The story is something about your basic electronics,
How it's work :-
The Basic transistor switching with arduino , for arduino Digital 7th Pin is Output if the arduino send logic 1 (HIGH), the mini cooling fan turns ON.
If the transistor Base terminal is 0 (LOW), then Fan turns off , for delay and other you can set with help of arduino IDE and arduino uno.
And one simple NPN transistor.
Cooling fan for my testing you can choose different 12v output one.