Fire Alarm 09
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Transcript of Fire Alarm 09
“FIRE ALARM USING THERMISTOR”
A PROJECT REPORT SUBMITTED
TO
WALCHAND COLLEGE OF ENGINEERING SANGLI
As a Partial Fulfillment
Of
ELECTRONICS CIRCUIT DESIGN
BY
MISS. DHAVALIKAR DEVIKA C. (ROLL NO. 03, W43450) MISS. GULAVANI POOJA S. (ROLL NO. 04, W43455) MISS. KOLEKAR SUPRIYA S. (ROLL NO. 09, W43468) MISS. PATIL AMRUTA S. (ROLL NO. 15, W43484) MISS. RAJPUT TRUPTI R. (ROLL NO. 16, W43490)
(DEPARTMENT OF ELECTRONICS)
Under the guidance of
MR. DHAYGUDE S.B. MR. HAJARE S.S.
DEPARTMENT OF ELECTRONICS ENGINEERING
WALCHAND COLLEGE OF ENGINEERING SANGLI.
NOVEMBER 2009
1
DECLARATION
We, the undersigned, hereby declare that the project report
entitled
“FIRE ALARM USING THERMISTOR”
written and submitted by us to Walchand College Of Engineering Sangli,
as a partial fulfillment for ELECTRONICS CIRCUIT DESIGN under the
guidance of Mr. Dhaygude S.B. & Mr. Hajare S.S. is our original work. The
empirical results in this project report are based on the data collected by us.
We understand that any such copying is liable to be punished as the
authorities deem fit.
Date :
Place : SANGLI.
By:
Miss. Dhavalikar Devika C. Miss. Gulavani Pooja S.
Miss. Kolekar Supriya S. Miss. Patil Amruta S.
Miss. Rajput Trupti R.
Forwarded through:
Head, of Department. Dean Academics Electronics Engineering, W.C.E.
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CERTIFICATE
This is to certify that the project report entitled
“FIRE ALARM USING THERMISTOR”
Submitted by
Miss. KOLEKAR SUPRIYA S. (Roll No. 09, W43468)
As a Partial Fulfillment
of
ELECTRONICS CIRCUIT DESIGN
to
WALCHAND COLLEGE OF ENGINEERING SANGLI,
has been completed under my guidance and supervision.
To the best of my knowledge and belief, the matter presented in this project
report is original and has not been submitted elsewhere for any other
purpose.
Date:
Place: SANGLI.
MR.DHAYGUDE S.B. Dept. of Electronics Engineering
3
ACKNOWLEDGEMENT
Gratitude is the hardest emotion to express and often one doesn’t find
adequate words to convey all that one feels.
It is our foremost duty to express our deep sense of gratitude and respect to the
guide Mr. Dhaygude S.B. & Mr. Hajare S.S.for his uplifting tendency and inspiring us
for taking up this project work completely successful.
We are also grateful to Dr. B.V.Pawar, Head of Department of Electronics
Engineering for providing all necessary facilities to carry out the project work and whose
encouraging part has been a perpetual source of inspiration.
We are indebted to the library personnel’s for offering all the help on
completing the project work. Last but not the least we are thankful to our colleagues and
those who helped us directly or indirectly throughout this project work.
By:
Miss. Dhavalikar Devika C. Miss. Gulavani Pooja S.
Miss. Kolekar Supriya S. Miss. Patil Amruta S.
Miss. Rajput Trupti R.
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FIRE ALARM USING THERMISTOR
1. INTRODUCTION
Fire causes tremendous destruction in domestic, industrial fields. It is
necessary to reduce this destructions. We have constructed ‘fire alarm’ as a preventive
measure to detect fire on small scale.
1.1 AIM: To construct a FIRE ALARM using thermistor to detect fire or increased
temperature.
1.2 COMPONENTS: IC 555
Thermistor
Resistors
Capacitors
Transistors
Speaker
Diode
Light Emitting Diode
Power Supply
IC 7806
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2. DETAILS OF COMPONENTS:
IC 555:
The IC 555 Timer is a highly stable device for generating accurate time delay or
oscillations. It is available in two package styles, 8-pin circular style TO-99 can or 8-pin
mini DIP or as 14-pin DIP. The 556 timer contains two 555 timers and is a 14-pin DIP.
A single 555 timer can provide time delay ranging from microseconds to hours. The SE
555 is designed for the operating temperature range from -550C to +1250C, while the NE
555 operates over a temperature range of 00C to 700C.
The 555 timer can be used with supply voltage in the range of +5 V to +18 V and
can drive load up to 200mA (source or sink). It is compatible with both TTL and CMOS
logic circuits.
THERMISTOR:
Symbol
A thermistor is a type of resistor whose resistance varies with temperature. The
word is a portmanteau of thermal and resistor. Thermistors are widely used as inrush
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current limiters, temperature sensors, self-resetting overcurrent protectors, and self-
regulating heating elements.
Thermistors differ from resistance temperature detectors (RTD) in that the
material used in a thermistor is generally a ceramic or polymer, while RTDs use pure
metals. The temperature response is also different; RTDs are useful over larger
temperature ranges, while thermistors typically achieve a higher precision within a
limited temperature range [usually -90C to 130C].
RESISTORS :
Symbol
A resistor is a two-terminal electronic component that produces a voltage across
its terminals that is proportional to the electric current through it in accordance with
Ohm's law:
V = IR
Resistors are elements of electrical networks and electronic circuits and are
ubiquitous in most electronic equipment. Practical resistors can be made of various
compounds and films, as well as resistance wire (wire made of a high-resistivity alloy,
such as nickel/chrome).
The primary characteristics of a resistor are the resistance, the tolerance,
maximum working voltage and the power rating. Resistors can be integrated into hybrid
and printed circuits, as well as integrated circuits. Size, and position of leads (or
terminals) are relevant to equipment designers; resistors must be physically large enough
not to overheat when dissipating their power.
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CAPACITORS:
Symbol
A capacitor or condenser is a passive electronic component consisting of a
pair of conductors separated by a dielectric. When a voltage potential difference exists
between the conductors, an electric field is present in the dielectric. This field stores
energy and produces a mechanical force between the plates. The effect is greatest
between wide, flat, parallel, narrowly separated conductors.
An ideal capacitor is characterized by a single constant value, capacitance,
which is measured in farads. This is the ratio of the electric charge on each conductor to
the potential difference between them. In practice, the dielectric between the plates
passes a small amount of leakage current.
Capacitors are widely used in electronic circuits to block the flow of direct
current while allowing alternating current to pass, to filter out interference, to smooth the
output of power supplies, and for many other purposes.
TRANSISTORS:
Symbol
A transistor is a semiconductor device commonly used to amplify or switch
electronic signals. A transistor is made of a solid piece of a semiconductor material, 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 flowing through another pair
of terminals. Because the controlled (output) power can be much more than the
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controlling (input) power, the transistor provides amplification of a signal. Some
transistors are packaged individually but most are found in integrated circuits.
The transistor is the fundamental building block of modern electronic devices,
and its presence is ubiquitous in modern electronic systems.
SPEAKER:
Symbol
A loudspeaker (or "speaker") is an electro-acoustic transducer that converts an
electrical signal into sound. The speaker pulses in accordance with the variations of an
electrical signal and causes sound waves to propagate through a medium such as air or
water.
Loudspeakers (and other electro-acoustic transducers) are the most variable
elements in a modern audio system and are usually responsible for most distortion and
audible differences when comparing sound systems.
DIODE:
Symbol
In electronics a diode is a two-terminal electronic component which
conducts electric current asymmetrically or unidirectionally; that is, it conducts current
more easily in one direction than in the opposite direction. The term usually refers to a
semiconductor diode, the most common type today, which is a two-terminal
semiconductor P-N junction.
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The most common function of a diode is to allow an electric current in one
direction (called the forward direction) while blocking current in the opposite direction
(the reverse direction). Thus, the diode can be thought of as an electronic version of a
check valve. This unidirectional behavior is called rectification, and is used to convert
alternating current to direct current, and remove modulation from radio signals in radio
receivers.
POWER SUPPLY:
Symbol
An electrical battery is a combination of one or more electrochemical cells,
used to convert stored chemical energy into electrical energy. Since the invention of the
first Voltaic pile in 1800 by Alessandro Volta, the battery has become a common power
source for many household and industrial applications,
Batteries may be used once and discarded, or recharged for years as in standby
power applications. Miniature cells are used to power devices such as wristwatches and
portable electronic devices; larger batteries provide standby power for telephone
exchanges or computer data centers
IC 7806:
The LM 78XX series of three terminal regulators are available with several
fixed output voltages. These ICs are designed as fixed voltage regulators and with
adequate heat sinking can deliver output currents excess in 1A. In the series, XX
indicates voltage options. These are available in output voltage range of 5, 6, 8, 12,
15, 18, 24 volts with input voltage in the range of 30-35 volts. These ICs have
internal thermal shutdown and short circuit current limiting.10
3. SPECIFICATIONS:
No. Name of Component Notation Value 1. IC 555 IC1
2. Thermistor TH1 10K
3.
Resistor
R1 R2 R3 R4 R5 R6 R7 R8
470Ω 33KΩ 470Ω 560Ω 47KΩ 2.2KΩ 470Ω 470Ω
4.
Capacitors
C1 C2 C3
10µF 0.04µF 0.01µF
5. Transistors T1 T2 T3
BC548 BC558 SL100B
6. Speaker LS1 8Ω, 1W
7. Diode D1 1N4001
8. Light Emitting Diode LED1
9. Power Supply BAT1 9 Volts
10. IC 7806 IC2 6 Volts
11
4. CIRCUIT DIAGRAM:
12
5. WORKING:
In this fire alarm circuit, a thermistor works as the heat sensor. When
temperature increases, its resistance decreases and vice versa. At normal temperature,
the resistance of the thermistor (TH1) is approximately 10 kilo-ohms, which reduces to
a few ohms as the temperature increases beyond 100°C. The circuit uses readily
available components and can be easily constructed on any general purpose PCB. Timer
IC NE555 (IC1) is wired as an astable multivibrator oscillating in audio frequency band.
Switching transistors T1 and T2 drive multivibrator NE555 (IC1).The output of IC1 is
connected to npn transistor T3, which drives the loudspeaker(LS1) to generate sound.
The frequency of IC1 depends on the values of resistorsR5 and R6 and
capacitor C2.When thermistor TH1 becomes hot, it provides a low-resistance path to
extend positive voltage to the base of transistorT1 via diode D1 and resistor R2.
Capacitor C1 charges up to the positive voltage and increases the ‘on’ time of alarm. The
higher the value of capacitor C1, the higher the forward voltage applied to the base of
transistor T1 (BC548).Since the collector of transistor T1 is connected to the base of
transistor T2, transistor T2 provides positive voltage to reset pin 4 of IC1
(NE555).Resistor R4 is used such that IC1 remains inactive in the absence of positive
voltage. Diode D1 stops discharging of capacitor C1 when the thermistor connected to
the positive supply cools down and provides a high-resistance(10-kilo-ohm) path. It also
stops the conduction of T1. To prevent the thermistor from melting, wrap it up in mica
tape. The circuit works off a 6V-12V regulated power supply. LED1 is used to indicate
that power to the circuit is switched on.
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6. SUMMARY & CONCLUSION:
Using IC 555 and thermistor, we have constructed ‘fire alarm’. A thermistor
works as the heat sensor. Timer IC NE555 (IC1) is wired as an astable multivibrator
oscillating in audio frequency band. The output of IC1 is connected to npn transistor T3,
which drives the loudspeaker(LS1) to generate sound. By using this circuit, we can
prevent hazardous effects of fire.
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7. COSTING
Sr. No. Name of component Quantity Price(Rs.)
1. IC 555 1 15/-
2. Thermistor 1 10/-
3. Resistors 8 8/-
4. Capacitors 3 6/-
5. Transistors 3 14/-
6. Diode 1 2/-
7. Light Emitting Diode 1 1/-
8. Loudspeaker 1 15/-
9. Power Supply 1 20/-
10. IC 7806 1 15/-
11. Connectors 5/-
Total 21 111/-
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