Extended data
PLC is the abbreviation of English Planar Lightwave Circuit, and programmable logic controller is a digital operation electronic system specially designed for industrial environment applications. It uses programmable memory, which stores instructions for logical operation, sequence control, timing, counting and arithmetic operation, and controls various types of mechanical equipment or production processes through digital or analog input and output.
classify
1, integrated PLC
Integrated PLC integrates power supply CPU, input/output interface and other components into a chassis, which has the characteristics of compact structure, small volume and low price.
2. Modular PLC
Modular PLC is to make each component of PLC into several independent modules, such as CPU module, input/output module, power module (partially included in CPU module) and various functional modules.
3. Stacked PLC
The so-called stacked PLC is formed by combining the characteristics of integral PLC and modular PLC. The CPU, power supply and input/output interface of stacked PLC are also independent modules, but each module can be stacked layer by layer through cable connection. In this way, the system not only can be flexibly configured, but also has a compact structure.
Functional characteristics
1, high reliability
Because PLC mostly adopts single chip microcomputer, the integration is high, and the corresponding protection circuit and self-diagnosis function improve the reliability of the system.
2. Simple programming
PLC programming mostly uses relay control ladder diagram and command statement, the number of which is far less than that of microcomputer instructions. Except for middle and high-grade PLC, ordinary small PLC is only about 16. Because the ladder diagram is vivid and simple, easy to master and use, it can be programmed without computer professional knowledge.
3. Flexible configuration
Because PLC adopts building block structure, users can flexibly change the function and scale of control system through simple combination, so it can be applied to any control system.
4. The input/output function module has been completed.
One of the biggest advantages of PLC is that it has corresponding templates for different field signals (such as DC or AC, switching value, digital or analog value, voltage or current, etc.). ), which can be directly connected with industrial field equipment (such as buttons, switches, induced current sensors, motor starters or control valves, etc.). ) and connected to the CPU motherboard through the bus.
5, easy to install
Compared with the computer system, the installation of PLC requires neither a special computer room nor strict shielding measures. When in use, it only needs to correctly connect the detection device with the I/O interface terminals of the actuator and PLC, and it can work normally.
6, the running speed is fast
Because the control of PLC is executed by program control, its reliability and running speed are incomparable with relay logic control.