PLC : Understand WHY?

PLC is short form of Programmable logic controller. It is a rough & tough computer which is used in industry where desktop computer cannot operate. PLC is an important component in automating processes and controlling systems. 

•PLC are small and large size as well. From 10 I/O ports to 1000 I/O ports. 

•PLC replaces hard-wire relay logic systems. PLC is compact and advanced.

•PLC are programmed for an operation. Earlier programmed in Ladder logic, few in Instruction List. Both of which are another chapter to learn PLC completely. 

•PLC runs program many times in cycles. 1 cycle = read input, execute program, give output. A PLC contains 5 major components- 1) CPU - takes input, does the required and sends output. 2) Power supply unit - converts AC from switchboard to DC for PLC operation. 3) Memory unit - stores all inputs and all programs entered. 4) I/O interface - to receive or send data to connected device 5) Communication interface - to send or receive I/O from PLC in other cities through internet.

•Two types of structure PLC is designed- 1) Brick/Box type 2) Racks/Rails type Programming Languages- Textual Languages- Structured text and Instruction list. Graphical languages- Ladder diagram, Function block diagram and sequential function chart. To understand PLC completely, its program should be written, tested and debugged. But, PLC is very costly and small errors can damage the system. For educational purpose, simulation software like PLCLogix is used.

•PLC can work in extreme surroundings with precise results. PLC replace electromechanical relay which serves as controller for electrical+ mechanical operations. 

•PLC has these built-in ports- USB, Ethernet, RS-232, RS-485 or RS-422 to connect with sensors, HMI etc. Communication is done over MODBUS or Ethernet/IP or P2P network. For humans to operate, GUI with buttons and screens are on PLC for easy operation.