Fire Alarm Based on NE555

INTRODUCTION:

Before going towards our project, we would like to share a glimpse of JLC PCB. With over 10 years of experience in PCB manufacturing, JLCPCB has more than 200,000 customers at home and abroad, with over 8,000 online orders ofPCB prototyping and small quantity PCB production per day.

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This project is made around IC 555 timer. A reversed biased germanium diode is

used here as a heat sensor. At room temperature the diode has very high

reverse resistance which is more than 10 kΩ. No effect is produced by it on the

transistor which conducts and beeps the reset pin 4 of the IC555 timer at ground

level and so the alarm does not sound.

When the temperature in the vicinity of the germanium diode increases in case of

a fire its reverse resistance drops. At about 70℃ temperature its resistance value

drops below 1 kΩ. This stops the transistor’s conduction and the reset pin of the

IC555 is turned positive. And this triggers the alarm.

COMPONENTS:

● Capacitors x 2 - 10 nF

● Capacitor x 1 - 1009

● 9V DC Power Source

● NE555 8 pin IC

● Npn Transistor

● Loud Speaker

● Germanium Diode

● Variable resistance -100 kΩ

● Resistances

○ R1 - 1 kΩ

○ R2 - 4.7 kΩ

○ R3 - 10 kΩ

○ R4 - 47kΩ

Procedure:

1) Connect all the components as per the circuit diagram.

2) Two or more reversed biased germanium diodes can be connected in

parallel and can be kept at different locations.

3) In case of fire or any rise in temperature can trigger the alarm.

This Project can be used in following application:

• Partially open building
• Production hall-warehouses
• Fully open building
• car parks
• Petro-chemical production
• Warehouses
• Petro-chemical plants
• Paint production,
• Chemical Mixing area
• Chemical Storage Area
• Air Craft Hanger
• High Roof Cargo Ware House
• Automatic Painting Booth
• High Roof Mall
• Basement Car Parking Area Semi Open Car Parking Area
• High Roof Rack Type Ware House
• Cable Trench
• High Roof Production Area
• Chemical or Flammable Liquid Pumping & Transporting area
• Indoor Stadium
• Coal Conveyor
• LPG Filling yard
• Cotton Godown
• Paint Storage
• Diesel Engine Room
• Pneumatic Exhaust Duct
• Engine Test Bed
• Cable Cellars
• Pneumatic Material Duct
• Floating Roof Tank Paint Booth
• Printing Machineries
• Gas Turbine Enclosure