Programmable Logic Controller-GIC India
The programmable logic controller is an industrial solid-state computer that monitors inputs and outputs and makes logic-based decisions for automated processes or machines.
Initially, industries used relays to control the manufacturing processes. The relay control panels had to be regularly replaced, consumed a lot of power and it was difficult to figure out the problems associated with it. To sort these issues, the Programmable logic controller (PLC) was introduced.
Input Module: Inputs are data given to PLC, classified in
Digital IP: Switch, Push Button, Proximity Sensors, etc which gives input of either 1 or 0 to PLC
Analog IP: Every analog sensor like Temperature, weight, distance, etc which gives analog data to PLC
Output Module: Output from PLC, classified in
Digital op: output signal either 1 or 0
Analog op: the variable output of 0 to 12 VDC or 4mA to 20mA DC.
CPU:
This component act as the brain of the system. CPU consist of Arithmetic Logic Unit, Program memory, Process image memory, Internal timers and counters, flags
It receives information from the I/P device, makes decisions depending upon the information and logic written and sends information through the O/P devices.
Power Supply: Certain PLCs have an isolated power supply. But, most of the PLCs work at 220VAC or 24VDC.
Memory: Stores the information about the status of input and output devices, and the values of timers, counters, and other internal devices.
Programming Device (Computer): This device is used to feed the program (logic) into the memory of the plc. First, we make a program in certain PLC software then we download it to PLC.
PLC Programming: It is a logic we make in Computer in PLC software. Based on that logic & conditions PLC gives output.
Most commonly used programming language is Ladder diagram (LD) also known as Ladder logic
Here the input is push button & output is light, so when PB is pressed due to the logic of PLC light will be turned ON.
PLC can be used in almost all industrial application solutions right from small machines to large manufacturing plants. Even it caters applications of redundant systems at critical process plants.
They are fast and designed for the rugged industrial environment.
Easy to change logic i.e. flexibility
Low power consumption
They are attractive to Cost-Per-Point Basis.
Analog signal handling and closed-loop control programming
Reliable due to the absence of moving parts
Easy to couple with the process computers
Counter, timer and comparator can be programmed
Capable of handling very complicated logic operations
Flexibility: One single PLC can easily run many machines.
