Some experiences and suggestions when learning PLC!

Today I would like to share with you some experience and suggestions from an expert on learning PLC!

1. Learning PLC programming requires strong perseverance and enough patience

Everyone has their own strengths. Some people regard programming as a long and boring job; some people regard programming as an interesting intellectual game. When I see the symbols arranged neatly according to my own ideas and the PLC runs in an orderly manner according to my requirements, my personal interests will be greatly satisfied.

2. Learning PLC programming requires the confidence to practice

Only by continuously running these instructions on the PLC and observing the results of the operation can we understand the role of the PLC instructions.

Many beginners are confused about PLC, often out of fear of damaging the equipment. And these fears are unreasonable. It is very important to read the manual carefully, but you can't become an engineer just by reading. What's more, the content in the manual is not exhaustive. When I come across unfamiliar instructions, I like to write a small program and let the PLC run. Then modify the conditions one by one, observe the results of the operation (MicroWin provides users with very good monitoring methods), and then re-understand the description of the manual, so that you can understand the role and use of these instructions very intuitively. Don't worry about any problems with the program you write, which will affect the normal operation of the PLC. Whether there is a problem with the program can only be discovered by running the PLC.

Finding and solving problems is the improvement of one's ability. Putting aside the hardware operation, I have never encountered a PLC damaged by software problems. There is no need to worry about the consequences of connecting the relay circuit incorrectly. Therefore, bold practice is the only way to program PLC. Of course, bold practice is not barbaric operation, but must follow the necessary specifications. Another thing to note is that before the reliability of the program is confirmed, do not connect the load to avoid unnecessary losses. The output of digital quantity has LED display; while analog quantity processing can be solved by some hardware or software simulation methods.

3. Learning PLC programming requires careful logical thinking

Programming itself is a logical thinking process. In high-level languages, the most commonly used are conditional judgment statements such as if then else and select, which are the cause and effect relationships in logic. PLC programs are composed of these cause and effect relationships: judging whether the conditions are met, and then deciding to execute the corresponding instructions. The original PLC was used to replace the relay logic circuit, so it inherited the description method of the relay circuit using contacts as trigger conditions.

In PLC, virtual contacts replace the metal contacts of relays, while the logical relationship expressed by the relay circuit is completely preserved. Even if the numerical processing process that relay circuits are not competent for is introduced, PLC is still fundamentally executing cause-and-effect relationships. Therefore, it is necessary to carefully prepare before programming to sort out the logical relationship between the various events of the object. After receiving a task, the first thing I do is to sort out a logical relationship diagram, discuss it repeatedly with the user, obtain the user's approval, and then really enter the program writing process.

4. Learn the indispensable knowledge of PLC

The PLC program directly affects the specific process of the object, so it is very important to understand the specific process of the object. In the process of communicating with users, I will use the knowledge of Unit Operation that I have mastered to analyze the user's process and help users organize the various logical relationships in process control, even including the configuration of various instruments and hardware.

5. Learning PLC requires developing good programming habits

Everyone has different programming habits and characteristics, and we cannot force them to be the same. However, some good habits should be followed by most people. First, sort out the logical relationship and timing relationship, and compile a program flowchart; second, reasonably allocate the main program, subroutine and interrupt program; third, reasonably allocate registers and compile a register symbol table.

Finally, PLC provides a wealth of instructions and modules, which is much more convenient than single-chip microcomputers. However, beginners should try to use simple instructions to achieve their goals when programming. Although it looks a bit rustic, it is still a good way to get started, and it will help you understand those more complex instructions. After you have a certain amount of experience, you should consider mastering the application of complex instructions and optimizing the program.