Mitsubishi Electric MELSEC iQ-F Series Training Manual page 3

Mechanism of PLC
The PLC is a microcomputer for industrial purposes.
Input devices
Limit switch
Relay contact
Toggle switch
Pushbutton switch
Power
supply
A PLC incorporates an electrical circuit mainly comprised of a microcomputer and memory.
Input/output interfaces exist between input/output devices and the electronic circuit to connect them.
The programming panel is used to write a program to the memory in the PLC.
Reference
In Japan, the term "sequencer" is widely used. While Japan Electrical Manufacturer's Association
(JEMA) officially names them Programmable Logic Controller (PLC), the name "sequencer" seems
easier to pronounce and more widely known.
Though there is evidence that the term "sequencer" was used before PLCs were invented.
Programming tool
PC
PLC
Memory
section
Memory
Processor
section
Microcomputer
The term "sequencer"
3
Programming software
GX Works3
Program creating, program
transferring, operation monitor,
forced ON/OFF and so on
Contactor
Lamp
Solenoid valve
(Solenoid valve)
Power
supply
Output
interface