PLC: Programmable Logic Controller.
PLC is a kind of digital operation electronic system specially designed for application in industrial environment. It uses a programmable memory to store instructions to perform logical operations, sequential control, timing, counting, and arithmetic operations, and to control various types of mechanical equipment or production processes through digital or analog inputs and outputs.
So in the industrial field with embedded, or with programmable logic controller (PLC)?
I. Suitable for embedded occasions
If you pay close attention to the words, if the mass production of standard industrial products, and the need for some complex calculations, then, usually use the embedded system. For example, frequency converter, standard industrial robot, some specialized equipment and so on.
Some products are mass-produced, the beginning of the use of embedded systems to specialize in research and development, you need to invest a certain amount of financial resources and manpower to do research, debugging and so on. Once the research and development is successful, the beginning of the research and development costs will be directly apportioned to the later mass production of each individual product, which will make the entire product research and development costs greatly reduced. If only mass production equipment, it should be said that embedded than PLC hardware costs are much cheaper.
In addition, many scenarios, with PLC is not ideal, such as some products require a large number of complex operations, such as inverters within the calculation of a large number of motor drag and control algorithms, such as automated handling robots SLAM navigation algorithms, etc., is only suitable for high-performance embedded operators to realize the PLC can not be calculated so complex algorithms.
Moreover, some occasions can not use PLC, such as inverter or a compact industrial equipment, although the PLC can be realized, but the volume is where it is placed, at least need a voltage regulator module, at least need a few input and output modules, at least need a communication module, so much stuff if stuffed into a standard compact industrial equipment, the appearance of looking at the unreasonable.
Again, is a standard industrial product, if only the PLC to control, that is usually a very large number of competitors of similar products, if the embedded system to do, relatively speaking, competitors to be less. Is also a side note, PLC control system is easy to copy, at least open the control cabinet to know how you do the control system, a few input and output modules, the external are connected to what sensors and so on. Embedded systems to designers to design their own peripheral integrated circuits, relatively speaking, to do a better job of protection.
A high value-added industrial equipment, if only PLC control to achieve, if the competitors are few, it must not be their control system to do with others have a big gap, the advantage must be in the mechanical structure, or patent protection, or understanding of the process. The control system must be embedded system control system, often its own control technology content is high, the algorithm is more complex, embedded systems contain embedded program is very valuable, there are certain technical barriers.
II. Suitable for occasions with PLC
The reality of a variety of industrial equipment to be put into specific project applications to try, and when it comes to the project that is very different. What is the most important requirement to do industrial projects, I believe that people engaged in industrial control must know, that is, "stable".
We can look at, but all do PLC companies, certainly no small companies, their PLC products must be very best-selling, and in all areas of the industry will be applied to, countless cases, PLC can appear in the transmission and distribution network road control system, can appear in the automatic three-dimensional warehouse stacker, can appear in the petrochemical industry, a piece of equipment, but also in the steel industry, the steel rolling control system. In the steel industry, it can also be found in the steel rolling control system. And this one project has helped other users to verify the stability of the PLC how good.
At the same time PLC to promote stability, but also specifically designed a module, a module out of the problem, just need to change a new one can be, the system can continue to use, the replacement speed is also very fast.
Imagine if a company won the bid to do a project, the deadline is 100 days, if the group A embedded way to develop control systems, then they are in the research and design to draw circuit boards, the PLC way the group B has begun to buy back the PLC module to write the control ladder diagram. And this does not even count the embedded system to do what way to control the output and through what coupling circuit to capture the input of the field, and these for the PLC, nothing to do, they need to do is just to the PLC manufacturer to select the appropriate module according to the need to insert into their own cabinets can be.
In addition, if the duration is long enough to use the embedded system is finally developed in a high-tech posture, the next time the project was awarded a bid is completely different process layout, then the embedded system should also be scrapped this time in a high profile, because there is no generality.
Furthermore, even if the embedded system is developed, the system is the first time the world, after the system who can guarantee that there will be no problem. Once the problem how to get, the control system completely replaced? If the designer who designed the embedded system has changed jobs, then what to do? And the above said PLC only need to do is to buy another module to replace the previous.
III. Summarize
In short, the use of PLC or microcontroller, according to the actual situation to choose, can not just look at the function can not be realized.