The programmable controller is developed from the relay […]
The programmable controller is developed from the relay control system. Due to the application of microprocessor and electronic technology, PLC has the following characteristics:
1.High reliability PLC adopts many anti-interference measures, such as electromagnetic shielding of CPU module, setting filter circuit in power circuit and I / O module, using optical isolation in input and output circuits, and using centralized sampling and centralized output when working A series of software and hardware anti-interference measures, so it has a strong anti-interference ability and can work reliably in harsh environments. In addition, compared with the relay control system, the PLC has less hard wiring, which greatly reduces the failure rate. The average MTBF of a general PLC can reach more than 50,000 hours. At the same time, the PLC also has a perfect self-diagnostic function. Once a fault occurs, it can be quickly and accurately found, reducing downtime.
2. Powerful PLC not only has the functions of switch value control, analog value control, arithmetic operation, data communication, interrupt control, etc., but also can easily expand the function and capacity. It can expand the number of input and output points and increase according to the needs of industrial control. control function.
3. Simple programming and easy to use. PLC provides a variety of user-oriented programming languages. Ladder diagrams, instruction statements, and function diagrams are commonly used. The ladder diagram language is similar to the electrical schematic diagram of the relay control system. This programming language image Intuitive, no special computer knowledge is needed, as long as you understand the principles of electrical control, you can easily master it. When the control process needs to be changed, the program can be modified with a handheld programmer or on a personal computer, and debugging and online modification can be performed on site. The running process can be monitored directly on the computer screen.
4. Small size and compact structure Due to the application of integrated circuits, the structure is compact, the volume is small, and it is easy to install in the machinery and equipment, so it has become the main control equipment for mechatronic products and industrial automatic control. 5. The programming language has not been unified. Although the programmable controllers produced by various manufacturers use the ladder diagram language for programming, the functions are similar, but each manufacturer has adopted its own instruction system, which has not yet reached a complete uniformity, which gives users to use different brands. PLC brings a lot of inconvenience.