Advantages of PLC and MCU and learning precautions

     There are many brands of PLC products on the market now, the most common ones are: Siemens, Omron, Mitsubishi, Delta, etc. The working principles of PLC are similar, but I think the only flaw is that the programming software is different, and the meaning of program instructions of each brand is different; even if you learn how to program Siemens S7-200 PLC, you can't program Siemens S7-300 PLC. Because S7-200 PLC and S7-300 PLC are products of the same company, the programming methods of the same products are very different, not to mention different brands. Because I have played more with Siemens S7-200 PLC, I will mainly talk about my learning experience for this series of products (in the form of questions). These questions are the questions I usually think about.

      1. In what occasions can plc better reflect its advantages? I think: a. Because plc has communication function and operation function, it is suitable for networking with the host computer to build an intelligent control system or real-time monitoring unit. On this basis, it is better if it is equipped with configuration software; so the application rate of plc in large assembly lines and numerical control devices is very high. As far as I know, the price of Siemens plc is at least more than one thousand yuan, so when designing circuit hardware, it is best not to use plc where it can be used, based on cost considerations. Many equipment in our unit, such as driving machines, car washing machines and other simple equipment, are actually equipped with plc control. There is no need to use plc to control such equipment composed of simple contact circuits, except for increasing costs. There is no benefit! b. plc is more suitable for industrial occasions with harsh environments, because plc has a photoelectric isolation modular design with strong anti-interference ability and safety. In industrial sites, the anti-interference ability of intelligent equipment directly determines the working reliability, stability and safety indicators of this equipment!

     2. What are the advantages of PLC over MCU or embedded system board? I think: a. PLC's anti-interference ability is definitely stronger than MCU or embedded system board. b. MCU or embedded system board generally has very powerful software redevelopment function, and generally has many AD or DA or PWM functions; for those who are proficient in C language, they can use MCU or embedded system board with many kinds of hardware to achieve many different functions! For example: MCU or embedded system board can be used with temperature and humidity chip or MP3 or MP4 chip or LCD display and other hardware expansion, which PLC cannot match.

     3. What issues should be paid attention to in PLC learning? I foolishly thought: the purpose of all learning is to apply it to practical work. At the beginning, I thought that as long as I learned the meaning of various ladder diagram instructions of Siemens PLC, the programming methods and the use of programming software, I could use PLC to do some practical activities. In fact, it’s wrong! How to connect the power supply of PLC and the power supply of IO port? How to use the expansion module? How to wire the IO port? How to make full use of the powerful function of step7 programming software to debug the program? How can a laptop computer communicate effectively with PLC? How to program when PLC is used with configuration software? Which IO ports have high-speed input and output functions? And so on, these problems are all problems that must be understood and learned in reality, otherwise it is impossible to use PLC to do projects. These problems are real problems encountered by me in practice, and they cannot be experienced without personal experience!

 

      Experience: Practice makes perfect! On the basis of practice, we should strengthen theoretical learning. Only by combining theory with practice can we improve our ability to deal with problems!