reffer to the following links
temperature sensor…
http://www.engineersgarage.com/content/ic-lm35
http://www.engineersgarage.com/electronic-circuits/full-range-centigrade-temperature-sensor-lm35
http://www.engineersgarage.com/electronic-circuits/fire-alarm-lm35
http://www.engineersgarage.com/microcontroller/8051projects/Celsius-scale-thermometer-AT89C51
http://www.engineersgarage.com/electronic-circuits/overheat-overcooling-circuit-breaker