uc 1 (design electronical control system).ppt

Industrial Automation and
Control Technology Management
 Unit of Competence: Design Electronic Control
Systems
 Module Title: Designing Electronic Control
Systems
 Module Code: EEL IAC5 01 0511
 Level:- V
1

An electronic controller is a device that receives
an input signal from a measured process
variable, compares this value with that of a
predetermined control point value (set point),
and determines the appropriate amount of
output signal required by the final control
element to provide corrective action within a
control loop.

What is process control
 Control in process industries refers to the
regulation of all aspects of the process.
 Precise control of level, temperature, pressure
and flow is important in many process
applications.
 Process control is the ability to monitor and
adjust a process to give a desired output.
3

What is process control
 It is used in industry to maintain quality
and improve performance.
 An example of a simple process that is
controlled is keeping the temperature of a
room at a certain temperature using a
heater and a thermostat.
4

History of process control
 The various methods for process control are as
follows
Manual
control
Hard-wired
control
Electronics
control
PLC
control

Manual control (Human – Aided
control)
 In this case a human has been added to the process.
 The human can adjust the height by opening and
closing the valve to change Q out in such a way that the
height can be adjusted .
 In this case the controlled variable is still the height,
but the height can be manipulated by a person
changing the manipulated or controlling variable Q
out

Manual control (Human – Aided
control)
sight tube
height

 In this process a human can regulate the level using a
sight tube ‘S’ to compare the level ‘h’ to the objective
‘H’ and adjust the value to change the level.
 By a succession of incremental opening and closing of
the valve, the human can bring the level to set point
value ‘H’ And maintain it there by continues
monitoring of the sight tube and adjustment of the
valve, the height is regulated.
Manual control (Human – Aided control)

Automatic control
 Automation is basically the delegation of human
control functions to technical equipment aimed
towards achieving
 For automatic control the system is modified as shown
below.
 An automatic level-control system replaces the human
with a controller and uses a sensor to measure the
level

In the previous slide the person is replaced by
an automatic control system.
The height is measured by a sensor (a float or
electronic), and a controller (typically a
microcomputer or other electronic circuit) will
signal an actuator to open/close the valve
controlling Qout
Again the height is adjusted to a set point H by
manipulating or controlling variable Qout

Advantages of automatic controller:
Higher productivity
Superior quality of end product
Efficient usage of energy and raw materials
Improved safety in working conditions
Time saving

 Although this method served the purpose for many
years, it had certain limitations as listed below
 Bulky and complex wiring
 Involves lot of rework to implement changes in
control logic.
 The work can be started only when the task is
fully defined and this leads to longer project time
 High power consumption

Electronics control
With the advantage of electronics, the logic gates started replacing the relays
and auxiliary contactors in the control circuits.
 The bimetallic and motorized timers were replaced by electronic timers,
counters.
 With incorporation of these changes, we got the benefits of
Reduced space requirements.
Energy saving
Less maintenance and hence greater reliability
Easy fault finding
 However even with electronic, the implementation of changes in the control
logic as well as reducing the project lead time was not possible.

Programmable Logic Controller
 A digitally operating electronic apparatus which
uses
 a programming memory for the internal storage
of instructions for implementing specific
functions such as
 logic, sequencing, timing, counting and
arithmetic to control through digital or analog
modules, various types of machines or process.
 Instead of achieving the desired control or
automation through physical wiring of control
devices, in PLC it is achieved through a program
or says software.

PROCESS CONTROL
 Process control refers to the methods that are used to
control process variables when manufacturing product.
 For example, factors such as the proportion of one
ingredient to another, the temperature of the materials,
how well the ingredients are mixed, and the pressure
under which the materials are held can significantly
impact the quality of an end product.
 Manufacturers control the production process for three
reasons:
 Reduce variability
 Increase efficiency
 Ensure safety

Reduce Variability
Process control can reduce variability in the end product,
which ensures a consistently high-quality product.
Manufacturers can also save money by reducing
variability.
For example, in a gasoline blending process, as many as 12 or
more different components may be blended to make a specific
grade of gasoline. If the refinery does not have precise control
over the flow of the separate components, the gasoline may
get too much of the high-octane components.
As a result, customers would receive a higher grade and more
expensive gasoline than they paid for, and the refinery would
lose money. The opposite situation would be customers
receiving a lower grade at a higher price.

uc 1 (design electronical control system).ppt

Increase Efficiency
 Some processes need to be maintained at a
specific point to maximize efficiency.
For example, a control point might be the
temperature at which a chemical reaction takes
place.
 Accurate control of temperature ensures process
efficiency.
 Manufacturers save money by minimizing the
resources required to produce the end product

Ensure Safety
 A run-away process, such as an out-of-control nuclear
or chemical reaction, may result if manufacturers do
not maintain precise control of all of the process
variables.
 The consequences of a run-away process can be
catastrophic
 Precise process control may also be required to ensure
safety.
 For example, maintaining proper boiler pressure by
controlling the inflow in preventing boiler implosions
that can clearly threaten the safety of workers.

The Control Loop
 Three Tasks
Control loops in the process control industry
work in the same way, requiring three tasks to
occur.
 Measurement
 Comparison
 Adjustment

 In Figure below, a level transmitter (LT) measures the
level in the tank and transmits a signal associated with the
level reading to a controller (LIC).
 The controller compares the reading to a predetermined
value, in this case, the maximum tank level established by
the plant operator, and finds that the values are equal.
 The controller then sends a signal to the device that can
bring the tank level back to a lower level—a valve at the
bottom of the tank.
 The valve opens to let some liquid out of the tank.

 Many different instruments and devices may or may not be
used in control loops (e.g., transmitters, sensors, controllers,
valves, pumps), but the three tasks of measurement, comparison,
and adjustment are always present.

Process Control Terms
Process Variable
 A process variable is a condition of the process fluid (a
liquid or gas) that can change the manufacturing process
in some way.
 In the example of you sitting by the fire, the process
variable was temperature.
 In the example of the tank in Figure above, the
process variable is level.

SETPOINT
The set point is a value for a process variable that
is desired to be maintained.
For example, if a process temperature needs to
kept within 5 °C of 100 °C, then the set point is 100
°C. A temperature sensor can be used to help
maintain the temperature at set point.
The sensor is inserted into the process, and a
controller compares the temperature reading from
the sensor to the set point.

 If the temperature reading is 110 °C, then the
controller determines that the process is
above set point and signals the fuel valve of
the burner to close slightly until the process
cools to 100 °C. Set points can also be
maximum or minimum values.
 For example, level in tank cannot exceed 20
feet
 Common process variables include:

Common process variables
include
 Pressure
 Flow
 Level
 Temperature
 Density
 Ph (acidity or alkalinity)
 Liquid interface (the relative amounts of
different liquids that are combined in a
vessel)
 Mass
 Conductivity

Process Control Control
Terminology
 Controlled variable (or “output variable”)
• Manipulated variable (or “input variable”)
• Disturbance variable (or “load variable”)

 Controlled variables (Measured variables) -
The measured variable is the condition of the
process fluid that must be kept at the designed
set-point., which are also called output
variables.
 Manipulated variables - these input variables
are adjusted dynamically to keep the controlled
variables at their set-points.
 Disturbance variables - these are also called
"load" variables and represent input variables
that can cause the controlled variables to
deviate from their respective set points.

Control Terminology(2)
 Set-point change - implementing a change in
the operating conditions.
 The set-point signal is changed and the
manipulated variable is adjusted
appropriately to achieve the new operating
conditions. Also called servomechanism (or
"servo") control.
 Disturbance change - the process transient
behavior when a disturbance enters, also
called regulatory control or load change. A
control system should be able to return each
controlled variable back to its set-point.

Control the tank temperature
at constant value
 The controlled variable is temperature
 The manipulated variable is heat
 The disturbance variable is tank inlet cold
water

Feedforward vs. Feedback Control

Feedback Control:
 Distinguishing feature: measure the
controlled variable
• It is important to make a distinction between
negative feedback and positive feedback.
 Engineering Usage vs. Social Sciences
• Advantages:
 Corrective action is taken regardless of the source
of the disturbance.
 Reduces sensitivity of the controlled variable to
disturbances and changes in the process

 Disadvantages:
 No corrective action occurs until
after the disturbance has upset the
process, that is, until after x differs
from xsp.
 Very oscillatory responses, or even
instability…

Feed forward Control:
Distinguishing feature: measure a disturbance
variable
• Advantage:
Correct for disturbance before it upsets the
process.
Takes corrective action before the process is
upset (cf. FB control.)
Theoretically capable of "perfect control“
Does not affect system stability

 Disadvantage:
 Must be able to measure the disturbance.
 No corrective action for unmeasured
disturbances.
 Disturbance must be measured (capital,
operating costs)
 Requires more knowledge of the process
to be controlled (process model)
 Ideal controllers that result in "perfect
control”: may be physically unrealizable.
Use practical controllers such as lead-lag
units

3) Feed forward Plus Feedback
Control
◦ FF Control
• Attempts to eliminate the effects of measurable
disturbances.
◦ FB Control
• Corrects for unmeasurable disturbances,
modeling errors, etc.

BATCH CONTROL
 Batch processes are those processes that are
taken from start to finish in batches.
 For example, mixing the ingredients for a juice
drinks is often a batch process.
 Typically, a limited amount of one flavor (e.g.,
orange drink or apple drink) is mixed at a time.
 Batch processes often involve getting the correct
proportion of ingredients into the batch.

 Level, flow, pressure, temperature, and often mass
measurements are used at various stages of batch
processes.
 A disadvantage of batch control is that the process
must be frequently restarted.
 Start-up presents control problems because,
typically, all measurements in the system are
below set point at start-up.
 Another disadvantage is that as recipes change,
control instruments may need to be recalibrated.

Error
 Error is the difference between the measured
variable and the Set point and can be either positive
or negative.
 In the temperature control loop example, the error
is the difference between the 110 °C measured
variable and the 100 °C set point—that is, the error
is +10 °C.

 The objective of any control scheme is to
minimize or eliminate error.
 Therefore, it is imperative that error be well
understood.
 Any error can be seen as having three major
components.
 These three components are shown in the
figure on the following page

Magnitude
 The magnitude of the error is simply the
deviation between the values of the set point and
the process variable.
 The magnitude of error at any point in time
compared to the previous error provides the
basis for determining the change in error.
 The change in error is also an important value.

Duration
 Duration refers to the length of time that an
error condition has existed.
Rate of Change
 The rate of change is shown by the slope of the
error plot.
process variable

Offset
 Offset is a sustained deviation of the process
variable from the Set point.
 In the temperature control loop example, if the
control system held the process fluid at 100.5 °C
consistently, even though the set point is 100 °C,
then an offset of 0.5 °C exists.

Control System Closed Loop Open Loop Control
System
A control loop is the fundamental building
block of industrial control systems.
It consists of all the physical components
and control functions necessary to
automatically adjust the value of a measured
process variable (PV) to equal the value of a
desired set-point (SP).

 It includes the process sensor, the
controller function, and the final control
element (FCE) which are all required for
automatic control.

 Definition of Control System
 A control system is a system of devices or
set of devices, that manages ,commands,
directs or regulates the behavior of other
devices or systems to achieve desired
results.

 control system can be rewritten as A control
system is a system, which controls other
systems.
 As the human civilization is being modernized
day by day the demand for automation is
increasing accordingly. Automation highly
requires control of devices.

 A control system is a set of mechanical or
electronic devices that regulates other devices or
systems by way of control loops. Typically, control
systems are computerized.
 Control systems are a central part of industry and
of automation.

 The types of control loops that regulate
these processes include
 industrial control systems (ICS) such as
supervisory control and data acquisition
(SCADA) and distributed control systems
(DCS).

 Programmable logic controllers (PLCs)—PLCs
are usually computers connected to a set of
input/output (I/O) devices.
 The computers are programmed to respond
to inputs by sending outputs to maintain all
processes at set point.

 Distributed control systems (DCSs)—
DCSs are controllers that , in addition to
performing control functions, provide
readings of the status of the process,
maintain databases and advanced man-
machine-interface.

Requirement of Good Control
System
Accuracy: is the measurement
tolerance of the instrument and
defines the limits of the errors made
when the instrument is used in
normal operating conditions.

Accuracy can be improved by
using feedback elements.
To increase accuracy of any
control system error detector
should be present in control
system.

 Noise: An undesired input signal is known as
noise.
 A good control system should be able to
reduce the noise effect for better
performance.
 Bandwidth :An operating frequency range
decides the bandwidth of control system.
 Bandwidth should be as large as possible
for the frequency response of good control
system

Speed : It is the time taken by
control system to achieve its
stable output.
A good control system possesses
high speed.
The transient period for such
system is very small.

Control systems are used to enhance
production, efficiency and safety in many areas,
including
Agriculture
Chemical plants
Pulp and paper mills
Quality control
Boiler controls and
 power plant
Nuclear power plants

Manual and Automatic Control
 Manual and Automatic Control
Before process automation, people, rather than machines,
performed many of the process control tasks. For
example, a human operator might have watched a level
gauge and closed a valve when the level reached the set
point. Control operations that involve human action to
make an adjustment are called manual control systems.
Conversely, control operations in which no human
intervention is required, such as an automatic valve
actuator that responds to a level controller, are called
automatic control systems.

Types of Control Systems
There are various types of control system
but all of them are created to control
outputs.
The system used for controlling the position,
velocity, acceleration, temperature,
pressure, voltage and current etc. are
examples of control systems.
There are two main types of control system.
They are as follow
1. Open loop control system
2. Closed loop control system

Open Loop Control System
 A control system in which the control
action is totally independent of
output of the system then it is called
open loop control system.
 Manual control system is also an
open loop control system.

 Fig - 1 shows the block diagram of
open loop control system in which
process output is totally independent
of controller action.
 Its out put affected by disturbance
and there is no mechanism by itself
to adjust it automatically.

Practical Examples of Open Loop Control System
1. Electric Hand Drier - Hot air (output) comes out as long as you keep your hand under the
machine, irrespective of how much your hand is dried.
2. Automatic Washing Machine - This machine runs according to the pre-set time irrespective of
washing is completed or not.
3. Bread Toaster - This machine runs as per adjusted time irrespective of toasting is completed or
not.
4. Automatic Tea/Coffee Maker - These machines also function for pre adjusted time only.
5. Timer Based Clothes Drier - This machine dries wet clothes for pre-adjusted time, it does not
matter how much the clothes are dried.
6. Light Switch - Lamps glow whenever light switch is on irrespective of light is required or not.
7. Volume on Stereo System - Volume is adjusted manually irrespective of output volume level.

A very simple introductory example of an open-loop system is
that of the clothes washing machine as shown in the block
diagram bellow. Here, the reference signal r(t) designates the
various operating conditions that we set on the ‘‘programmer,’’
such as water temperature, duration of various washing
cycles, duration of clothes wringing, etc. These operating
conditions are carefully chosen so as to achieve satisfactory
clothes washing.

 The controller is the ‘‘programmer,’’ whose output u(t) is the control
signal. This control signal is the input to the washing machine and
forces the washing machine to execute the desired operations
reassigned in the reference signal r(t), i.e., water heating, water
changing, clothes wringing, etc. The output of the system y(t) is the
‘‘quality’’ of washing, i.e., how well the clothes have been washed. It is
well known that during the operation of the washing machine, the
output (i.e., whether the clothes are well washed or not) it not taken
into consideration.
 The washing machine performs only a series of operations contained
in u(t) without being influenced at all by y(t). It is clear that here u(t) is
not a function of y(t) and, therefore, the washing machine is a typical
example of an open-loop system. Other examples of open-loop
systems are the electric stove, the alarm clock, the elevator, the traffic
lights, the worldwide telephone communication system, the computer,
and the Internet

Advantages of Open Loop Control System
Simple in construction and design.
2. Economical.
3. Easy to maintain.
4. Generally stable.
5. Convenient to use as output is difficult to measure.
Disadvantages of Open Loop Control System
1. They are lower inaccurate.
2. They are unreliable.
3. Any change in output cannot be corrected
automatically.

Closed Loop Control System
Control system in which the output has an effect on the
input quantity in such a manner that the input quantity will
adjust itself based on the output generated is called closed
loop control system.
 Open loop control system can be converted in
to closed loop control system by providing a
feedback.
This feedback automatically makes the suitable
changes in the output due to external
disturbance.
 In this way closed loop control system is called
automatic control system.
Prepared by Oumer

 Figure below shows the block diagram of
closed loop control system in which
feedback is taken from output and fed in
to input

Example of closed loop control
system

Prepared by Oumer Hassen

Advantages of Closed Loop Control
System
1. Closed loop control systems are more accurate even
in the presence of non-linearity.
2. Highly accurate as any error arising is corrected due to
presence of feedback signal.
3. Bandwidth range is large.
4. Facilitates automation.
5. The sensitivity of system may be made small to make
system more stable.
6. This system is less affected by noise.

Disadvantages of Closed Loop Control
System
1. They are costlier.
2. They are complicated to design.
3. Required more maintenance.
4. Feedback leads to oscillatory response.
5. Overall gain is reduced due to presence of
feedback.
6. Stability is the major problem and more care is
needed to design a stable closed loop system.

Components of Control Loops
 Primary element/sensor
 Recorder
 Controller
 Correcting element/final control element
 Actuator
Transducer
Converter
Transmitter
Signal
Indicator

TRANSDUCERS AND CONVERTERS
A transducer converts any form of energy into
another form.
In electrical instrumentation field Transducers
are devices which converts a physical variable
into electrical signals. Another name transducers
are Pick-ups.
 A transducer is a device that translates a
mechanical signal into an electrical signal.
 For example, inside a capacitance pressure
device, a transducer converts changes in
pressure into a proportional change in
capacitance.

 A converter is a device that converts
one type of signal into another type
of signal.
 For example, a converter may convert
current into voltage or an analog
signal into a digital signal.
 In process control, a converter used
to convert a 4–20 mA current signal
into a 3–15 psig pneumatic signal
(commonly used by valve actuators)
is called a current-to-pressure

Common electroacoustic transducers:
Loudspeaker – Converts an electrical signal
into sound
 Microphone – Converts sound waves in air into an
electrical signal
electrical signal Hydrophone - Converts sound
waves in water into an electrical signal.
Common electromagnetic transducers:
 Magnetic cartridge – Converts motion in a
magnetic field into an electrical energy

Electromechanical Transducers
Strain gauge – Converts the deformation(strain) of an
object into electrical resistance
Galvanometer– Converts the electric current of a coil in a
magnetic field in movement
Generators – Converts mechanical energy (motion) into
electrical energy.
Motor – Converts electrical energy into mechanical energy
(graphic below)

Photoelectric Transducers:
Cathode ray tube (CRT) –Converts electrical signals
into light energy for a visual output (graphic above)
Light bulb –Converts electrical energy into visible
light and heat (explained in next section)
Photodiode - Converts light energy into electrical
energy
Thermoelectric Transducers:
Thermocouple – Converts heat energy into electrical
energy Temperature sensitive resistor
(Thermistor) – a variable resistor affected by
temperature changes (heat energy to electrical
energy)

Photovoltaic Transducers
 Sandwich design of a metal base plate and a thin transparent
metallic layer with a semiconductor material in between
 Light strikes barrier between transparent metal layer and
semiconductor material, and a voltage is generated
 Most widely used application of photovoltaic cell is the light
exposure meter in photographic work

Converter
 A converter is a device that converts one type
of signal into another type of signal.
 For example, a converter may convert
current into voltage or an analog signal into a
digital signal.
 In process control, a converter used to
convert a 4–20 mA current signal into a 3–15
psi pneumatic signal (commonly used by valve
actuators) is called a current-to-pressure
converter.

Transmitters:
Transmitters are devices that convert the
signal into a standard signal
that can be transmittable through the control
loop and the parameters can be monitored
remotely.
• Pressure transmitters
• Flow transmitters
• Temperature transmitters
• Level transmitters
• Analytic transmitters

TRANSMITTERS
 A pressure transducer, often called a pressure
transmitter, is a transducer that converts pressure
into an analog electrical signal. Pressure applied
to the pressure transducer produces a deflection of
the diaphragm which introduces strain to the
gages.
 Flow transmitters provide electrical outputs
that are proportional to flow inputs.
 They use flow meters to measure the flow of
liquids and gases.
 Flow transmitters use three basic types of
meters: mass, volumetric, and velocity.

 Temperature transmitter is an electrical
instrument, which interfaces the temperature
sensor to isolate, amplify, filter noise and convert
the signal from the sensor to send it to the
control device.
 It is a tool to help measure and alert temperature
changes.
 Level transmitters provide continuous level
measurement over the range of the system rather
than at a single point and produce an output
signal that directly correlates to the level within a
vessel.
 The output signal generated can be used to
display the depth or to actuate control functions.

Signals
 There are three kinds of signals that exist for
the process industry to transmit the process
variable measurement from the instrument to
a centralized control system.
◦ Pneumatic signal
◦ Analog signal
◦ Digital signal


 Pneumatic signal: Pneumatic signals are
signals produced by changing the air
pressure in a signal pipe in proportion to
the measured change in a process
variable.
 The common industry standard
pneumatic signal range is 3–15 psig. The
3 corresponds to the lower range value
(LRV) and the 15 corresponds to the

Analog Signals
 The most common standard electrical signal is
the 4–20mA current signal.
 With this signal, a transmitter sends a small
current through a set of wires.
 The current signal is a kind of gauge in which
4mA represents the lowest possible
measurement, or zero, and 20mA represents
the highest possible measurement.
 Other common standard electrical signals
include the 1–5 V (volts) signal and the
pulse output.
90

Analog Signals
 For example, imagine a process that must be maintained at 100
°C.
 An RTD temperature sensor and transmitter are installed in the
process vessel, and the transmitter is set to produce a 4 mA signal
when the process temperature is at 95 °C and a 20 mA signal
when the process temperature is at 105 °C.
 The transmitter will transmit a 12 mA signal when the
temperature is at the 100 °C Set-point.
91

 As the sensor’s resistance property changes in
response to changes in temperature, the
transmitter outputs a 4–20 mA signal that is
proportionate to the temperature changes.
 This signal can be converted to a temperature
reading or an input to a control device, such as a
burner fuel valve.

Digital signals
 Digital signals are the most recent
addition to process control signal
technology.
 Digital signals are discrete levels or values
that are combined in specific ways to
represent process variables and also carry
other information, such as diagnostic
information.
 The methodology used to combine the digital
signals is referred to as protocol.
93

INDICATORS
 indicator is a human-readable device that
displays information about the process.
 Indicators may be as simple as a pressure or
temperature gauge or more complex, such as a
digital read-out device.
 Some indicators simply display the measured
variable, while others have control buttons
that enable operators to change settings in the
field.
94

RECORDERS
 A recorder is a device that records the output of a
measurement devices.
 Many process manufacturers are required by law to
provide a process history to regulatory agencies, and
manufacturers use recorders to help meet these
regulatory requirements.
 In addition, manufacturers often use recorders to
gather data for trend analyses.
 By recording the readings of critical measurement
points and comparing those readings over time with
the results of the process, the process can be
improved.
95

 Different recorders display the data
they collect differently.
 Some recorders list a set of readings
and the times the readings were
taken;
 others create a chart or graph of the
readings.
 Recorders that create charts or graphs
are called chart recorders.

CORRECTING ELEMENTS/FINAL CONTROL
ELEMENTS
 The correcting or final control element is
the part of the control system that acts to
physically change the manipulated
variable.
 In most cases, the final control element is
a valve used to restrict or cut off fluid
flow, but pump motors, louvers (typically
used to regulate air flow), solenoids, and
other devices can also be final control
elements.
 Final control elements are typically used
97

 For example, a final control element may regulate
the flow of fuel to a burner to control temperature,
the flow of a catalyst into a reactor to control a
chemical reaction, or the flow of air into a boiler to
control boiler combustion.
 In any control loop, the speed with which a final
control element reacts to correct a variable that is
out of set point is very important. Many of the
technological improvements in final control
elements are related to improving their response
time.

ACTUATORS
 An actuator is the part of a final control
device that causes a physical change in the
final control device when signaled to do so.
 The most common example of an actuator is
a valve actuator, which opens or closes a
valve in response to control signals from a
controller.
 Actuators are often powered pneumatically,
hydraulically, or electrically.
 Diaphragms, bellows, springs, gears, hydraulic
pilot valves, pistons, or electric motors are often
parts of an actuator system.
99

CONTROLLERS
 A controller is a device that receives data from
a measurement instrument, compares that
data to a programmed set-point, and, if
necessary, signals a control element to take
corrective action.
 Local controllers are usually one of the three
types: pneumatic, electronic or programmable.
 Controllers also commonly reside in a digital
control system.
100

CONTROLLERS
 Controllers may perform complex mathematical functions to
compare a set of data to set-point or they may perform simple
addition or subtraction functions to make comparisons.
 Controllers always have an ability to receive input, to perform a
mathematical function with the input, and to produce an output
signal.
 ON/OFF controller (PLC), PID, Fuzzy controller. .
.are type of controller.
101

Programmable Logic
Controller for Process
Control System
CONTROLLER DESIGN
102

Prepared by Shimels Chekol 103
Prepared by Oumer Hassen

1. Design a PLC program to control the
level of a water storage tank by turning a
discharge pump ON and OFF based on
Low and High levels.
Logic Description :
Auto :if Auto Mode selected in Local
Control Panel, then pump will be logically
controlled based on Low Level Switch
and High Level Switch
Manual :if Manual Mode Selected in
Local Control Panel, then irrespective of
Low Level Switch & High Level Switch
Status, Pump will be controlled manually
using ON/OFF button in Local Control 104

When the water level reaches low level
then pump will be stopped.
if the level of the water reaches high point, the
pump will started so that the water can be
drained and thus lowering the level.
Indication Panel : This panel contains LED’s to
show the status of the water level control. It has
Pump Running, Low Level & High Level Signals
If pump is running then the Pump Running status
lamp will be ON.
then, if Low Level Switch activated then Low
Level Status lamp will be ON.
if High Level Switch activated then High Level
Status lamp will be ON.
105

Controller; Programmable Logic
Controller (PLC)
Hardware
1. Input device of controller
2. Output device of
controller
Stop push button =I1
Start push button=I2
Low level sensor=I3
High level sensor=I4
 Pump motor =Q1
 Pump running indicator
lamp=Q2
 Low level indicator
lamp=Q3
 High level indicator
lamp=Q4
106

Design PLC controller for
automatic water level control
system
107
Prepared by Oumer

Level Sensors
Prepared by Shimels Chekol 108

uc 1 (design electronical control system).ppt

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