My first simple project! It all started when I bought a new Vantec UV LED 92mm case fan to replace my existing one. Fan runs at 2600rpm, noise 33dbA. Before I bought it I thought it would be quiet enough.. but I was wrong! So had to find a way reduce noise.

I dug out some junk and managed to find parts to make a voltage regulator..
LM350 (LM317 is sufficient actually)
1k resistor
10k variable resistor
veroboard
1uF capacitor (from some unknown junk)
heatsink (from old broken PSU)
big 3 pin male socket (from old broken MB)
small 3 pin male socket (from old broken MB)
big 3 pin to small 3 pin cable (from old celeron)
ISA card back bracket (from old modem)

Total cost would be under rm5.. since I used mostly junk parts (there's value in junk!) LM350, resistors and veroboard were leftover from old projects. If you're lucky you can find all the parts needed from junk, so will cost next to nothing. To buy the parts I'm not sure where to get the 3 pin connectors and cable.. anyone knows?


This is the simple schematic.. pretty much standard. The capacitor on the output is optional.. just to smooth out the voltage. Some people put one on the inputs as well. But anyway it's just a fan so don't need so perfect output. The output voltage is calculated as 1.25*(1+(variable resistor)/1k), so if the variable resistor is max at 10k, output will be 11.25V.


The completed product! Two pins on the connector are 12V and GND. The remaining is the speed sense pin, which is direct connected to the output speed sense pin. Only two pins on the variable resistor are connected.. the middle and right one. So turning anticlockwise means max fan speed.



The back view.. cuts have to be made on the marked areas.



Installed in casing.. the input cable connects to my case's front panel fan rpm monitor, 3 pin connector. Output goes to the fan of course.



Back view of the installed controller.. the variable resistor was too tall initially, so it wouldn't fit. Had to cut and shave off the bottom part where the 3 leads are. Now it's just nice.. the nut and washer screws onto the case, making it extra secure.


The results! Set at medium speed, 1600rpm. Max can be achieved is 2200rpm. Voltage regulator takes up some power, so can't achieve the fan's rated 2600rpm.. will need a bypass switch for that. I wired the temp sensor to the heatsink.. slightly warm at 42C. I estimate it's dissipating about 1W of power, so nothing to worry about. The slower the fan speed, the hotter it will become. I haven't tried setting the fan slower bcos afraid will screw up the speed sensor.

Future:
Maybe add more fans.. still lots of space on the board for additional connectors. The LM350 can handle up to 3A of current.. so can control multiple fans together.

References:
http://casemods.pointofnoreturn.org/vregtu...orial-full.html
http://www.st.com/stonline/products/litera.../2154/lm317.pdf

Nice!!!
Old mod, but always nice to run through.
Suddenly feel like digging up all my DIY guides again. Not to mention my electronics inventory

nice mod. is it possible to make one variable speed fan controller which uses pulse instead of limiting the power to the fan? from what i know. wrong variable resistor will result in burnt variable resisters. correct me if i'm wrong

woah... cool...

Now i am rethinking of reinstalling my Fan Controller again...

Removed it....

Now my pc is noisy, i think i shud put it back in....

Why dun juz put the CPU into the air-cond room while using best cooling and low cost

cool mod.

what u r trying to say is it do it PWM style pulse width modulation. it is entirely possible, and your CPU fan is controlled via PWM as well. however the design will be a lil complicated as u need a timer (555 will do) and a variable resistor to change the duty cycle (pulse on time)

btw, tidy mod there... doesnt hurt the eyes ^^

This post has been edited by jsnkok: May 3 2006, 10:33 PM

very nice mod but if u look closely at the controller side u can see "phone line"

im not good in electronics but im curios........cant i just put a variable (reostat) only ......... how does the circuit work actually?

sory again for the newb Q ........

anyway a good mod indeed

U mean just connect a variable resistor (VR) btwn wires frm molex & fan?

Depends on the fan's power consumption. If it's lower than that of the VR's, then np

But usually that isnt the case. And that's why we need these controller circuits

can elaborate more?quite interested 2 do it if it's safe

This circuit is safe alrite,

i have 3 circuits running in my pc rite now.

very interesting... i have a vantec torando 80mm 6000rpm that runs very noisily (52dBA)..i've been thinking of making a switch for it, but using VR seems better...

nyway..nice clean job here dude