How do I control a voltage controlled fan?

I’d like to control my fan’s speed (to make it more silent under heavy load). I disassembled a Laptop to build a custom PC, fitted a gigantic 9x9cm tower cooler with a Noctua fan on it to absorb the CPU’s and GPU’s heat, so realistically the fan does not need to run at full speed ever. I am not sure what is currently controlling the fan speed, but it ramps up and down or stands still depending on the usage (temperature or cpu load? – I don’t know.)

I tried everything from this thread, but I keep failing to detect the fan.
How to control fan speed? I have a 3 PIN header, so not a pwn controlled one, but the voltage can be adjusted to make the fan stand still or spin slow to fast. So I can tell by its behaviour and a multimeter which reads 2,5V on standstill and 5V on max power.

Now I want to take control of the Voltage on that fan header.

There is no option to do this in the BIOS, although it may be outdated. I tried contacting Chiligreen, but there seems to be no way to do that.
Bios Version is 1.04.QUA
EC Version 1.07
Build Date: 09.02.2011

Just to make it clear, I have no thermal issues at all, my system is running nice and cool. You can find a picture here, so you can imagine why I want to slow down my fan.. Link to the picture

Thank you in advance, guys!

I am running Ubuntu 21.10
Gnome Version 40.4.0

Hardware model: "A15HV01" aka. chiliGREEN Platin TS
Intel® Core™ i3-2330M CPU @ 2.20GHz × 4
Intel® HD Graphics 3000 (SNB GT2)

Asked By: viktor spett


The original CPU-fan would turn slowly with 2.5V and would cool the system down at low load.
At some point the controller/bios on the mainboard detects a rising temperature and set the speed to maximum.
The functionality is not made for such a big fan.

With this gigantic cooling-system you do not need a regulation of the fan-speed, one setting will do the job.

This means, you have to see where you can get +5V from the mainboard and use some wires (Ground and +5V) to connect them with a little PCB, where you can add a resistor to reduce the voltage.
Hole grid PCB:

If the current of the fan is 100mA and you need a voltage drop of 2 volt, then you need a 20 Ohm resistor. R=U/I

You can find cheap adjustable StepDown-Voltage regulator on eBay.
A linear voltage regulator would work too, but he would generate a little bit of heat and they have mostly 2 volt drop on the inner resistance. So if you need 5V, then they need 7V or more to deliver the 5V.

Answered By: MikroPower
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