Fire Alarm

Here we have used some what different concept.normally we use LDR for light sensitive circuits.but here we use this LDR to detect smoke.I will explain you, how we can do this.first of all we should keep in the kitchen or in a place where the fire can be occurred then keep LDR and the bulb face to face and let smoke to pass between the LDR and the light.when the smoke passes that area it begins to make a sound