How does a smoke detector work?

[biboy_]

hai evry one i need ur help in research, about smoke detector how it works, and its circuits..... im a 5th year student and doing my research project... i really need your...
thank you.....

 

[jaywant007]

smoke detector

first thing...get some backgorund info on LDR (Light dependent resistors) or IR (Infra red sensors)

coz most of them are used....when smoke fills the chamber in which the sensor is placed the resistance changes....accordinly u can turn on the alarm...dont forget the helped button..if this post helps....!!