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 ...

A temperature sensor monitors the room temperature from afar, and a solid-state relay (SSR) controls the power for the heater. Now he just needed a PID library — readily available from Arduino ...

This is an easy tutorial showing how you can control the brightness of an LED or adjust the speed of a DC fan using Arduino Board, a small BC547 transistor and a potentiometer.

So if you want to modify it to add more fans, change the message on the LCD, or use a different temperature sensor, you can easily give it a go even if you're a beginner at Arduino coding.