Programmable Logic Controller (PLC) is a digital operational electronic system designed for use in industrial environments. It uses a programmable memory to store instructions for performing logical operations, sequential control, timing, counting, and arithmetic operations internally, and controls various types of mechanical equipment or production processes through digital or analog input and output.
The working principle of a programmable logic controller (PLC) is to use sequential scanning and continuous cycling. During the operation of PLC, it will perform periodic cyclic scanning according to the step number or address number of instructions pre programmed and stored in the program memory by the user. If there is no jump instruction, the PLC will execute the user program sequentially from the first instruction until the program ends. Afterwards, it will automatically return to the first instruction and start the next round of scanning. During each scanning process, the PLC also needs to complete key tasks such as sampling the input signal and refreshing the output status.
PLC executes instructions such as logical operations, sequential control, timing, counting, and arithmetic operations through programmable memory to achieve automated control of mechanical equipment. Its core functions include:
Logic control: replacing traditional relay circuits to achieve complex logical operations (such as AND, OR, NOT).
Sequential control: Execute multi-stage process flow according to preset steps (such as automated production line assembly).
Motion control: Control the position, speed, and acceleration of servo motors and stepper motors through pulse output or communication protocols.
Process control: PID regulation of analog quantities such as temperature, pressure, and flow rate (such as temperature control of chemical reaction vessels).
Data processing: Collect sensor data, perform calculations, and output control signals (such as quality inspection sorting).
Communication networking: Supports protocols such as Modbus, Profibus, EtherCAT, etc., enabling data exchange and remote monitoring between devices.
Power supply: Providing stable working power for PLC circuits is an important part of the entire system.