What are the points of plc compared with relay control system?

Traditional relay control systems use a large number of intermediate relays, time relays due to poor contact, easy to fail, PLC software instead of a large number of intermediate relays and time relays, leaving only a small amount of hardware related to inputs and outputs, wiring can also be reduced! Plus the advantages of the PLC itself, so now more and more instead of the original relay control system! PLC relative to the advantages of the relay line 1, strong function, high performance-price ratio of a small PLC within the hundreds of programming elements available to the user, there are very strong functions, can achieve very complex control functions. Compared with the same function of the relay, has a high performance-price ratio. Programmable controllers can be networked through communication to achieve decentralized control, centralized management. 2, complete hardware, user-friendly, adaptable programmable controller products have been standardized, serialized, modular, equipped with a full range of hardware devices for users to choose from. Users can flexibly and conveniently configure the system to form a different function, not the size of the system. The installation and wiring of the flute programmed controller is also very convenient, generally use the terminal block to connect the external wiring.PLC has a strong load capacity, can directly drive the general solenoid valves and AC contactors.3, high reliability, anti-interference ability of the traditional relay control system uses a large number of intermediate relays, time relays. Due to poor contact, prone to failure, PLC software instead of a large number of intermediate relays and time relays, leaving only a small amount of hardware related to inputs and outputs, wiring can be reduced to mutual relay control system 1/10-1/100, due to poor contact failure caused by a significant reduction in the PLC has adopted a series of hardware and software anti-interference measures, with strong anti-interference capability. PLC has a strong anti-interference ability, the average failure-free time of tens of thousands of hours or more, can be directly used in industrial production sites with strong interference, PLC has been recognized by the majority of users as one of the most reliable industrial control equipment. 4, system design, installation, commissioning workload is less PLC with software functions to replace a large number of relay control system in the intermediate relay, time relay, counter and other devices to make the control cabinet design, installation, wiring and commissioning workload is less. Control cabinet design, installation, wiring workload is greatly reduced.PLC ladder program is generally used in the sequence control design method. This programming method is very regular and easy to master. For complex control systems, the ladder diagram design time is much less than the design of relay system circuit diagrams.PLC user programs can be simulated in the laboratory debugging, input signals with small switches to simulate, through the PLC on the light-emitting diode can be observed through the status of the output signal. After completing the installation and wiring of the system, the problems found in the field of the unification process can be solved by modifying the program, the commissioning time of the system is much less than the relay system. 5, the programming method is simple ladder diagram is the most used programmable controller programming language, its circuit symbols and expressions and relay circuit schematic diagrams are similar to the ladder diagram language image is intuitive and easy to learn and understand, familiar with the relay circuit diagram of the electrical technicians. Relay circuit diagrams familiar with the electrical technicians as long as a few days to familiarize with the ladder diagram language, and used to prepare user programs. Ladder language is actually a user-oriented high-level language, programmable controller in the implementation of the ladder program, with the interpretation of the program will be "translated" into assembly language and then go to the implementation of the 6, maintenance workload, maintenance is convenient PLC's failure rate is very low, and there is a perfect self-diagnostics and display functions. PLC or external input devices and actuators failures, according to the PLC on the light-emitting diode or programmer to provide the residence of the rapid identification of the cause of the failure, with the replacement of the module can be quickly troubleshooting. 7, small size, low energy consumption for complex control systems, the use of PLC, you can reduce a large number of intermediate relays and time relays, the volume of the small PLC is equivalent to a few relay size, so you can switch the switchgear cabinet, the size of the intermediary relays and time relays. The size of a small PLC is equivalent to the size of several relays, so the volume of the switchgear can be reduced to the original indeed 1/2-1/10. PLC wiring than the relay control system wiring is much less, so you can save a lot of wiring and accessories, reduce the installation of a large number of wiring hours, you can reduce the cost of a lot of money.