Fan Types
The common cooling fans used in computers use standardized connectors with 2 to 4 pins. The first two pins are always used to deliver power to the fan motor, while the rest can be optional, depending on fan design and type:
- Ground
- Power - +12 V
- Sense - a tachometer that measures the actual speed of the fan as a pulse train, frequency being proportional to speed. With each fan rotation, there are two pulses sent through this pin.
- Control - PWM signal (Pulse-width modulation), gives the ability to adjust the rotation speed on the fly without changing the input voltage delivered to the cooling fan
The color of the wires connected to these pins varies depending on the number of connectors, but the role of each pin is standardized and guaranteed to be the same on any system.
Cooling fans equipped with either 2 or 3 pin connectors are usually designed to accept a wide range of input voltages, which directly affects the rotation speed of the blades.
Read more about this topic: Fan Control
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