Programmable logic controller
Programmable logic controller
Scope of application ：
Programmable logic controller (PLC) is a digital operation electronic system specially designed for industrial applications.
product details
Basic structure:
1)power supply
The power supply is used to convert alternating current into the direct current needed in PLC.
(2)central processing unit(CPU)
The CPU is the control center of PLC,and also the core component of PLC.Its performance determines the performance of PLC.
The CPU consists of a controller,an arithmetic unit,and a register.These circuits are concentrated on a single chip and are connected to the input/output interface circuits of the memory via the address bus and the control bus.The role of the CPU is to process and run user programs,perform logical and mathematical operations,and control and coordinate the entire system.[4]
(3)storage
Memory is a semiconductor circuit with memory function.Its function is to store system programs,user programs,logic variables and other information.Among them,the system program is the program that controls PLC to realize various functions,written by PLC manufacturer,and solidified to read only memory(ROM),the user cannot access.[4]
(4)input unit
The input unit is the input interface between PLC and the controlled equipment,and it is the bridge for the signal to enter PLC.The types of input are dc input,ac input and ac-dc input.[4]
(5)output unit
The output unit is also the connecting part between PLC and the controlled device.Its function is to transmit the output signal of PLC to the controlled device,which converts the weak current signal sent by the CPU into level signal and drives the executive component of the controlled device.Output types are relay output,transistor output,crystal gate output.
PLC in addition to the above several parts,according to the different types of external equipment,its role is to help programming,monitoring and network communication.Commonly used external equipment programming,printers,cassette tape recorders,computers,and so on.
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