What Is a Cooling Fan?
A cooling fan is a cooling component that creates airflow by spinning a propeller with a motor and, with this airflow, removes heat from components. Most modern fans are BLDC-based.
Why Is It Needed?
Power components and processors produce heat while running. Excess heat lowers performance and shortens life. A fan pushes out hot air and brings in cool air, keeping the component temperature within safe limits.
Wire Count
Fans are referred to by wire count: 2-wire is power only (fixed speed); 3-wire adds a speed feedback (tacho); 4-wire also offers speed control with PWM.
| Wires | Function |
|---|---|
| 2-wire | Power (+/–), fixed speed |
| 3-wire | + tacho (RPM measurement) |
| 4-wire | + PWM speed control |
Speed Control
4-wire fans have a separate PWM wire; this adjusts the fan speed without cutting the power. So the MCU manages the fan speed by temperature, balancing both cooling and quietness.
Tacho Signal
The tacho output on 3- and 4-wire fans produces a pulse every revolution; the system counts this to confirm the fan is actually spinning and its RPM. A fan failure is thus detected.
Common Mistakes
- Air direction: mounting the fan's blow/suction direction backwards spoils the airflow.
- Throttling with voltage: lowering the voltage instead of PWM stalls some fans.
- Dust/blockage: if the air path is blocked, there's no cooling even if the fan spins.
Frequently Asked Questions
What's the difference with a 4-wire fan?+
What is the tacho wire for?+
Search parts related to "What Is a Cooling Fan?"
Find the right part by comparing price, stock and distributors.