Temperature_Controlled_DC_Fan_Using_Ther.docx

A Project Work
Submitted to the Institute of Information Technology, Jahangirnagar University, Savar, Dhaka in
partial fulfillment of the requirements for the B.Sc (Hons.) degree in IT.
SUBMITTED BY
Al Mamun Parvez
ROLL: 2111
SUPERVISED BY
Zamshed Iqbal Chowdhury
Lecturer
Institute of Information Technology
Jahangirnagar University
Savar, Dhaka-1342, Bangladesh.
Institute Of Information Technology
Savar, Dhaka-1342, Bangladesh.

DECLARATION
This project report is submitted to the Institute of Information Technology, Jahangirnagar
University, Savar, Dhaka in partial fulfillment of the requirements for having the B.Sc
(Hons.) degree in IT. This is also needed to certify that the projec t work is under the 1st
Year 1s t Semester course of the IIT “IT-1100: Semester Project & Viva”’. So, we, here
declaring that this project report has not been submitted elsewhere for the requirement
of any kind of degree, diploma or publication.
1. Al Mamun Parvez
IIT
Roll : 2111
45th batch, JU.

ACCEPTANCE
This project report is submitted to the Institute of Information Technology, Jahangirnagar
University, Savar, Dhaka in partial fulfillment of the requirements for having the B.Sc
(Hons.) degree in IT.
Zamshed Iqbal Chowdhury
Lecturer
Institute of Information Technology (IIT)
Savar, Dhaka-1342, Bangladesh

ACKNOWLEDGEMENT
We feel pleased to have the opportunity of expressing my heartfelt thanks and gratitude
to those who all rendered their cooperation in making this report. First of all we would like
to thank the Almighty for giving us the opportunity to complete this work successfully.
This project was performed under the supervision of Zamshed Iqbal Chowdhury, Lecturer
of IIT, Jahangirnagar University, Savar, Dhaka. During our project work he has supplied us
a number of links, books, journals, and research papers related to the present
investigation. Without his help, kind support and generous time spans he has given, we
could not perform the project work successfully in due time. First and foremost, we wish
to acknowledge our profound and sincere gratitude to him for his guidance, valuable
suggestions, encouragement and cordial cooperation.
We thankfully acknowledge the valuable Lab support and help that we have got frequently
from Circuit Lab Technicians and staffs of IIT. Last but not least, we express our gratitude
to all other sources from where we have found help. We are indebted to those who have
helped us directly or indirectly in completing this project.

ABSTRACT
The purpose of making a final project entitled Automatic Fan Control System Based with
Thermistor For Temperature Controller is to allow users to adjust the fan speed automatically. So
it can save and streamline the work that is usually done manually which could then work
automatically and effective for humans.
The study was conducted with the design and manufacture of Automatic Fan Control System.
Further functional testing tools, as well as temperature sensor is used.
Fan can be controlled manually by pressing on the switch button where in this method, any
change in the temperature will not give any change in the fan speed, except the usage change the
speed of the fan which is manually.
Over the last decade, advances in digital electronics have made computers maller, cheaper and
faster. Throughout this revolution as well mobile computing environment such as PDA has been
created and undoubtedly other advances in technology like smart home also play an important
role towards better life in the future.
This project is about how we can control the fan basedon temperature sensor regardless of
traditional thermostat It is also part of smart home application where the fan will gradually
increase live speed if the temperature of the environment is increasing. Besides that, the
component that made up the temperature sensor is known as thermistor. A sensor is a type of
transducer. In a broader sense, a transducer is sometimes defined as any device that converts
energy from one form to another .There are two types of thermistor depend on the sign of k.
Firstly is positive temperature coefficient (PTC). PTQ thermistor works by increasing the
resistance will increasing temperature.
Secondly k negative temperature coefficient (NTC). NTC thermistor works by decreasing the
resistance will increasing temperature. This project will focus on NTC type of thermistor.
Experiment can be followed to evaluate whether this circuit can save energy through the use of
temperature sensor and thus promote efficiency. Finally. After some experiments have done, the
result of the experimentation and finding can be concluded.
Keyword–Op-Amp, Resistor, NTC Thermistor, Potentiometer, Transistor, Diode, Power supply,
Dc Motor .

TABLE OF CONTENTS
Contents
1 Introduction:............................................................................................................................ 7
2 Project Background: ................................................................................................................ 7
3 Project Statement:................................................................................................................... 7
4 project Objective:.................................................................................................................... 8
5 project Scope:.......................................................................................................................... 8
6 Component List:....................................................................................................................... 8
7 Mojor Component description:.............................................................................................. 9
7.1 THERMISTOR:................................................................................................................... 9
7.2 POTENTIOMETER:.......................................................................................................... 10
7.3 DIODE:............................................................................................................................ 11
7.4 OP-AMP 741:...................................................................Error! Bookmark not defined.1
7.5 TRANSISTOR:...................................................................Error! Bookmark not defined.4
7.6 POWER SUPPLY:..............................................................Error! Bookmark not defined.5
7.7 RESISTORS (47 ohms, 47k ohms):..................................Error! Bookmark not defined.5
8 Circuit Diagram and it’s working:...........................................Error! Bookmark not defined.6
9 Analysis .................................................................................................................................. 16
10 PCB Layout of the circuit ..................................................................................................... 18
11 Specification......................................................................................................................... 18
12 Advantage and Disadvantage ............................................................................................. 18
13 Application:.......................................................................................................................... 19
14 Concluton:............................................................................................................................ 19
15 References: .......................................................................................................................... 19

1.Introduction:
Electronic fan is one of the most popular electrical devices due to its cost effectiveness and low
power consumption advantages. It is a common circuit and widely used in many applications. It
is also one of the most sensible solutions to offer a comfortable and energy efficient. In fact the
fan has been long used and still available in the market.
Nowadays, the demand for accurate temperature control and air freshening control has
conquered many of industrial domains such as process heat, automotive, industrial places or
office buildings where tine air is cooled in order to maintain a comfortable environment for is
occupants. One of the most important concern involved in heat area consist in the desired
temperature achievement and consumption optimization. So. An automatic temperature control
system technology is needed for the controlling purpose in the fan speed according to the
temperature changes.
Many researches focusing on automatic temperature control system application in different fields
will gain the benefits. For examples, an automatic temperature controller for multi element array
hyperthermia systems, multi loop automatic temperature control system design for fluid
dynamics .design of automatic temperature- control circuit module in tunnel microwave heating
system, live automatic temperature system with FUZZY self-adaptive Proportional-Integral-
Derivative (PID) control in semiconductor laser.
2. Project Background:
Sometime electric fan usage is wasting power because of human attitude. Human also mostly
demands something that easily to be used without wasting energy. To minimize or reduce the
power usage, this project developed an automatic fan system where speed is controlled by the
room temperature.
3. Problem Statement:
Most human feels the inconvenient about changing tie fan speed level mutually when the room
temperature changes. So, the automatic fan system that automatically changes the speed level
according to temperature changes is recommended to be built for solving this problem.

4. Objective:
The objectives of this project are to:
i. Enable the electric fan to automatically change the speed level according to temperature
changes.
ii. Develop an automatic fan system that can change the speed level due to the environment
temperature changes.
iii. Develop an automatic fan system that can preview the status of the temperature and the speed
level by using NTC thermistor.
5. Project Scope:
The system is built using:
i. IC 741 n NTC Thermistor as the main controller.
it The temperature sensor as the input for tie microcontroller.
ii The DC motor as the output for the system
6. Component List:
 R1 = 4.7K
 R2 = 47 Ohm
 NTC Thermistor = 4.7K
bead type thermistor
 Potentiometer (Vr) = 500K
 OP AMP IC 741
 Transistor T1 = BD140 (or other PNP transistor may work)
 12V DC fan which is also used in computer (CPU)
 Diode 1N4007
 12 V DC power supply

Introduction To Several Basic Electronic Components
There are many electronic components that will be used during the development of temperature
controlled fan circuit. There are some that we familiar with and some are rarely used. Al
components play its important role and interrelated between each other in completing the circuit
design.
7.1 Thermistor:
According to Wikipedia.com. Thermistor is a type resistor used to measure Temperature
changes, relying in its resistance with changing temperature.
Thermistor symbol
There are two types depending on the sign of K. If K is positive, the resistance increases with
increasing temperature. This is known as positive temperature coefficient (PTC) thermistor.
However, if the k is negative, tie resistance decreases with increasing temperature. This is known
as negative temperature coefficient (NTC) thermistor.

7.2 Potentiometer:
A potentiometer is a manually adjustable variable resistor with 3 terminals. Two terminals are
connected to both ends of a resistive element, and the third terminal connects to a sliding contact,
called a wiper, moving over the resistive element. The position of the wiper determines the
output voltage of the potentiometer. The potentiometer essentially functions as a variable voltage
divider. The resistive element can be seen as two resistors in series(potentiometer resistance),
where the wiper position determines the resistance ratio of the first resistor to the second resistor.
A potentiometer is also commonly known as a potmeter or pot. The most common form of
potmeter is the single turn rotary potmeter. This type of pot is often used in audio volume control
(logarithmic taper) as well as many other applications. Different materials are used to construct
potentiometers, including carbon composition, cermet, wire wound, conductive plastic or metal
film.
Potentiometer symbol

7.3 Diode:
A diode is a device which only allows unidirectional flow of current if operated within a
rated specified voltage level. A diode only blocks current in the reverse direction while the
reverse voltage is within a limited range otherwise reverse barrier breaks and the voltage at
which this breakdown occurs is called reverse breakdown voltage. The diode acts as a valve in
the electrical and electronic circuit. A Pn junction is the simplest form of the diode which
behaves as ideally short circuit when it is in forward biased and behaves as ideally open circuit
when it is in the reverse biased. Beside simple PN junction diodes, there are different types of
diodes although the fundamental principle is more or less same. So a particular arrangement of
diodes can convert AC to pulsating DC, and hence, it is sometimes also called as a rectifier. The
name diode is derived from "di-ode" which means a device having two electrodes.
Diode symbol
7.4 Op-amp 741:
An operational amplifier (often op-amp or op-amp) is a DC-coupled high-gain electronic
voltage amplifier with a differential input and, usually, a single-ended output.An op-amp produces
an output potential (relative to circuit ground) that is typically hundreds of thousands of times
larger than the potential difference between its input terminals.

Figure: Op-amp feature
An op-amp can be connected to a single voltage rail (called UNIPOLAR SUPPLY - 0v to
Vcc) or a dual voltage rail (called BIPOLAR SUPPLY +/-Vcc).
When connected to a single voltage rail, the output can go from 0v to approx. full rail voltage.
The OP-AMP has two inputs. A "+" input for non-inverting and "–" for inverting. When the "+"
input is a few millivolts higher than the "–" input, the output goes HIGH.
For our projectwe have usedOP-AMP741. It isone of the most popularand cheapestOP-AMP.The pin-
out for an LM741 is shown below:
Figure: Practical image of Op-amp 741

The basic parameters for a 741 are:
Rail voltage: +/- 15v DC (+/- 5v min, +/- 18v max)
Input impedance: approx. 2M
Low Frequency voltage gain: approx. 200,000 V
Input bias current: 80nA
Slew rate: 0.5v per microsecond
Maximum output current: 20mA
Recommended output load: not less than 2k
In our project to achieve our respective goal we have used op-amp 741 as a positive voltage
comparator. A comparator is a device that compares two voltages or currents and outputs a
digital signal indicating which is larger. It has two analogue input terminals V+ and V- and one
binary digital output Vo .The output is ideally
The comparator output satisfies the following rules:
o When V+ is larger than V- the output bit is 1.
o When V+ is smaller than V- the output bit is 0.
The Op-amp comparator compares one analogue voltage level with another analogue voltage
level, or some preset reference voltage, VREF and produces an output signal based on this voltage
comparison.
The standard operational amplifierischaracterized byits open-loopgainAOandthatits outputvoltage
is givenbythe expression:VOUT= AO(V+– V-) where V+ and V- correspondto the voltagesat the non-
inverting and the inverting terminals respectively.
WhenVIN isgreaterthanVREF,the op-ampcomparatorsoutputwillsaturate towardsthe positivesupply
rail, Vcc. When VIN is less than VREF the op-amp comparators output will change state and saturate at
the negative supply rail, 0v as shown.

7.5 Transistor:
A transistor is a semiconductor device used to amplify or switch electronic signals and electrical
power. It is composed of semiconductor material usually with at least three terminals for
connection to an external circuit. A voltage or current applied to one pair of the transistor's
terminals changes the current through another pair of terminals. Because the controlled
(output) power can be higher than the controlling (input) power, a transistor can amplify a signal.
Today, some transistors are packaged individually, but many more are found embedded
in integrated circuits.
Fig: Transistor Symbol

7.6 Power Supply:
Figure: 12v Battery Figure: Battery Clip Figure: Battery Symbol
7.7 Resistors:
Fig: 47 ohms Fig: 47k ohms
Fig: Resistor Symbol
Figure: Resistors
A resistor is a passive two-terminal electrical component that implements electrical resistance as
a circuit element. Resistors actto reduce current flow, and, at the same time, act to lower voltage
levels within circuits. In electronic circuits,resistors are used to limit current flow, to adjust signal
levels, bias active elements, and terminate transmission lines among other uses.

8. Circuit diagram:
Following figure shows circuit diagram of temperature controlled DC fan using
thermistor.
Temperature Controlled DC fan using Thermistor
9. Working of circuit & Analysis:
The basic working principle of temperature controlled DC fan is based on the working
principle of thermistor. Thermistor is component which changes its resistance as its
temperature changes. There are twotypes of thermistor available which are NTC i.e.
negative temperature coefficient and other is PTC which is positive temperature
coefficient.
In temperature controlled DC fan we have used a NTC type thermistor. It is called NTC
because its resistance increases when its temperature decreases and vice verse. Similarly
in PTC its resistance increases when temperature increases and vice verse.
Op amp IC741 is used as a voltage comparator which compares the voltage between its
two inputs i.e. inverting and non inverting terminals. Pin number 2 is inverting terminal
which is connected to the potentiometer and pin number 3 is non inverting terminal

which is connected in between thermistor and R1 which makes a voltage divider circuit.
Thus the output of op amp is responsible for the speed of fan.
When the temperature of surrounding increases, temperature of thermistor also
increases which causes its resistance to decrease, therefore voltage divider circuit causes
more voltage across pin number 3. Thus the output voltage increases causing speed of
fan to increase

10. PCB layout of the circuitr:
11. Project Significance:
a) To monitor the environments that is not comfortable, or possible, for humans to monitor,
especially for extended periods of time.
b) Prevents waste of energy when it’s not hot enough for a fan to be needed.
c) To assist people who are disabled to adjust the fan speed automatically.
12. Advantages and disadvantages:
 Advantages of Temperature Controlled Fan:
 It is very economical and easy to handle by the user.
 Speed varies automatically, so that it controls the speed without using it
manually.
 It is help full to disabled people.
 It is very easy to install in offices, houses etc.
 Save energy by slowing down its speed in low temperature.

 Disadvantages of Temperature Control Fan
 Micro controller is the heart of the circuit, if controller is damaged the whole
system will be interrupted.
 Speed control is independent of individual preference.
13. Application:
Typical applications include automotive, telecom equipment, laptops, server, and many other
portable and non-portable electronic devices. Sometimes you could find fans used in conjunction
with a heat sink to increase overall airflow. This is known as a forced air system.
14. Conclusion :
❖ This circuit is very simple and easy to build.
❖ This paper elaborates the design and construction of fan speed control system to control the
room temperature. The temperature sensor was carefully chosen to gauge the room temperature.
Moreover, the fan speed will increase automatically if the temperature room is increased. As
conclusion, the system which designed in this work was perform very well, for any temperature
change and can be classified as automatic control.
15. References:
1. https://www.techshopbd.com/
2. https://en.wikipedia.org/wiki/Bipoler junction transistor/
3. http://www.myclassbook.org /
4. http://www.slideshare.net/PankajJagadale1/
5. http://www.talkingelectronics.com/projects/OP-AMP/OP-AMP-1.html
6. http://www.homemade-circuits.com/2012/03/how-to-use-ic-741-as-comparator.html
7. http://www.slideshare.net/jessinikolasmkt786/
8. http://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-
resistor-color-code-4-band
9. https://en.wikipedia.org/wiki/Transistor/

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