Unintentionally saw a post in the forum "SCM can change the world." All of you are dying me and saying that I really want to ask what I am doing with industrial control. Are you all in factories? Have you seen the industrial environment? Just look at it in the surveillance room at most.
Understand the degree of industrial protection it? Understand the redundant system? What is the need to understand the industrial sector?
Real name opposition to all the above that a single-chip microcomputer can replace PLC in the industrial field, you really stay in the lab for a long time do not know outside the fog.
First, first from the basic theory, stability and reliability, you have a single-chip stability and reliability than IP67 products? Do you understand the degree of protection? Have you seen the bad industrial scene? Have you seen open field equipment operations?
After a heavy rain, wet and wet, you are sure that your microcontroller can do? The temperature below zero in the winter can you guarantee that it can run? I do not believe it.
Second, industry, such as automotive production lines, or large-scale power plant coal and other fields, sometimes hundreds of I / O sometimes thousands, you use a microcontroller to give me a look, and on the PLC this kind of sloppy goods have to Get a set of redundant systems, your microcontroller is able to letter spring brother ah or self-healing ability 100% will not die, and then you are not able to do a set of redundant microcontroller? I'll serve you, but one thing is for sure, A second seconds KO you.
Third, the control of the industrial sector is only a part of, but also need to collect, communication, host, configuration, motion control and display and other fields, these things need to rely on a complete industrial system and communication protocols to do, for example, Siemens has a set of things to achieve these Function, how do you want to microcontroller? What's the implementation of various Modbus, profibus, profinet, OPC and other things?
Fourth, the development cycle, each PLC manufacturers are constantly improving their own programming software, so that it can be more and more simple to serve the engineer, and various program blocks are also more and more convenient to humanized to call, such as PID module , motion control modules, etc., greatly reducing the pressure on the development of engineers also shortened the development cycle, microcontroller? Do you have confidence in yourself to defeat Siemens engineers?
This is something on a configuration software, how to realize the single chip microcomputer? Developed by one person? Exhausted it, the domestic motionless time is a serious shortage of time, and how PLC is highly integrated modular things are often stretched in front of the duration of the project, microcontroller development is estimated to be a year of the monkey, not to mention support for HMI, visualization The control system, hundreds of brands and hardware drivers on the market, even if you really do come and meet dozens of inverters, do you think that the microcontroller can withstand interference? When a large-scale project was completed, a high-voltage, high-power motor was used. When the system was started up, the entire power grid shuddered. The various values ​​of the SCM must not be the same as those of the Monkeys.
Fifth, the distance problem
In the industrial field, sometimes it is necessary to integrate and monitor across regions. The communication methods used are mostly Ethernet (long communication distance) plus repeaters, or direct access to civilian broadband fiber (in some cases, the distance is several kilometers and dozens of kilometers). , The things used to the end is likely to be used by Microsoft's IE browser (yes, you did not mistake, Siemens WINCC WEB), you use a microcontroller to give me a try? There is an unexpected situation, if unattended or a major accident, the need to send a text message to the relevant personnel (such as leadership) by the PLC communication module according to the situation, the microcontroller can? How long does it take for development?
Say so much, not to mention all, but can not understand those who think that use the microcontroller instead of PLC laboratory staff, really can use it, you feel that the power plant in the hundreds of thousands of sets of AB system are waste ?
Although the master chip in most PLCs is an MCU microcontroller.
The advantage of PLC is that you can use ladder diagram for secondary development. First of all, you have to make it clear that PLC is used by electrical engineers. Electrical engineers are not electrical engineers. Their job is not just to consider how your MCU drives relays to control the machine. Even some electrical engineers don't have C language or assembly language like MCU development language (how do you let people play?). A few years ago there was a guy on 21ic who wanted to develop a new PLC and use C language instead of trapezium. In the picture, he disappeared after spending a month or two on the forum.
Second, the advantage of PLC is its strong stability. You may think that the iPhone's APP suddenly flashes back and it doesn't matter. Just re-open it and it will not work. However, the equipment on the industrial site is not acceptable, and one second of the crash may be a human life...
So you want to use MCU, relays, and optocouplers as PLCs, but you don't have strict planning and design, debugging and testing, and various anti-interference test certifications. Most of them are called relay controllers, not real PLCs that can be used in industrial fields. . General industrial field equipment, after the completion of development and design, after passing the certification test, will not be modified, the subsequent mass production are produced according to the certification test of the circuit, the underlying program to modify any line of chip driver code needs Recertification.
SCM is a component, PLC is a system composed of components and a large software set. Asking the former to replace the latter is like asking: Can pork replace the Wanchai wharf pork dumpling in the freezer?
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