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.

EXPANDED TECHNICAL DETAILS

Logic-Level Power Switching

This project project explains how to use a low-current Arduino pin to control a high-current 12V DC cooling fan.

• NPN Transistor Hub: Uses a 2N2222 or TIP120 NPN transistor acting as an electronic switch. The Arduino provides a small current to the "Base" pin, which allows a much larger current to flow from the collector to the emitter, effectively powering the fan.
• Protective Circuitry: Highlights the use of a 1k-ohm Base Resistor to protect the Arduino and a 1N4007 Flyback Diode across the fan motor to prevent inductive spikes from damaging the transistor.

Proportional Cooling

• PWM Integration: The Arduino can use analogWrite() on the Base pin to vary the fan speed via Pulse Width Modulation, providing a quiet and efficient cooling solution.