Computer fan control

This is commonly accomplished by the motherboards having hardware monitoring circuitry, which can be configured by the end-user through BIOS or other software to perform fan control.

Cooling fans equipped with either two- or three-pin connectors are usually designed to accept a wide range of input voltages, which directly affects the rotation speed of the blades.

Like other series regulators, the diode will dissipate power equal to its voltage drop times the current passing through it.

Through this procedure, 10, 17 and 24 V voltages can be achieved, with voltages exceeding 12 V being potentially damaging to the computer fans rated at 12 V. However, the combination of modern power supplies no longer being required to provide a −5 V power line and the limited power delivery capability of the −12 V line (usually less than 1 A of current) reduces the total capacity for volt modded fans in modern systems.

Also, the components inside the computer using +5 V power might be exposed to over 5 V in case of a short circuit in the fan.

As with other linear regulators, the waste heat that is produced will be roughly P = (Vin - Vout) Iout.

The control signal is a square wave operating at 25 kHz, with the duty cycle determining the fan speed.

25 kHz is used to raise the sound of the signal above the range of human hearing; use of a lower frequency could produce an audible hum or whine.

[9] Many motherboards feature firmware and software that regulates these fans based on processor and computer case temperatures.

Another method, popular with PC hardware enthusiasts, is the manual fan speed controller.

Most modern motherboards feature hardware monitoring chips, which are capable of performing fan control,[1] usually through the PWM method as described above.

This automatic control offered by some chips may be called Thermal Cruise mode for maintaining a thermal envelope, as well as Fan Speed Cruise mode for maintaining a specific fan speed automatically.

Many companies now provide software to control fan speeds on their motherboards under Microsoft Windows or Mac OS X/MacOS.

There are also third-party programs that work on a variety of motherboards and allow wide customization of fan behavior depending on temperature readings from the motherboard, CPU, and GPU sensors, as well as allowing manual control.