The document discusses programmable logic controllers (PLCs). It defines PLCs as digital electronic devices that use programmable memory to store instructions to control machines and industrial processes (sentence 1). PLCs were invented to replace sequential relay circuits for machine control and are now widely used for automation in factories, amusement rides, and other industrial applications (sentences 2-3). The document then provides details on the history and development of PLCs, their basic components and functions, programming methods, applications, advantages and disadvantages (sentences 4-15). It concludes by discussing trends in PLC usage, such as their suitability for hazardous environments and the growing market for programmable automation controllers (sentences 16-18).

1. Presented by:
Debdatta Naskar
EE 3rd year

2.  The programmable logic controller is defined as a digital electronic device
that uses a programmable memory to store instructions and to implement
functions such as logic, sequencing, timing, counting and arithmetic words to
control machines and processes.
 A PLC is a digital computer used for automation of typically
industrial electromechanical processes, such as control of machinery
on factory assembly lines, amusement rides, or light fixtures.
 PLC was invented to replace the necessary sequential relay circuits for
machine control.

3.  In 1968, the hydrometric division of the General Motors Corporation
specified the design criteria for the first programmable controller and it was
invented by Dick Morley.
 In 1974, hardware CPU controller, with logic instructions, memory and I/O
points was developed.
 In 1977, microprocessors- based PLCs were first introduced,

4. It processes the information
collected from measurement
system and takes logical decisions
based on the information. Then
it sends this information to
actuators or output devices.
It stores.
a. the input data collected from
sensors
b. the programs to process the information and to take necessary decisions or actions. Program is
a set of instructions written for the processor to perform a task.
These are used to communicate with the outside world.
PROCESSOR
MEMORY
INPUT/OUTPUT DEVICES

5. Step 1 - CHECK INPUT STATUS-First the PLC takes a look at each input to determine if
the sensor connected to all the inputs are on and records this data into its memory to be
used during the next step.
Step 2 - EXECUTE PROGRAM-Next the PLC
executes the program one instruction at a
time. Since it already knows which inputs are on/off
from the previous step it will be able to decide
whether the output should be turned on based on the
state of the input. It will store the execution results
for use later during the next step.
Step 3 - UPDATE OUTPUT STATUS-Finally the PLC updates the status of the outputs based on
which inputs were on during the first step and the results of executing the program during the second
step.
CHECK INPUT STATUS
EXECUTE PROGRAM
UPDATE OUTPUT STATUS

6.  The most widely used form of PLC programming is called ladder logic.
 Ladder logic uses symbols, instead of words, to emulate the real world relay
logic control. These symbols are interconnected by lines to indicate the flow
of current through relay like contacts and coils.
 The left and right rails indicate the positive and ground of a power supply.
The rungs represent the wiring between the different components.
 The completed program is downloaded from the PC to the PLC using a special
cable that’s connected to the CPU. The CPU is then put into run mode so that
it can start scanning the logic and controlling the outputs.

7. P L C
INDUSTRIAL FIELD TRANSPORT:
ESCALATOR, LIFT,
MONITORED SAFETY CONTROL
SYSTEM
MANUFACTURING
INDUSTRY (LEAD- ACID
BATTERY PLANT,
EXTRUDER FACTORY)
PRINTING INDUSTRY
(OFFSET WEB PRESS
PRINT REGISTER
CONTROL, MULTISTAGE
SCREEN WASHING)
TEXTILE INDUSTRY (INDUSTRIAL
BATCH WASHING MACHINE
CONTROL, CLOSED LOOP TEXTILE
SHRINKAGE SYSTEM)
AGRICULTURAL:
GLASSHOUSE HEATING,
VENTILATION &
WATERING SYSTEM
IMAGE PROCESSING TENSION CONTROL IN CABLE LINE
CONVEYOR BELT

9. • Cost effective
• Flexibility and ability to use similar system for other processes.
• Programming interface is easier in comparison to other processers
• Resistant to impact and vibration
• Resistant towards electrical and mechanical noise
• Ability to work at high temperatures
• There's too much work required in connecting wires.
• There's difficulty with changes or replacements.
• It's always difficult to find errors; And require skilful work force.
•When a problem occurs, hold-up time is indefinite, usually long.

10.  PLCs are most easier and safe control system for industrial applications like toxic Chemical
substances spraying and skyscraper’s glass washing using robot.
 PLCs will continue to experience growth as robust, emerging economies to create buoyant demand
for increasing automation.
 The market is demanding the programmable automation controller (PAC), a multi-disciplined
controller capable of providing real-time logic, motion and process control, in addition to HMI and
other functions, on a single platform.
 The PLC-based PAC market growth is expected to be higher than the overall PLC market.
 In the upcoming future, PLCs continue to be the best option for a variety of industrial
automation applications.