Introduction

Today, Industrial Automation has taken over the production process in industries and it is very
difficult to imagine a production line without automation systems. There are several factors that
lead to the implementation of automation system in industrial production like requirement of high-
quality products, high expectations in product reliability, high-volume production etc.

What is Industrial Automation?

Industrial Automation is a process of operating machines and other industrial equipment with the
help of digital logical programming and reducing human intervention in decision making and
manual command process with the help of mechanized equipment.

Example to Understand Industrial Automation

Consider a manual industrial production process, where an operator is observing the temperature
of an oven. Assume the task is to reach a certain temperature and maintain that temperature for
about 30 minutes.

So, the operator has to first adjust the amount of fuel to the oven by controlling a valve to rise
the temperature to the desired amount. Once the necessary temperature is achieved, it has to be
maintained by constantly adjusting the valve i.e. either increase or decrease the fuel depending on
the temperature for the next 30 minutes.

Now, with industrial automation, the whole process is taken care of without the help of an
operator. First, there is a temperature sensor placed near the oven which reports the temperature
to a computer.

Now, there is motorized valve, which is also controlled by the computer, for the fuel to be
supplied to the oven. Based on the temperature readings from the sensor, the computer will open
the valve to allow more fuel in the beginning. Once the desired temperature is achieved, the valve
is shutoff.

Motivation for Industrial Automation

the fundamental motivations for implementing industrial automation are:

● Increase production
● Reducing cost, especially, human-related cost
● Improving the quality of the product
● Efficient use of raw materials
● Reduce energy consumption
● Increase business profits
Levels of Industrial Automation Process

There are several ways to describe the levels of an Industrial Automation Process, but the simplest
of all is the following hierarchical triangle of three level representation of a typical Industrial
Automation Application.

Supervisor Level

Sitting at the top of hierarchy, the supervisor level usually consists of an Industrial PC, which is
usually available as a desktop PC or a Panel PC or a Rack-mounted PC. These PCs run on standard
operating systems with a special software, usually provided by the supplier for industrial process
control.

Control Level

The Control Level is the mid-level in the hierarchy and this is the level where all the automation
related programs are executed. For this purpose, generally, Programmable Logic Controllers or
PLCs are used, which provide real-time computing capability.

PLCs are usually implemented using 16-bit or 32-bit microcontrollers and run on a proprietary
operating system to meet the real-time requirements. PLCs are also capable of being interfaced
with several I/O devices and can communicate through various communication protocols like CAN.

Field Level

The terminal equipment like Sensors and Actuators are categorized into Field Level in the
hierarchy. The sensors like temperature, optical, pressure etc. and actuators like motors, valves,
switches etc. are interfaced to a PLC through a field bus and the communication between a Field
Level device and its corresponding PLC is usually based on a point-to-point connection.

Both wired and wireless networks are used for communication and using this communication, the
PLC can also diagnose and parameterize various components.
Additionally, an industrial automation process system also requires two major systems. They are:

● Industrial Power Supply

● Security and Protection
The power requirements of different systems in different levels of the hierarchy can be
extremely different. For example, PLCs usually run on 24V DC, while heavy motors run on
either 1-phase or 3-phase AC.

So, a wide range of proper input power supply is required for a trouble-free operation.
Additionally, there should be security for the software being used to control the PLCs as it can be
easily be modified or corrupted.

Types of Industrial Automation Systems

Now that we have seen a little bit about the layout of a typical industrial automation system, let
us proceed with the discussion of the different type of Industrial Automation Systems. Industrial
Automation Systems are usually categorized into four types.

● Fixed Automation System

● Programmable Automation System
● Flexible Automation System
● Integrated Automation System

Fixed Automation System

In a Fixed Automation System, the production equipment is fixed with a fixed set of operations or
tasks and there are rarely any changes to these operations. Fixed Automation System is usually
used in continuous flow processes like conveyors and mass production systems.

Programmable Automation System

In Programmable Automation System, the sequence of operations as well as the configuration of

the machinery can be changed using electronic controls. This system requires a significant amount
of time and effort to reprogram the machines and usually used in batch process production.

Flexible Automation System

A Flexible Automation System is usually, always controlled by computers and are often
implemented where the product varies frequently. CNC machines are the best example for this
system. The code given by the operator to the computer is unique to a particular job and based on
the code, the machine acquires the necessary tools and equipment for the production.

Integrated Automation System

An Integrated Automation System is a set of independent machines, processes and data, all
working synchronously under the command of a single control system to implement an automation
system of a production process. CAD (Computer Aided Design), CAM (Computer Aided
Manufacturing), computer-controlled tools and machines, robots, cranes and conveyors are all
integrated using complex scheduling and production control.

Advantages and Disadvantages of Industrial Automation

Advantages

● The task performed by human operators involving tedious physical work can be easily
replaced.
● Human operators can avoid working in dangerous production environments with extreme
temperatures, pollution, intoxicating elements or radio-active substances.
● The tasks that are difficult for a typical human operator can be easily done. These tasks
include lifting heavy and large loads, working with extremely tiny objects etc.
● Production is always faster and the cost of the product is significantly less (when
compared to the same product that is produced with manual operation).
● Several quality control checks can be integrated into the production process to provide
consistency and uniformity.
● The economy of the industry can be significantly improved, which has a direct impact on
the standard of the living.

Disadvantages

● Loss of jobs. Since, majority of the work is done by machines, the requirement for
manual labor is very less.
● All the desired tasks cannot be automated using the current technology. For example,
products with irregular shapes and sizes are best left for manual assembly. (This trend
seems to be changing with advanced computers and algorithms).
● It is feasible to use automation for certain process i.e. high-volume production,
repeatable and consistent products.
● The initial cost of implementing an automation system is very high.
● A set of skilled personnel is always a requirement for maintenance and service.

Control System

A Control System is a System where the output is controlled by varying / adjusting the input.
Another definition of Control System is it is a combination of subsystems and processes working
together to obtain a desired output and performance with a specified input.

There are several ways to classify Control Systems. Some of the popular classifications of
control systems are:

● Open Loop System and Closed Loop System – based on feedback signal
● Linear and Non–Linear Systems – based on their differential equations
● Continuous and Discrete Systems – based on the type of signal in their system
● Time Varying and Time Invariant Systems – based on their time dependency
Based on the feedback connection i.e., if feedback is used or not, the control systems are
classified into two types. They are:

● Open Loop Control System

● Closed Loop Control System

Open Loop Control System

In open loop control system, the output does not affect the control action of the system. In other
words, the system whose working depends on time is known as the open loop control system. The
open loop system is free from the feedback. Let’s understand this with the help of the few
examples.

Example 1: Consider the clothes dryer whose control action is done manually by the operator.
Depending on the wetness of the clothes, suppose the operator set the timer for 30 minutes.
After 30 minutes the timer will stop even after the clothes are wet.
The dryer stops working even if the desired output is not obtained. This shows that the system
has no feedback. Here clothes dryer is the example of the open loop system and the timer is the
controller of the system.

Example 2: The automatic washing machine is the example of the open loop system. The operator
manually sets the operating time of the machine. The machine stops operating after the set time,
even the desire cleanliness of clothes are not obtained. This happens because the machine has no
feedback system which signals the control action of the system for desired output.

The open loop system is simple, require less maintenance. Also, it is fast in operation and very
economical. But the accuracy of the system is less, and it is less reliable.

Open Loop System Applications

We use open loop control systems in many applications of our day-to-day lives. Some of the
popular systems, which are designed based on the concept of open loop control systems, are
mentioned below:

● Washing Machine
● Electric Bulb
● Electric Hand Dryer
● Time based Bread Toaster
● Automatic Water Faucet
● TV Remote Control
● Electric Clothes Dryer
● Shades or Blinds on a window
● Stepper Motor or Servo Motor
● Inkjet Printers
● Door Lock System
● Traffic Control System

Advantages of Open Loop Control System

The main advantages of the open loop control system are listed below:

● Open Loop Control Systems are very simple and easy to design.
● These are considerably cheaper than other types of control systems.
● Maintenance of an open loop control system is very simple.
● Generally, open loop systems are stable up to some extent.
● These types of systems are easy to construct and are convenient to use.

Disadvantages of Open Loop control System

The disadvantages of open loop system are:

● The bandwidth of open loop control system is less.

● The non-feedback system doesn’t facilitate the process of automation.
● Open loop systems are inaccurate in nature and also unreliable.
● If their output is affected by some external disturbances, there is no way to correct them
automatically as these are non-feedback systems.

Closed Loop Control System

The closed-loop control system means the output of the system depends on their input. The system
has one or more feedback loops between its output and input. The closed-loop system design in
such a way that they automatically provide the desired output by comparing it with the actual
input. The closed-loop system generates the error signal which is the difference between the
input and output.

Example 1: Suppose in the above example of a closed dryer we are using the transducer which
senses the dryness of the clothes and provides the feedback signal to the controller relating to
dryness. Here the dryness is the output of the system. The sensor act as a feedback system. The
sensor gives the signal to the controller of the machine, and hence the dryer provides the desired
output.

Example 2: The air conditioner is the example of the closed-loop system. The air conditioner
regulates the temperature by comparing it with the surrounding temperature. The comparison of
temperature is done with the help of the thermostat. When the AC provides the error signal
which is the difference between the surrounding temperature and room temperature the
thermostats turn on or off the compressor.

more Examples

We use closed loop control systems in many applications of our day to day life. Some of the
systems designed based on the concept of open loop control systems are given below.

● Automatic Electric Iron –Depending on the temperature of the iron, heating elements were
controlled automatically.
● Servo Voltage Stabilizer – Stabilization in voltage is achieved by feeding the output
voltage back to the system.
● Water Level Controller– Water level in the reservoirs decides the input water into it.
● Air Conditioner –Air conditioner automatically adjusts its temperature depending on its
room temperature.
● In motor speed regulator using a tachometer and/or current sensor , the sensor senses the
speed and sends feedback to the system to regulate its speed.

Elements of Process Control

In most processes, there are six basic elements.Process control elements are
1. Controlled variable
What you want to control (temperature pressure, level, flow rat, dimensions, position, etc.)
2. Measured variable
What you observe in order to determine the actual condition of the controlled variable
In most cases, you measure the controlled variable itself. For instance, if you want to know how
fast a car is going, you measure its speed. In other cases, you measure a different variable to
determine the condition of the controlled variable. For instance, you can determine the level
(controlled variable) of liquid in an open or vented tank by measuring the pressure (measured
variable) at the bottom of the tank.
3. Set Point
The desired value of the controlled variable; for example, 70 room temperature
4. Deviation
The difference between the set point and the actual value of the controlled variable (which is the
measured variable). For example, if your indoor thermometer reads 65 and you would like a room
temperature of 70, the deviation is 5
5. Manipulated variable
The variable that is adjusted to close the gap (deviation, difference, or error) between the set
point and the controlled variable; for example, the amount of electricity or gas to the heater.
6. Disturbances
Anything that affects the process and could cause deviation from the set point; for example, a
window left open, poor insulation, a damaged thermostat.

Watch the videos in the following links to get information about automations in industry and PLC

https://youtu.be/9li-zEtzcq0
https://youtu.be/GLg7Ialifd4
https://youtu.be/j3gJoIl6r0g
https://youtu.be/Jikiy4KLO0k
https://youtu.be/ze7ngDzxBIQ
https://youtu.be/afn9q_vDEC4
https://youtu.be/NrDouhBl1cc
https://youtu.be/Nsx-LTd2IXM
https://youtu.be/JvTCgq5vss0
https://www.mobileautomation.com.au/plc-industrial-application/

Programmable Logic Controller

(PLC) is used to control the industrial process according to the user program or logic. This user
program or logic can be prepared by the instructions that are given in the programming software
and often known as PLC Program.

Bit Logic Instructions

In this blog, we will see the bit logic instructions and PLC programming examples using these
instructions. These are very basic but very important instructions, almost all the user uses these
instructions. This is the list of Bit logic instructions:
● Normally Open
● Normally Close
● NOT logic
● Coil
● Set Coil
● Reset Coil
● Negative Edge
● Positive Edge

Normally Open
This instruction works like a normally open contact, when there is no signal at the input it will not
allow the power to flow further in the rung.

Normally Close

This instruction works exactly opposite to the normally open contact, when there is a signal it will
not allow the power to flow through it.

Coil
The coil is an output instruction; the user program monitors the status of the input. According to
the program when the output coil is energizing in the program, it will activate the physical
output and the connected load is activated after that.

Not

This instruction works like NOT gate, when the input of this instruction is “0” then it will give
the output “1” and when the input of the NOT is “1” it will give the output “0”.

Set Coil
This instruction has an inbuilt latching function, when we activate the set coil once by giving
power or by pressing the switch it will activate the output. The output coil will remain active even
after releasing the switch.
Reset Coil
This instruction is used to deactivate the output coil. When we give power to this instruction it
will de-activate the output coil.

Positive Edge
This is the instruction used to detect the positive edge or signal change stat of “0” to “1”. When
it detects a change in the input signal from “0” to “1”, it will allow the power to flow only that
much of the time that signal is changing its stat from “0” to “1”. After that, it will stop the
power to flow.

Negative Edge

This instruction detects the change in the signal stat from “1” to “0”. It will allow the power to
flow when it detects a negative change in the input signal like “1” to “0” and allow the power only
this much of time. After that, it will stop the power to flow.

These five steps will help you in your PLC program development.

1. Define the task.

2. Define the inputs and outputs.
3. Develop a logical sequence of operation.
4. Develop the PLC program.
5. Test the program.
Step 1 – Define the task
This step is a collection of information about how the machine is to function. Conversations with
owners, engineers, maintenance, operators, etc. are a few people to help you understand how the
machine will function. Write this information down and summarize your findings. The next step
will sometimes force you to go back to individuals and ask further questions. This is one of the
most important steps for your program development. Good note-taking is important.

Step 2 – Define the Inputs and Outputs

The information in step 1 will help you to determine the inputs and outputs required to perform the
operations. This input and output list may also be provided to you. Review the requirements and
ensure that everything is included.
The inputs and outputs refer to both discrete (on/off) and analog. Any special communications can
also be included in this step. An example would be a temperature controller that will communicate
Modbus RTU.
Inputs:
Master Switch – On/Off
Upper Limit Switch – On/Off
Lower Limit Switch – On/Off
Outputs:
Down Solenoid – On/Off
Up Solenoid – On/Off
If a control panel is required, make sure the inputs like start, stop, reset, emergency stop, etc
are included. Outputs like lights, counters, etc are sometimes forgotten on the panel.
Step 3 – Develop a logical sequence of operation
This is where the majority of time is spent in PLC program development. Steps 1 and 2 allow you
to systematically express what has to happen in the PLC program. Based on the logic, you may
have to modify the inputs/outputs or sequence of the program. This is the easiest place to make
changes.

This can be done with the use of a flow chart or sequence table. You can use anything to fully
understand the logic of the operation before programming. Many people do not use this step and
jump straight to programming.
Fully understanding the logic before starting to program can save you time and frustration.
Step 4 – Develop the PLC program
Utilizing the above steps, we will now actually write the plc program. This can be in several
different languages. In the majority of cases, ladder logic is used.

Step 5 – Test the program

Test the logic that you have developed. Once again the previous steps are helpful in this process.
First, start with what is referred to as ringing out the IO. This is where you would trigger the
inputs and set the outputs to verify the wiring and communication. PLC program development
testing is an important step to test for all conditions of the logic. (Power Cycle, Sensors Fail,
Safety, etc.)
Test the program with a simulator or actual machine. Make modifications as necessary. Check
with the people most knowledgeable on the machine, to see if it is doing what they expect. Do
they need anything else? Follow up after a time frame to see if any problems arise that need to
be addressed.
Watch the video below for a review of the 5 steps to PLC program development.

PLC Timers
Timers are very important in ladder logic programming. Timers gives the precision in time. Timer on delay
starts timing when instruction is true. Timers are used to track time when instruction are on or off. They could
also keep track on a retentive base.

Definition
The following is a list of timer instructions in SLC 500:

● TON - Timer On Delay

● TOF - Timer Off Dealy
● RTO - Retentive Timer

TON Timer On Delay

Symbol

or
Definition

● Count time base intervals when the instruction is true.

● The Timer On Delay instruction begins to count time base intervals when rung conditions become true.
As long as rung conditions remain true, the timer adjust its accumulated value (ACC) each evaluation
until it reaches the preset value (PRE). The accumulated value is reset when rung conditions go false,
regardless of whether the timer has timed out.

TOF Timer Off Delay

Symbol

OR

Definition

● Counts time base intervals when the instruction is false.

● The Timer Off Delay instruction begins to count time base intervals when the rung makes a true to
false transition. As long as rung conditions remain false, the timer increments its accumulated value
(ACC each scans until it reaches the preset value (PRE). The accumulated value is reset when rung
conditions go true regardless of whether the timer has timed out.

Retentive Timer

Symbol

Definition

● Counts time base intervals when the instruction is true and retains the accumulated value when the
instruction goes false or when power cycle occurs.
● The Retentive Timer instruction is a retentive instruction that begins to count time base intervals when
rung conditions become true.
● The Retentive Timer instruction retains its accumulated value when any of the following occurs:
● Rung conditions become false.
● Changing Processor mode from REM run /Test / program mode.
● The processor loses power while battery back up is still maintained.and a fault occurs.
Types of the PLC Counter

Basically, PLC counter operates into four modes such as up mode, down mode, bidirectional mode,
and the quadrature mode.

Counters in PLC are classified into three main different parts.

1. Up Counter (operates up mode)
2. Down Counter (operated in down mode)
3. Up/Down Counter (operates in bidirectional and quadrature mode)

Let’s see the counter and their mode one-by-one.

1. Up Counter

Up counter counts from zero to the preset value. Basically, it increases the pulse or number.

Up counter is known as the ‘CTU’ or ‘CNT’

Up counter function block diagram:

We can also set the initial and target value as an input to the counter.
Here, the up-counter in PLC can count the value from the initial value to the target value. This
initial value must be less than the target value. Most of the time, it is set as zero.

2. Down Counter

The down counter counts from the preset value to zero. It decreases the pulse or number.
Down counter is shortly known as the ‘CTD’ or ‘CD’.
Down counter function block diagram:
The down counter counts from target value to the initial value by decreasing it. This initial value
must be less than the target value.
3. Up-Down Counter

The up-down counter counts the value from zero to the preset value or from the preset value to
zero.In other words, this counter can be act as down counter or up counter.

Up-down counter is known as ‘CTUD’.

For the bidirectional and quadrature operation mode, the up-down counter is selected depending on
the status (high or low) of the specified count input terminal.
Up-down counter function block diagram:
In PLC programming, the up/down counter instruction is mostly used for the increment and
decrement counting pulse or units.

Video demos

Industrial Automation || Industrial Automation & It's types

link https://www.youtube.com/watch?v=1BZpjKZ1G6c

Industrial Automation || Industrial Automation & It's types

link https://www.youtube.com/watch?v=1BZpjKZ1G6c

https://www.youtube.com/watch?v=DKh7qbtH2p4

MIXING TANK PROCESS DESCRIPTION

A normally open start and normally closed stop pushbuttons are used to start and stop the process. When the start
button is pressed, solenoid A energizes to start filling the tank. as the tank fills , the empty level sensor switch
closes .when the tank is full , the full-level sensor switch closes. Solenoid A is de-energized. The mixer Motor
starts and runs for 3 minutes to mix the liquid . when the agitate motor stops , solenoid B is energized to empty the
tank .When the tank is completely empty , the empty sensor switch opens to de-energize solenoid B . the start button
is pressed to repeat the sequence.
PROCESS DIAGRAM

DEVELOPING LADDER DIAGRAM

Explanation of ladder diagram operation

● Network 1: when external input push button is pressed, the valve 1 connected to output Y0 is turned on and
timer T0 starts counting delay output M0 is used to hold on the timer count when it is reached 100. at the
same time D0=T0-0 is used to indicate rising liquid level in DOPsoft.

● Network 2: When T0=100, Y0 is stopped as a NC contact of T0 is connected in series with Y0. and the
mixing motor connected to Y1 is turned on. Y3 is used to connect tank full indicators. output M1 is used to
hold on timer count. time T0 starts counting delay for mixing operation.

● Network 3: When T1=100, Y1 and Y3 is stopped as a NC contact of T0 is connected in series with Y1 and Y3.
and the drain valve connected to Y2 is turned open. output M2 is used to hold on timer count. time T2 starts
counting delays. D2=T0-T2 is used to indicate falling liquid level in DOPsoft.

● Network 4: When D2=0 Y4 is turned on to indicate bottom liquid level.

INPUT AND OUTPUT WIRING DIAGRAM

 CONVEYOR OPERATION

PROCESS DESCRIPTION

The system to be controlled by PLC consists of two conveyor belts. If the start button is pressed, conveyor Belt-1 will
begin to run. After 5 seconds Conveyor Belt-2 will be active. After the whole system runs For 15 seconds, conveyor
Belt-1 will stop. Then conveyor Belt-2 continues to move for 5 seconds.And then it will stop, too. Also the system can
be reset by the emergency –stop button at any time.

Selection of inputs and outputs

Explanation of Ladder diagram

● Network 1: When On push button X0 is pressed Conveyor 1 motor connected to Y0 is tuned ON and timer T0
starts counting delay for 5 sec.
● Network 2: When T0= 50 (5Sec) Conveyor 2 motor connected to Y1 is tuned ON and timer T1 starts counting
delay for 15 sec. when T1=150 conveyor 1 motor connected to Y0 is turned off by the same time the off delay
timer T2 starts counting delay for 5 sec. after 5 sec conveyor 2 motor connected to Y1 is turned off

Developing a ladder diagram

Process HMI diagram

Input and output wiring diagram

Automatic stamping operation description

When the start switch is turned on, the system gets ready to run. When the operator puts a box at the beginning of
the conveyor (on LS 1) the motor runs and the conveyor moves. Upon reaching the middle of the conveyor (on LS 2) the
conveyor motor stops .Then the stamp comes down and puts the stamp on the box. When this process is finished,the
stamp goes up and the conveyor moves again to the other end of the conveyor. After the box reaches the end of the
conveyor on (LS 3), the motor stops .The system waits for the box to get and the box to be placed at the beginning of
the conveyor. If the start switch is turned off, the system cannot run even if there is a box on the conveyor. The
light on the start box indicates that the system is active whereas UP and Down lights indicate that the stamp is in the
Up and Down position respectively.
Selection of inputs and outputs

Developing a ladder diagram

Process diagram

Input and output wiring diagram

Explanation of ladder diagram

● When the start switch X0 is turned on, the system gets ready to run.
● When the operator puts a box at the beginning of the conveyor (on LS 1) X1 gets closed and the motor runs
and the conveyor moves.
● Upon reaching the middle of the conveyor (on LS 2) X2 gets closed and the conveyor motor stops .Then the
stamp comes down and puts the stamp on the box and limit switch X4 gets closed so as output Y3 goes off by
X4 stamp goes up and the conveyor gets on by X4 and moves again to the other end of the conveyor.
● After the box reaches the end of the conveyor on (LS 3) connected to X3 gets closed, the motor stops.The
system waits for the box to get and the box to be placed at the beginning of the conveyor.
● If the start switch (X5) is turned off, the system cannot run even if there is a box on the conveyor.

Shift Registers in plc

In many applications it is necessary to store the status of an event that has previously happened. As we've seen in past
chapters this is a simple process. But what do we do if we must store many previous events and act upon them later.

We use a register or group of registers to form a train of bits (cars) to store the previous on/off status. Each new
change in status gets stored in the first bit and the remaining bits get shifted down the train.

The shift register goes by many names. SFT (ShiFT), BSL (Bit Shift Left), SFR (Shift Forward Register) are some
of the common names. These registers shift the bits to the left. BSR (Bit Shift Right) and SFRN (Shift Forward
Register Not) are some examples of instructions that shift bits to the right. We should note that not all
manufacturers have shift registers that shift data to the right but most all do have left shifting registers.

A typical shift register instruction has a symbol like that shown above. Notice that the symbol needs 3 inputs and has
some data inside the symbol.

The reasons for each input are as follows:

● Data- The data input gathers the true/false statuses that will be shifted down the train. When the data
input is true the first bit (car) in the register (train) will be a 1. This data is only entered into the register
(train) on the rising edge of the clock input.
● Clock- The clock input tells the shift register to "do its thing". On the rising edge of this input, the shift
register shifts the data one location over inside the register and enters the status of the data input into the
first bit. On each rising edge of this input the process will repeat.
● Reset- The reset input does just what it says. It clears all the bits inside the register we're using to 0.

Define the task:

Shift Register – Conveyor Reject

Motor Encoder – On/Off – This will give a discrete signal when the conveyor is moving. It picks up the movement of
the freewheel.
Sensor A (Part Reject) – On/Off – NO
Sensor B (Part Present) – OA start push button (NO) is used to start the conveyor, and a stop pushbutton (NC) is used
to stop. Sensor B detects a product on the conveyor belt, and sensor A will see if it is too large and needs to be
rejected. The product is tracked along the conveyor belt, and when under the reject station, the Reject Blow Off will
expel the wrong product. The product is randomly placed on the conveyor belt, so an incremental encoder is used to
track the conveyor movement. The reset pushbutton (NO) will signal that all of the product on the conveyor has been
removed between the sensors and reject blow-off.
Define the Inputs and Outputs:
PLC Connections for the Shift Register Conveyor Example
Inputs:
Start Switch – On/Off (Normally Open) – NO
Stop Switch – On/Off (Normally Closed) – NC
Reset Switch – On/Off – NO
n/Off – NO
Outputs:
Motor – On/Off (Conveyor Run)
Air Blow Off – On/Off (Reject)
Develop a logical sequence of operations:

Fully understanding the logic before starting to program can save you time and frustration.
Sequence Table: The following is a sequence table for our conveyor reject application.

It is a simple sequence table but clarifies the following: The sequence will continue when the power goes off and
comes on. This means that the shift sequencer must be memory retentive. Sensors A and B must be on to get tracked
with a shift register.
Shift Registers: The Shift Register (SR) instruction shifts data through a predefined
number of BIT locations. These BIT locations can be a range of BITs, a single Word or DWord,
or a range of Words or DWords. The instruction has three inputs. Data, Clock, and Reset.
The data input will load the beginning bit with a ‘1’ if it is on or ‘0’ if it is not. The clock
input is used to shift the data through the shift register. In our example, we will use the
conveyor’s encoder to track the rejected container. So each pulse of the clock represents a
distance on the conveyor. The last input is the reset. It will place ‘0’ in all of the bits within the shift register.

Conveyor Reject program explanation

Start and stop the conveyor motor.
Shift register to track the rejected parts. This will move the bits with each pulse of the encoder. Note that the ‘V’
memory is used because it is memory retentive.
This will look at the bit in front of the reject station. We can measure and count off the length (conveyor) and then
determine the bit location at the reject location.
Test the PLC program:
Test the program with a simulator or actual machine.
Develop the PLC program:

Sorting station
Develop and test a LAD using simulation
software to sort three different types of jobs.
identify sensors, switches and actuators
required to implement the sytem.
Explanation of ladder diagram
● When start push button X0 is pressed ,conveyor motor connected to Y0 is turned ON
● Three shift register are used to shift the bits sensed by the objects by the sensors connected to X2,
X3 and X4 for small , medium and big objects to each shift register. the shift registers are
clocked by internal clock pulse M1013.
● Three sorting stations operated pneumatically with solenoids are connected to Y1,Y2 and Y3
respectively for small, medium and big objects
● when bit M7 is high small object is separated from the conveyor by solenoid connected to Y1
● when bit M27 is high small object is separated from the conveyor by solenoid connected to Y2
● when bit M47 is high small object is separated from the conveyor by solenoid connected to Y3

Process diagram
Jump Instruction
which enables part of a
program to be jumped over and the way in which subroutines in ladder programmes
can be called up. Subroutines enable commonly occurring operations in a program to
be repeatedly called up and used over again. 8.1 Jump A function often provided
with PLCs is the conditional jump.
Figure 8.1 illustrates this in a general manner. When there is an input to In 1, its
contacts close and there is an output to the jump relay. This then results in the
program jumping to the rung in which the jump end occurs, so missing out
intermediate program rungs. Thus, in this case, when there is an input to Input 1,
the program jumps to rung 4 and then proceeds with rungs 5, 6, etc. When there
is no input to Input 1, the jump relay is not energised and the program then proceeds
to rungs 2, 3, etc.

Subroutine
Subroutines are small programs to perform specific tasks which can be called for use in larger programs. Thus with
a Mitsubishi program we might have the situation shown in Figure 8.5(a). When input 1 occurs, the subroutine P is
called. This is then executed, the instruction SRET indicating its end and the point at which the program returns to
the main program. To clearly indicate where the main program ends the FEND instruction is used.
With Allen-Bradley, subroutines are called by using a jump-tosubroutine JSR instruction, the start of the
subroutine being indicated by SBR and its end and point of return to the main program by RET (Figure8.5(b)).
PLC Comparison instructions:

As an example, suppose a LES instruction is presented with two values. If the first value is less than the second, then
the comparison instruction is true.

Equal (EQU) Instruction

Use the EQU instruction to test whether two values are equal. If source A and source B are equal, the instruction is
logically true. If these values are not equal, the instruction is logically false.

Source A must be an address.

Source B can be either a program constant or an address.

Values are stored in two’s complementary form.

Not Equal (NEQ) Instruction

Use the NEQ instruction to test whether two values are not equal.

If source A and source B are not equal, the instruction is logically true.
Source A must be an address.

Source B can be either a program constant or an address.

Values are stored in two’s complementary form.

Less Than (LES) Instruction

Use the LES instruction to test whether one value (source A) is less than another (source B).

If source A is less than the value at source B, the instruction is logically true.

Source A must be an address.

Source B can be either a program constant or an address.

Values are stored in two’s complementary form.

Less Than or Equal (LEQ) Instruction

Use the LEQ instruction to test whether one value (source A) is less than or equal to another (source B).If the value
at source A is less than or equal to the value at source B, the instruction is logically true.

Source A must be an address.

Source B can be either a program constant or an address.

Values are stored in two’s complementary form.

Greater Than (GRT) Instruction

Use the GRT instruction to test whether one value (source A) is greater than another (source B).

If the value at source A is greater than the value at source B, the instruction is logically true.

Greater Than Or Equal (GEQ) Instruction

Use the GEQ instruction to test whether one value (source A) is greater than or equal to another (source B).
If the value at source A is greater than or equal to the value at source B, the instruction is logically true.

Masked Comparison for Equal (MEQ)

Use the MEQ instruction to compare data at a source address with data at a compare address.

The Use of this instruction allows portions of the data to be masked by a separate word.

Source is the address of the value you want to compare.

Mask is the address of the mask through which the instruction moves data.

The mask can be a hexadecimal value.

Compare is an integer value or the address of the reference.

If the 16 bits of data at the source address are equal to the 16 bits of data at the compare address (less masked bits),
the instruction is true.

The instruction becomes false as soon as it detects a mismatch.

Limit Test (LIM) Instruction

Use the LIM instruction to test for values within or outside a specified range, depending on how you set the limits.

The Low Limit, Test, and High Limit values can be word addresses or constants, restricted to the following
combinations:

● If the Test parameter is a program constant, both the Low Limit and High Limit parameters must be word
addresses.

● If the Test parameter is a word address, the Low Limit and High Limit parameters can be either a program
constant or a word address.

Math Instructions
Increment
Whenever this instruction is enabled, it increments the content of the destination by one.

In above example, whenever X0 becomes false to true, D0 is incremented by one.

Decrement
Whenever this instruction is enabled, it increments the content of the destination by one.
In the above example, whenever X0 becomes false to true, D0 is Decremented by one.

Control panel components

Elements of logic panel:-
DIN rail
It is a zinc – plated or chromated metal rail which is used for setting up terminal blocks
to connect multiple components to a single data logger installing equipment like a
MCB’S, contactors, power supplies and OLR etc. Without using screws inside the
control panel

Cable channel
It is an inspection type of PVC enclosed channel with linear extruded profiles, which
provides a pathway for electrical wiring inside the control panel. It has the opening slots on
the sides to facilitate good ventilation and visuals. Used to protect cables, and wiring in
numerous home, commercial, industrial, medical applications.
Terminals for wire connection
It is the set of insulated screw terminals at both sides used to connect the accessories
of the control panel with external control switches, limit switches, input supply and
motor terminals etc.
Terminal connectors with barrier strips and clamping plates provide a tight and
electrically sound termination. It is available in various size, current and voltage
ratings.
VFD ( variable frequency drive )
A variable – frequency drive (VFD) is a type of motor drive used in an electro -
mechanical drive system to control AC motor speed and torque by varying motor input
frequency and associated voltage or current variation. VFD also known as ‘AFDs’
(adjustable frequency drive), ‘ASDs’ (adjustable – speed drives), ‘VSDs’ (variable -
speed drives), ‘AC drives’, ‘micro drives’,’inverter drives’ or, simply drives’
VFDs are used in applications ranging from small appliances to large compressors. An
increasing number of end users are showing greater interest in electric driver systems
due to more stringent emission standards and demands for increased reliability and
better availability. Systems using VFDs can be more efficient than those using
throttling control of fluid flow, such as in systems with pumps and damper control
for fans. However, the global market penetration for all applications of VFDs is
relatively small
Over the last four decades, power electronics technology has reduced VFD cost and size and has improved
performance through advances in semiconductors switching devices, drive topologies, simulations and control
techniques, and control hardware and software
VFDs are made in a number of different low and medium - voltage AC –AC and DC-AC topologies
A variable – frequency drive is a device used in a drive system consisting of the following three
main sub-systems: AC motor, main
drive controller assembly, and
drive/operator interface
PROGRAMMABLE LOGIC
CONTROLLER (PLC)

A PROGRAMMABLE LOGIC
CONTROLLER (PLC) is an
industrial computer control system
that continuously monitors the state of input
devices and makes decisions based upon a
custom program to control the state of output
devices.
There are many advantages of PLC or
Programmable Logic Controller that is why it is
widely used. The main advantages of PLC are

1. Industrial automation using PLC very

efficient.
2. They are very fast in operation.
3. Additional advanced tasks can be perform
using PLC.
4. Easy to use and very good experience.
5. Automated control is also a great advantage of PLC

Block Diagram of PLC

Here a typical block diagram of PLC is given below. From the below block diagram you can understand the total
concept and working procedure of Programmable Logic Controller.

Main Parts of PLC

As you see in the above figure, PLC has main three parts,
1. CPU or Central Processing Unit
2. Input Module and Output Module
3. Programming device
Generally, microcontroller or microprocessor is used in Programmable Logic Controller and they are programmed by
an external computer. After installing the appropriate program, PLC works.
PLC Working Procedure
Now, let's discuss each block of the Programmable Logic Control circuits which will help you to understand the
working principle of PLC.
CPU(Central Processing Unit)
It is the main part of the PLC. It processes all the instructions required for working of the circuit. First, we store
the program or instruction in memory. In the operation time, the CPU takes the commands from the input module and
then processes and ultimately gives the output to the output module.
Memory
It is a storage device which stores all data, programs, and instructions.
Programming Device
It is the device where the program or instruction is written and then using this device the program or instruction is
stored to the PLC Memory. The programming device may be a computer, laptop or a handheld device etc
Input and Output Module
The CPU or Microprocessor can work with 5V DC supply and it can deliver very small output current. But the input
devices or sensor may not work with the same voltage that is 5V DC. So to interface real-world input devices and
sensors with the microprocessor, the input module is used. Here the input module always gives a 5V DC input signal to
the CPU.
Another important point is that the microprocessor can work with only the digital signal but all the input devices or
sensors may not produce a digital signal. In fact, most of the sensors create an analog signal. So another important
function of the input module is to convert the analog signal into a digital signal.
Microprocessor or CPU can deliver a very small amount of current (in a few mA) at 5V DC as output. So we can not
drive the loads directly with the microprocessor. Here the output Module solved this problem.
Power Supply
The power supply circuit provides the power supply to all devices such as CPU, Memory, Input module, and output
module. Generally, the PLC works with up to 24V DC supply.
SMPS ( SWITCH MODE POWER SUPPLY )
SMPS, an acronym for Switch Mode Power Supply is a type of power supply unit that produces regulated dc output
by using semiconductor switching techniques. Basically, here the regulated dc output signal is converted form of ac
or dc unregulated input signal. It is sometimes also known as switched mode power supply or switching mode power
supply.

Advantages
● The switch mode power supply encompasses a smaller size.
● The switch mode power supply has light weight.
● It includes a way better power effectiveness ordinarily 60 to 70 percent.
● It features a solid against interference.
● SMPS has a wide yield range.
Disadvantages
● The switch mode power supply is complex.
● The SMPS has higher yield swell and its control is worse.
● It can be utilized as a step down regulator.
● It has as it were one output voltage.
● SMPS moreover cause harmonic distortion.
RELAYS
A switch is a component that opens (turn off) & closes (turn on) an electrical circuit. whereas, a
relay is an electrical switch that controls (switch on & off) a high voltage circuit using a low
voltage source. A relay completely isolates the low voltage circuit from the high voltage circuit.
Relays are the essential component for protection & switching of a number of the control circuits
& other electrical components. All the Relays react to voltage or current with the end goal that
they open or close the contacts or circuits.

Wire Connectors
Wire connectors used to connect the wires to terminals of the equipments or terminal blocks
There are several types of wire connectors shown in the following table. each tailored to a specific purpose. Usually,
the product name is directly related to how to use the wire connector. This can help you select the correct connector
for your job.
Contactors
A contactor is a component used to switch an
electrical circuit on or off. It is considered to be
part of the relay family, but the main difference
is that they are used for applications or in circuits
that require more current. They are generally used
to supply power to lighting circuits or electrical
motors
Contactors include multiple contacts which are used
to control other components and send signals within
an electrical system or circuit. The contacts are
generally normally open but can be normally closed
also. Typically the contacts are used to supply the
power to the load when the contactor coil has been
energized.
The most common applications for contactors are
when a high current load is present. An example of
this is supplying power to an electrical motor. An
electrical motor produces arcs when they are interrupted. By using a contactor we reduce the number of arcs and
control them to be safe.
Power sockets
A socket is a device or point in a wall where you can connect electrical equipment to the power supply.

Fans
AC Compact Fans all metal also known as External Rotor Motor Fans are basically compact fans with metal blades
working on an alternating current. All metal AC Fans are designed with an external rotor motor and a compact
structure making speed regulation possible. Such AC fans are durable and can withstand extreme temperature and
pressure conditions. These AC Cooling Fans in frequencies of 50 Hz and 60Hz. These cooling fans are available in
varying voltages of 24VAC, 115VAC, 230VAC& 415VAC. The sizes of AC Axial Fans metal blade vary from 120 mm
to 280 mm. These AC Axial Fans are available in both low speed as well as high speed depending upon the application.

Transformer
Transformer is an electrical static device. Transformer power transforms one
circuit to another circuit without changing frequency. It works on the principle of
electromagnetic induction ( mutual induction).
It is used in audio circuits and it can block the radio frequency interference or the
DC component of audio signals. It could provide impedance matching between high
and low impedance circuit. It is a magnetic device so it is susceptible to external
magnetic fields. It could split or combine audio signals, it can do impedance
matching between a high impedance instrument output and a low
HMI ( Human machine interface)
Human Machine Interface, often known by the acronym HMI, refers to a
dashboard or screen used to control machinery. Line operators, managers and
supervisors in industry rely on HMIs to translate complex data into useful
information.
For example, they use HMIs to monitor machinery to make sure it’s working
properly. Easy-to-understand visual displays give meaning and context to near
real-time information about tank levels, pressure and vibration measurements,
motor and valve status and other variables.
But the advanced capabilities of today’s HMIs enable managers and supervisors to
do much more than control processes. Using historical and trending data they
offer vast new opportunities to improve product quality and make systems more
efficient.
For all these reasons, HMIs play a key role in the smooth and effective running of factories and manufacturing
operations.

Selector switches
Selector switches can be rotated right, left, or in the center in order to
open or close the electrical contacts. The function of a selector switch is
to control devices as well as switch between a minimum of two or more
circuits. The perfect use for a selector switch is when used for
controlling an output of a device. For example, on an audio device a
selector switch can be used to connect an audio output to multiple sets of
speakers.
Selector switches come as a complete unit often listed as a terminal block
meaning the selector switch is a complete block (consisting of selector
switch actuator, contact block, and fixing collar) which makes it simple
and easy to install. This is not to be confused with rotary knobs or
encoders, as Selector switches are a complete panel mount switch.
Push button switches
Push button switch
A push button switch is a simple mechanism that initiates power to a
machine, device, or appliance. The body is typically metal or plastic,
featuring a durable and ergonomic design. With switches available that
provide latching or momentary action, there are push button switches for
virtually any relevant application. This blog will explain how push button
switches work and discuss typical applications for various push button
switch types.

Types of push button switches

Push button switches come in two types: momentary switches or push-pull switches.
• Momentary: The momentary push button switch has a single pole and is initially in an off state. When the
operator presses the push button switch, it changes to on. There are also double-pole momentary switches that
provide an additional state of functionality.

• Push-pull: Push-pull or Maintained switches are typically in an off state until an operator presses the
button and engages the actuator. The machine or device will remain on until an operator pulls the actuator to its
initial position.
Indicating lamp
The indicator light is a panel-mounted lamp assembly consisting of the indicator
housing, an internal lamp, terminals, and a lens. The light source of indicator
light is a high brightness pure colour LED or incandescent bulb.
As the name implies, indicator lights reveal the status (ON or OFF) of an
electrical apparatus in switchboards. In more sophisticated systems, the
indicating lights may annunciate the cause of the current interruption, such as
line-to-ground fault, overload, and overcurrent condition.
The customer usually selects the colour of the lights for a particular indicating
function. In selecting indicating lights, it is of paramount importance to know
their voltage and resistance rating because these parameters establish the minimum current rating of the contact that
controls the switching of the lights.
A motor’s fuses, circuit breakers, magnetic starters, and relays are all housed within a metallic cabinet—located on
what is commonly known as a motor control center on the front panel where the indicator lights and the start-stop
pushbuttons are located.
Indicator lights include a coloured lens such as red, green, blue, yellow/amber, clear, or white. These coloured
lenses symbolize the condition of the machine or equipment to which the lights are connected.

Types of PLCs
When it comes to the types of PLC, these two are the most common answer that you will
find in any source from the internet simply because they are the least subtle of all the
classifications available.
1. Fixed ( Integrated or Compact) PLC
2. Modular PLC
1. Fixed/Integrated/Compact PLC

This type of PLC is most commonly called the Fixed I/O PLC.
“Fixed I/O” actually stands for Fixed “Input/Output”. When you buy Compact PLCs, you
will notice that the input section and the output sections of the PLC are integrated into the
microcontroller itself.
This means that every type of output or input is fixed and is determined by the
manufacturer.
Furthermore, the number of inputs and outputs may not be expanded in this type of PLC.
2. Modular PLC

The modular PLC is a type that allows multiple expansions of the PLC system through the
use of modules, hence the term “modular”.
Modules give the programmable logic controller additional features like increased number
of I/O units, and they are usually easier to use because each component is independent of
each other.
The power supply, communications module, Input/Output module are all separate to the
actual microcontroller so you have to manually connect them to each other to create your
PLC control system.
A type of modular PLC is the rack-mounted or rack mount PLC. In a rack mount PLC, the
communications module of the PLC resides in the rack itself, so all connections are
centralized.

Some of the Brands of PLCs include:

● Allen Bradley
● ABB
● Siemens
● Mitsubishi PLC
● Hitachi PLC
● Delta PLC
● General Electric (GE) PLC
● Honeywell PLC
Comparison of brands of PLC
Selection of PLC for given application

To select a suitable PLC for a given application following points are considered
1. Number of I/O’s:
It is very important that you know the exact number of input and output that are going to be used in the process for
best and economical use. PLC36 system must have enough termination points to connect all signal and control lines for
the process.
2. Type of I/O’s:
On selecting PLC, we have to consider what types of I/Os are needed, such as digital input like Sensor, Push Buttons
etc, or analog inputs like pressure and temperature. Just like that we consider output, digital outputs are Relay,
Contactor, Lamp etc. or you need an Analog output like Drive and Control Valves.
3. Memory and Programming Requirements:
Memory size is normally related to the amount of I/O points required in the system. The other factor that affects the
amount of memory required is the control program that is to be installed. Program size is also related to the number
of I/O points since it must include instructions for reading from or writing to each point.
4. Compact or Modular PLC :
PLC can select between modular and compact types, modular type allows us to design the PLC for our purpose and
which has Power supply and controller in different housing while Compact Type PLC are those which has Power
supply and controller in the same housing.
5. Instruction Set/CPU:
All PLC handle logic control, sequencing, etc, but difference in the area of data handling, special functions and
communications. Larger programmable controllers tend to have more powerful instructions than smaller ones in these
areas.
6. PLC Scan Time:
PLC scan time is a time needed for PLC to completely Scan one cycle of PLC. It may consist of reading PLC input
status, clearing PLC memory, Executing the PLC program and updating the Output. It is sometimes needed PLC with
less scan time but it is costly.
7. Sinking & Sourcing PLC:
Making a PLC at the source in Input or causing a PLC to sink into the input depends on the user’s requirements for the
PLC to be chosen in that way. Some PLCs can support both sink and source input and output.
8. Manufacturer’s Support and Backup:
Before choosing a PLC from a manufacturer, it should be considered the manufacturer’s assistance and service
provided. It is a great advantage if the supplier/manufacturer can offer assistance with the system design work.

TOOLS REQUIDMENT FOR INSTALLING CONTROL PANEL

● Flat-head screwdriver: Used to tighten or loosen slotted screws.

● Phillips-head screwdriver: Used to tighten or loosen cross-headed screws.
● Tor screwdriver: Used to tighten or loosen screws that have a star-like depression on the top, a feature
that is mainly found on laptops.
● Hex driver: Used to tighten or loosen nuts in the same way that a screwdriver tightens or loosens screws
(sometimes called a nut driver).
 ● Needle-nose pliers: Used to hold small parts.
● Wire cutters: Used to strip and cut wires.
● Tweezers: Used to manipulate small parts.
● Part retriever: Used to retrieve parts from locations that are too small for your hand to fit.
● Flashlight: Used to light up areas that you cannot see well.
● Wire stripper: A wire stripper is used to remove the insulation from wire so that it can be twisted to other
wires or crimped to connectors to make a cable.
● Crimper: Used to attach connectors to wires.
● Punch-down tool: Used to terminate wire into termination blocks. Some cable connectors must be connected
to cables using a punch down tool.
● A digital multimeter, as shown in Figure 2-3, is a device that can take many types of measurements. It
tests the integrity of circuits and the quality of electricity in computer components. A digital multimeter
displays the information on an LCD or LED.

Week 4
Power Requirements and Safety Circuitry
Power Requirements
Common AC Source. The system power supply and I/O devices should have a common AC source (see Figure 6).
This minimizes line interference and prevents faulty input signals stemming from a stable AC source to the power
supply and CPU, but an unstable AC source to the I/O devices. By keeping both the power supply and the I/O
devices on the same power source, the user can take full advantage of the power supply’s line monitoring feature.
If line conditions fall below the minimum operating level, the power supply will detect the abnormal condition and
signal the processor, which will stop reading input data and turn off all outputs.

Isolation Transformers. Another good practice is to use an isolation transformer on the AC power line going to
the controller. An isolation transformer is especially desirable when heavy equipment is likely to intro- duce noise
into the AC line. An isolation transformer can also serve as a step-down transformer to reduce the incoming line
voltage to a desired level. The transformer should have a sufficient power rating (in units of volt- amperes) to
supply the load, so users should consult the manufacturer to obtain the recommended transformer rating for their
particular application.

Safety Circuitry
The PLC system should contain a sufficient number of emergency circuits to either partially or totally stop the
operation of the controller or the controlled machine or process (see Figure 7). These circuits should be routed
outside the controller, so that the user can manually and rapidly shut down the system in the event of total
controller failure. Safety devices, like emergency pull rope switches and end-of-travel limit switches, should
bypass the controller to operate motor starters, solenoids, and other devices directly. These emergency circuits
should use simple logic with a minimum number of highly reliable, preferably electromechanical, components.

Emergency Stops. The system should have emergency stop circuits for every machine directly controlled by the
PLC. To provide maximum safety, these circuits should not be wired to the controller, but instead should be left
hardwired. These emergency switches should be placed in locations that the operator can easily access. Emergency
stop switches are usually wired into master control relay or safety control relay circuits, which remove power
from the I/O system in an emergency.

Master control relay (MCR) and safety control relay (SCR) circuits provide an easy way to
remove power from the I/O system during an emergency situation (see Figure 8). These control
relay circuits can be de-energized by pushing any emergency stop switch
connected to the circuit. De-energizing the control relay coil removes power to the input and output devices. The
CPU, however, continues to receive power and operate even though all of its inputs and outputs are disabled.

An MCR circuit may be extended by placing a PLC fault relay (closed during normal PLC operation) in series with
any other emergency stop condition. This enhancement will cause the MCR circuit to cut the I/O power in the case
of a PLC failure (memory error, I/O communications error, etc.). Figure 9 illustrates the typical wiring of a
master control relay circuit.

supply should use a properly rated emergency power disconnect, thus providing a way to remove power from the entire
programmable controller system (refer to Figure 9). Sometimes, a capacitor (0.47 mF for 120 VAC, 0.22mF for
220 VAC) is placed across the disconnect to protect against an outrush condition. Outrush occurs when the power
disconnect turns off the output triacs, causing the energy stored in the inductive loads to seek the nearest path to
ground, which is often through the triacs.

I/O Installation, Wiring, and Precautions

Input/output installation is perhaps the biggest and most critical job when installing a programmable controller
system. To minimize errors and sim- plify installation, the user should follow predefined guidelines. All of the
people involved in installing the controller should receive these I/O system

installation guidelines, which should have been prepared during the design phase. A complete set of documents
with precise information regarding I/O placement and connections will ensure that the system is organized properly.
Furthermore, these documents should be constantly updated during every stage of the installation. The following
considerations will facilitate an orderly installation.

I/O Module Installation

Placement and installation of the I/O modules is simply a matter of inserting the correct modules in their proper
locations. This procedure involves verifying the type of module (115 VAC output, 115 VDC input, etc.) and the slot
address as defined by the I/O address assignment document. Each terminal in the module is then wired to the field
devices that have been assigned to that termination address. The user should remove power to the modules (or rack)
before installing and wiring any module.

Wiring Considerations
Wire Size. Each I/O terminal can accept one or more conductors of a particular wire size. The user should check
that the wire is the correct gauge and that it is the proper size to handle the maximum possible current.

Wire and Terminal Labeling. Each field wire and its termination point should be labeled using a reliable
labeling method. Wires should be labeled with shrink-tubing or tape, while tape or stick-on labels should identify
each terminal block. Color coding of similar signal characteristics (e.g., AC: red, DC: blue, common: white,
etc.) can be used in addition to wire labeling. Typical labeling nomenclature includes wire numbers, device names or
numbers, and the input or output address assignment. Good wire and terminal identification simplifies maintenance
and troubleshooting.

Wire Bundling. Wire bundling is a technique commonly used to simplify the connections to each I/O module. In
this method, the wires that will be connected to a single module are bundled, generally using a tie wrap, and then
routed through the duct with other bundles of wire with the same signal
characteristics. Input, power, and output bundles carrying the same type of signals should be kept in separate
ducts, when possible, to avoid interference.
 Wiring Procedures
Once the I/O modules are in place and their wires have been bundled, the wiring to the modules can begin. The
following are recommended procedures for I/O wiring:

• Remove and lock out input power from the controller and I/O before any installation and
wiring begins.
• Verify that all modules are in the correct slots. Check module type and model number by
inspection and on the I/O wiring diagram. Check the slot location according to the I/O address
assignment document.
• Loosen all terminal screws on each I/O module.
• Locate the wire bundle corresponding to each module and route it through the duct to the
module location. Identify each of the wires in the bundle and check that they correspond to that
particular module.
• Starting with the first module, locate the wire in the bundle that connects to the lowest
terminal. At the point where the wire is at a vertical height equal to the termination point,
bend the wire at a right angle towards the terminal.
• Cut the wire to a length that extends 1/4 inch past the edge of the terminal screw. Strip
approximately 3/8 inch of insulation from the end of the wire. Insert the uninsulated end of
the wire under the pressure plate of the terminal and tighten the screw.
• If two or more modules share the same power source, jumper the power wiring from one
module to the next.
• If shielded cable is being used, connect only one end to ground, preferably at the rack
chassis. This connection will avoid possible ground loops. A ground loop condition exists when
two or more electrical paths are created in a ground line or when one or more paths are created
in a shield (Section 7 explains how to identify a ground loop). Leave the other end cut back and
unconnected, unless other- wise specified.
• Repeat the wiring procedure for each wire in the bundle until the module wiring is complete.
• After all of the wires are terminated, check for good terminations by gently pulling on
each wire.

Special I/O Connection Precautions

Certain field device wiring connections, however, may need special attention. These connections include leaky inputs,
inductive loads, output fusing, and shielded cable.

Connecting Leaky Inputs. Some field devices have a small leakage current even when they are in the OFF state.
Both triac and transistor outputs exhibit this leakage characteristic, although transistor leakage current is much
lower. Most of the time, the leaky input will only cause the module’s input indicator to flicker; but sometimes,
the leakage can falsely trigger an input circuit, resulting in misoperation. A typical device that exhibits this
leakage situation is a proximity switch. This type of leakage may also occur when an output module drives an input
module when there is no other load.

Figure 17 illustrates two leakage situations, along with their corrective actions. A leaky input can be corrected by
placing a bleeding (or loading) resistor across the input. A bleeding resistor introduces resistance into the circuit,
causing the voltage to drop on the line between the leaky field device
and the input circuit. This causes a shunt on the input’s terminals. Conse- quently, the leakage current is routed
through the bleeding resistor, minimiz- ing the amount of current to the input module (or to the output device).
This prevents the input or output from turning ON when it should be OFF.

Suppression of Inductive Loads. The interruption of current caused by turning an inductive load’s output OFF
generates a very high voltage spike. These spikes, which can reach several thousands of volts if not suppressed,
can occur either across the leads that feed power to the device or between both power leads and the chassis ground,
depending on the physical construction of the device. This high voltage causes erratic operation and, in some cases,
may damage the output module. To avoid this situation, a snubber circuit, typically a resistor/capacitor network
(RC) or metal oxide varistor (MOV), should be installed to limit the voltage spike, as well as control the rate of
current change through the inductor (see Figure 18).

Most output modules are designed to drive inductive loads, so they typically include suppression networks.
Nevertheless, under certain loading condi- tions, the triac may be unable to turn OFF as current passes through
zero (commutation), thus requiring additional external suppression in the system.

An RC snubber circuit placed across the device can provide additional suppression for small AC devices, such as
solenoids, relays, and motor starters up to size 1. Larger contactors (size 2 and above) require an MOV in addition
to the RC network. A free-wheeling diode placed across the load can provide DC suppression. Figure 19 presents
several examples of inductive load suppression.

Fusing Outputs. Solid-state outputs normally have fusing on the module, to protect the triac or transistor from
moderate overloads. If the output does not have internal fuses, then fuses should be installed externally (normally
at the terminal block) during the initial installation. When adding fuses to an output circuit, the user should
adhere to the manufacturer’s specifications for the particular module. Only a properly rated fuse will ensure that
the fuse will open quickly in an overload condition to avoid overheating of the output switching device.

Shielding. Control lines, such as TTL, analog, thermocouple, and other low- level signals, are normally routed
in a separate wireway, to reduce the effects of signal coupling. For further protection, shielded cable should be
used for the control lines, to protect the low-level signals from electrostatic and magnetic coupling with both lines
carrying 60 Hz power and other lines carrying rapidly changing currents. The twisted, shielded cable should have
at least a one-inch lay, or approximately twelve twists per foot, and should be protected on both ends by shrink-
tubing or a similar material. The shield should be connected to control ground at only one point (see Figure 20),
and shield continuity must be maintained for the entire length of the cable. The shielded cable should also be
routed away from high noise areas, as well as insulated over its entire length.

PLC Start-Up and

Checking
Procedures
Static Input Wiring Check
Proper input wiring can be verified using the following procedures:

• Place the controller in a mode that will inhibit the PLC from any automatic operation. This mode will vary
depending on the PLC model, but it is typically stop, disable, program, etc.
• Apply power to the system power supply and input devices. Verify that all system diagnostic indicators show
proper operation. Typical indicators are AC OK, DC OK, processor OK, memory OK, and I/O communication OK.
• Verify that the emergency stop circuit will de-energize power to the I/O devices.
• Manually activate each input device. Monitor the corresponding LED status indicator on the input module
and/or monitor the same address on the programming device, if used. If properly wired, the indicator will turn ON.
If an indicator other than the expected one turns ON when the input device is activated, the input device may be
wired to the wrong input terminal. If no indicator turns ON, then a fault may exist in either the input device, field
wiring, or input module.
• Take precautions to avoid injury or damage when activating input devices that are connected in series with
loads that are external to the PLC.

Static Output Wiring Check

The following procedures should be used to verify output wiring:

• Locally disconnect all output devices that will cause mechanical motion.
• Apply power to the controller and to the input/output devices. If an emergency stop can remove power to the
outputs, verify that the circuit does remove power when activated.
• Perform the static check of the outputs one at a time. If the output is a motor or another device that has
been locally disconnected, reapply power to that device only prior to checking. The output operation check can be
performed using one of the following methods:

• Assuming that the controller has a forcing function, test each output, with the use of the programming
device, by forcing the output ON and setting the corresponding terminal address (point) to 1. If properly wired,
the corresponding LED indicator will turn ON and the device will energize. If an indicator other than the expected
one turns ON when the terminal address is forced, then the output device may be wired to the wrong output
terminal. If no indicator turns ON, then a fault may exist in either the output device, field wiring, or output
module.

• Program a dummy rung, which can be used repeatedly for testing each output, by programming a single
rung with a single normally open contact (e.g., a conveniently located push button) controlling the output. Place
the CPU in either the RUN, single-scan, or a similar mode, depending on the controller. With the controller

in the RUN mode, depress the push button to perform the test. With the controller in single-scan mode, depress
and maintain the push button while the controller executes the single-scan. Observe the output device and LED
indicator, as described in the first procedure.

Dynamic System Checkout

The following practices outline proce- dures for the dynamic system checkout:

• Load the control program into the PLC memory.

• Test the control logic using one of the following methods:
• Switch the controller to the TEST mode, if available, which will allow the execution and
debugging of the control program while the outputs are disabled. Check each rung by
observing the status of the output LED indicators or by monitoring the corresponding output
rung on the programming device.

• If the controller must be in the RUN mode to update outputs during the tests, locally
disconnect the outputs that are not being tested, to avoid damage or harm. If an MCR or similar
instruction is available, use it to bypass execution of the outputs that are not being tested, so
that disconnection of the output devices is not necessary.
• Check each rung for correct logic operation, and modify the logic if necessary. A useful
tool for debugging the control logic is the single scan. This procedure allows the user to
observe each rung as every scan is executed.
• When the tests indicate that all of the logic properly controls the outputs, remove all of
the temporary rungs that may have been used. Place the controller in the RUN mode, and test
the total system operation. If all procedures are correct, the full automatic control should
operate smoothly.
• Immediately document all modifications to the control logic, and revise the original
documentation. Obtain a reproducible copy of the program as soon as possible.

PLC System Maintenance

Programmable controllers are designed to be easy to maintain, to ensure trouble-free operation. Still, several
maintenance aspects should be considered once the system is in place and operational. Certain maintenance measures,
if performed periodically, will minimize the chance of system malfunction. This section outlines some of the
practices that should be followed to keep the system in good operating condition.
PREVENTIVE MAINTENANCE
Preventive maintenance of programmable controller systems includes only a few basic procedures, which will
greatly reduce the failure rate of system components. Preventive maintenance for the PLC system should be
scheduled with the regular machine or equipment maintenance, so that the equipment and controller are down for a
minimum amount of time. However, the schedule for PLC preventive maintenance depends on the controller’s
environment, the harsher the environment, the more frequent the maintenance. The following are guidelines for
preventive measures:

• Periodically clean or replace any filters that have been installed in enclosures at a frequency
dependent on the amount of dust in the area. Do not wait until the scheduled machine
maintenance to check the filter. This practice will ensure that clean air circulation is present
inside the enclosure.
• Do not allow dirt and dust to accumulate on the PLC’s components; the central processing unit
and I/O system are not designed to be dust proof. If dust builds up on heat sinks and electronic
circuitry, it can obstruct heat dissipation, causing circuit malfunction. Further- more, if
conductive dust reaches the electronic boards, it can cause a short circuit, resulting in possible
permanent damage to the circuit board.
• Periodically check the connections to the I/O modules to ensure that all plugs, sockets,
terminal strips, and modules have good connections. Also, check that the module is securely
installed. Perform this type of check more often when the PLC system is located in an area
that experiences constant vibrations, which could loosen terminal connections.
• Ensure that heavy, noise-generating equipment is not located too close to the PLC.
• Make sure that unnecessary items are kept away from the equipment inside the enclosure.
Leaving items, such as drawings, installation manuals, or other materials, on top of the CPU
rack or other rack enclosures can obstruct the airflow and create hot spots, which can cause
system malfunction.
• If the PLC system enclosure is in an environment that exhibits vibration, install a vibration
detector that can interface with the PLC as a preventive measure. This way, the programmable
controller can monitor high levels of vibration, which can lead to the loosening of connections.

SPARE PARTS

It is a good idea to keep a stock of replacement parts on hand. This practice will minimize downtime resulting from
component failure. In a failure situation, having the right spare in stock can mean a shutdown of only minutes,
instead of hours or days. As a rule of thumb, the amount of a spare part stocked should be 10% of the number of
that part used. If a part is used infrequently, then less than 10% of that particular part can be stocked.

Main CPU board components should have one spare each, regardless of how many CPUs are being used. Each power
supply, whether main or auxiliary, should also have a backup. Certain applications may require a complete CPU
rack as a standby spare. This extreme case exists when a downed system must be brought into operation
immediately, leaving no time to determine which CPU board has failed.

Replacement of I/O Modules

If a module must be replaced, the user should make sure that the replacement module being installed is the correct
type. Some I/O systems allow modules to be replaced while power is still applied, but others may require that power
be removed. If replacing a module solves the problem, but the failure reoccurs in a relatively short period, the user
should check the inductive loads. The inductive loads may be generating voltage and current spikes, in which case,
external suppression may be necessary. If the module’s fuse blows again after it is replaced, the problem may be that
the module’s output current limit is being exceeded or that the output device is shorted.

Troubleshooting the PLC System

Troubleshooting Ground Loops

As mentioned earlier, a ground loop condition occurs when two or more electrical paths exist in a ground line. For
example, in Figure 21, the transducers and transmitter are connected to ground at the chassis (or device enclosure)
and connected to an analog input card through a shielded cable. The shield connects to both chassis grounds,
thereby creating a path for current to flow from one ground to another since both grounds have different
potentials. The current flowing through the shield could be as high as several amperes, which would induce
significant magnetic fields in the signal transmission. This could create interference that would result in a
possible misreading of the analog signal. To avoid this problem, the shield should be connected to ground on only
one side of the chassis, preferably the PLC side. In the example shown in Figure 21, the shield should only be
connected to ground at the analog input interface.

Figure 21. Ground loop created by shielded cable grounded at both ends.
 To check for a ground loop, disconnect the ground wire at the ground termination and measure the resistance from
the wire to the termination point where it is connected (see Figure 22). The meter should read a large ohm value. If a
low ohm value occurs across this gap, circuit continuity exists, meaning that the system has at least one ground loop.

Figure 22. Procedure for identifying ground loops.

DIAGNOSTIC INDICATORS
LED status indicators can provide much information about field devices, wiring, and I/O modules. Most
input/output modules have at least a single indicator—input modules normally have a power indicator, while output
modules normally have a logic indicator.

For an input module, a power LED indicates that the input device is activated and that its signal is present at the
module. This indicator alone cannot isolate malfunctions to the module, so some manufacturers provide an
additional diagnostic indicator, a logic indicator. An ON logic LED indicates that the input signal has been
recognized by the logic section of the input circuit. If the logic and power indicators do not match, then the
module is unable to transfer the incoming signal to the processor correctly. This indicates a module malfunction.

An output module’s logic indicator functions similarly to an input module’s logic indicator. When it is ON, the
logic LED indicates that the module’s logic circuitry has recognized a command from the processor to turn ON. In
addition to the logic indicator, some output modules incorporate either a blown fuse indicator or a power indicator
or both. A blown fuse indicator indicates the status of the protective fuse in the output circuit, while a power
indicator shows that power is being applied to the load. Like the power and logic indicators in an input module, if
both LEDs are not ON simultaneously, the output module is malfunctioning.

LED indicators greatly assist the troubleshooting process. With both power and logic indicators, the user can
immediately pinpoint a malfunctioning module or circuit. LED indicators, however, cannot diagnose all possible
problems; instead, they serve as preliminary signs of system malfunctions.

Troubleshooting PLC Inputs

If the field device connected to an input module does not seem to turn ON, a problem may exist somewhere between
the L1 connection and the terminal connection to the module. An input module’s status indicators can provide
information about the field device, the module, and the field device’s wiring to the module that will help pinpoint
the problem.

The first step in diagnosing the problem is to place the PLC in standby mode, so that it is not activating the output.
This allows the field device to be manually activated (e.g., a limit switch can be manually closed). When the field
device is activated, the module’s power status indicator should turn ON, indicating that power continuity exists. If
the indicator is ON, then wiring is not the cause of the problem.
The next step is to evaluate the PLC’s reading of the input module. This can be accomplished using the PLC’s test
mode, which reads the inputs and executes the program but does not activate the outputs. In this mode, the PLC’s
display should either show a 1 in the image table bit corresponding to the activated field device or the contact’s
reference instruction should become highlighted when the device provides continuity (see Figure 23). If the PLC is
reading the device correctly, then the problem is not located in the input module. If it does not read the device
correctly, then the module could be faulty. The logic side of the module may not be operating correctly, or its
optical isolator may be blown. Moreover, one of the module’s interfacing channels could be faulty. In this case,
the module must be replaced.

Figure 23. Highlighted contact

indicating power continuity.

If the module does not read the field device’s signal, then further tests are required. Bad wiring, a faulty field
device, a faulty module, or an improper voltage between the field device and the module could be causing the
problem. First, close the field device and measure the voltage to the input module. The meter should display the
voltage of the signal (e.g., 24 volts DC). If the proper voltage is present, the input module is faulty because it is
not recognizing the signal. If the measured voltage is 10–15% below the proper signal voltage, then the problem
lies in the source voltage to the field device. If no voltage is present, then either the wiring or the field device is
the cause of the problem. Check the wiring connection to the module to ensure that the wire is secured at the
terminal or terminal blocks.

To further pinpoint the problem, check that voltage is present at the field device. With the device activated,
measure the voltage across the device using a voltmeter. If no voltage is present on the load side of the device (the
side that connects to the module), then the input device is faulty. If there is power, then the problem lies in the
wiring from the input device to the module. In this case, the wiring must be traced to find the problem.

TROUBLESHOOTING PLC OUTPUTS

PLC output interfaces also contain status indicators that provide useful troubleshooting information. Like the
troubleshooting of PLC inputs, the first step in troubleshooting outputs is to isolate the problem to either the
module, the field device, or the wiring.

At the output module, ensure that the source power for switching the output is at the correct level. In a 120 VAC
system, this value should be within 10% of the rated value (i.e., between 108 and 132 volts AC). Also, examine the
output module to see if it has a blown fuse. If it does have a blown fuse, check the fuse’s rated value.
Furthermore, check the output device’s current requirements to determine if the device is pulling too much current.

If the output module receives the command to turn ON from the processor yet the module’s output status does not
turn ON accordingly, then the output module is faulty. If the indicator turns ON but the field device does not
energize, check for voltage at the output terminal to ensure that the switching device is operational. If no voltage
is present, then the module should be replaced. If voltage is present, then the problem lies in the wiring or the
field device. At this point, make sure that the field wiring to the module’s terminal or to the terminal block has a
good connection and that no wires are broken.

After checking the module, check that the field device is working properly. Measure the voltage coming to the
field device while the output module is ON, making sure that the return line is well connected to the device. If
there is power yet the device does not respond, then the field device is faulty.
Another method for checking the field device is to test it without using the output module. Remove the output
wiring and connect the field device directly to the power source. If the field device does not respond, then it is
faulty. If the field device responds, then the problem lies in the wiring between the device and the output module.
Check the wiring, looking for broken wires along the wire path.

Troubleshooting the CPU

PLCs also provide diagnostic indicators that show the status of the PLC and the CPU. Such indicators include
power OK, memory OK, and communi- cations OK conditions. First, check that the PLC is receiving enough power
from the transformer to supply all the loads. If the PLC is still not working, check for voltage supply drop in
the control circuit or for blown fuses. If the PLC does not come up even with proper power, then the problem lies
in the CPU. The diagnostic indicators on the front of the CPU will show a fault in either memory or
communications. If one of these indicators is lit, the CPU may need to be replaced.

AUTOMATIC CAR PARKING SYSTEM

The parking lot which has a capacity of 100 cars is to be controlled by a PLC system. The sensor S1 and S2 are used
to count the car at the entrance and exit. If the number of the cars reaches 100, the red light is lit and the gate arm
is closed. The arm stays closed until one or more parking spaces are available in the lot. The gate arm is controlled by
activating/deactivating the gate solenoid (GS)

Selection of inputs and outputs

Development of ladder diagram

Ladder explanation

● The parking lot which has a capacity of 5 cars is to be controlled by a PLC system.

● The sensor S1 and S2 are used to count the car at the entrance and exit by using incrementing and
decrementing D0 respectively and the entry and exit gate operating motors energised simultaneously with
outputs Y1 and Y2. or by The gate arm is controlled by activating/deactivating the gate solenoid (GS)

● If the number of the cars reaches 5, the D0>5 instruction energises the output Y3 and the red light is
light and the gate arm is closed as NC of Y3 connected in series withY1.

● The arm stays closed until one or more parking spaces are available in the lot, i.e. when a car exited from
the parking area and D0 is less than 5.

● If the number of the cars reaches 0, the D0<1 instruction energises the output Y4 and exit gate arm is
closed as NC of Y4 connected in series withY2.

Process diagram

Input and output PLC wiring diagram

Automatic Bottle Filling System

process description
Develop and Test a LAD for this system using simulation software. Identify and select sensors, switches and actuators required to implement the Automatic Bottle
Filling system.

Selection of Inputs and Outputs

Developing of ladder diagram

Ladder explanation

● When switch S0 is closed, power on indicator Y0 and the conveyor motor connected to Y1
are turned ON.
● An internal clock pulse M1013 is taken to represent the encoder pulses connected to the
 conveyor shaft.
● A proximity sensor connected to S2 supplies a high bit to memory bit M0 and this bit is
shifted left one bit for every clock pulse supplied by encoder the bits M0 to M12 are used
to animate movement of bottles on the conveyor in DOPsoft.
● When a bottle reaches below the filling station, bit M6 is used to open the solenoid valve
to fill the liquid to the bottle and a counter C0 counts the number of bottles filled.

Process diagram

Input and output wiring diagram

Induction Motor Speed Control Methods:

The only way to control the speed of a synchronous motor is to control the input frequency and voltage such as to keep
V/f constant. The Induction Motor Speed Control, on the other hand, can be controlled by the following means:
1. Stator Voltage Control
2. Frequency Control
1. Stator Voltage Control:
This is applicable for small motors and for fan-type load, where the load torque increases with speed. there are two
ways of controlling the rms value of the stator voltage—phase-control and integral cycle control.

The torque-speed characteristics of an induction motor with stator voltage control are drawn in Fig. 11.37. The
maximum torque reduces as the square of the voltage.
The figure also illustrates that speed regulation is only possible for a load whose torque decreases with speed. Even
then speed regulation is not achieved for low speeds—here the speed drops off sharply.

2. Frequency Control:
Here the input frequency is varied by means of an inverter; for subnormal frequency the stator voltage is also varied
to keep V/f constant which maintains the resultant flux/pole in the air-gap.

Constant flux density. And AC induction motors.

● The torque-speed characteristics of variable-frequency, constant-V/f control were illustrated in Fig. 11.39.
● It may be seen that the maximum torque does not alter because the flux/pole is kept at a fixed value.
● This is the most popular method for controlling the speed of an induction motor.
● As in the above method, if the supply frequency is reduced keeping the rated supply voltage, the air gap
flux will tend to saturate.
● This will cause excessive stator current and distortion of the stator flux wave.
● Therefore, the stator voltage should also be reduced in proportional to the frequency so as to maintain the
air-gap flux constant. The magnitude of the stator flux is proportional to the ratio of the stator voltage
and the frequency.
● Hence, if the ratio of voltage to frequency is kept constant, the flux remains constant. Also, by keeping
V/F constant, the developed torque remains approximately constant.
● This method gives higher run-time efficiency. Therefore, the majority of AC speed drives employ a
constant V/F method (or variable voltage, variable frequency method) for the speed control. Along with a
wide range of speed control, this method also offers 'soft start' capability.VFD is the short form of a
Variable Frequency Drive or adjustable frequency drive.
● The frequency determines the motor RPM and by controlling the AC frequency the motor RPM can be
controlled.
● Different types of VFDs are available in the electronics and electrical market ranging from small motor
related applications to the high power induction motors. Other than the three-phase VFDs, single phase
VFDs are also available.

Variable Frequency Drive (VFD)

VFD is the short form of a Variable Frequency Drive or adjustable frequency drive. The frequency determines the
motor RPM and by controlling the AC frequency the motor RPM can be controlled. Different types of VFDs are
available in the electronics and electrical market ranging from small motor related applications to the high power
induction motors. Other than the three-phase VFDs, single phase VFDs are also available.
A VFD circuit consists of three parts.
1.The rectifier section
2.The filter section
3.The switching or inverter section.
In the below image the three sections are shown inside a block diagram. This is a basic circuit block diagram of a
three phase VFD.

Rectifier Section of VFD Circuit

The rectifier section uses 6 diodes. The diodes D1, D2, and D3 are connected with the positive rail and the diodes D4,
D5 and D6 are connected with the negative rail. Those 6 diodes act as a diode bridge which converts the three-phase
AC signal into a single DC rail. The three-phase R, B, and Y are connected across the diode. Depending on the
sinusoidal wave polarity the diodes gets forward biased or reverse biased thus providing a positive pulse or a negative
pulse in both positive and negative rail.
To learn more about how rectifiers work, just follow the link.
Filter Section of VFD Circuit

As we know the standard rectifier diodes only convert the AC signal to DC, but the output DC signal is not smooth
enough because frequency dependent AC ripples are also associated with it. To rectify the AC ripple and to make a
smooth DC output there is a requirement of some sort of ripple rejection filter. The standard component for the
filter is to use different types of large capacitors and inductors. In the filter section, mainly the capacitor filters
out the AC ripple and provides smooth DC output.
In some cases, other types of filters are also used to reduce the input AC noises and harmonics.
Switching or Inverter section of VFD Circuit
The switching or inverter section inverts the DC to AC. In this section, different types of electronic switches are
used, ranging from high power transistors, IGBT or MOSFETs. The switches are rapidly turned on or off and the
load receives a pulsating voltage that is very similar to AC. The output frequency is proportional to the switching
rate. High switching rate provides high-frequency output whereas low switching rate provides a low-frequency
output.

Different types of VFD

Depending on how VFD converts AC power to DC power and makes the rectification there are other types of VFDs
available in the market.
The main three types of VFD are VSI, CSI, and PWM.

VSI type VFDs

VSI stands for Voltage-source inverter. This is the most common type of variable frequency driver. In this type of
VFDs, a simple diode bridge is used to convert the AC signal into DC and a capacitor is used to store the energy. An
inverter switching circuit uses the stored energy in the capacitor and provides the output.

CSI type VFDs

CSI stands for current source inverter. VSI type VFDs are designed in such a way that it could provide smooth voltage
output depending on the variable frequency range but in CSI type VFDs the construction is dependable on current
instead of the voltage. Also, In the case of CSI, instead of the diode bridge rectifier, SCR bridge converter is used.
The output energy is filtered using series inductors as an alternative of capacitors for smooth current output. CSI
type VFDs act the same as a constant current generator. Instead of a square wave of voltage, CSI type VFDs are
capable of providing square waves of current.

PWM type VFDs

This is an improved and modified version of VSI type VFDs. PWM stands for pulse width modulation. Using the
PWM technique the VFDs are capable of providing stable voltage output maintained with a frequency ratio. The
construction uses a diode bridge to rectify the AC signal into a DC signal. The switching circuit controls the duty
cycle in a variable frequency range. An additional regulator is used to regulate the PWM output to provide stable and
proper voltage and current to the Load.

VFD Control Panels

● VFD stands for Variable Frequency Drive. These panels are mainly used to control the speed of the electric
motors and also of the feed pumps that are used in various industrial facilities.
● Every motor has varying frequency and voltage; hence they need a separate control panel that will
effectively monitor and control them.
● A VFD control panel brings together or combines motor control devices and circuit protection devices in an
enclosure.
● This control panel also offers protection to these devices from moisture, corrosion, dust, and other
damaging factors.

Application of VFD
The main function of a VFD is to vary the supply frequency of AC but it can also vary the voltage. Here are some
applications of VFD.
● The variable-frequency feature is used for controlling the speed of an induction motor whose speed only
depends on frequency.
● It is used for precise motor speed control with smooth starting and stopping in conveyor belt systems to
avoid any accidents and have increased production.
● The precise speed control is also used in the cooling system to maintain temperature.
● Lifts and escalators use the smooth start and stop feature of VFD.
● They are used for water pumps and also for crushers in mining.
● Hoist and crane use VFD for precise control of speed and positioning.

Test the communication port, cable and module of VFD

DELTA MS300 Modbus-RTU Setting

In addition to the basic parameters of the inverter installed according to the motor, we need to set the following
parameters so that the inverter can be controlled by Modbus-RTU:

● P00.20 = 1 (Frequency Control via RS485)

● P00.21 = 2 (Motor Control via RS485)
● P09.00 = 1 (Address Slave = 1)
● P09.01 = 9.6 (Baudrate = 9600 bps)
● P09.02 = 0
● P09.03 = 1.0 (Time Com. Err)
● P09.04 = 14 (Modbus-RTU 8/E/1)

Connect and Commission the given VFD

STEP 1: Make sure everything is correctly sized and accounted for

● Look at the nameplate on your motor and make sure your VFD is sized correctly.
● How many full load amps does your motor draw?
● Is your VFD rated for the amount of amps your motor draws?
● How many volts does your motor require (460V or 230V)?
STEP 2: Make sure you have a properly-sized circuit breaker rated for your amps and VFD
● Locate your breaker panel.
● Install your 3 pole amp rated, volt rated, circuit breaker.
STEP 3: Run Wires - (3) power wires and (1) ground wire from your breaker panel to your VFD
STEP 4: Run wires from VFD to motor
● Use the same gauge wires as you did from the circuit breaker to the VFD.
STEP 5: Terminate wires to your VFD
● Terminate your load wires (wires going to the motor) to the terminals U, V, W.
● Terminate your line wires (wires coming from the circuit breaker) to terminals R/L1, S/L2, T/L3.
STEP 6: Terminate your wires to your circuit breaker in your panel
● Land your 3 power wires to the circuit breaker.
● Land your ground wire to the ground bus bar.
STEP 7: Start up
● Turn the circuit breaker on.
● Program your VFD to your preferred parameters
● Use your preferred starting method (e.g., start/stop buttons, Keypad on VFD) to start the motor.
● Enjoy the speed control that is now possible with your VFD.

Configure and run the motor with factory settings.

● Connect Live to R and Neutral to S for single phase input supply
● Connections U/T1, V/T2, W/T3 go to the motor
● Connect 3 phase input supply to L1/R, L2/S, L3/T
● `Connections U/T1, V/T2, W/T3 go to the motor
SPEED CONTROL OF 3 PHASE INDUCTION MOTOR BY USING VFD

by UP and DOWN arrows in the digital keypad.

AIM: To control the speed of 3 phase induction motor by VFD, with factory setting using UP and DOWN arrows in the digital keypad.

CIRCUIT DIAGRAM
PARAMETER SETTINGS
(1) 00.02 set to 9 All parameters are Reset to factory setting for 50Hz

(2) 01.00 Maximum frequency required to 50Hz

(3) 01.01 Change the value to match Hz on motor nameplate to 50Hz

(4) 01.02 Change to match voltage on motor nameplate 415V

(5) 01.10 Upper limit frequency to 50Hz

(6) 01.11 Lower limit frequency to 20Hz

(7) 05.01 set as motor nameplate current 2.74 A

(8) 05.02 set to motor nameplate KW 0.75KW

(9) 05.03 set the motor speed 1400 RPM

(10) 5.04 set to 4 pole

PROCEDURE
(1) Switch ON the power supply to VFD and Motor

(2) Set the parameters of VFD as per the list

(3) Run the motor using VFD, very the speed using UP and DOWN arrows in both direction

(4) Switch off the power supply

Result: we are getting the output as per description given in aim.

Conclusion: all outputs are getting as per process explanation for different combinations of inputs.
SPEED CONTROL OF 3 PHASE INDUCTION MOTOR BY USING VFD

b) by using a potentiometer provided in digital keypad.

AIM: To control the speed of 3 phase induction motor by VFD, with factory setting and very frequency by using potentiometer provided in digital keypad.

CIRCUIT DIAGRAM

PARAMETER SETTINGS
(1) 00.02 set to 9 All parameters are Reset to factory setting for 50Hz

(2) 01.00 Maximum frequency required to 50Hz

(3) 01.01 Change the value to match Hz on motor nameplate to 50Hz

(4) 01.02 Change to match voltage on motor nameplate 415V

(5) 01.10 Upper limit frequency to 50Hz

(6) 01.11 Lower limit frequency to 20Hz

(7) 05.01 set as motor nameplate current 2.74 A

(8) 05.02 set to motor nameplate KW 0.75KW

(9) 05.03 set the motor speed 1400 RPM

(10) 05.04 set to 4 pole

(11) Set the parameters as listed above expat that change the parameter 00.20 to 7 to Run using digital keypad potentiometer.
 PROCEDURE
(1) Switch ON the power supply to VFD and Motor.

(2) Set the parameters of VFD as per the list.

(3) Run the motor using VFD, very the speed using the potentiometer provided in the digital keypad.

(4) Switch off the power supply.

Result: we are getting the output as per description given in aim.

Conclusion: all outputs are getting as per process explanation for different combinations of inputs.

MOTOR SPEED CONTROL USING VFD AND PLC

Aim: To control the speed of 3 phase induction motor using VFD and PLC

LADDER DIAGRAM

CIRCUIT DIAGRAM
INPUTS
M0 = Internal input for start from HMI

M1 = Internal input for stop from HMI

M2 = Internal input for forward and reverse direction selection

If M2 forced ON VFD forward ON

If M2 forced off VFD Reverse ON

OUTPUTS
Y20 = PLC output used to connect MI1 to DCM for external operation control in forward direction

Y21 = PLC output used to connect MI2 to DCM for external operation control in Reverse direction

Figure A
PARAMETER SETTINGS
(1) 00.02 set to 9 All parameters are Reset to factory setting for 50Hz

(2) 01.00 Maximum frequency required to 50Hz

(3) 01.01 Change the value to match Hz on motor nameplate to 50Hz

(4) 01.02 Change to match voltage on motor nameplate 415V

(5) 01.10 Upper limit frequency to 50Hz

(6) 01.11 Lower limit frequency to 20Hz

(7) 05.01 set as motor nameplate current 2.74 A

(8) 05.02 set to motor nameplate KW 0.75KW

(9) 05.03 set the motor speed 1400 RPM

(10) 05.04 set to 4 pole

11) To control Frequency from the Potentiometer on the Digital keypad set the parameter 00.20 to 7.

12) Set 00.21to 1 source of master Operation command to External terminals.

PROCEDURE:
1) Make the connections of external operation Control as shown in fig A.

2) Draw the Ladder Diagram in Computer Using ISP software.

3) Establish the communication between PLC and Computer and Download the Ladder Diagram program to PLC.

4) Design HMI screen with Start and Stop pushbutton and to Display running condition of Motor on the screen in DOP software.

5) Establish the communication between HMI and Computer. Download the HMI program to HMI.

6) Set the basic parameters of VFD.

7) Keeping PLC in run mode operate the Motor and control the speed by using potentiometer on Digital keypad.

Result: we are getting the output as per description given in aim.

Conclusion: all outputs are getting as per process explanation for different combinations of inputs.

Week 6

INTRODUCTION OF SERVO MOTORS

What is a servo motor?

Servo motors are electrical devices made up of various parts that move and rotate parts of a machine with efficiency
and precision. Servo motor functions include precise control of angular or linear position, velocity and acceleration.
Servo drives are responsible for motion control by precisely calculating the path and trajectory needed and sending
command signals to the motor. Drives can control position, velocity as well as torque.
TYPES OF SERVO MOTORS
There are three types of servo motors:
1) SM (synchronous) series AC servo motor
2) IM (induction) series AC servo motor
3) DC servo motor

WHAT IS A SERVO SYSTEM?

A servo motor control system is one where the system’s error (in positioning, speed, or torque) is corrected through
feedback generated when it compares the system’s actual performance with the commanded performance.
Servo systems have three primary components as follows.

Servo motor: A servo motor is a self-contained electrical device that moves and rotates parts of a machine efficiently
and with precision. The servo motor is a closed-loop mechanism that incorporates positional feedback to control the
rotational or linear speed and position. Feedback is typically provided by an encoder—either internal or external to the
motor—or a resolver that serves as a sensor.
Servo drive: Servo drivers are responsible for the motion control by precisely calculating the path or trajectory
needed and sending command signals to the motor. Servo drives can control velocity, position, as well as torque; which
is the main parameter it controls. Servo drives tell the servo motor what to do and how to do it at lightning speed.
Servo controller: Considered the brain of the servo system, the servo controller (or motion controller) contains the
motion profile including the desired acceleration, speed and deceleration. It sends signals to the drive which causes the
motor to execute the desired motion.
The controller also has the important task of closing the loop on the system by constantly reading the encoder
feedback and modifying the signal to the motor (through the drive) to correct any errors in the actual versus desired
parameters.

AC servo drive working principle and control method

Servo drives are used in digital signal processors (DSP) as the control. It can achieve more complex control algorithms
and develop for digital, networked and smart. Power Module widely used in the intelligent power module (IPM) as the
core design of the drive circuit. At the same time have over-voltage, over current, overheating, undervoltage
protection circuit fault detection. The main circuit also joined the soft-start circuit to reduce the impact on startup
drive
 First, the power drive unit via a three-phase full bridge rectifier circuit or three-phase mains input is rectified
to get relative DC. After a good three-phase power rectifier or mains, and then to variable frequency AC servo
motor driven by three-phase sinusoidal PWM voltage source inverter. The whole process of the power drive unit can
simply say that AC-DC-AC process of rectifying unit (AC-DC) is the main circuit topology of three-phase full-
bridge controlled rectifier circuit
drives.

● Torque mode – Also known as current mode, torque mode closes the current loop. The drive will regulate the
current flow to the motor to achieve a desired torque. This is the most basic and usually the bare-minimum
level of control for a servo drive, since current and torque have a directly proportional relationship.
● Velocity mode – In addition to closing the current loop, a servo drive in velocity mode also closes the velocity
loop, primarily by regulating the output voltage so that the motor runs at a target speed. Unlike torque
mode, a drive running in velocity mode will make adjustments to maintain the motor running at a specific
speed despite changes to the load.
● Position mode – As you probably guessed, position mode closes the position loop in addition to the current and
velocity loops. In position mode, the drive will regulate the output current and voltage to ensure the motor
reaches or maintains the desired position targets.

Motion control applications of Servo Motors

Servo motors are small and efficient but critical for use in applications requiring precise position control. servo
motor is controlled by a signal (data) better known as a pulse-width modulator (PWM). Here are several of the more
common servo motor applications in use today.
 ● Robotics: A servo motor at every "joint" of a robot is used to actuate movements, giving the robot arm its
precise angle.
● Conveyor Belts: Servo motors move, stop, and start conveyor belts carrying product along to various stages,
for example, in product packaging/bottling, and labeling.
● Camera Auto Focus: A highly precise servo motor built into the camera corrects a camera's lens to sharpen
out-of-focus images.
● Robotic Vehicle: Commonly used in military applications and bomb detonation, servo motors control the
wheels of the robotic vehicle, generating enough torque to move, stop, and start the vehicle smoothly as
well as control its speed.
● Solar Tracking System: Servo motors adjust the angle of solar panels throughout the day so that each
panel continues to face the sun, harnessing maximum energy from sunup to sundown.
● Metal Cutting & Metal Forming Machines: Servo motors provide precise motion control for milling machines,
lathes, grinding, centering, punching, pressing, and bending in metal fabrication for such items as jar lids
to automotive wheels.
● Antenna Positioning: Servo motors are used on both the azimuth and elevation drive axis of antennas and
telescopes such as those used by the National Radio Astronomy Observatory (NRAO).
● Woodworking/CNC: Servo motors control woodturning mechanisms (lathes) that shape table legs and stair
spindles, for example, as well as augering and drilling the holes necessary for assembling those products
later in the process.
● Textiles: Servo motors control industrial spinning and weaving machines, looms, and knitting machines that
produce textiles such as carpeting and fabrics as well as wearable items such as socks, caps, gloves, and
mittens.
● Printing Presses/Printers: Servo motors stop and start the print heads precisely on the page as well as move
paper along to print multiple rows of text or graphics in exact lines, whether it's a newspaper, a magazine,
or an annual report.
● Automatic Door Openers: Supermarkets and hospital entrances are prime examples of automated door
openers controlled by servo motors, whether the signal to open is via push plate beside the door for
handicapped access or by radio transmitter positioned overhead.

https://youtu.be/Gzo9m0tMD0A

https://youtu.be/bOb7xDGIFbU

https://youtu.be/rkyjxBzlg6w

SERVO DRIVES FOR ELECTRIC MOBILITY

a) For Automated Guided Vehicle (AGV)

● The Automated Guided Vehicle (AGV) market – including UGVs, hybrid vehicles, robotic utility
vehicles, and other types of electric vehicles – has recently experienced significant growth due to
demand for automation across multiple industries.
● Designing servo drive components for these types of applications requires key specifications, such
as efficiency and taking advantage of regenerative braking to achieve a longer battery
life/autonomy of the vehicle.
● Size, power density, and weight also play an important factor to deliver a more compact solution
that can fit into an existing system’s mechanics.
● Supporting the standard communication protocols of CANopen/EtherCAT,and having safety
certifications such as STO, gives end-customers the best solution possible when selecting a servo
drive for their robotic vehicle application design.

b) For robotic applications

○ Servo motors provide numerous benefits in robotic applications. They are small, powerful, easily
programmable, and accurate. Most importantly, though, they allow for near perfect
repeatability of motion. They are used in robotic applications such as:
○ Robotic Welding: Servo motors are mounted in every joint of a robotic welding arm, actuating
movement and adding dexterity.
○ Robotic Vehicles: Servos are used in the steering systems of the autonomous vehicles used to
disarm and dispose of bombs.
○ A robotic application may involve the following types of motion –
■ Vertical motion – moving a part of robot up and down usually by means of shoulder
swivel
■ Radial motion – Moving a part of robot in and out
■ Rotational motion – Clockwise or anticlockwise rotation about vertical or horizontal axis
or about a plane in three-dimensional frame
■ Pitch motion – Up and down movement with simultaneous rotational motion
■ Roll motion – Rotation of a part of robot with reference to the rest of the robotic body in
a parallel axis
■ Yaw motion – Rightward or Leftward swiveling motion of a part of robot
■ Locomotion – movement of robot over a surface or in a medium
Various communication standards and protocols used in Drives.
There are two communication protocols are used for servo drive
1. RS232 communication
2. Modbus communication
Diagnose the simulated faulta and explore the remedial measures of servo drives.
 JOG control of servo motor using servo drive

AIM : Conduct the jog operation of the servo motor by setting the parameters in digital keypad of the
servo drive

Connection diagram

PROCEDURE

1) Switch ON the power supply of the servo drive, make factory reset using parameters P2-10 set to 000 and
P2-08 set to 10.
2) Set parameters P2-15 , P2-16 , P2-17 to 0
3) For jog operation use parameter P4-05 and set RPM. JOG will be display.
4) Use UP/down arrow keys for forward and reverse “ JOG” control.
5) Switch off the power supply.
RESULT : The jog operation of the servo motor by setting the parameters in digital keypad of the servo drive is
conducted.

CONCLUSION : We can set the RPM by using parameter P4-05.

Monitor various motor parameters using the given drive software.

AIM:-Forward JOG and revrese JOG operation of servo drive using ASDA-B2 soft.

Follows below steps:

Step 1:- Switch ON the power supply to servo drive and factory reset by using parameter P2-08=10 using digital
keypad on servo drive, power off and power ON the servo drive once again

Step 2:- Open ASDA-B2 software. Next open window this type, know set and select the setting as per shown in
below fig.

Step 3:- Observe “ONLINE” in green colour as shown in below fig.

Step 4:- Go to the parameter function parameter editor.

Step 5:- Next open window this type.

Step 6:- Read parameters of the servo drive. Shown in fig

Step 7:- when read parameters read from servo drive, this type of window will appearance. know click ok, Shown in
below

Step 8:- When open window this type. Don’t change any parameters. Save all parameters as files. Shown in below

Step 9:- Go to P1-XX command. Set parameter P1-34 ,P1- 35 and P3-05 parameter command.
P1-34 = 300 ms (Acceleration constant of s- curve)
P1-35 = 200 ms (Deceleration constant of s- curve)
P2-08 = 10 (rest all parameters)
Check and set P2- 10 = 101
P2- 15 = 0
P2- 16 = 0
P2- 17 = 0
P3- 05 = 1 (Communication mechanism)

Step 10:- After set the parameter above mentioned. Click the write parameters shown in below fig.
Step11:- Switch OFF the servo drive and switch ON the servo drive.

Step 12:- Go to tools command and click the Digital IO/JOG control, shown below in fig

Step 13:- Set the parameters and settings

Click or enable the edit DI/0 items digital input(DI):ASDA-B2 servo: Pt Mode
Select [0x01] servo on OK, Shown in below fig.
Step 14:- Set the speed of servo motor as per your required. Servo motor REV JOG and FWD JOG

NOTE:- Set the speed of servo motor less than rated speed.(motioned at servo motor name-plate)OG operation using
these buttons. Shown in below fig.

Integrating the given PLC, HMI and servo drive for position control operation

AIM: Configure a servo Drive, from the given PLC and Control the motor speed for
fixed steps and direction for indexing operations and integrate the given PLC, HMI and
servo drive systems.

CONNECTION DIAGRAM:
LADDER DIAGRAM:
HMI design:

Procedure:

1. Set the electronic gear ratio by using parameters P1- 44 (Electronic Gear Ratio (1st Numerator)
(N1) and P1- 45 Electronic (Electronic Gear Ratio (Denominator) (M)) to 10.

2. When internal input M0 is enabled (forced on) through HMI, external output Y2 becomes
true, which is used to enable Servo ON.

3. When internal input M2 is enabled (forced on) through HMI, pulse output instruction is
enabled, in that instruction, S1 represents frequency of pulse output and S2 represents
 number of pulses, which will be loaded to D0 register through HMI and we get pulses at Y0
output of PLC. These pulses are applied to servo drives at pulse input.

4. When internal input M1 is enabled (forced on) through HMI, external output Y1 becomes
true, which is used to change the direction of the servo motor through the sign/direction
input of the servo drive.

5. The number of revolutions or the position of the rotor depends upon the electronic gear
ratio and the number of pulses given through the D0 register.

7 th week

A Human-Machine Interface (HMI)

A Human-Machine Interface (HMI) is a user interface or dashboard that connects a person to a machine, system, or
device. While the term can technically be applied to any screen that allows a user to interact with a device, HMI is
most commonly used in the context of an industrial process.

Features of DOPsoft HMI software

● PLC Serial Drives Support
● Windows® Fonts Support for ScrEdit Software
● Quick Execution and Communication Macro
● Rapid USB Upload/Download
● It provides a useful recipe editor that is similar to Microsoft Excel for users to edit recipes easily and input
multiple recipes simultaneously (size limit is 64K).
● Direct Communication with Two or Three PLCs.
 ● Offline as well as online Simulation Functions.
● Multiple Security Protection.
● USB Host Port (USB Host) Equipped.
● Multi-Language Support.

Specifications of 103BQ delta HMI

1. 4.3”(480*272) 65,536 Colors TFT
2. Cortex-A8 800MHz CPU
3. 256 MB RAM
4. 256 MB ROM
5. 1 COM port / 1 extension COM port
6. USB Host
7. USB Client
8. CE / UL certified
9. Operation Temperature: 0℃ ~ 50℃
10. Storage Temperature: -20℃ ~ 60℃
11. Pressing times: >1,000K times
Various industry interfaces on HMI panels
HMI technology is used by almost all industrial organizations, as well as a wide range of other companies, to interact
with their machines and optimize their industrial processes.
● Food processing
● Pharmaceutical manufacturing
● Oil and gas
● Mining operations
● SCADA systems
● Robotics applications
● Transportation
● And much more

Configure PLC with HMI

Introduction
The DirectLink function of the HMI Delta is used to communicate with the PLC and HMI, making it possible to upload
/ download and monitor both with a single cable.
Configuring the HMI serial communication
To access the PLC via the HMI, it must be configured as [Delta (DVP / AS / AH) PLC] and set the same
communication format as the PLC. Delta's standard serial format is: (RS485 / 232: 9600, 7, E, 1).
Configuring HMI USB communication
1. For DOP-B series HMI
In DOPSoft 2.0, go to Options> Configuration> Others> USB Download.

1. For Windows XP, the upload / download mode must be set to 0 (Normal Mode).
2. For Windows 7, 8 or 10, the upload / download mode must be set to 1 (Disk Mode).
3. If USB permission is restricted, set to mode 2 (CDC Mode).
4. There is an automatic detection mode (Auto) that automatically detects the connection mode.

Animation with graphical objects

You can create multiple state pictures or import GIF images with the Animated Graphic element. Previously, DOPSoft
decomposes a GIF file into multiple images, then the user sets the corresponding state one by one, which is
inconvenient for programming. The new version of DOPSoft has improved the method for importing GIF images,
which is one state corresponds to one GIF image.
Troubleshooting of communication problems with HMI/PLC
Communication loss between HMI and PLC may due to following reasons
● Failure of power supply to either PLC or to HMI or to both.
● open or short circuit of communication cables.
● Interference of communication signals.
● Wrong communication parameter setting.
● Un supported communication protocol.
● More length of communication cable.
● Faulty PLC or HMI.

Week 8
Supervisory control of two field devices by HMI
AIM: Set up and configure HMI with PLC and perform supervisory control to turn ON/OFF output field device
1(Fan) and device 2(Lamp).
Selection of inputs and outputs :

PROCEDURE :
1) Select proper input and output devices.
2) Develop the ladder diagram for the above application.
3) Download to simulator and check the working of ladder diagram.
4) Open DOPsoft HMI software and configure the model and communication between PC and HMI software.
5) Design the HMI for the above application and test with ISPsoft in offline simulation.
6) Make the input/output connection to PLC kit.
7) Establish the communication between PLC kit, HMI software and PC.
8) Download the ISPsoft programme to PLC.
9) Check the working of the design with HMI, PLC and external devices

LADDER DIAGRAM :
HMI DESIGN :

PLC INPUT AND OUTPT WIRING DIAGARAM :

RESULT : Two devices device 1 (Fan) and device 2 (Lamp) can be controlled independently through HMI and PLC in
this experiment.
CONCLUSION : Graphic animation in HMI is done using following Macro code.
IF {Link2}1@M0==1
$0=$0+1
IF $0>5
$0=0
ENDIF
ENDIF

HMI screen to monitor motor status.

HMI DESIGN :

Macro program

IF {Link2}1@M0==1
$0=$0+1
IF $0>5
$0=0
ENDIF
ENDIF

IF {Link2}1@Y0==1
$0=$0+1
IF $0>5
$0=0
ENDIF
ENDIF

PLC INPUT AND OUTPT WIRING DIAGARAM :

RESULT : Motor is monitored through HMI screen for forward and reverse direction.

CONCLUSION : Graphic animation in HMI is done using following Macro code.

 Mixing plant and programming

AIM: Wiring and identifying the sensors and valves in Mixing plant and programming it for mixing of the two to
ingredients.

Selection of inputs and outputs:

Developing Ladder logic diagram:

HMI design:

Procedure:
1) When Start pushbutton (S0) in HMI is pressed, tank-1 valve connected to Y0 output of PLC will open, then
the liquid is Filling to Tank 4 from the Tank 1.

2) By the same time, tank-2 valve connected to Y1 output of PLC will also open, then the liquid is Filling to
Tank 4 from the Tank 2.

3) After the completion filling from Tank-1 and Tank-2.The mixing motor is connected to PLC output Y2 is
energize and mixing operation is initiated.

4) When mixing operation is completed(15sec) the valve connected to Y3(Tank-4 drain valve) is energized and
 liquid is drained from Tank-4.

PLC input and output wiring:

Result: We are getting the output as per description given in the aim.

Conclusion: All outputs are getting as per process explanation for different combinations of
inputs.

Automatic sorting operation using PLC and HMI

AIM: Select sensors and actuators and develop ladder diagram for sorting big object and small
object from the conveyor.

SELECTION OF INPUTS AND OUTPUTS:

Ladder diagram:

HMI design:
PLC Input and output wiring:

Procedure:

1) When an object is placed on the conveyor, the optical proximity sensor 1 connected
 to external input X0 is activated and detects the object, so that the conveyor motor
connected to external output Y0 is energized and the conveyor starts moving.

2) Whenever, optical proximity sensor 2 connected to external input X1 detects the

big objects, then the DCV2 (solenoid valve for double acting cylinder) connected to
Y1 output of PLC, is energized to push the big object into a box which collects the
big objects.

3) Whenever optical proximity sensor 3 connected to external input X2 detects the

small objects, then the DCV3 (solenoid valve for double acting cylinder) connected
to Y2 output of PLC, is energized to push the small object into a box which
collects the small objects.

Result: We are getting the output as per description given in the aim

Conclusion: All outputs are getting as per process explanation for different combinations of
inputs.

AUTOMATIC PACKAGING SYSTEM

AIM: Write the program and automate a working module of PLC based Automatic packing
system.

SELECTION OF INPUTS AND OUTPUTS:

Developing ladder logic diagram:

HMI DESIGN:
PROCEDURE:

1) When an object is placed on the conveyor, the optical proximity sensor 1 connected
to external input X0 is activated and detects the object, so that the conveyor motor
connected to external output Y0 is energized and the conveyor starts moving.

2) Whenever optical proximity sensor 2 connected to external input X1 detects the big
objects, then the DCV2 (solenoid valve for double acting cylinder) connected to Y1
output of PLC, is energized to push the big object into the packing box which
collects the big objects.

3) Whenever optical proximity sensor 3 connected to external input X2 detects the

small objects, then the DCV3 (solenoid valve for double acting cylinder) connected
to Y2 output of PLC, is energized to push the small object into the packing box
which collects the small objects.

4) After collecting both 5 Big objects and small objects, the conveyor motor will
stop.

PLC Input and Output wiring:

Result: We are getting the output as per description given in aim.

Conclusion: All outputs are getting as per process explanation for different combinations of
inputs.