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 ...

In an afternoon I built a smart sensor that reads and displays soil-moisture levels, light intensity, and temperature. What You'll Need • Bolts, nuts, ring terminals ($5) ...

The system here monitors temperature, humidity, and smoke levels and alerts you if those levels reach a certain point.