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134 lines
4.9 KiB
Plaintext
134 lines
4.9 KiB
Plaintext
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fancontrol - automated software based fan speed regulation
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Introduction
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fancontrol is a shellscript for use with lm_sensors. It reads its
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configuration from a file, then calculates fan speeds from temperatures and
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sets the corresponding pwm outputs to the computed values. It is included in
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lm_sensors since version 2.8.0. For easy configuration, there's a script
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named pwmconfig which lets you interactively write your configuration file for
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fancontrol. Alternatively you can write this file yourself using the
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information from the configuration section of this document.
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Please be careful when using the fan control features of your mainboard, in
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addition to the risk of burning your CPU, at higher temperatures there will be
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a higher wearout of your other hardware components, too. So if you plan to use
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these components in 50 years, _maybe_ you shouldn't use fancontrol/your
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hardware at all. Also please keep in mind most fans aren't designed to be
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powered by a PWMed voltage, for more detailed information on this I recommend
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this appnote: http://www.maxim-ic.com/appnotes.cfm/appnote_number/707
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In practice it doesn't seem to be a major issue, the fans will get slightly
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warmer, just be sure to have a temperature alarm and/or shutdown call, in case
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some fan fails, because you probably won't hear it anymore ;)
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Configuration
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Since most of you are going to use the pwmconfig script, the config
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file syntax will be discussed last. First I'm going to describe the various
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variables available for changing fancontrol's behaviour:
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INTERVAL
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This variable defines at which interval in seconds the main loop of
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fancontrol will be executed
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FCTEMPS
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Maps pwm outputs to temperature sensors so fancontrol knows which
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temperature sensors should be used for calculation of new values for
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the corresponding pwm outputs.
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FCFANS
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FCFANS records the association between a pwm and a fan.
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Then fancontrol can check the fan speed and restart it if it
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stops unexpectedly.
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MINTEMP
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The temperature below which the fan gets switched to minimum speed.
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MAXTEMP
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The temperature over which the fan gets switched to maximum speed.
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MINSTART
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Sets the minimum speed at which the fan begins spinning. You should
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use a safe value to be sure it works, even when the fan gets old.
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MINSTOP
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The minimum speed at which the fan still spins. Use a safe value here,
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too.
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MINPWM
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The PWM value to use when the temperature is below MINTEMP.
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Typically, this will be either 0 if it is OK for the fan to plain
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stop, or the same value as MINSTOP if you don't want the fan to
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ever stop.
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If this value isn't defined, it defaults to 0 (stopped fan).
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MAXPWM
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The PWM value to use when the temperature is over MAXTEMP.
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If this value isn't defined, it defaults to 255 (full speed).
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A graph might help you understand how the different values relate
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to each other:
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PWM ^
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255 +
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| ,-------------- MAXPWM
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| ,'.
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| ,' .
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| ,' .
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| ,' .
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| ,' .
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| ,' .
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| MINSTOP .' .
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| | .
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MINPWM |---------------' .
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| . .
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| . .
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| . .
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0 +---------------+-------------+---------------->
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MINTEMP MAXTEMP t (degree C)
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The configuration file format is a bit strange:
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VARIABLE=chip/pwmdev=value chip/pwmdev2=value2 [...]
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VARIABLE2=[...]
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Each variable has its own line. The variable name is followed by an equal sign
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and the device=value pairs. These consist of the path to the pwm output for
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which the value is valid, equal sign followed by the value and are separated
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by a blank. Path can be absolute or relative (from /sys/bus/i2c/devices or
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/sys/class/hwmon depending on the kernel version).
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Example:
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MINTEMP=hwmon0/device/pwm1=40 hwmon0/device/pwm2=54
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You have to play with the temperature values a bit to get happy. For initial
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setup I recommend using the pwmconfig script. Small changes can be made by
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editing the config file directly following the rules above.
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The algorithm
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fancontrol first reads its configuration, writes it to arrays and loops its
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main function. This function gets the temperatures and fanspeeds from
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kernel driver files and calculates new speeds depending on temperature
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changes, but only if the temp is between MINTEMP and MAXTEMP. After that, the
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new values are written to the pwm outputs. The pwm value increases
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linearly with rising temperature.
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Planned features
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rc-scripts for some gnu/linux-distributions
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smoother regulation (temp interpolation)
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gui for configuration
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If you have other wishes or want to contribute something, please let me know:
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marius.reiner${AT}hdev.de
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