TELCO optical sensor LR101TB255

TELCO optical sensor LR101TB255

PLC, also known as Programmable Logic Controller, is a digital operational electronic system specifically 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.

PLC programming is an electronic system for digital operations, designed specifically for use in industrial environments. It uses programmable memory to store instructions for performing logical operations, sequential control, timing, counting, and arithmetic operations internally, and controls various types of machinery or production processes through digital and analog inputs and outputs. Programmable controllers and their related devices should be designed according to the principle of easy integration of industrial control systems and easy expansion of their functions.

With the rapid development of microprocessors, computers, and digital communication technology, computer control has expanded to almost all industrial fields. Modern society requires the manufacturing industry to respond quickly to market demand, producing small batches, multiple varieties, multiple specifications, low-cost, and high-quality products. In order to meet this requirement, the control systems of production equipment and automatic production lines must have reliability and flexibility. PLC programming emerged in response to this requirement, and it is a general-purpose industrial control device based on microprocessors.

PLC works in a "sequential scanning, continuous cycling" manner. When the PLC is running, the CPU compiles a program stored in the user's memory according to the user's control requirements, and performs periodic cyclic scanning according to the instruction step number (or address number). If there is no jump instruction, the user program is executed sequentially from the first instruction until the program ends, and then returns to the first instruction to start the next round of scanning. During each scanning process, the CPU also completes tasks such as sampling the input signal and refreshing the output status

A scanning cycle of PLC must go through three stages: input sampling, program execution, and output refresh.

In the input sampling stage of PLC, the on/off status or input data of all input terminals temporarily stored in the input latch are first read in sequence in a scanning manner, and written into the corresponding input status registers, that is, the input is refreshed, and then the input port is closed, entering the program execution stage.

During the program execution phase, PLC scans and executes each instruction in the order in which the user program instructions are stored. After corresponding operations and processing, the results are written into the output status register, and all contents in the output status register change with the execution of the program.