Automatic Smoke Detector Alarm

Gasleak/smoke detection methods became a concern after the effects of harmful gases on human health were discovered. Before modern electronic sensors, early detection methods relied on less precise detectors. Through the 19th and early 20th centuries, coal miners would bring canaries down to the tunnels with them as an early detection system against life threatening gases such as carbon dioxide, carbon monoxide and methane. Before the development of electronic household carbon monoxide detectors in the 1980s and 90s, carbon monoxide presence was detected with a chemically infused paper that turned brown when exposed to the gas. Since then, many technologies and devices have been developed to detect, monitor, and alert the leakage of a wide array of gases.
In this project we are going to design the circuit to control the exhaust fan speed automatically according to the smoke concentration in the room. Fan speed control is based on adjusting the voltage which gets to the fan. Fan speed control has been possible for many decades by using adjustable power resistors and adjustable transformers. Those methods have been used in movie theatres, houses and other public places.