I used an LCD shield to display the current temperature and speed of the fan, but you can use the circuit without the LCD display. You also need to select the transistor by the type of fan that you ...

It is no secret that semiconductor junctions change their behavior with temperature, and you can use this fact to make a temperature sensor. The problem is that you have to calibrate each device ...

If you want to make your own system for doing so, Instructables user ICStation shows off how to use an Arduino to do it. The system here monitors temperature, humidity, and smoke levels and alerts ...