# Fan controller for PWM fans



## 2tts (Dec 3, 2010)

Hey
Im on the lookout for a fan controller that is made for controlling pwm fans.
By this i mean that it (ofc has a 4 pin connector with 4 leads) supplies a constant 12v at the power leads, and controls the fans by outputting the pwm signal over the control lead.

I have yet to find one that does this. There are many tricksters out there as the defenition "PWM fan controller" can be used 2 ways..

My problem is that my Corsair SP120 PWM quiet fans make this "vibrate" or "rattle" noise.
Which i suspect is because it is controlled by modulating the power voltage as my current NZXT Sentry 2 controller does.
Doing this is also supposed to drastically decrease the pwm fans lifespan.

Thanks


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## Masterchiefxx17 (Feb 27, 2010)

Any reason you've not used the PWM connectors on your motherboard?


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## 2tts (Dec 3, 2010)

Oh yea, forgot to mention that..

They simply dont work


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## Masterchiefxx17 (Feb 27, 2010)

As in they are broken or you don't like them?

You can use something like this if needed. It adjusted the amount of power towards the fan depending on the slider:

NZXT SEN-MIX2 Sentry Mix 2 Fan Controller - Newegg.com


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## 2tts (Dec 3, 2010)

Theyre broken. Just running at full power all the time.. 
Its because of some damage a while back.

The one youre linking to is one of the tricksters mentioned.
Does it have 4-pin connector? Yes
Does it use some form of PWM? Yes
But does it supply continuous 12v to power leads and pwm signal to control lead? No. It only got 2 leads in the 4-pin connector and is modulating the 12v supply by pwm.
Which is what all fan controllers i can find does. Which i dont want.

Worst case scenario ill have to see if my current controller can be modded to meet my wishes.

Do any of you have experience with pwm controlling the SP120 quiets?


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## gcavan (Aug 13, 2009)

I don't believe the Sentry 2 nor the Sentry Mix 2 are PWM at all, even though they have 4pin connectors. Both control your fans by limiting the output voltage level. The fan chatter you describe seems to be a common issue with the Sentry 2.

Multi channel PWM controllers are rare if available at all. Take a look at 
Zalman PWM Mate - single channel but could be used with a splitter.
Zalman ZM-MFC3 - four channel. 3 voltage, 1 PWM


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## 2tts (Dec 3, 2010)

Its PWM by the means of that the 12v supply is the modulated voltage.

The PWM Mate was interesting, but id like stepless controll from outside the case. It isnt pretty to look at 5 of those wired to the outside of the case..

Same with the other one, as all my 5 fans that i want to control is PWM.

Looking at this one though, using a potmeter with no other visible components seems odd to me as i dont know the wiring of it.


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## Masterchiefxx17 (Feb 27, 2010)

2tts said:


> Its PWM by the means of that the 12v supply is the modulated voltage.
> 
> The PWM Mate was interesting, but id like stepless controll from outside the case. It isnt pretty to look at 5 of those wired to the outside of the case..
> 
> ...


Appears to be no different then to what I posted and mentioned above. It will adjust the power, therefore slowing down the fan.

How many fans are you using? Just one? Is it too loud to run at max speeds?


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## 2tts (Dec 3, 2010)

Its that they look to be similar that is my concern..
Using only a potmeter to slow down the fans is not something i want, as the only way that can work (to my knowledge) is by regulating the 12 supply.

As gcavan said this seems to be a common problem with the Sentry 2, i dug up some old fans and did some testing.
I tried another PWM fan from Nexus and a standard 3-pin fan from corsair(one that came with my H70 cooler, they are loud).
Both made the same kind of rattle noise when limiting the fan with the Sentry 2.
But as i dont have any other means of slowing down a fan i cant test further.

As said above id also like to be able to control them easily from the outside of the case. Or by software.
I have 5 fans, that is too loud for me at max speed when doing something soundless on my conputer.

So maybe the solution is just to get another standard fan controller that does ok with pwm fans and hope they dont impact lifespan?


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## Done_Fishin (Oct 10, 2006)

To my knowledge the only thing that the third wire on the fan does is to send back tacho pulses so that the speed can be measured. This may or may not be used by the CPU to regulate the speed of the fan by changing the voltage across it. The fans are brushless, using a break in the magnet ring to signal the change in polarity. I suspect that you may be confusing your terminology expecting pulses from the power rail to maintain constant speed.


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## 2tts (Dec 3, 2010)

Done_Fishin said:


> I suspect that you may be confusing your terminology *expecting pulses from the power rail to maintain constant speed.*


Im sorry, but cant figure out what you mean by this..

However im not interested in the third wire at all, its the fourth PWM control wire id like a signal on 

Merry Christmas!!


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## Done_Fishin (Oct 10, 2006)

Any good with a solfdering iron ?? 

take a look at this to build your own

ADI - Analog Dialogue | Fan Speed Control

and this for a project that someone made for an external hard drive (only to get an idea since it may not be exactly the same as you require)

PWM Fan Controller - Alan Parekh’s Electronic Projects


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## 2tts (Dec 3, 2010)

Ive had a look at making something myself, but i dont have enough experience to design the circuit myself, and there is little on the internet when it comes to creating PWM at a steady and specific frequency as the duty cycle is changed.

I also dont have an oscilloscope to measure the output, so trail and error is hard too.

What im thinking of now is using 555 timers(conveniently i got 5 of them laying aroaund) with some crystal oscillators to get in the frequency range that the fans expect. If this is even possible....

Ive based my work on this document:
http://www.formfactors.org/developer\specs\4_Wire_PWM_Spec.pdf

In the ADI link they are talking about commutation when PWM controlling a brushless fan..?? Isnt commutation only used in brushed motors?


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## Done_Fishin (Oct 10, 2006)

Apparently not .. it's the action that they are dscribing and not the method 

Commutate | Define Commutate at Dictionary.com


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## 2tts (Dec 3, 2010)

Both of those say its by the use of a commutator, which is only used in brushed dc motors.
As in brushless motors there is no current physically transferred from the stator to the rotor.

Id guess the word commutation is originating from the word commutator... Solid guess?
Also, brushless motors dont change the direction of the current.


But back to my problem..
Do you have any circuit designing skills?


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## gcavan (Aug 13, 2009)

The author is speaking of commutation _noise_, or _switching noise_ which is an issue with brushless motors. 



> At each transition from one stator coil to another, the rotor receives a sudden torque pulse when the next coil switches on. Each of these torque pulses causes a minute deformation of the whole fan structure. Depending on rpm, torque and the material of the fan, this can result in noticeable noises.


Suppressing Acoustic Noise in PWM Fan Speed Control Systems


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## Done_Fishin (Oct 10, 2006)

2tts said:


> Do you have any circuit designing skills?


Limited and this is not something I heve ever delved into ..\ however found this circuit










here

Page 2 | Building PWM Controller for 4 wires PWM fan | Overclockers Forums


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## Done_Fishin (Oct 10, 2006)

There is another project here which appears much simpler and uses trhe 555

High Frequency PWM Fan Controller


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## 2tts (Dec 3, 2010)

gcavan said:


> The author is speaking of commutation _noise_, or _switching noise_ which is an issue with brushless motors.


Oh, ok. But sholdnt this acoustic noise be above the audible range when pwm frequency is at 25kHz?



Done_Fishin said:


> There is another project here which appears much simpler and uses trhe 555


Those circuits look promising, ive ordered the parts i dont have and will try to build the last one you linked using the 555, as i already have those.
Then the hard part is mounting it nicley in the case with the knobs on the outside and the electronics on the inside xD


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## Done_Fishin (Oct 10, 2006)

Good Luck with that ... go carefully, it's not so difficult, just requires proper care and attention.


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## 2tts (Dec 3, 2010)

Well.. Now i've made the circuit on the picture below, from the link Done Fishin linked to in post 18.




4-pin PWM fan plug in the bottom right corner. 12V supply in the upper right.



The results:

I first tried the Nexus fan as it already is outside the case, but this gave me some kind of high pitched noise when throttling the fan.
So then i tried two of the Corsair fans in my case, and it was really smooth.
I had to have my ear "in" the fan to hear anything else than air noise. 

I have some perfboard that will most likley be used to make the final thing, if i have enough.. 
Ill only make 4 of them at first, but i dont have the courage to start with that today. But luckily it worked for my fans 

Im also thinking of getting another fan if this works out nice to get overpressure inside the case by controlling the speeds.
This so the dust dont bypass the filters on the intake by beeing sucked in through any other hole.
Then hopefully it will be dust-proof AND quiet 

Only thing left then is to mount it in the case... Still not sure how to do this..
The guy i bought the potmeters from didnt send with the knobs to put on it so it wont be that pretty either way..


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## Masterchiefxx17 (Feb 27, 2010)

I've never seen somebody make a fan controller, so well done! :grin:

You can mount it in the rear of the case or even in a hard drive bay.


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## 2tts (Dec 3, 2010)

The thing is i want to be able to control them from the outside...
I do have some spare pci slot covers that may be able to hold a few potmeters... hmmmm

Or if there exist some solid 5.25" bay covers that might be something


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## Done_Fishin (Oct 10, 2006)

Did you by a ready made PC or build your own ?? I have a box full of plastic covers that I kept for "playing around" from all my builds .. one thing I noticed though is that it is very rare to find that a plastic cover from one case fits any other ! Every Manufacturer seems to have his own style & method !!


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## 2tts (Dec 3, 2010)

I built my own.
However my case came with mesh covers.. 
Good luck making nice holes and mount something small in that.

Im just thinking that a 5.25" drive bay is just as big in any case, right?
A standard fan controller fits in all cases??
Its just a plate with long tabs that got holes in them...

Could try bending my own, but i think thats going to far just to get a horrific result.

Like this one:
Amazon.com: Lian Li 3.5" Aluminum Drive Bay Cover Solid Bezel Black: Computers & Accessories
Had it only been 5.25" and not 40$ shipping...


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## Done_Fishin (Oct 10, 2006)

depending on your PC and front panel, you might be able to mount the potentiometer (using wires to connect to your pcb) on the side or the inside of the front panel ( some are just held by plastic pop retainers which are part of the front panel whilst others are held to the metal box by screws) by removing it carefully & checking that there is sufficient room to fit the pot without it impeding replacement. Check to see where it would be most convenient for you to mount without causing problems & drill the hole for mounting. 

*Isolate all bare contacts and wiring with sleeving. *

Since it's unlikley that the potentiometer will draw sufficient current to need a standard size potentiometer, a miniature size panel mounted potentiometer may well fit better. Cut off any excess length spindle before mounting and fit a knob for easier handling and adjustment.


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## 2tts (Dec 3, 2010)

There are no way of mounting them in the case without doing something with a new plate or cover of some sort.
This is getting more and more time consuming, and im going to drop the ability to control it from the outside.

Ill just make the circuits and stick them behind the fan i got in the lower 3 5.25" drive bays. 
Lots of room and quite hidden as well as pretty easy to reach after removing the side panel held by two thumbscrews.

I also got to find a fan-grill that isnt making noise..


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## Done_Fishin (Oct 10, 2006)

Whatever you feel like .. it's your project .. Most cases I have seen have a lot of room behind the Front Plate or Panel .. in fact if your pot axle is long enough you could still mount in it a bay as you said but feed it through the front panel anyway .. even if it means running it through the esh and the plastic .. just throwing ideas at you here .. :wave:


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## 2tts (Dec 3, 2010)

Yea, i probably got a 10cm cube of free space in the lower drive bays.

The problem with the mesh is that you cant do anything to it without it looking really horrible imo. I tried mounting a button in some mesh once in an unrelated project, gave up after first try, ~2min into the project.
Its REALLY unmanageable stuff.

Also having the flimsy pots sticking out one would have to be careful with transporting it.. Its just getting easier to put them inside the more i think about it.

I really appreciate the idea throwing though ;P

Been busy lately, but hopefully ill start making it soon


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## Done_Fishin (Oct 10, 2006)

Good Luck and keep us informed !!


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## 2tts (Dec 3, 2010)

Here we are again..

Ive got it onto a stripboard now. Well one of them....

Since its me thats doing this, ofc im going to make it as small as possible, like always.
Even though i have lots of space in there.
This ofc making everything really tedious :doh:

The board itself, without the potmeter, came in at 20x30mm. 
Could be smaller, but i lost my patience towards the end, therefore i leave the remainder for another day.

Some pics of the thing:

Twisted red/black pair - Power
3 colored ones - Power and signal to fan







The back of the board looks like a mess as expected, so i didnt bother..

My test bench also works as a bed.
12VDC wall adapter



And yes, it is still working :smile:
I have however modified the plan of making one for each fan, to just making two.
One for intake and one for exhaust, by just putting multiple fans on one controller.
Which is not a problem as its not handling any power, and it still gives me the option to run over-pressure in the case.
And hopefully do it quiet, as that is the main goal.


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## JimE (Apr 16, 2009)

Have you tested multiple fans on one? I would suspect the fan signals could interfere with each other.


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## 2tts (Dec 3, 2010)

No, i havent, as i dont see a reason it should produce any backfeed or distort the signal to each other.
4-pin fan splitters, that just feed the same pwm signal to multiple fans do exist.
I dont know how successful they are though, so i will have to try before mounting it.


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## JimE (Apr 16, 2009)

Nevermind. After looking at the schematic, you are just using the throttle and not monitoring.


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