Programmable Logic Controller

UNIT-IV
PROGRAMMABLE LOGIC
CONTROLLER
PRESENTED BY
S.VALAI GANESH M.E-CAD/CAM
RAMCO INSTITUTE OF TECHNOLOGY

Introduction –
Basic structure
Input and
output
processing
– Programming
Mnemonics –
Timers, counters &
internal relays
Data handling
Selection of PLC
SOME PRACTICAL
EXERCISES
01
02
03 04
SYLLABUSPLC

INTRODUCTION
A programmable Logic Controller (PLC) 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 in order to control
machines and processes
SYLLABUS
01
PLCInput from
devices
Output to
devices
Control
Program

INTRODUCTION
INPUT DEVICES
Inputs are real world signals giving the controller
real time status of variables. These variables may be in the
form of Analog or Digital.
Typical Analog inputs like limit switch, thermocouple,
transducer, flow, pressure, strain gauge are converted into
binary signals.
CPU
CPU electronically scan the control plan logic stored
in memory along with the status of input. It then executes a
specified command to the appropriate output.
In addition to this it performs timing, counting,
sequencing, latching, comparing and storage operation.
01
SYLLABUS

MEMORY
The basic memory unit is word. Memory sizes from
256 words to 192K words. There are two types of memory
used. They are Volatile memory and Non Volatile memory.
PROGRAMMING DEVICE
It is used to communicate between user and PLC. It
is used to convey the PLC by means of instructions, how to
execute and carryout the control plan.
LADDER DIAGRAM
A schematic representation of system hardware and
process controller is called as ladder diagram. Each parallel
connection on the ladder is called as rungs.
INTRODUCTION01
SYLLABUS

BASIC STRUCTURE OF PLC02SYLLABUS

CPU
The CPU controls and processes all the operations
within the PLC.
It is supplied with a clock frequency of 1 to 8 MHz.
This frequency determines the operating speed of the
PLC and provides the timing and synchronization for all
elements in the system
The information within the PLC is carried by means
of digital signals.
The processor is a microprocessor that executes a
program to perform the operations in a ladder diagram or a
set of Boolean operations.
It performs ALU and other logical applications.
BASIC STRUCTURE OF PLC02
SYLLABUS

CONTROL UNIT
It is used to control the timing of operations.
The controller can perform only one operation at a
time. So, it scans each of the inputs sequentially, evaluates
the ladder program, provide each output and repeat the
whole process.
MEMORY UNIT
The sequence of instructions to be executed,
programs are stored in the memory unit.
During entering and editing the program is stored in
the temporary storages called RAM.

BUSES
A set of parallel lines that provides communication
between various devices of a system is termed as bus.
The information is transmitted in binary form as 0 or
1.
PLC consist of four buses. They are explained below
DATA BUS
It contains 8, 16 or 32 parallel signal lines for sending
data between the various devices of a system.
This means that CPU can read data in from memory
or from I/O unit on these lines or it can send data out to
memory or to I/O unit on these lines
BASIC STRUCTURE OF PLC02
SYLLABUS

ADDRESS BUS
Every memory location is given a distinct unique
address to locate easily and accessed by the CPU either to
read or write data.
CONTROL BUS
Control signals are memory read, memory write, I/O
read and I/O write.
I/O SYSTEM BUS
This bus provide the communication between the
I/O ports and I/O units.

After entering the program into the controller and
placing the controller in RUN mode initiates an operating
cycle.
PLC operating cycle consists of a series of operations
performed sequentially and repeatedly unless altered by
program logic.
PLC OPERATING CYCLE02
SYLLABUS

INPUT SCAN
The time required for the controller to scan and read all input
data is called as input scan time. This can be accomplished within few
microseconds.
PROGRAM SCAN
It is the time required to execute the instructions in the
program. The program scan time varies depending on the instructions
used.
OUTPUT SCAN
It is the time required for the controller to scan and write all
output data.
SYLLABUS

SERVICE COMMUNICATION
During this operation communication takes place
with the peripheral devices.
OVERHEAD
It is the time spent on memory management and
updating timers and internal registers.
SYLLABUS

(a)I/O SPECIFICATION
Number of I/O channels.
AC/DC inputs and etc.
(b)THROUGHPUT
Throughput is time required to sense an input and energies a
corresponding output.
(c)MEMORY CAPACITY
(d)SCAN TIME
(e)EXECUTION SPEED
(f)COMPATABILITY
(g)NO.OF COUNTERS
(h)NO.OF TIMERS AND NOISE IMMUNITY.
SPECIFICATION OF PLC02
SYLLABUS

INPUT CHANNEL OF PLC03
SYLLABUS

RELAY TYPE
With relay type, the signal from the PLC output is used
to operate a relay and so is able to switch currents of the
order of few amperes in an external circuit. The relay isolates
the PLC from the external circuit and can be used for both d.c
and a.c switching Relays are relatively slow to operate
OUTPUT CHANNEL OF PLC03
SYLLABUS

TRANSISTOR TYPE
The transistor type of output (fig) uses a
transistor to switch current through the external circuit. This
provides a faster switching action. Opto isolators are used
with transistor switches to provide isolation between the
external circuit and the PLC. The transistor output is only for
D.C. switching
SYLLABUS

TRIAC TYPE
Triac outputs can be used to control external
loads which are connected to the a.c. power supply. Opto
isolators are again used to provide isolation.
SYLLABUS

CURRENT SOURCING
In Current sourcing mode the input device
receives current from the input module.
Similarly if the current flows from the output
module to output load then the output module is referred as
sourcing.
SYLLABUS

CURRENT SINKING
In Current sinking mode the input device
supplies current to the input module.
Similarly if the current flows to output module
then the output device is referred as sinking.
SYLLABUS

Many things can be thought of as existing in one of
two states.
These two states can be defined as “high” or “low”,
“on” or “off”, “yes” or “no”, and “1” or “0”.
5V
high, on, yes, 1
low, off, no, 0
Binary
Signal
THE BINARY CONCEPT03
SYLLABUS

This two-state binary concept, applied to gates,
can be the basis for making decisions.
The gate is a device that has
one or more inputs with which
it will perform a logical decision
and produce a result at its
one output.
THE BINARY CONCEPT03
SYLLABUS

AND
Gate
Light Switch
High Beam Switch
High Beam
Light
The automotive high beam light
can only be turned on when the
light switch AND high beam switch
are on.
The Logical AND
GATE DECISION MAKING03
SYLLABUS

OR
Gate
Passenger Door Switch
Driver Door Switch
Dome
Light
The automotive dome light will
be turned on when the passenger
door switch OR the driver door
switch is activated.
The Logical OR
GATE DECISION MAKING03
SYLLABUS

The outcome or output is called Y and the input signals
are called A, B, C, etc.
Binary 1 represents the presence of a signal or the
occurrence of some event, while binary 0 represents
the absence of the signal or nonoccurrence of the event.
AND Function03
SYLLABUS

AND Gate Function Application – Example 1
If all inputs are 1,
the output will be 1
If any input is 0,
Basic Rules
The device has two
or more inputs and
one output
SYLLABUS

AND Gate Function Application – Example 2
The AND gate operates
like a series circuit.
The light will be “on”
only when both
switch A and switch B
are closed.
SYLLABUS

An OR gate can have any number of inputs but only
one output.
The OR gate output is 1 if one or more inputs are 1.
OR Function03 SYLLABUS

OR Gate Function Application – Example 1
If one or more
inputs are 1, the
output will be 1
Basic Rules
If all inputs are 0,
SYLLABUS

OR Gate Function Application – Example 2
The OR gate operates
like a parallel circuit.
The light will be “on”
if switch A or switch
B is closed. SYLLABUS

The NOT function has only one input and one output.
The NOT output is 1 if the input is 0.
The NOT output is 0 if the input is 1.
Since the output is always the reverse of the input
it is called an inverter.
NOT Function03
SYLLABUS

NOT Gate Application – Example 1
The light will be “on” if
the pushbutton is not
pressed.
Acts like a normally
closed pushbutton
in series with the
output.
The light will be “off”
if the pushbutton is n
pressed.
SYLLABUS

NOT Gate Application – Example 2
An example of a NOT
gate control system is
a light that comes on
when it becomes dark,
that is, when there is
no light input to the
light sensor there is an
output.
Low-pressure
indicating circuit
SYLLABUS

The NAND gate functions like an AND gate with an
inverter connected to its output.
The only time the NAND gate output is 0 is when
all inputs are binary 1.
NAND Function03
SYLLABUS

The NOR gate functions like an OR gate with an
inverter connected to its output.
The only time the NAND gate output is 1 is when
all inputs are binary 0.
NOR Function03
SYLLABUS

The output of this gate is HIGH only when one
input or the other is HIGH, but not both.
The XOR function has
two inputs and one output.
It is commonly used for comparison of two binary
numbers.
EX-OR Function03 SYLLABUS

1. The two binary states can be defined as:
(a) “high” or “low”
(b) “on” or “off”
(c) 1” or “0”
(d) all of these
2. A gate can have one or more
outputs but
only one input. (True/False)
QUESTIONS03
SYLLABUS

3. The ______ table shows the resulting output
for each possible gate input conditions.
a. input status c. data
b. output status d. truth
4. A light that is "off" or a switch that is "open"
would normally be represented by a binary 1.
(True/False)
5. The OR function, implemented using contacts,
requires contacts connected in series. (True/False)
QUESTIONS03
SYLLABUS

6. With an AND gate, if any input is 0, the output
will be 0. (True/False)
7. The symbol shown is that of
a(an)
_________ .
(a) AND gate
(b) OR gate
(c) NAND gate
(d) inverter
QUESTIONS03
SYLLABUS

9. The basic rule for an XOR function is that if
one or the other, but not both, inputs are 1 the
output is 1. (True/False)
10. A NAND gate is an AND gate with an inverter
connected to the output. (True/False)
8. Which of the following gates is commonly used
for the comparison of two binary numbers?
(a) NAND
(b) NOR
(c) XOR
(d) NOT
QUESTIONS03
SYLLABUS

Gate Boolean Equations
A
B
YAND Y = A B
Gate Boolean Equation
OR
A
B
Y Y = A + B
NOTA Y Y = A
SYLLABUS

Boolean Equation – Example 1
Each logic function can be
expressed in terms of a
Boolean expression
SYLLABUS

Any combination of control can be expressed
in terms of a Boolean equation
Y =
Y =
SYLLABUS

Y=
Y =
SYLLABUS

Circuit Development Using A Boolean Expression
– Example 1
1. AND gate with Input A and B
2. OR gate with Input C an output from
previous AND gate.
SYLLABUS

Circuit Development Using A Boolean Expression
– Example 2
AND gate with Input B and C
SYLLABUS

Producing A Boolean Expression From A Given
Circuit – Example 1
SYLLABUS

Producing A Boolean Expression From A Given
Circuit – Example 2
Logic equation: Y = AB + AB
SYLLABUS

Hard Wired versus Programmed Logic
The term hardwired logic refers to logic control
functions that are determined by the way devices
are interconnected.
Hardwired logic can be
implemented using relays
and relay ladder schematics.
Hardwired logic is fixed:
it is changeable only by altering
the way devices are connected.
SYLLABUS

Hardwired Stop/Start Motor Control Circuit
Control scheme is drawn
between two vertical
supply lines.
Ladder rung
Ladder rail
SYLLABUS

Example 4-1
SYLLABUS

Example 4-2
SYLLABUS

Example 4-3
SYLLABUS

Example 4-4
SYLLABUS

Example 4-5
SYLLABUS

Example 4-6
SYLLABUS

Example 4-7
SYLLABUS

Example 4-8
SYLLABUS

Example 4-9
SYLLABUS

11. Hardwired logic is changeable only by altering
the way devices are connected.
(True/False)
12. Each programmed rung is a combination of
input conditions connected from left to right with
the symbol that represents the output at the far
right.
(True/False)
QUESTIONS03
SYLLABUS

13. Which gate logic shown represents the Boolean
equation: ( A + B ) C = Y
(a) (b)
(c) (d)
SYLLABUS

14. The correct Boolean equation for the
combination logic gate circuit shown is:
a. Y = A B C D c. Y = ( A + B ) ( C + D )
b. Y = ( AB ) + ( CD ) d. Y = ( AB ) + ( CD )
SYLLABUS

a. Y = ( A + B + C ) D c. Y = ( AB + C ) D
b. Y = ( A + B ) ( C + D ) d. Y = ( ABC ) D
SYLLABUS

a. Y = A B C c. Y = A + B + C
b. Y = ( A B ) C d. Y = ( AB ) + ( BC )
SYLLABUS

17. The correct Boolean equation for the ladder
logic program shown is:
a. Y = (A B) + (CD) c. Y = A + B + C + D
b. Y = (A+B ) (C+D) d. Y = ABCD
SYLLABUS

18. The correct Boolean equation for the ladder
logic program shown is:
a. Y = (A B) + (CD) c. Y = A + B + C + D
b. Y = AB (C+D) d. Y = ABC + D
SYLLABUS

19. If you want to know when matching
bits in two different words are both "on",
you would use the _____ logic instruction.
a. AND c. XOR
b. OR d. NOT
20. If you want to reverse the state of bits
in a word, you would use the ______ logic
instruction.
a. AND c. XOR
b. OR d. NOT SYLLABUS

Ladder diagram is a graphical method for
representing and programming an event driven sequential
process.
ELEMENTS OF LADDAR DIAGRAM
Relays
Motors
Solenoids
Lamps or indicators
Switches
LADDER DIAGRAM04
SYLLABUS

• Ladder diagrams are specialized schematics
commonly used to document industrial control logic
systems.
• They are called "ladder" diagrams because they
resemble a ladder, with two vertical rails (supply
power) and as many "rungs" (horizontal lines) as
there are control circuits to represent.
• If we wanted to draw a simple ladder diagram
showing a lamp that is controlled by a hand switch,
it would look like this:
LADDER DIAGRAM04
SYLLABUS

• The left and right uprights represent power. If we
connect the left and right uprights through a load,
power can flow through the rung from the left
upright to the right upright
• Ladder logic diagrams are read from left-to-right,
top-to-bottom.
• Rungs are sometimes referred to as networks
LADDER DIAGRAM04
SYLLABUS

• The load(s) must always be located
nearest the grounded power conductor
in the ladder diagram
• The PLC then runs the ladder and
monitors the input continually and
controls output. This called scanning
LADDER DIAGRAM04
SYLLABUS

• The main function of PLC program is to
control outputs based on the condition
of inputs
• The symbols used in ladder logic
programming can be divided into two
broad categories: Contacts (inputs) and
Coils (outputs)
LADDER DIAGRAM04
SYLLABUS

Contacts
• Most inputs to a PLC are simple devices that are either on
(true) or off (false). These inputs are sensors and
switches that detect part presence, empty or full status,
and so on.
• Contacts can be thought of as switches. The two basic
kinds of switches are normally open and normally closed:
– A normally open switch does not pass current until it
closed
– A normally closed switch allows current flow until it
closed
LADDER DIAGRAM04
SYLLABUS

Coil
• Coils are output symbols. There are many
types of real-world output devices: motors,
lights, pumps, counters, timers and relays
• The PLC examines the contacts (inputs) in
the ladder and turns the coils (outputs) on or
off, depending on the condition of the inputs
LADDER DIAGRAM04
SYLLABUS

Basic Programming Instruction
• Programmable control is based on the basic
logic function (AND, OR, NOT) to form the
instruction.
• Parallel contacts are equivalent to an OR
gate.
• Series contacts are equivalent to an AND
gate.
• Normally-closed contacts are equivalent to a
NOT gate (inverter).
LADDER DIAGRAM04
SYLLABUS

Mnemonic Code
• When using programming console, ladder
diagram need to be converted into mnemonic
code for entering the programming
instructions.
• The operand or data, is the item to be
operated on by the operation.
• Address is the memory storage location of
the operand.
LADDER DIAGRAM04
SYLLABUS

PLC Processor Memory Size
The size of the programmable controller relates to the
amount of user program that can be stored.
The 1 K word memory
size shown can store
1,024 words, or 16,380
(1,024 x 16) bits of
information using
16-bit words or 32,768
(1,024 x 32) using
32 bit words.
SYLLABUS

RULES TO BE FOLLOW WHILE DRAWING LADDAR DIAGRAM
(a) The vertical lines of diagram represent the
power rails between which the circuits are connected.
(b) Each rung of ladder defines one operation
in the control process.
(c) The ladder diagram must be read from left
to right and top to bottom.
(d) In RUN mode, PLC goes through entire
ladder program to the end. Then it came back to start position
LADDER DIAGRAM04
SYLLABUS

(e) Each rung must start with at least one
input and one output
(f) Electrical devices are shown in their
normal condition.
(g) A Particular device can appear more than
one rung in a ladder. Some identification number is used to
identify device in each situation.
(h) All inputs and outputs are identified by
their addresses, the notation used depending on the PLC
manufacturer.
LADDER DIAGRAM04
SYLLABUS

LADDER DIAGRAM04
SYLLABUS

SYMBOLS USED IN LADDAR DIAGRAM
(a)Push Button Switch
(b)Limit Switches
LADDER DIAGRAM04
SYLLABUS

(c) Pressure Switch
(d) Temperature Switches
(e) Level Switches
LADDER DIAGRAM04
SYLLABUS

(f) Relay Contacts
(g) Output Devices
LADDER DIAGRAM04
SYLLABUS

Might be used, followed by its address. To indicate the
start of a junction
Might be pressed; to indicate the end of a junction path
LADDER DIAGRAM04
SYLLABUS

LATCHING A CIRCUIT
LADDER DIAGRAM04
SYLLABUS

BASIC PROGRAMMING
LADDER DIAGRAM04
SYLLABUS

QUESTIONS
1. Decide whether each of these statements is True (T) or
False (F).
Figure shows a ladder diagram rung for which:
(i) The input contacts are normally open.
(ii) There is an output when there is an input to the contacts.
LADDER DIAGRAM04
SYLLABUS

QUESTIONS
False (F).
(i) The input contacts are normally open.
(ii) There is an output when there is an input to the contacts.
LADDER DIAGRAM04
SYLLABUS

QUESTIONS
False (F).
(i) When only input 1 contacts are activated, there is an
output.
(ii) When only input 2 contacts are activated, there is an
output.
LADDER DIAGRAM04
SYLLABUS

QUESTIONS
False (F).
Figure shows a ladder diagram rung for which there is an
output
when:
(i) Inputs 1 and 2 are both activated.
(ii) Either one of inputs 1 and 2 is not activated.
LADDER DIAGRAM04
SYLLABUS

QUESTIONS
False (F). Figure shows a ladder diagram rung for which
there is an output
when:
(i) Input 1 is momentarily activated before reverting to its
normally open state.
(ii) Input 2 is activated.
LADDER DIAGRAM04
SYLLABUS

QUESTIONS
Questions 6 to 9 refer to the following logic gate systems:
A AND B OR C NOR D NAND
6. Which form of logic gate system is given by a ladder diagram with a
rung having two normally open sets of contacts in parallel?
rung having two normally closed gates in parallel?
rung having two normally closed gates in series?
rung having two normally open gates in series?
LADDER DIAGRAM04
SYLLABUS

QUESTIONS
Problems 10 to 13 concern Boolean expressions for inputs A and B.
A Input A is in series with input B, both inputs being normally off.
B Input A is in parallel with input B, both inputs being normally
off.
C Input A, normally off, is in series with input B which is normally
on.
D Input A is in parallel with input B, both inputs being normally
on.
10. Which arrangement of inputs is described by the Boolean relationship
A.B?
LADDER DIAGRAM04
SYLLABUS

QUESTIONS
Problems 10 to 13 concern Boolean expressions for inputs A and B.
A Input A is in series with input B, both inputs being normally off.
B Input A is in parallel with input B, both inputs being normally
off.
C Input A, normally off, is in series with input B which is normally
on.
D Input A is in parallel with input B, both inputs being normally
on.
A + B?
LADDER DIAGRAM04
SYLLABUS

QUESTIONS
14. The arrangement of inputs in Figure is described by the Boolean
expression:
A A.B.C
B (A + C).B
C (A + B).C
D A.C + B
LADDER DIAGRAM04
SYLLABUS

QUESTIONS
15. Draw the ladder rungs to represent:
(a) Two switches are normally open and both have to be closed for a
motor to operate.
(b) Either of two, normally open, switches have to be closed for a coil
to be energised and operate an actuator.
(c) A motor is switched on by pressing a spring-return push button
start switch, and the motor remains on until another spring-return
push button stop switch is pressed.
(d) A lamp is to be switched on if there is an input from sensor A or
sensor B.
(e) A light is to come on if there is no input to a sensor.
(f) A solenoid valve is to be activated if sensor A gives an input.
LADDER DIAGRAM04
SYLLABUS

TIMERS
A timer is a special counter ladder function
that allows the PLC to perform timing operations based on
a precise internal clock.
ON DELAY TIMER
PLC PROGRAMMING04
SYLLABUS

OFF DELAY TIMER
CASCADED TIMERS
PLC PROGRAMMING04
SYLLABUS

ON OFF TIMER
ONE SHOT TIMERS
PLC PROGRAMMING04
SYLLABUS

PULSE TIMER
PLC PROGRAMMING04
SYLLABUS

COUNTERS
A Counter is a simple device that allow a
number of occurrences of input signals to count or record
the number of times some event occurs.
PLC PROGRAMMING04
SYLLABUS

The mnemonics codes used by different PLC
manufacturers differ but an international standard has
been proposed and is widely used.
MNEMONICS USED IN PLC05SYLLABUS

LD -Start a rung with an open contact
OUT -An output
AND -A series element and so an AND logic instruction
OR -Parallel elements and so an OR logic instruction
I -A NOT logic instruction
.... I -Used in conjunction with other instructions to indicate the inverse
OR1 -An OR NOT logic function
AN1 -An AND NOT logic function
LDI - Start a rung with a closed contact
ANB -AND used with two sub circuits
ORB-OR used with two sub circuits
RST -Reset shift register/counter
SHF -Shift
K - Insert a constant
END -End ladder
MNEMONICS USED IN PLC05
SYLLABUS

Instructions Description
LD A starting instruction for logic line
AND This is used to connect two or more inputs in serial
OR This is used to connect two or more inputs in parallel
AND LD This is used to connect two blocks in serial
OR LD This is used to connect two blocks in parallel
NOT NOT invert its inputs
Often used to form an NC (Normally Closed) input or
output.
NOT can be used with LD, OUT, AND or OR
OUT This is used to connect output /designated operand
bit
END This is used to indicate the end of program.
The last instruction in any program must be an END
instruction.
MNEMONICS USED IN PLC05 SYLLABUS

AND Logic Function
Address Instructions Data
00000 LD 00000
00001 AND 00001
00002 AND NOT 00002
00003 OUT 01000
00004 END(01)
SYLLABUS

OR Logic Function
Address Instructions Data
00000 LD 00000
00001 OR 00001
00002 OR NOT 00002
00003 OUT 01000
00004 END(01)
SYLLABUS

Combining The Logic Functions
END
Address Instruction Data
0000 LD 0001
0001 AND 0002
0002 OR 0003
0003 AND 0004
0004 AND NOT
0005 OUT 1000
END(01)
0001 0002 0004 0005 1000
0003
SYLLABUS

AND LD
END
0000 LD 0001
0001 OR 0002
0002 LD 0003
0003 OR NOT 0004
0004 AND LD
0005 OUT 1000
0006 END(01)
0001 0003 1000
0002 0004

OR LD
END
0000 LD 0001
0001 AND 0002
0002 LD 0003
0003 AND NOT 0004
0004 OR LD
0005 OUT 1000
0006 END(01)
0001 0002
0003 0004
1000
SYLLABUS

Combining AND LD and OR LD
END
0000 LD 00001
0001 AND NOT 00002
0002 LD NOT 00008
0003 AND 00003
0004 OR LD
0005 LD 00004
0006 AND 00005
0007 LD 00006
0008 AND 00007
0009 OR LD
0010 AND LD
0011 OUT 1000
0012 END(01)
0001 0002 0004 0005 1000
0007000600030008

A Systematic Approach of Control
System Design using a PLC
1. Determine the Machine Sequence of
Operation
2. Assignment of Inputs and Outputs
3. Writing of the Program
4. Programming into Memory
5. Running the System
SYLLABUS

SYLLABUS

Conditional Jump is a function provided in
PLCs. If a certain condition exists, then a section of the
program is ignored and the program control is jumped. In
the ladder diagram shown, program A is followed by
input1 and the conditional jump relay CJP. If input 1 is
OFF, the program B follows. The end of program B is
indicated by EJP end of jump relay coil. If input 1 is ON,
then the program jumps to the program 'C' skipping
program B.
JUMP CONTROL IN PLC05
SYLLABUS

JUMP CONTROL IN PLC05 SYLLABUS

DATA HANDLING06 SYLLABUS
In some cases, it may be required to deal with
related group of bits, i.e. a block of eight inputs and
operates on them as data word. The operations that may
be carried out with a PLC on data words normally include.
1. Data movement
2. Data comparison
3. Arithmetic operations
4. Conversions between BCD, binary & octal.

DATA MOVEMENT
Data movement instruction has move
instruction, source address of the data and destination
address of the data. For example, to move from Dl to D2.

DATA COMPARISON
Data comparisons include less than (<or LES),
equal to (=or EQU), less than or equal to (or LEQ), greater
than (> or GRT), greater than or equal to ( or GEQ) and not
equal to (# or <> or NEQ)

ARITHMETIC OPERATIONS
Addition and subtraction operations are commonly
found in all PLCs. Even more arithmetic operations are
possible in some PLCs. ADD & SUB instruction contains
address of the addend, augend and the result registers
along with the arithmetic operation to be performed.
These operations may be used to change the preset values
of the timers or counters.

CODE CONVERSIONS
In a PLC, all the internal operations are carried out
in binary form only. However, it may be required to handle
decimal or octal numbers at the input or output in which
case a conversion from binary to decimal to octal or a
conversion from decimal/octal to binary is required. For
example to convert a BCD number in the source register
to a binary number and store the result in destination
register, refer the figure

Draw a ladder diagram that the alarm keeps
sounding when the sensor temperature is above 80°C and
stops sounding when the temperature falls below 70°C.

CASE STUDIES06
Develop the ladder diagram for block opening and
closing door operation. Sensor is placed in front of doors.
The door will remain in open for 10 seconds whenever
person cross the door.
SYLLABUS

CASE STUDIES06
Develop the ladder diagram for bus opening and
closing door operation. When driver press the button door
will open and driver press the same button for second
time door will close.
SYLLABUS

CASE STUDIES06
Develop the ladder diagram for A+B+B-A- operation
SYLLABUS

CASE STUDIES06
Develop the ladder diagram for A+B+A-B- operation
SYLLABUS

CASE STUDIES06
Develop the ladder diagram for punching operation.
First cylinder is used to clamp the work piece. Second
cylinder is used for downward (vertical) movement of
punching machine. Second cylinder retracts and first
cylinder unclamp the object.
SYLLABUS

CASE STUDIES06
Figure shows how directional control valves can be
used for a control system of a robot. When there is an
input to solenoid A of valve 1, the piston moves to the
right and causes the gripper to close. If solenoid B is
energized with A de-energized, the piston moves to the
left and the gripper opens. When both solenoids are de-
energized, no air passes to either side of the piston in the
cylinder and the piston keeps its position without change.
Likewise, inputs to the solenoids of valve 2 are used to
extend or retract the arm. Inputs to the solenoids of valve
3 are used to move the arm up or down. Inputs to the
solenoids of valve 4 are used to rotate the base in either a
clockwise or anticlockwise direction.
SYLLABUS

Given two push-to-ON buttons (PB1,PB2), Red and
Green lamps, develop a ladder diagram to meet the
following objectives.
(a) When PB1 is pushed, RED lamp should be ON and it
will continue to be ON till PB2 is pushed
(b) When PB2 is pushed, GREEN lamp should be ON and it
will continue to be ON till PB1 is pushed
(c) If PB1 and PB2 both are pushed simultaneously, both
light should be OFF.
CASE STUDIES06 SYLLABUS

CASE STUDIES06
Given four normally open switches (P1,P2,S1 and S2)
with DC motor (M). Draw a PLC program to satisfy
following objectives:
(a)When P1 is pushed the cycle shall start. The cycle shall
continue to remain ON until P2 is pushed.
(b) When S1 is pushed and S2 is not pushed then Motor is
ON clockwise direction.
(c) When S2 is pushed and S1 is not pushed then Motor is
ON counter clockwise direction.
(d) When P2 is pushed the program stops.
SYLLABUS

CASE STUDIES06
A small electric furnace has two heating elements.
When switched on, first element starts and after 2
minutes second starts. A temperature sensor is used to
shut down the furnace if over heating occurs. Draw
ladder diagram.
SYLLABUS

CASE STUDIES06
Prepare the physical and programmed ladder
diagram for the control problem is shown in figure. The
objective is to heat the liquid to a specified temperature
and keep it there for 30 minutes.
SYLLABUS

MPS STATIONS
SYLLABUS
CLICK HERE TO SEE MPS STATIONS

MPS STATIONS
SYLLABUS
DISTRIBUTING STATION

Programmable Logic Controller

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