The following introduces several characteristics of PLC programming:

1. Programming method is easy to understand, easy to learn

Ladder diagram is the most used programming language of PLC. Its circuit symbol and expression are similar to relay circuit schematic diagram. Ladder diagram language is visual and easy to learn. It only takes a few days for electrical technicians who are familiar with relay circuit diagram to be familiar with ladder diagram language and use it to compile user program.

Ladder diagram language is actually a high-level language for users. When PLC executes ladder diagram program, it will be translated into assembly language and then executed.

2. Complete hardware, user-friendly, adaptable

PLC products have been standardized, serialized, modular, equipped with a full range of hardware devices for users to choose, users can flexibly and easily configure the system to form different functions, different scales of the system. The installation and wiring of PLC is also very convenient. Generally, terminals are used to connect external wiring. PLC with load capacity, can directly drive the general solenoid valve and small and medium AC contactor.

After the hardware configuration is determined, by modifying the user program, it can quickly adapt to the changes of process conditions.

3. Strong function, high performance price ratio

There are hundreds of programming elements in a small PLC which can be used by users. It has strong functions and can realize very complex control functions. Compared with the relay system with the same function, it has a high performance price ratio. PLC can realize decentralized control and centralized management through communication networking.

4. The workload of system design, installation and debugging is less

PLC replaces a large number of intermediate relays, time relays, counters and other devices in the relay control system with software functions, which greatly reduces the workload of design, installation and wiring of the control cabinet.

The ladder program of PLC can be designed by sequential control design method. This programming method is very regular and easy to master. For complex control system, if we master the correct design method, the time of designing ladder diagram is much less than that of designing relay system circuit diagram.

The user program of PLC can be simulated and debugged in the laboratory. The input signal is simulated by a small switch, and the state of the output signal can be observed through the LED of PLC. After the installation and wiring of the system, the problems found in the process of on-site unified debugging can be solved by modifying the program, and the debugging time of the system is much less than that of the relay system.

5. High reliability and strong anti-interference ability

Traditional relay control system uses a large number of intermediate relays and time relays. Due to the poor contact of the contact, it is easy to have faults. PLC uses software to replace a large number of intermediate relays and time relays, leaving only a small number of hardware components related to input and output. The wiring can be reduced to one tenth to one percent of the relay control system, and the faults caused by poor contact are greatly reduced.

PLC uses a series of hardware and software anti-interference measures, has a strong anti-interference ability, the average time between failures reaches tens of thousands of hours, can be directly used in industrial production site with strong interference, PLC users recognized as one of the most reliable industrial control equipment.

6. Small size, low energy consumption

For complex control system, the use of PLC can reduce a large number of intermediate relays and time relays. The volume of small pic is only equivalent to the size of several relays, so the volume of switch cabinet can be reduced to the original 1 / 2 ~ 1 / 10.

The wiring of PLC control system is much less than that of relay control system, so it can save a lot of wiring and accessories, reduce a lot of installation and wiring time, and reduce the volume of switch cabinet, which can save a lot of costs.

7. The maintenance workload is small and the maintenance is convenient

The failure rate of PLC is very low, and it has perfect self diagnosis and display function. When the PLC or the external input device and the actuator fail, the cause of the failure can be easily found out according to the information provided by the LED or programmer on the PLC, and the failure can be quickly eliminated by replacing the module.

PLC programming is widely used, powerful and easy to use. It has become one of the main devices of modern industrial automation. It has been widely used in all fields of industrial production, and has been rapidly developed in other fields (such as civil and home automation).

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