.
2. Completion method:
Completion is to complete the incomplete place. This kind of learning method is mainly used when doing the problem. It is a commonly used method of solving the problem. The structure of the topic is generally complete, but the proposition sometimes deliberately saves some components according to the meaning of the context to increase the difficulty of the test. . When doing the question, it is necessary to review the meaning of the question, analyze the structure, and make up the omitted part. This method can train students to understand other people's thinking process, and then turn this thinking into their own way of thinking. For example, in the 2008 college entrance examination English six questions, the proposition coping strategy has a structural complementation method. This method is also applicable to PLC ladder design. If there is an indicator light, the control requirement is: after pressing the start button, it will be on for 5 seconds, off for 5 seconds, and repeat the work. Complete the ladder diagram below.
3. Experience method:
Students have learned relay control circuits and have experience in designing control circuits with relays. PLC's ladder design experience method is to rely on the design experience accumulated in the usual design ladder diagram. In the early stage of PLC development, the design of the ladder diagram was designed according to the method of designing the electrical circuit diagram. Based on the existing typical relay circuit diagram, the ladder diagram was continuously modified according to the control requirements of the controlled object. This method has no universal rules to follow, and everything must be realized by the designer's experience. It is to transform the thinking of designing the relay circuit diagram into the PLC ladder design thinking. It is generally used for ladder diagram designs with simpler logic relationships.

4. Blocking method:
The purpose of the block is to break down a complex project into a number of relatively simple tasks. For example, in mathematics, when matrix operations with higher number of rows and columns are used, the matrix block method is often used to make the operation of large matrices into small matrices. The matrix is ​​divided into a number of small matrices by a plurality of vertical and horizontal lines to make a large matrix. The computational problem of computing into a small matrix is ​​much better solved. This way of thinking is to grasp the key points of the proposition, to solve the big problems and small problems. Many control problems in PLC can use the block method to design the ladder diagram. For example, the automatic control program of the air-conditioning pump can be divided into three small blocks to perform trapezoidal ladders. Figure design, (1) first design the timing program (starting at 8:00 in the morning, stopping at 23:00 in the evening). (2) Redesign the manual start and stop (X001 X002) and automatic start and stop (M0 M1) program, (Y001 output to the main contactor Y002 output to the star contactor Y003 output to the triangular contactor) motor star triangle step-down start. (3) Finally, the self-protection function program is designed (it cannot be started and stopped three times in 0.5h). After the design is completed separately, the three parts can be combined with the requirements of the topic to complete the control requirements. The specific ladder diagram design is as follows:
(1) Design the timing program first (start at 8:00 in the morning and stop at 23:00 in the evening)
(2) Redesign the manual start and stop (X001 X002) and automatic start and stop (M0 M1) program (motor star delta step-down start)
(3) Finally, the self-protection function program is designed (it cannot be started and stopped three times in 0.5h)
The first two methods of the above four methods are an effective learning method for beginners to learn the basic instructions of the PLC and then design the ladder diagram. The latter two methods are designed for students who already have a design basis. At the same time, the training effect was strengthened and the results were achieved with half the effort.

Second, the intensive training of PLC ladder design thinking

1. Strengthen through repeated training of typical exercises

PLC is a course for students. After studying, there are few opportunities to use during school. In addition, there are many contents in the learning process and the time is short. Therefore, it is easy to be unfamiliar after the process, and the ladder of some typical control is solidified in the brain. It will play an important role in the re-learning and level improvement of PLC ladder design in the future, and the realization of this kind of curing can be realized through repeated training of typical exercises, which is also the founding of the famous American psychologist, the theory of connectionist learning. The practice law in the three main learning laws summarized by Mandak.

2. Do more discussion and analysis, compare the advantages and disadvantages of various methods

There are more than one way to achieve the goal, often each has its own merits, and its variety, advantages and disadvantages are important ways to design the best ladder diagram and skilled use of various instructions. The various design methods for ladder diagrams of a specific topic are discussed in groups of three to five people, and then discussed and analyzed in class. Under the guidance of the teacher, they summarize and summarize their respective advantages, disadvantages and applications. Sex. In this way, the credibility of the best design method in the student's thinking can be improved, the exploratory thinking time after the student gets the problem can be reduced, and the concentration in the thinking can be improved, and the ladder design is also improved. s efficiency.

3. Debug each ladder designed to determine its correctness

Practice is the only criterion for testing truth. Even the best programming, if you don't go to the machine for debugging and verification, the designer's psychology is always unsure. The self-confidence of his own design is not certain, and his own thinking method is not certain. It is impossible to cure this kind of design thinking in the brain. At the same time, the machine will debug the designed program. If it succeeds, it will create a sense of accomplishment for the designer and increase interest. If it is unsuccessful, it will find out the problems and deficiencies, and it will help to correct the way of thinking of the designed program.

Third, the sublimation of PLC ladder design thinking

1. Conduct more actual visits and establish a clear emotional understanding

Familiarity with various controlled devices, sensors and processes has made designers very useful in clear thinking, design improvement and refinement. It is hard to imagine that a closed-door car can be designed. PLC ladder diagram. Therefore, in the process of theoretical study, it is imperative to arrange the visits related to the course in a timely manner. The strengthening and clarification of perceptual knowledge will help the designer to “follow the mind”.

2. Read more programs

"The stone of other mountains can be used to attack jade". Read the procedures designed by others, analyze the benefits, and the disadvantages. It can help designers understand and learn other people's design thinking, take advantage of others, make up their own shortcomings, and make themselves Continuous improving.

A good PLC ladder design thinking mode can make the designer work well in the actual work or after getting the problem, such as a fish, and its establishment, strengthening, and sublimation process is difficult, and needs to be gradual.