Fan control is the management of the rotational speed of an electric fan. In computers, various types of computer fans are used to provide adequate cooling, and different fan control mechanisms balance their cooling capacities and noise they generate. 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. [1]
As modern PCs grow more powerful so do their requirements for electrical power. Computers emit this electrical power as heat generated by all major components. Heat production varies with system load, where periods of compute-intensive activity generate much more heat than the idle time does. [1]
Processors in most early x86-based computers, up to some of the early 486s, did not need active ventilation. Power supplies needed forced cooling, and power supply fans also circulated cooling air through 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 of air and thus need to be more powerful. Since they must move more air through the same area of space, fans will become more noisy.
Fans installed in a PC case can produce noise levels of up to 70 dB. Since fan noise increases with the fifth power of the fan rotation speed, [2] reducing revolutions per minute (RPM) by a small amount potentially means a large reduction in fan noise. This must be done cautiously, as excessive reduction in speed may cause components to overheat and be damaged.[ needs update ] If done properly fan noise can be drastically reduced.
The common cooling fans used in computers use standardized connectors with two to four 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:
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 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.
In this style of fan control, the fan is either on or off. Temperature inside the chassis is checked, and if an outside-of-range temperature is detected, fans are set to their maximum speed. When the temperature drops below a threshold again, the fans are turned back off. This control method reduces noise issues and power requirements during periods of low usage, but when the system is operating at capacity, the fan noise can become a problem again.
A standard cooling fan is a DC motor with blades attached. 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, as described below.
Resistors in series with a fan's power pin 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, potentiometers 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.
A diode in series with the fan will reduce the voltage being output to the fan. A silicon diode provides a relatively constant voltage drop of about 0.7 V per diode; data sheets for a specific diode specify its voltage drop, for example the 1N4001 silicon diode's voltage drop varies from approximately 0.7 to 0.9 V as the current varies from 0.01 to 1 A. [3] The power rating should be noted and some diodes may require cooling to operate at their rated current. The voltage drop across the diode will fall with temperature, causing the fan to speed up.
Like other series regulators, the diode will dissipate power equal to its voltage drop times the current passing through it.
The voltage a computer cooling fan receives is defined by the difference between the voltage wire (+12 V) and the ground wire (+0 V). By connecting one or both wires to a different voltage, the voltage the fan receives will be different from the default 12 V the fan was designed for.
Increasing the voltage [4] over the default 12 V can be achieved by e.g. connecting the −12 V or −5 V power line instead of the ground wire in the fan connector, and by connecting the 5 V power line in the +12 V input of the fan connector. 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.
Connecting the +5 V power line to the +12 V input of the fan reduces the voltage the fan receives to +5 V. Some fans will not work at such low voltage at all, while some other fans may run at +5 V once they have started rotating at a reasonable speed.[ citation needed ]
Another method of reducing the fan speed [5] is by moving the 5 V wire in the classical Molex power connector in the place of the Ground wire going to the fan, thereby delivering +7 V (12 V − 5 V = 7 V) to the fan. However, this is a potentially risky method, because +5 V PSU line is intended to source current only, not sink it, so the PSU is likely to get damaged in case of load on 5 V PSU line being below the load generated by 7 V fans (e.g. when PC enters idle/sleep state). 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.
Common voltage regulator ICs like the popular LM78xx series are sometimes used to provide variable or constant voltage to fans. When thermally bonded to the computer's chassis, one of these ICs can provide up to 1 A of current at a voltage of 6, 8, 9 or 10 V for the LM7806, LM7808, LM7809 and LM7810, respectively. [6] Adjustable versions like the popular LM317 also exist; when combined with a potentiometer, these adjustable regulators allow the user to vary the fan speed of several fans at currents far in excess of what a standard potentiometer could handle. [7]
For higher currents, discrete linear regulators are relatively simple to construct using a power transistor or MOSFET and a small signal transistor or a Zener diode as a voltage reference. While discrete regulators require additional components (a minimum of two transistors, three resistors and a small capacitor), they allow for arbitrarily high currents, allowing for the regulation of additional fans and accessories.
As with other linear regulators, the waste heat that is produced will be roughly P = (Vin - Vout) Iout. [8]
Pulse-width modulation (PWM) is a common method of controlling computer fans. A PWM-capable fan is usually connected to a 4-pin connector (pinout: Ground, +12 V, sense, control). The sense pin is used to relay the rotation speed of the fan and the control pin is an open-drain or open-collector output, which requires a pull-up to 5 V or 3.3 V 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 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. 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 behavior at low control levels (linear, off until a threshold value, or a minimum speed until a threshold) is manufacturer dependent. [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. They can be mounted in an expansion slot or a 5.25" or 3.5" drive bay or come built into a computer's case. Using switches or knobs, attached fans can have their speeds adjusted by one of the above methods.
Most modern motherboards feature hardware monitoring chips, which are capable of performing fan control, [1] usually through the PWM method as described above. These chips can be configured through BIOS, [10] : §11.1 or by using specialised software once the operating system has booted.
Processors produce varying levels of heat depending on system load, thus it makes sense to reduce the speed of the fans during idle to decrease the noise produced by fans running full speed, until the load does goes up, at which point fan speed must be adjusted promptly to avoid overheating. Modern hardware monitor chips, once configured, are capable of independently running this monitoring loop without any need for a functioning BIOS or an operating system. 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. [10] : §12
However, not all software is capable of accessing these advanced configuration parameters provided by some chips, and it is very common that the generic software implements only the most basic interfacing with the chips, namely, an explicit setting for the duty cycle for each fan control setting, subsequently performing the duty cycle adjustments itself in software, and thus requiring that both the operating system, as well as this third-party software itself to continue running on the main CPU to perform the monitoring loop. [10] : §11.3 This may not be a problem until the system or the utility crashes, at which point the system may overheat due to the failure of the fans to maintain adequate cooling whilst running at reduced voltage and speed.
Many companies now provide software to control fan speeds on their motherboards under Microsoft Windows or Mac OS X/MacOS. Different software is used by different motherboards. 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. Two such programs are SpeedFan [11] and Argus Monitor. [12]
A motherboard is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It holds and allows communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard usually contains significant sub-systems, such as the central processor, the chipset's input/output and memory controllers, interface connectors, and other components integrated for general use.
Pulse-width modulation (PWM), also known as pulse-duration modulation (PDM) or pulse-length modulation (PLM), is any method of representing a signal as a rectangular wave with a varying duty cycle.
In computing, overclocking is the practice of increasing the clock rate of a computer to exceed that certified by the manufacturer. Commonly, operating voltage is also increased to maintain a component's operational stability at accelerated speeds. Semiconductor devices operated at higher frequencies and voltages increase power consumption and heat. An overclocked device may be unreliable or fail completely if the additional heat load is not removed or power delivery components cannot meet increased power demands. Many device warranties state that overclocking or over-specification voids any warranty, but some manufacturers allow overclocking as long as it is done (relatively) safely.
A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a result, power supplies are sometimes referred to as electric power converters. Some power supplies are separate standalone pieces of equipment, while others are built into the load appliances that they power. Examples of the latter include power supplies found in desktop computers and consumer electronics devices. Other functions that power supplies may perform include limiting the current drawn by the load to safe levels, shutting off the current in the event of an electrical fault, power conditioning to prevent electronic noise or voltage surges on the input from reaching the load, power-factor correction, and storing energy so it can continue to power the load in the event of a temporary interruption in the source power.
In electronics, a linear regulator is a voltage regulator used to maintain a steady voltage. The resistance of the regulator varies in accordance with both the input voltage and the load, resulting in a constant voltage output. The regulating circuit varies its resistance, continuously adjusting a voltage divider network to maintain a constant output voltage and continually dissipating the difference between the input and regulated voltages as waste heat. By contrast, a switching regulator uses an active device that switches on and off to maintain an average value of output. Because the regulated voltage of a linear regulator must always be lower than input voltage, efficiency is limited and the input voltage must be high enough to always allow the active device to reduce the voltage by some amount.
A quiet, silent or fanless PC is a personal computer that makes very little or no noise. Common uses for quiet PCs include video editing, sound mixing and home theater PCs, but noise reduction techniques can also be used to greatly reduce the noise from servers. There is currently no standard definition for a "quiet PC", and the term is generally not used in a business context, but by individuals and the businesses catering to them.
A voltage regulator is a system designed to automatically maintain a constant voltage. It may use a simple feed-forward design or may include negative feedback. It may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages.
Power electronics is the application of electronics to the control and conversion of electric power.
A general-purpose input/output (GPIO) is an uncommitted digital signal pin on an integrated circuit or electronic circuit board which may be used as an input or output, or both, and is controllable by software.
A variable-frequency drive is a type of AC motor drive that controls speed and torque by varying the frequency of the input electricity. Depending on its topology, it controls the associated voltage or current variation.
An electronic speed control (ESC) is an electronic circuit that controls and regulates the speed of an electric motor. It may also provide reversing of the motor and dynamic braking. Miniature electronic speed controls are used in electrically powered radio controlled models. Full-size electric vehicles also have systems to control the speed of their drive motors.
A computer fan is any fan inside, or attached to, a computer case used for active cooling. Fans are used to draw cooler air into the case from the outside, expel warm air from inside and move air across a heat sink to cool a particular component. Both axial and sometimes centrifugal (blower/squirrel-cage) fans are used in computers. Computer fans commonly come in standard sizes, such as 92 mm, 120 mm, 140 mm, and even 200–220 mm. Computer fans are powered and controlled using 3-pin or 4-pin fan connectors.
A system monitor is a hardware or software component used to monitor system resources and performance in a computer system.
A power supply unit (PSU) converts mains AC to low-voltage regulated DC power for the internal components of a computer. Modern personal computers universally use switched-mode power supplies. Some power supplies have a manual switch for selecting input voltage, while others automatically adapt to the main voltage.
In computer architecture, dynamic voltage scaling is a power management technique in which the voltage used in a component is increased or decreased, depending upon circumstances. Dynamic voltage scaling to increase voltage is known as overvolting; dynamic voltage scaling to decrease voltage is known as undervolting. Undervolting is done in order to conserve power, particularly in laptops and other mobile devices, where energy comes from a battery and thus is limited, or in rare cases, to increase reliability. Overvolting is done in order to support higher frequencies for performance.
A fan coil unit (FCU), also known as a Vertical Fan Coil-Unit (VFC), is a device consisting of a heat exchanger (coil) and a fan. FCUs are commonly used in HVAC systems of residential, commercial, and industrial buildings that use ducted split air conditioning or with central plant cooling. FCUs are typically connected to ductwork and a thermostat to regulate the temperature of one or more spaces and to assist the main air handling unit for each space if used with chillers. The thermostat controls the fan speed and/or the flow of water or refrigerant to the heat exchanger using a control valve.
A battery management system (BMS) is any electronic system that manages a rechargeable battery, such as by protecting the battery from operating outside its safe operating area, monitoring its state, calculating secondary data, reporting that data, controlling its environment, authenticating it and / or balancing it.
Servos are small, cheap, mass-produced servomotors or other actuators used for radio control and small-scale robotics.
The Arduino Uno is an open-source microcontroller board based on the Microchip ATmega328P microcontroller (MCU) and developed by Arduino.cc and initially released in 2010. The microcontroller board is equipped with sets of digital and analog input/output (I/O) pins that may be interfaced to various expansion boards (shields) and other circuits. The board has 14 digital I/O pins, 6 analog I/O pins, and is programmable with the Arduino IDE, via a type B USB cable. It can be powered by a USB cable or a barrel connector that accepts voltages between 7 and 20 volts, such as a rectangular 9-volt battery. It has the same microcontroller as the Arduino Nano board, and the same headers as the Leonardo board. The hardware reference design is distributed under a Creative Commons Attribution Share-Alike 2.5 license and is available on the Arduino website. Layout and production files for some versions of the hardware are also available.
This glossary of electrical and electronics engineering is a list of definitions of terms and concepts related specifically to electrical engineering and electronics engineering. For terms related to engineering in general, see Glossary of engineering.
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