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#1
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How fan speed control works
I'm unclear on how fan speed can be controlled by the BIOS, the
motherboard, programs like SpeedFan, etc. Hard-wiring in a potentiometer somewhere in the power wires to the fans allows regulation of the voltage to the fan, and so fan speed. But I don't see how the motherboard, BIOS, or SpeedFan does this. There is the one line to the mobo from the fan that let the mobo *monitor* the fan's speed (presumably the RPM?). But the fan power comes from the power supply directly, and I don't see how that's changed by the mobo or SpeedFan. Could someone please explain? Thanks. |
#2
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How fan speed control works
The faster the fan goes the more current it requires, so the software
can probably monitor the change in the current being drawn and from that information estimates its rotation speed. Eric, PC Buyer Beware! http://www.pcbuyerbeware.co.uk/ |
#3
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How fan speed control works
If you have a three pin fan connector that connects to a fan header on the
motherboard, the bios (if it has the capability) controls the fan by adjusting the voltage to that header. If you have a fan that connects directly to a four pin molex connector, the bios/motherboard/speedfan cannot control the speed at all. "Tim" wrote in message ups.com... I'm unclear on how fan speed can be controlled by the BIOS, the motherboard, programs like SpeedFan, etc. Hard-wiring in a potentiometer somewhere in the power wires to the fans allows regulation of the voltage to the fan, and so fan speed. But I don't see how the motherboard, BIOS, or SpeedFan does this. There is the one line to the mobo from the fan that let the mobo *monitor* the fan's speed (presumably the RPM?). But the fan power comes from the power supply directly, and I don't see how that's changed by the mobo or SpeedFan. Could someone please explain? Thanks. |
#4
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How fan speed control works
Tim wrote: I'm unclear on how fan speed can be controlled by the BIOS, the motherboard, programs like SpeedFan, etc. Hard-wiring in a potentiometer somewhere in the power wires to the fans allows regulation of the voltage to the fan, and so fan speed. But I don't see how the motherboard, BIOS, or SpeedFan does this. There is the one line to the mobo from the fan that let the mobo *monitor* the fan's speed (presumably the RPM?). But the fan power comes from the power supply directly, and I don't see how that's changed by the mobo or SpeedFan. The mobo can turn the fans on and off, so SpeedFan and similar programs exploit this ability to pulse the fan on and off rapidly and thereby vary the average voltage applied to the fan. For example, if the 12VDC is pulsed on for 5ms and off for 5ms, the average voltage will be 6V, while if it's pulsed on for 7.5ms and off for 2.5ms, the average will be 9V. This is "pulse width modulation" and is used by many hardware fan controllers. A website that explains it better is he www.cpemma.co.uk/pwm.html. It also shows lots of other fan controllers, including this ultra-simple one: www.cpemma.co.uk/reg.html Programs like SpeedFan use any third wire on the fan only for monitoring the RPM. |
#5
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How fan speed control works
On 20 Apr 2006 19:40:40 -0700, "larry moe 'n curly"
wrote: Tim wrote: I'm unclear on how fan speed can be controlled by the BIOS, the motherboard, programs like SpeedFan, etc. .... snip ...... A website that explains it better is he www.cpemma.co.uk/pwm.html. It also shows lots of other fan controllers, including this ultra-simple one: www.cpemma.co.uk/reg.html Good info. Thanks. Geo |
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