PLC - PRIYA SRIVASTAVA

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Automation is a step beyond

mechanization.

Automation is the use of control

systems & information

technologies to reduce the need

for human work in the production of goods & services.

AUTOMATION

Automation Components

Sensor for sensing physical

conditions

TransmittersControl Systems

Output Devices

AUTOMATION: TYPICAL INSTALLATION

Sensors placed in the field

Junction Box

Control Hardware

SCADA Software

 Field Cabling  

COMMUNICATION CABLE

Automation : Typical installation .

PLC’s History:

• Developed to replace relays in the late 1960s.

• PLC began in the 1970s, and has become the most common choice for manufacturing controls.

• The PLC was invented in response to the needs of the American automotive manufacturing industry (primarily General motors).

• Costs dropped and became popular by 1980s.

• Now used in many industrial designs.

Programmable Logic Controllers

A PLC is a solid state / industrial

computer that performs discrete or sequential

logic in a factory environment.

It was originally developed to

replace mechanical relays, timers, counters.

A sequence of instructions is

programmed by the user to the PLC memory. Its purpose is to monitor

crucial process parameters and adjust process

operations accordingly.

It performs functions

as:

On/Off

Control

Timing

Counting

Arithmetic

PLC Saves

Material cost

Installation cost

Troubleshooting

Labor cost

Value added benefits

Reliability

Flexibility

Advanced Function Communication

Speed

Diagnostics

ByReduced wiring &

associated errors

Less spaceNo moving

parts – rugged

ADVANTAGES

Advantages of PLC’s:

-Reliable in operation.-Flexibility in programming and

reprogramming in the plant.-Online/offline modifications.-Cost effective for controlling complex

systems.-Small physical size, shorter project

time.-Speed of operation.-Ability to communicate with

computer systems in the plant.-Ease of maintenance

/troubleshooting. -Documentation.-Security.

Disadvantages of PLC’s:

Most PLCs manufacturers offer on closed

architectures for their

products .

PLC devices are proprietary

which limit the

design and cost options.

Packaging

Material Handling

Power Generation

Security Systems

Paint Lines

Bottling & Canning

Machining

Automated assembly

Water treatments

HVAC/Building Automation

Industry

Cement

Automobile

Chemicals

Plastics

Any application in any industry that requires electrical control.

APLLICATIONS

Various Brands of PLCs

Allen Bradley( USA)

Siemens (Germany)

Modicon (France)

Mitshubishi (Japan)

GE Fanuc (USA)

Programming Languages

Ladder Diagram (LD)

Functional block Diagram (FBD)

Structured Text (ST)

Instruction List (IL)

Sequential Functional Chart

(SFC)

Programming languages used to program a PLC.

• Ladder logic is the most commonly used PLC programming language.

• Ladder logic programming has been expanded to include such functions as counters, timers ,shift registers and math operations.

LADDER DIAGRAM:

. Symbols for PLC programming:

Normally Open Pushbutton

Normally Closed Pushbutton

Normally Open switch

Normally Closed switch

Normally Open contact

Normally closed contact

OPERATIONS

Each rung or network on a ladder program represents a logic operation. In the rung above, both inputs A and B must be true (1) in order for the output C to be true (1).

A B C

PLC PROGRAMMING SOFTWARE

COMPONENTS OF PLC

A. Processor.

B. Memory unit.

C. Power supply.

D. Input/Output Modules.

E. Programming device.

Major Components of a Common PLC

19

PROCESSOR

POWERSUPPLY

I MN O P D U UT L E

O M U OT DP UU LT E

PROGRAMMING DEVICE

From SENSORS

Pushbuttons,contacts,

limit switches,etc.

ToOUTPUT

Solenoids, contactors,

alarmsetc.

A. Processor:

Processor is the central processing units (CPU) of the programmable controller, it executes the various logic and sequencing functions by operating on the PLC inputs to determine the appropriate output signals.

. Field sensors: switches, flow, level, pressure, temp. transmitters, etc. Field output devices: motors, valves, solenoids, lamps, etc.

B. Memory unit:

Memory unit is connected to the CPU, which contains the programs of logic, sequencing and I/O operation.

This memory unit is referred to as the user or application memory because its contains are entered by the user and also direct the execution of control program and coordinates I/O operations with the aid of system memory.

C. Power supply:

A power supply of 120v alternating current (ac) used to drive the PLC (some units operate on 240v ac)

These low voltages are used to operate equipment that many have much higher voltage and power ratings than the PLC itself.

D. Input/Output Modules:

1) Input Module:Input to the PLC are signals come from: Limit-switchs, Pushbutton, Sensors and other on/off devices.

2) Output Module:• Outputs from the controller are on/off signals to operate: Motors, Valves, and other devices required to actuate the process

E. Programming device:

Programming device is used to entered the required program into the memory of the processor.

THANK YOU…!!!