You also need to select the transistor by the type of fan that you use. In my case I used the well-known BD139 transistor and a 9V battery to provide power to the fan and transistor. The LM35 ...

Arduino Sketch //Room Temperature Monitor //T.K.Hareendran #include <LiquidCrystal.h> // Include the library to use a LCD display #define tempSensor 0 // Define the A0 pin as “sensor” int Vin; // ...