PLC Ladder Diagram Basics

What is a  PLC Ladder Diagram?

A Ladder diagram is a symbolic and schematic representation of both the process hardware and process control. It is  called a ‘Ladder’ because all the devices are connected across the supply lines making it look like a ladder.Each parallel connection is called a ‘Rung’, it can contain many inputs but only one output.

Logic Symbols:

A PLC can do Mathematical Instruction as well as Data handling Instructions also.

Math Instructions are:
a)   ADD: addition
b)  SUB: subtraction
c)   DIV: division
d)  DDV: double division
e)   CLR: clear
f)    SQR: square root

Data handling Instructions are:

a)   MOV: move
b)  MVM: masked move
c)   AND: AND gate Operation
d)  OR: OR gate Operation
e)   XOR: Exclusive OR gate Operation
f)    NOT: NOT gate Operation
g)  NEG: Negate

For power point presentation please visit:
http://www.slideshare.net/sdd2311/plc-ladder-diagram

Programmable Logic Controller

Definition

A PLC is a digitally operational electronic equipment which uses programmable memory of internal storage of instructions to implement a specific function.

The PLC Processor

The processor is programmable, and since it can perform many logic and arithmetic functions its also known as the Microprocessor.

Its classified as per bit size and clock speed

 

 

The bit size determines the no. of bits of data the microprocessor can manipulate and clock speed determines the speed of execution of the instruction.

The ROM with fixed operating system program interfaces to the control section. It manages the operation of the PLC.

The Control Section, contains a Control unit with storage registers. The Control Section determines which operating sections are to be functional, in what order and for how long.

The I/P Scan block, scans the I/Ps and places the I/p statuses in the Ram Memory, when required to do so.

After analysis the Logic Scan updates the O/P Scan Block to the Appropriate state and changes the O/P respectively.

The O/P Scan Block then scans the O/P and updates their statuses in the RAM.

:::::To view the powerpoint presentation visit

 http://www.slideshare.net/sdd2311/programmable-logic-controller-29752693