Start page
PC modifications mainpage
Simple temperature regulated FAN speed controller

This regulator uses a P-FET to change the positive supply voltage to a FAN
an NTC resistor mounted on the device that needs cooling will change the fan speed,
the temperature on the heat sink will therefore be constant, while the FAN speed will change, depending on power disipated

The RPM output signal from most FAN types will continue to function, due to the positve voltage regulation.
There is many other ways to do this, but since I have fine access to P-FETS and they have super hight gain, a perfect solution !

The Fan regulator schematic, the gate capasitors filter the NTC voltage so regulation is nice smooth,
The output capasitor remove FAN noise when it is running on low voltage, the FAN draw it's current in pulses so without this cap it will noise.
If you have a 10K NTC you use a 10-22K trimmer, if you have a 22K NTC use 22-47K trimmer, 47K NTC use 47-100K trimmer and so on.

Here is the PCB and components placement, seen from top side.

Here are all the components you need.

Components on PCB.

Be carefull to use heat shrink tube to make a good looking NTC cable connection.

Now ready to install

It can be installed on an unused rear plate.

Maybe it is a better idea to solder wires and connector for MOBO input like this.

It can also be installed in an unused plastic front plate.

if you are carefull, it is possibe to drill the holes from rear side, with out making scratches.

Nice close up picture.

The switch short the FET to make MAX fan speed in position up, the LED is then RED,
position down, LED is green, and fan speed is now controlled by the preset temperature set using the variable resistor.

The two green wires makes the FET short circuit via the switch.

The NTC temperature sensor is glued on the bottom side of the huge VULCANO 7 (TM) cooler, using araldite glue,
the alu surface was cleened using sandpaper first, so that the glue will work good.

The original Vulcano FAN NTC was removed and the two wires for that NTC was soldered together, and secured with a bit heatshrink tube.
3 new wires and new connector was made for the fan, length 50 cm to reach front panel mounted new homemade regulator.

Here it is complete.

It is now possible to set any CPU working temperature we desire,
The regulator will keep same temperature no matter what CPU loading we make..
we tried with 47C max load, then the fan speed was about 3000 as usual.
then we enabled the NB cooling bit to set the CPU idle, now almost instantly,
the fan speed started to go down and down and after 20 sec it stopped !!! WOW what a dream..

CPU tested: XP2000 slightly overclocked from 1667 to 1800 MHz !!

Greatings to Snow !! I hope you like your new fan controller :-)