3
ACADEMIC YEAR 2020-21
III B.TECH II SEM EIE (R18)
INDUSTRIAL AUTOMATION
UNIT – III
PLC Intermediate
and
Advanced Functions
P.Srinivas
Assistant Professor
CONTENTS
Arithmetic functions
Number comparison functions
Skip and MCR functions
data move systems.
Utilizing digital bits
sequencer functions
Matrix functions.
PLC Advanced functions:
Analog PLC operation
Networking of PLC
Arithmetic functions
Fig: PLC SUBTRACT FUNCTION
Fig:Using the SUBTRACT function for a Conveyor
Count
Fig: Repetetive Clock Circuit
MULTIPLY Function
Fig: DIVIDE Function
PLC BASIC COMPARISION
FUNCTIONS
Skip and MCR functions
SKIP FUNCTION
SKIP Function PLC Operation
SKIP Function Application Layout
SKIP Application Program
THE MASTER CONTROL RELAY FUNCTION AND APPLICATIONS
MCR FUNCTION
MCR Function PLC Operation
MCR Application Program
Data Move Systems
The MOVE Function
MOVE Timing Example
MOVE-Addition System
MOVE-Addition Program
BLOCK TRANSFER Function
TABLE-TO-REGISTER MOVE System
TABLE-TO-REGISTER MOVE
Function
REGISTER –TO-TABLE MOVE System
REGISTER –TO-TABLE MOVE Function
UTILIZING DIGITAL BITS
INTRODUCTION
• Most PLCs are capable of working with digital bits.
• Instead of controlling output devices from individual contacts,
these PLCs use register bits in groups.
• The PLC not only uses fixed pattern of register bits , but can
easily manipulate and change individual bits.
• The PLC can pick , set , latch and manipulate each individual
bits in chosen registers.
• It can also shift the register contents to the right or left.
INTRODUCTION
• Registers shift can be set to move the bits one position per
input pulse.
• Shifts may also be set for multiple position movement (two ,
three or more)
• This multiple shift function is often designated as N-bit shift.
• MOVE function enables to replace the entire register contents
in order to change the 16 output commands.
• If we want an on-off pattern changed , shift in an appropriate
new register pattern.
INTRODUCTION
• The digital bit system is the foundation of
multiple machine control.
• The bit system is used extensively in all types
of automation systems.
BIT PATTERNS IN A REGISTER
• In some PLCs ,the internal slots for memory and operations
are called addresses.
• In others , the slots are called registers.
• For illustration purposes , the register bits in HR0207 have
been arbitrarily given the values shown.
0111 1000 0101 0001 HR 0207
HR 0207 has an equivalent BCD value of 7851 and
equivalent of decimal value of 30,801.
Binary bit patterns can be applied to any type of register , not
just holding registers.
Fig: BIT-PICK CONTACT CONTROL
Fig: Ten ouputs controlled by 10 Register Bits
CHANGING A REGISTER BIT STATUS
•Bit status changes are more quickly
accomplished by using one of three PLC
functions:
1. BIT SET(BS)
2. BIT CLEAR (BC)
3. BIT FOLLOW (BF)
BIT SET(BS)
To change bit 4 in HR0207 from 0 to 1.
When BS function is enabled , bit 4 of HR0207 is set to 1(if it was
not already a 1).
Turning the function off would have no effect on the bit-it would
remain a 1
Fig: BIT SET Function
BIT CLEAR(BC)
It has the opposite effect of BIT SET
To change bit 5 in HR0207 from 1 to 0.
When BC function is enabled , bit 5 of HR0207 is changed from 1 to 0
If BC function applied to bit 6 nothing would have happened , because
bit 6 is already a 0.When BC is turned off ,nothing further happens.
Fig: BIT CLEAR Function
BIT FOLLOW (BF)
Fig shows the BF function as applied to bit 4
When BF function is enabled , the function sets the bit to 1
When disabled or off,the function sets the it to 0.
Note that BF differs from BS and BC: on and off are both active and
significant in BIT FOLLOW function.
Fig: BIT FOLLOW Function
SEQUENCER FUNCTIONS
The PLC SEQUENCER function is often called the DRUM
CONTROLLER
This function can be designated using DR instead of SQ which has
been already designated for square root.
The SEQUENCER concept has evolved from the mechanical drum
switch which is an important control device.
PLC sequencer function handles large sequencing control problems
more easily than does the drum switch.
Another advantage of the PLC is that its SEQUENCER programming
is relatively straightforward and user friendly
SEQUENCER FUNCTIONS
Traditional drum switches are manually operated.
If a timing of the steps being controlled by the drum switch is
required, manual operation timed by a clock is needed.
The PLC SEQUENCER functions can operate between steps by
programmed time sequences.
Some PLCs use the TABE-TO-REGISTER or file-to-word functions
as an alternative to the SEQUENCER FUNCTION.
In addition to the basic SEQUENCER function,there are additional
SEQUENCER functions which have specific additional uses in
process control
ELECTROMECHANICAL SEQUENCING
• Fig1 shows a small , electromechanical drum
controller.
Fig1:Electromechanical Drum Switch
ELECTROMECHANICAL SEQUENCING
Internal electrical connections are illustrated in
Fig2.for each of its three positions.
Fig2:Internal Contact Switching
Motor reversing is accomplished by reversing any two leads for
three phase alternating current (AC),reversing the start leads with
respect to the main leads for single phase AC , or reversing the
field leads with respect to the armature leads for direct
current(DC).
Drum switches are limited to a maximum of seven positions and
about 12 pairs of contacts.
However , it has one major advantage . It is a good, economical
control device for handling applications with a fixed sequence and
a limited number of required contacts.
• To begin the discussion of PLC,a simple sequence of operation
is shown in fig.3
• Three lights are to be in the on or off state in five consecutive ,
different combinations.
• The five steps are to be in a given
sequence,1through 5.
• A 1indicates the light is to be on and
a 0 off.
Fig 3:Light Pattern Sequence
Fig 4:Toggle Switch Light Pattern
• As an alternative to using toggle switches,the three lights
could be connected to the output of a PLC using coil/contact
syatem as shown in fig 5.
Fig 5:PLC Coil/Contact Light Pattern Control
THE PLC SEQUENCER FUNCTION
Instead of three by five sequence,if we have to program 14
outputs on-off through 47 steps then
Using toggles or PLC contact coil system would be a long and
complicated system.
However,programming with a PLC SEQUENCER function is
relatively easy
THE PLC SEQUENCER FUNCTION
There are three inputs:
1. Step Circuit
2. Reset Circuit
3. Enable Circuit
THE PLC SEQUENCER FUNCTION
Fig 6:Typical PLC SEQUENCER FUNCTION
THE PLC SEQUENCER FUNCTION
The SEQUENCER function block is programmed with
following information:
Number of steps to be sequenced through
The starting register used for the sequence
Step pointer location. An HR that shows which step
you are on
Destination is the OG register, a group of HRs that
are to be controlled on and off by the SEQUENCER
function
THE PLC SEQUENCER FUNCTION
Fig 7:PLC SEQUENCER FUNCTION and Pattern for the
Light Sequence
A BASIC PLC SEQUENCER APPLICATION WITH TIMING
• The dishwasher has six functions that must be turned on and
off periodically . These are
Soap release solenoid
Input valve for hot water
Wash-impeller operation
Drain water valve
Drain Pump motor
Heat element for drying cycle
Fig 8:Dishwasher Function Matrix and Register Pattern
Fig 9:Sequencer with Timer Pulsing
Matrix functions
Fig.1:Long Repetitive Programs
Fig 2: Four Outputs with Two series Inputs
Fig3 : Matrix Arrangement for Fig2
Fig 4 : Two by Two AND Analysis for Fig 3
Fig 5 : PLC Matrix for 53 functions
PLC Advanced functions:
Analog PLC operation
Networking of PLC
