Flame detector

Introduction

Nobody should take lighter the hazards of fire accidents in any place/building or set up. The prize which one pays for the fire accidents is devastating. Fire accidents may lead to heavy loss of human life as well as to the property. Large fire accidents may affect the environment too. Hence every caution should be taken of the happenings of fire accidents. 

Fire accidents most of the time can be prevented if one is alert on the recurrence/site of the fire. It can be easily prevented when one knows the beginning moment of such fire occurrences. Hence one should be alert when a fire starts. But in practice and day-to-day life, it becomes difficult always to watch and find out the occurrence. Some mechanism is necessary to detect the starting of the fire as it is not possible to be alert all 24 hours of a day. 

Fire alarm circuits become handy to detect the momentary occurrence of fire. The alarm circuit detects the fire and sounds alarmed as a warning. Immediately action can be taken to prevent it from spreading or even one can put out it immediately. The alarm circuit should be simple and should be installed wherever the risk perception is high. It should be in operation throughout the day and night. i.e 24 hours. 

fortunately, fire detectors/sensors are easily available and a reliable circuit can be built around them. one such circuit is described here for assembly and installation. 

The circuit

Working of the circuit

Q1 transistor gets ut s base bias through R2 and Phototransistor U2. At normal times the phototransistor shows high resistance. When light falls on the phototransistor its collector-emitter path becomes low resistance and starts conducting making proper bias for Q1 and starts conducting. In turn, the relay gets activated resulting in the buzzer connected to the power supply making the alarm sounds. Here instead of light the flame of the fire activates the sensor that is phototransistor to conduct. 

Parts List

Q1 - BC 549 NPN Silicon transistor

D1 = 1N4148 Diode

U2 = Photo detector

R1= 330 ohms Resistor

R2= 22K ohm Preset

C1 = 100 MFD 25VDC electrolytic capacitor

K1 =SPST 9V Relay

SG1= 12V Buzzer

PCB Design full view

Copper track with copper fill

To sum up

This fire alarm circuit can be readily assembled on the ready-made PCB design given here. The component count is very low and the layout is neat. An interesting project to assemble by electronics enthusiasts. Pl. give your valuable comments for the betterment of the blog to all.