1. A
Mini project presentation on
LOW COST FIRE ALARM
Vaagdevi College of Engineering,Warangal
Presented by:
V.Ajay kumar(09641A0415)
V.Srinivas(09641A0424)
Under guidance of S.Durgaprasad(09641A0402)
Mrs.Vijaya T.Jagadeeshwar(09641A0450)
(Assoc.Prof)
2. INTRODUCTION:
These project is entitled low cost fire alarm.
The main aim of the project is to provide best security from
fire asserts at low cost. This project uses a thermistor which can
be used as a sensor to create a heat detection alarm systems.
It can be used in industries to protect the
goods , security at warehouses,etc,.
4. CIRCUIT DESCRIPTION:
• The circuit consist s of
1.Thermistor103
2. Slider switch
3. LED
4.Buzzer
5.9V battery
6.Transistors(A2222 , BC547)
7.Resistors(560 ohm,220K,10K)
8. Variable resistor(10K) and
9. Relay circuit
10.Buzzer
5. • 9V batteries are commonly used in pocket transistor radios ,
carbon monoxide alarms , smoke dectectors and as backup
power to the time in digital.
• Thermistor is a type of resistor whose resistance varies
significantly with temperature , more so than in standard
resistors.
• Thermistors are widely used as inrush current limiters ,
temperature sensors , self-resetting overcurrent protectors and
self-regulating heating elements.
• Transistors used are BC547,A2222 which for amplification
purpose.
6. • Relay is a electrically operated switch which can have two
contacts NC,NO and have sliding arm moving between them.
• Piezo buzzer is an electronic device commonly used to
produce sound based on inverse piezoelectric effect.
• LED is a semiconductor light source ,based on
semiconductor device and diode will be ON when it is in
forward biased and light glows.
• Slide switch works on the principle of connecting
disconnected parts to each others.
7. CIRCUIT OPERATION:
•When we give the supply to the circuit by using slide switch.
•The current passes through 10K resistor and the base of
transistor A2222 become high and collector point become
zero , hence the relay will activate .
•In this project initial the 6V relay will be in on condition ,
when we apply heat to the thermistor , then thermistor
resistance will decrease .
8. • The current flow from the thermistor to base of transistor
BC547 and the collector will becomes low means zero , and
at the same the base of the transistor A2222 will be zero.
• The collector will be high means relay will deactivate , when
the relay is deactivated .
• The point NC is connected the buzzer which gives sound ,
means there is fire.
9. • The common point C of relay is connected to 9V Vcc ,
when relay is ON , the point C will connect to NO , when
relay is OFF , point C connect to NC.
• Thermistor is a component which decrease it resistance
when it sense heat ,when the resistance decrease the
flow of current will increase.
10. ADVANTAGES:
• Low cost
• Less complex circuitry
• Portable
• Simple and efficient
• More efficient
11. DISADVANTAGES:
• Very high temperatures are not applicable
• Delay time
• Variable resistor should be set properly if transistor may
damage
12. APPLICATIONS:
• Home security
• To protect valuable in go-downs
• Museums
• Theatres
• All electric departments
• Industries
13. CONCLUSION:
• The important of these is it gives sound from fire alarm when
fire attacks to industries , warehouses , etc,.
• It is most efficient , simple and less complex circuit which
can be designed as small equipment , which eases the
portability.
• It can be used to provide security at warehouses where
storage and protection of various types of goods is main
concern and works home security too.
14. • These circuit uses the thermistor sensing property of the
temperature by increasing the temperature resistance
resistance will decrease.
