a. Power supply
The power supply of the PLC plays a very important role in the whole system. It can't work properly without a good and reliable power supply system, so PLC manufacturers also attach great importance to the design and manufacture of power supplies. Generally, the AC voltage fluctuates in the range of +10% (+15%), and the PLC can be connected directly to the AC grid without other measures
b. Central Processing Unit (CPU)
The central processing unit (CPU) is the control center of the PLC. It receives and stores the user program and data typed from the programmer in accordance with the functions given by the PLC system program; Check the status of power, memory, I/O, and alert timers, and diagnose syntax errors in user programs. When the PLC is put into operation, first it receives the status and data of each input device in the field in the form of scanning, and stores them in the I/O image area respectively, and then reads the user program one by one from the user program memory, and sends the results of logic or arithmetic operation according to the provisions of the instruction into the I/O image area or data register after the command interpretation. After all user programs have been executed, the output status of each I/O image area or the data in the output registers is transferred to the corresponding output device, and so on until the operation is stopped.
In order to further improve the reliability of PLCs, in recent years, large-scale PLCs have been used to form a redundant system with two CPUs, or a voting system with three CPUs. This way, even if one CPU fails, the entire system will still function normally.
c. Memory
The memory that holds the system software is called the system program memory.
The memory that holds the application software is called the user program memory.
d. Input and output interface circuits
1. The field input interface circuit consists of the opto-coupling circuit and the input interface circuit of the microcomputer, which is the input channel of the interface interface between the PLC and the field control.
2. The field output interface circuit is integrated by the output data register, the strobe circuit and the interrupt request circuit, and the PLC outputs the corresponding control signal to the execution component of the field through the field output interface circuit.
e. Functional module
Such as counting, positioning and other functional modules
f. Communication module
Such as Ethernet, RS485, Profibus-DP communication module, etc
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1) Hand arc welding (STICK)
Shielded Arc Welding (abbreviated SMAW) in English,
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A PLC (Programmable Logic Controller) is an electronic system designed for digital operations in an industrial environment.
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2. Regardless of the system working or shutdown, the electrical cabinet door should always be closed, and the electrical components should be kept in a good state.
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