1. What is PLC?
PLC control system, Programmable Logic Controller, programmable logic controller, a kind of electronic device for digital operation planned for industrial production, it uses a kind of programmable memory, which is used to store programs internally, perform logic operations, sequence control, timing, counting and arithmetic operations and other user-oriented instructions, and control various types of machinery or production processes through digital or analog input/output. It is the core part of industrial control.
Second, the usefulness of PLC
1. It is used for switching control
The ability of PLC to manipulate switching quantities is very strong. The number of points in and out of the control, less than a dozen points, dozens of points, more can be hundreds, thousands, and even tens of thousands of points, because it can be networked, the number of points is simply unlimited, no matter how many points can be controlled, the logical problems manipulated can be so varied: combination, timing, immediate, delayed, no need to count, demand counting, fixed order, random operations, etc., can be carried out.
The hardware structure of the PLC is variable, and the software program is programmable, which is very sensitive when used for control. If necessary, multiple sets or groups of programs can be written and called according to requirements. It is very suitable for the needs of multi-working conditions and multi-condition replacement in industrial sites. There are many examples of switching quantity control with PLC, metallurgy, machinery, light industry, chemical industry, textile, etc., and it is simply used in all industrial occupations. At present, the first goal of PLC, which cannot be compared with other controllers, is that it can be easily and reliably used for the control of switching quantities.
2. It is used for analog control
Analog quantities, such as current, voltage, temperature, pressure, etc., vary in size one after another. Industrial production, especially in successive production processes, often requires the manipulation of these physical quantities. As an industrial control electronic device, if PLC cannot control these quantities, it is a big shortage, so PLC manufacturers have carried out a lot of development in this regard. At present, not only large and medium-sized machines can be operated in analog quantities, but also small machines can also be operated in this way.
3. It is used for sports control
The actual physical quantity, in addition to the switching quantity, the analog quantity, and the motion control. For example, the displacement of machine tool components is often expressed as a digital quantity. Movement manipulation, the useful method is NC, which stands for Digital Manipulation Skill. This is a computer-based control skill born in the United States in the 50s. It's ubiquitous and perfect today. At present, the proportion of metal cutting machine tools in advanced countries has exceeded 40%-80%, and some are even higher. PLC is also based on computer skills and is becoming more and more perfect. The PLC can accept counting pulses with frequencies up to a few ks to tens of kHz, and can be accepted in a variety of ways, as well as in multiple ways. Some PLC also has pulse output function, pulse frequency can also reach tens of k, with these two functions, plus PLC has data processing and computing ability, if equipped with the corresponding sensor (such as rotary encoder) or pulse servo device, it can be completely in accordance with the principle of NC to complete all kinds of control.
4. For data collection
As PLC skills develop, their data storage areas are getting bigger and bigger. For example, the PLC of Devison company can reach 9999 words in its data storage area (DM area). Such a large data store is capable of storing a large amount of data. Data collection can be used to record the number of collected pulses with a counter and transfer them to the DM area at regular intervals. Data collection can also be done in A/D units, where analog quantities are converted into digital quantities and then transferred to the DM area at regular intervals. The PLC can also be equipped with a small printer to type out the data in the DM area on a regular basis. The PLC can also communicate with the computer, and the computer will read out the data in the DM area, and the computer will process the data. At this point, the PLC becomes the data terminal of the computer. Power users have used LS power production PLC to record the electricity consumption of users in real time, so as to complete the charging methods of different electricity consumption times and different pricing, and encourage users to use more electricity when the electricity consumption is low, so as to achieve the purpose of reasonable electricity consumption and electricity saving.
5. It is used for signal monitoring
There are many PLC self-test signals and many internal components, and most users do not make full use of their effects. In fact, it can be used to monitor the operation of the PLC itself, or to monitor the control object. For a complex control system, especially the automatic control system, it is necessary to monitor and further self-diagnosis, which can reduce the failure of the system, find the fault, improve the cumulative mean trouble-free operation time, reduce the fault correction time, and improve the reliability of the system.
6. It is used for networking and communication
PLC networking and communication capabilities are very strong, and new networking structures are constantly being introduced. The PLC can be connected to the personal computer for communication, and the computer can be used to participate in the programming and control of the PLC, making the PLC more convenient. In order to give full play to the effect of the computer, one computer can be implemented to control and handle multiple PLCs, up to 32 sets. It is also possible for one LS PLC to communicate with two or more computers to exchange information to complete the monitoring of the PLC control system. PLC and PLC can also communicate, one-to-one PLC communication, several PLC communication, more than tens, hundreds.
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