INTRODUCTION TO AUTOMATION SYSTEM
EEM451 INDUSTRIAL CONTROL SYSTEMS
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UNIT 1
INTRODUCTION TO AUTOMATION SYSTEM
Objective ;
1.
Understand automation system
a. Understand type of automation
b. Comparison type of automation
2.
Understand relays, contactors, electromechanical timer and
electromechanical counter (symbol, building diagram,
operation and application examples)
a. Develop simple logical control/ automation sequence
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UNIT 1
INTRODUCTION TO AUTOMATION SYSTEM
Automation System
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Automation is the use of control systems and information
technologies to reduce the need for human work in the production of
goods and services.
In the scope of industrialization, automation is a step beyond
mechanization.
Whereas mechanization provided human operators with machinery
to assist them with the muscular requirements of work, automation
greatly decreases the need for human sensory and mental
requirements as well
Type of Automation system :
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fixed/ hardwired automation
programmable automation
flexible automation
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INTRODUCTION TO AUTOMATION SYSTEM
Fixed/ Hardwired Automation
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Custom-engineering, special – purpose equipment to automate a fixed
sequence of operations.
High production rates, inflexible product design
Programmable Automation
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Equipment designed to accommodate a specific class of product changes.
Batch production, medium volume
Flexible Automation
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Design to manufactured a variety of product or parts
Low production rates, varying product design and demand
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UNIT 1
INTRODUCTION TO AUTOMATION SYSTEM
Comparison Types of Automation
Automation
When to consider
Advantages
Disadvantages
Fixed
High demand volume, long
product life cycle

maximum efficiency
 low unit cost

large initial investment
 inflexibility
Programmable
Batch production, products
with the different options

flexibility to deal with
changes in product
 low unit cost for large
batches

Flexible
Low production rates, varying
demand, short product life
cycles

flexibility to deal with
design variations
 customized product

new product requires
long set up time
 high unit cost relative
to fixed automation
large initial investment
 high unit cost relative
to fixed or
programmable
automation
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UNIT 1
INTRODUCTION TO AUTOMATION SYSTEM
Relays

Define
A relay is usually an electromechanical device that is actuated by an electrical
current. The current flowing in one circuit causes the opening or closing of another
circuit. Relays are like remote control switches and are used in many applications
because of their relative simplicity, long life, and proven high reliability. Relays are
used in a wide variety of applications throughout industry, such as in telephone
exchanges, digital computers and automation systems. Highly sophisticated relays are
utilized to protect electric power systems against trouble and power blackouts as well
as to regulate and control the generation and distribution of power. In the home, relays
are used in refrigerators, washing machines and dishwashers, and heating and airconditioning controls

Symbol
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UNIT 1
INTRODUCTION TO AUTOMATION SYSTEM

How does a relay work?
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All relays contain a sensing unit, the electric coil, which is powered by AC or DC
current. When the applied current or voltage exceeds a threshold value, the coil
activates the armature, which operates either to close the open contacts or to
open the closed contacts. When a power is supplied to the coil, it generates a
magnetic force that actuates the switch mechanism. The magnetic force is, in
effect, relaying the action from one circuit to another. The first circuit is called the
control circuit; the second is called the load circuit.
There are three (3) basic functions of a relay:
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On/Off Control: Example: Air conditioning control, used to limit and control a “high power”
load, such as a compressor.
Limit Control: Example: Motor Speed Control, used to disconnect a motor if it runs slower or
faster than the desired speed.
Logic Operation: Example: Test Equipment, used to connect the instrument to a number of
testing points on the device under test.
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INTRODUCTION TO AUTOMATION SYSTEM

Operation

When no voltage is applied to pin 1, there is no current flow through the
coil. No current means no magnetic field is developed, and the switch is
open. When voltage is supplied to pin 1, current flow though the coil
creates the magnetic field needed to close the switch allowing continuity
between pins 2 and 4.
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UNIT 1
INTRODUCTION TO AUTOMATION SYSTEM
Contactors

Define
Contactors are used to indicate an open or closed path of current flow.
Contacts are shown as normally open (NO) or normally closed (NC).
Contacts shown by this symbol require another device to actuate them.
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Symbol
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UNIT 1
INTRODUCTION TO AUTOMATION SYSTEM
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Building Diagram
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INTRODUCTION TO AUTOMATION SYSTEM

Operation
Normally Open Contact
In the following illustration the circuit
is first shown in the de-energized
state. The contacts are shown in their
normally open (NO) state. When the
relay is energized, the contacts
close, completing the path of current
and illuminating the light. The
contacts have been highlighted to
indicate they are now closed.
Normally Open Contact
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INTRODUCTION TO AUTOMATION SYSTEM

Operation
Normally Close Contact
In the following illustration the
contacts are shown as normally
closed
(NC),
meaning
the
contacts is closed when the relay
is de-energized. A complete path
of current exists and the light is
on. When the relay is energized,
the contacts open turning the light
off.
Normally Close Contact
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INTRODUCTION TO AUTOMATION SYSTEM
Coil
Coils are used in electromagnetic starters, contactors, and relays. The purpose
of contactors and relays is to open and close associated contacts.
Contactors and relays use an electromagnetic action to open and close these
contacts.
SBO/ PMM/ EJ501/ Jun2011
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UNIT 1
INTRODUCTION TO AUTOMATION SYSTEM
Coil
Coils are used in electromagnetic starters, contactors, and relays. The purpose
of contactors and relays is to open and close associated contacts.
Contactors and relays use an electromagnetic action to open and close these
contacts.
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INTRODUCTION TO AUTOMATION SYSTEM
Electromechanical Timer
Electromechanical timers are used to start or stop a machine or other device
at preset or delayed intervals. They consist of both electrical and mechanical
components, and often feature an electric motor that drives one or more
gears. They typically accept electric or electronic inputs to operate a
mechanical output such as rotating wheels or knobs.
The electrical symbol for time-delay devices uses the head or tail of an
arrow. The tail of the arrow is used to indicate time delay-on and the head of
the arrow pointing down is used to indicate a time delay-off function
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INTRODUCTION TO AUTOMATION SYSTEM
Electromechanical Timer

Delay on timers open or close a switch’s contacts after an input signal is
received and a predetermined amount of time has passed. If the switch’s
contacts are normally open (NO), the load is energized. If the contacts are
normally closed (NC), however, then the load is de-energized.

Delay off timers begin their timing function when the power supply is
interrupted. In other words, when a predetermined amount of time has
elapsed, the output relay contacts release. Often, this capability is called
delay on release, delay on break, or release delay.
SBO/ PMM/ EJ501/ Jun2011
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UNIT 1
INTRODUCTION TO AUTOMATION SYSTEM
Electromechanical Timer
EX:DELAY ON TIMERS
Timers are widely used in industrial applications to control the starting time of
larger motors so that they don’t all try to start at the same time. When a
motor starts, it will draw a larger current than when it’s running at full speed.
This starting current is called locked rotor amperage (LRA) or in-rush current
and it’s caused by the armature not turning when power is first applied to the
motor. As the motor shaft begins to rotate, the current drops to normal levels
as the motor comes up to full speed. If a machine has several large hydraulic
pump motors, they will all try to start at the same time when power is turned
on. The starting cycle of the motors can be staggered by using on-delay
timers so that the effects of in-rush current will be minimized.
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INTRODUCTION TO AUTOMATION SYSTEM
Electromechanical Timer
EX:DELAY ON TIMERS
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INTRODUCTION TO AUTOMATION SYSTEM
Electromechanical Timer
EX:DELAY OFF TIMERS
In some applications it’s necessary to ensure that a motor continues to
operate for several minutes after power is turned off to the main system. For
instance, in large industrial heating systems, the fan may need to run for up
to 2 minutes after the heating element or gas valve has been de-energized.
The additional time the fan is allowed to run after the heat source is turned
off will allow the system to capture all of the heat that has built up in the
heating chamber and use it. This provides a degree of efficiency, since this
heat would be lost if the fan was turned off at the same time as the heating
element.
The off-delay timer allows the heating control to dc-energize the heating
element several degrees prior to the setpoint, and allows the fan to continue
to operate for several additional minutes to dissipate the remaining heat. 19
UNIT 1
INTRODUCTION TO AUTOMATION SYSTEM
Electromechanical Timer
EX:DELAY OFF TIMERS
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UNIT 1
INTRODUCTION TO AUTOMATION SYSTEM
Electromechanical Timer
EX:DELAY ON TIMERS
Timers are widely used in industrial applications to control the starting time of
larger motors so that they don’t all try to start at the same time. When a
motor starts, it will draw a larger current than when it’s running at full speed.
This starting current is called locked rotor amperage (LRA) or in-rush current
and it’s caused by the armature not turning when power is first applied to the
motor. As the motor shaft begins to rotate, the current drops to normal levels
as the motor comes up to full speed. If a machine has several large hydraulic
pump motors, they will all try to start at the same time when power is turned
on. The starting cycle of the motors can be staggered by using on-delay
timers so that the effects of in-rush current will be minimized.
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UNIT 1
INTRODUCTION TO AUTOMATION SYSTEM
Electromechanical Counter
Electromechanical counters are used to detect, totalize, and indicate a
sequence of events. They typically accept electric or electronic inputs to operate
mechanical outputs such as rotating wheels or knobs. These devices may count
UP and/or DOWN, support multiple functions, and provide reset capabilities.
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UNIT 1
INTRODUCTION TO AUTOMATION SYSTEM
Electromechanical Counter
Electromechanical counters are used to detect, totalize, and indicate a
sequence of events. They typically accept electric or electronic inputs to operate
mechanical outputs such as rotating wheels or knobs. These devices may count
UP and/or DOWN, support multiple functions, and provide reset capabilities.
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