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Controlling a Non-PWM fan with PWM Project

post #1 of 3
Thread Starter 
Hey guys Im ordering myself some Fans that are Non-PWM and Im going to be getting a Maximus IC Gene-z so I said hmm 5 PWM headers and only 1 PWM fan (the CPU fan)..... I wonder if I can make a small circuit to control the fan with PWM

I have some experience with electronics and after a bunch of reading and thinking I cam across this



Seems good to me but I was wondering if anyone else here has any input on the circuit design

I decided to look for an OpAmp circuit because I understand they dont interfere with the Tachometer
Im not sure how the PWM would interact with LEDs though
Id have to isolate the LEDs of the fan in order for them to not get dimmed by the PWM controller correct?
Or are the LEDs generally already on a separate circuit so that the LEDs always draw their 3.3V (or whatever x amount of Volts)

Other thoughts, what do you guys think of only using the PWM pin of the mobo and using the 12V pin from a molex as to not over draw current from the motherboard for higher current fans?
Although im not using any of those insane Delta fans, so is that even worth doing?
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post #2 of 3
Hi mate

Cant really help with the circuit side, im self taught and rusty with only remembering half the stuff i use to. But i can give a bit of info to get the load off the motherboard.

How i set up the pwm fans for mobo and fan controller, or like how you want to the psu.

Lets say your pwm fan has 4 wires and a molex kk fan adapter, stick a thin screwdriver in to the plug to remove the Positive wire(heat shrink it) goes to mobo. Now soldier a 3-pin Molex KK female fan adapter to the fan, and do the same as above on the Negative(heat shink it) so now there are to fan cables, this goes to the fan controller or to your psu, need psu adapter or solder the right fitting to start with, i would go 3-pin in case you get a fan controller one day. Bit of info, got to have the negative(close the circuit to trick the mobo there is a fan) for the motherboard to recognise the pwm cable, and hold true again for the Signal cable(needs the negative to close the circuit). And the fan controller only needs positive and sensor. Now with a fan controller you'll have your rpm's and the same for the mobo, and its regulated by the mobo pwm, plus you can under volt the fan by the fan controller. Setting it up like this purely owns, especially if you got some AP's

Simple recap version
Negative - 0 - Sensor - PWM <-- 4 pin to motherboard
0 - Positive - Sensor <-- 3 pin to controller or psu needing adapter
Edited by Tigerpaws - 7/21/11 at 6:26pm
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post #3 of 3
Thread Starter 
that part is pretty simple its the PWM circuit that is the tricky part xD
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Core i5 2500k Asus Maximus IV Gene-Z EVGA GTX 560 TI SC DS 8GB 2x4GB Corsair Vengeance 
Hard DriveHard DriveOptical DriveCooling
WD Caviar Green 640GB Corsair Force GS 240GB Sony DVD Burner Aerocool Shark Fan 14cm Devil Red Edition x4 & ... 
CoolingOSMonitorKeyboard
EVGA Superclock CPU Cooler Windows 7 Ultimate 64-bit 2x22" ViewSonic 1080p LED Ducky Shine II TKL 9087 
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My Rig :D
(16 items)
 
  
CPUMotherboardGraphicsRAM
Core i5 2500k Asus Maximus IV Gene-Z EVGA GTX 560 TI SC DS 8GB 2x4GB Corsair Vengeance 
Hard DriveHard DriveOptical DriveCooling
WD Caviar Green 640GB Corsair Force GS 240GB Sony DVD Burner Aerocool Shark Fan 14cm Devil Red Edition x4 & ... 
CoolingOSMonitorKeyboard
EVGA Superclock CPU Cooler Windows 7 Ultimate 64-bit 2x22" ViewSonic 1080p LED Ducky Shine II TKL 9087 
PowerCaseMouseMouse Pad
Corsair HX650 Lancool K63 Microsoft Wheel Mouse Optical 1.1a EVGA Mousepad 
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