Fan control
Encyclopedia
Fan control is the management of the rotational speed of an electric fan. There are many types of electric fans and many types of fan controls. This article principally describes the control of a computer fan
, to provide adequate cooling
while lowering noise
.
grow more powerful so do their requirements for electrical
power. Computer
s convert most of this electrical power into heat
generated by all major components
.
Some early generation PCs did not need active ventilation. Power supplies
eventually needed forced cooling, and soon took up the duty of cooling the rest of the PC with the ATX
standard. The byproduct of increased heat generation is that the fan(s) need to move increasing amounts air and thus, need to be more powerful. Since they must move more air through the same area of space, fans
will naturally become more noisy.
In fact, if one installs extra fans in a PC case, the noise levels can reach 70 dB. Since fan noise increases with the fifth power of the fan rotation speed, reducing rotations per minute (RPM) by a small amount potentially means a reduction in fan noise. This must be done cautiously, as excessive reduction in speed may cause components to overheat and be damaged. If done properly fan noise can be drastically reduced.
Two-pin fans operate either as an on/off fan, or can be controlled by varying the voltage.
Fans will have either two, three, or four pins on the connector.
checks the temperature inside the chassis, and if it detects a temperature outside of range, it spins the fans up to maximum. When the temperature drops below a threshold again, the fans are turned back off. This control method reduces power requirements during periods of low usage, but when the system is operating at capacity, the fan noise can become a problem again.
. By varying the voltage input across the acceptable range for a fan, the speed of the fan will increase (to added voltage) and decrease (to reduced voltage). A faster fan, means more air moved and thus a higher heat exchange rate. There are a few ways to perform this regulation.
s are the simplest method of reducing fan noise, but they add to the heat generated inside the computer case
. Since the voltage drop is proportional to the current, the fan may not start. They need to be of the appropriate power rating. For variable fan control, potentiometer
s could be used along with a transistor
such as a MOSFET
whose output voltage is controlled by the potentiometer. It is possible to use a rheostat instead.
in series with the fan will reduce the voltage being output to the fan. You can use a silicon diode with a fixed voltage drop of about 0.7V per diode. The power
rating should be noted.
of the fan to the +5V rail and the positive wire to the +12V rail of a typical PC power supply to achieve a theoretical +7V (positive seven volts). However, this is a potentially risky method: the parts on the +5V power line might be exposed to overvoltage in case of a short in the fan. A less common variation is to increase the voltage to the fan by connecting the ground wire to a -12V rail (located on the motherboard ATX connector) and the positive wire to the +12V rail, producing a total of +24V. 24V can destroy the fans, other options are 17V and 15.3V.
This is not a good idea, if there is nothing else on +5V rail. Because it will cause the current to go into +5V instead out of it as normal. PSU is not designed for that.
(PWM) is a common method of controlling computer fans. A PWM capable fan is usually connected to a 4-pin connector (pinout: Ground, +12V, sense, control). The sense pin is used to measure the rotation speed of the fan and the control pin is a open-drain or open-collector output, which requires a pull-up to 5V or 3.3V in the fan. Unlike linear voltage regulation, where the fan voltage is proportional to the speed, the fan is driven with a constant supply voltage; the speed control is performed by the fan based on the control signal.
The control signal is a square wave operating at 25kHz, with the duty cycle
determining the fan speed. Typically a fan can be driven between about 30% and 100% of the rated fan speed, using a signal with up to 100% duty cycle. The exact speed behaviour (linear, off until a threshold value, or a minimum speed until a threshold) at low control levels is manufacturer-dependent.
or come built into the computer's case. Using switches or knobs, attached fans can have their speeds adjusted by one of the above methods.
(see above).
Many companies now provide software to control fan speeds on their motherboards under Microsoft Windows
.
Computers running Linux
can use lm sensors
.
Computer fan
A computer fan is any fan inside, or attached to, a computer case used for cooling purposes, and may refer to fans that draw cooler air into the case from the outside, expel warm air from inside, or move air across a heatsink to cool a particular component...
, to provide adequate cooling
Computer cooling
Computer cooling is required to remove the waste heat produced by computer components, to keep components within their safe operating temperature limits.Various cooling methods help to improve processor performance or reduce the noise of cooling fans....
while lowering noise
Noise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...
.
Need for fan control
As modern PCsPersonal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
grow more powerful so do their requirements for electrical
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...
power. Computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
s convert most of this electrical power into heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
generated by all major components
Computer hardware
Personal computer hardware are component devices which are typically installed into or peripheral to a computer case to create a personal computer upon which system software is installed including a firmware interface such as a BIOS and an operating system which supports application software that...
.
Some early generation PCs did not need active ventilation. Power supplies
Power supply
A power supply is a device that supplies electrical energy to one or more electric loads. The term is most commonly applied to devices that convert one form of electrical energy to another, though it may also refer to devices that convert another form of energy to electrical energy...
eventually needed forced cooling, and soon took up the duty of cooling the rest of the PC with the ATX
ATX
ATX is a motherboard form factor specification developed by Intel in 1995 to improve on previous de facto standards like the AT form factor. It was the first big change in computer case, motherboard, and power supply design in many years, improving standardization and interchangeability of parts...
standard. The byproduct of increased heat generation is that the fan(s) need to move increasing amounts air and thus, need to be more powerful. Since they must move more air through the same area of space, fans
Fan (mechanical)
A mechanical fan is a machine used to create flow within a fluid, typically a gas such as air.A fan consists of a rotating arrangement of vanes or blades which act on the air. Usually, it is contained within some form of housing or case. This may direct the airflow or increase safety by preventing...
will naturally become more noisy.
In fact, if one installs extra fans in a PC case, the noise levels can reach 70 dB. Since fan noise increases with the fifth power of the fan rotation speed, reducing rotations per minute (RPM) by a small amount potentially means a reduction in fan noise. This must be done cautiously, as excessive reduction in speed may cause components to overheat and be damaged. If done properly fan noise can be drastically reduced.
Fan types
Common cooling fans have at least two pins on the connector. These two pins connect to the fan motor, usually a brushless DC type. Extra pins may be present, with either or both of the following features:- A tachometer that measures the actual speed of the fan as a pulse train, frequency being proportional to speed.
- Control of fan speed using PWM (Pulse-width modulationPulse-width modulationPulse-width modulation , or pulse-duration modulation , is a commonly used technique for controlling power to inertial electrical devices, made practical by modern electronic power switches....
.)
Two-pin fans operate either as an on/off fan, or can be controlled by varying the voltage.
Fans will have either two, three, or four pins on the connector.
No control
The simplest method of fan control is simply to leave the fan on all the time. This creates quite a bit of noise and increases power requirements, but keeps the system the coolest.Thermostatic
In this style of fan control, the fan is either on or off. A system thermistorThermistor
A thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard resistors. The word is a portmanteau of thermal and resistor...
checks the temperature inside the chassis, and if it detects a temperature outside of range, it spins the fans up to maximum. When the temperature drops below a threshold again, the fans are turned back off. This control method reduces power requirements during periods of low usage, but when the system is operating at capacity, the fan noise can become a problem again.
Linear voltage regulation
A standard cooling fan is essentially a bladed DC motorDC motor
A DC motor is an electric motor that runs on direct current electricity.-Brush:The brushed DC electric motor generates torque directly from DC power supplied to the motor by using internal commutation, stationary magnets , and rotating electrical magnets.Like all electric motors or generators,...
. By varying the voltage input across the acceptable range for a fan, the speed of the fan will increase (to added voltage) and decrease (to reduced voltage). A faster fan, means more air moved and thus a higher heat exchange rate. There are a few ways to perform this regulation.
Resistors
ResistorResistor
A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...
s are the simplest method of reducing fan noise, but they add to the heat generated inside the computer case
Computer case
A computer case is the enclosure that contains most of the components of a computer...
. Since the voltage drop is proportional to the current, the fan may not start. They need to be of the appropriate power rating. For variable fan control, potentiometer
Potentiometer
A potentiometer , informally, a pot, is a three-terminal resistor with a sliding contact that forms an adjustable voltage divider. If only two terminals are used , it acts as a variable resistor or rheostat. Potentiometers are commonly used to control electrical devices such as volume controls on...
s could be used along with a transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
such as a MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
whose output voltage is controlled by the potentiometer. It is possible to use a rheostat instead.
Diodes
A diodeDiode
In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...
in series with the fan will reduce the voltage being output to the fan. You can use a silicon diode with a fixed voltage drop of about 0.7V per diode. The power
Electric power
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.-Circuits:Electric power, like mechanical power, is represented by the letter P in electrical equations...
rating should be noted.
Voltmodding
Voltmodding describes the practice of varying the voltage fed to a component; in this case, a computer fan. This can be achieved by connecting the ground wireGround (electricity)
In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
of the fan to the +5V rail and the positive wire to the +12V rail of a typical PC power supply to achieve a theoretical +7V (positive seven volts). However, this is a potentially risky method: the parts on the +5V power line might be exposed to overvoltage in case of a short in the fan. A less common variation is to increase the voltage to the fan by connecting the ground wire to a -12V rail (located on the motherboard ATX connector) and the positive wire to the +12V rail, producing a total of +24V. 24V can destroy the fans, other options are 17V and 15.3V.
This is not a good idea, if there is nothing else on +5V rail. Because it will cause the current to go into +5V instead out of it as normal. PSU is not designed for that.
Pulse-width modulation
Pulse-width modulationPulse-width modulation
Pulse-width modulation , or pulse-duration modulation , is a commonly used technique for controlling power to inertial electrical devices, made practical by modern electronic power switches....
(PWM) is a common method of controlling computer fans. A PWM capable fan is usually connected to a 4-pin connector (pinout: Ground, +12V, sense, control). The sense pin is used to measure the rotation speed of the fan and the control pin is a open-drain or open-collector output, which requires a pull-up to 5V or 3.3V in the fan. Unlike linear voltage regulation, where the fan voltage is proportional to the speed, the fan is driven with a constant supply voltage; the speed control is performed by the fan based on the control signal.
The control signal is a square wave operating at 25kHz, with the duty cycle
Duty cycle
In engineering, the duty cycle of a machine or system is the time that it spends in an active state as a fraction of the total time under consideration....
determining the fan speed. Typically a fan can be driven between about 30% and 100% of the rated fan speed, using a signal with up to 100% duty cycle. The exact speed behaviour (linear, off until a threshold value, or a minimum speed until a threshold) at low control levels is manufacturer-dependent.
Fan speed controllers
Another method, popular with gamers, is the manual fan speed controller. They can be mounted in an expansion slot, a 5.25" or 3.5" drive bayDrive bay
A drive bay is a standard-sized area for adding hardware to a computer. Most drive bays are fixed to the inside of a case, but some can be removed....
or come built into the computer's case. Using switches or knobs, attached fans can have their speeds adjusted by one of the above methods.
Software
The method by which the software physically controls the fan is usually PWMPulse-width modulation
Pulse-width modulation , or pulse-duration modulation , is a commonly used technique for controlling power to inertial electrical devices, made practical by modern electronic power switches....
(see above).
Many companies now provide software to control fan speeds on their motherboards under Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
.
- AOpenAOpenAOpen is a major electronics manufacturer from Taiwan that makes computers and parts for computers. AOpen used to be the Open System Business Unit of Acer Computer Inc. which designed, manufactured and sold computer components. It incorporated in December 1996 as a subsidiary of Acer Group with an...
motherboards can use "SilentTEK". - ASUSASUSASUSTeK Computer Incorporated is a multinational computer technology and consumer electronics product manufacturer headquartered in Taipei, Taiwan. Its product range includes motherboards, desktops, laptops, monitors, tablet PCs, servers and mobile phones...
motherboards can use "Q-Fan". - MSIMicro-Star InternationalMicro-Star International Co., Ltd is a Taiwan-based electronics company and one of the world's largest motherboard and video card manufacturers.-Overview:MSI is one of the top three motherboard and video card manufacturers worldwide...
motherboards can use "Core Center". - Universal abit motherboards can use "μGuru".
- GigabyteGigabyte TechnologyGigabyte Technology Co., Ltd. is a Taiwan-based manufacturer of computer hardware products best known for its motherboards. The company is publicly held and traded on the Taiwan Stock Exchange .-Company:...
motherboards can use "EasyTune 6". - Intel desktop boards (older socket 478 etc.) use "Active Monitor" and "Desktop Control Centre".
- Intel desktop boards (newer socket 775 etc.) use "Desktop Utilities".
- Dell Inspiron/Latitude/Precision computers can use "I8kfanGUI".
- Various computers can use the freeware "SpeedFanSpeedFanSpeedFan is software that can read temperatures, voltages and fan speeds of computer components. It can change computer fan speeds depending on the temperature of various components....
".
Computers running Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
can use lm sensors
Lm sensors
lm_sensors , a free open source software-tool for Linux, provides tools and drivers for monitoring temperatures, voltage, and fans...
.