FBMSVH FOXBORO
In the late 20th century,the development characteristics of programmable logic controllers were more suitable for the needs of modern industry.During this period,large and ultra small computers were developed,various special functional units were born,various human-machine interface units and communication units were produced,making it easier to match industrial control equipment using programmable logic controllers
The power supply is used to convert AC power into DC power required within the PLC,and most PLCs use a switch type regulated power supply for power supply.
Central processing unit
The central processing unit(CPU)is the control center and core component of the PLC,and its performance determines the performance of the PLC.
The central processing unit(CPU)is composed of a controller,arithmetic unit,and register,all of which are concentrated on a single chip and connected to the input/output interface circuit of the memory through an address bus and control bus.The role of the central processing unit is to process and run user programs,perform logical and mathematical operations,and control the entire system to coordinate.
storage
Memory is a semiconductor circuit with memory function,which is used to store system programs,user programs,logical variables,and other information.The system program is a program that controls the PLC to achieve various functions,written by the PLC manufacturer and solidified into read-only memory(ROM),which cannot be accessed by users.
input unit
The input unit is the input interface between the PLC and the controlled equipment,serving as a bridge for signals to enter the PLC.Its function is to receive signals from the main command and detection components.The types of inputs include DC input,AC input,and AC/DC input.
output unit
The output unit is also a connecting component between the PLC and the controlled equipment.Its function is to transmit the output signal of the PLC to the controlled equipment,which converts the weak current signal sent by the central processing unit into a level signal and drives the execution components of the controlled equipment.The types of outputs include relay output,transistor output,and crystal gate output.
In addition to the above components,PLC also has various external devices according to different models,which are used to assist in programming,monitoring,and network communication.Commonly used external devices include programmers,printers,cassette tape recorders,computers,etc
