Building a 300W Fan Controller from an ATX PSU

Howto by geoffrey @ 2008-05-24

What do you if you have more than 20x high speed fans in your PC and want to control them through an easy front-end? Build your own fan controller of course! In this tutorial we show you how to convert that old 300W ATX PSU into the most powerful rheobus you have seen.
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Mods applied, pictures & video

Modifications applied

Before closing up the unit here are some pictures I've shot of how the internals look like now. On the picture below you see the self-made low power converter which makes the 12V, 5V and 3,3V voltage levels used for tricking the live monitoring circuit of the SG6105. The power converter is feed with 220V AC and is placed on the circuit board after the mains fuse. For easier regulating I used a linear one-turn variable resistor, this way it could easily adjust the three output voltage until they were in between the SG6105 safety boundaries.

Madshrimps (c)


Drawing of the added circuitry beneath. Caution, components of choice is crucial here; study this diagram first before actually adapting it into another circuit.

Madshrimps (c)


The low voltage side of the PSU. The 20-pin ATX connector and other connectors which were of no use later on have all been removed. Instead a new cable is to be found, this cable, type TPVF, is used to hook up a remote on/off switch, a voltage reading module and off course the potentiometer used to regulate the power supply. The SG6105 FET driver/controller is found left side of the PCB, you can see the many wires connected up to it.

Madshrimps (c)


Here is the voltage reading module in action. I was thinking about using an analog panel meter first, but since the price of the digital meter was not that high either I took the latter, it will probable appeal better too once the PSU has been fully integrated. The model I bought was made by Velleman, order code: PMLED/5

Madshrimps (c)


The digital panel meter however requires a stable 5V input supply voltage in order to function properly and since the PSU's 5V line is change along with the 12V I have to come up with another trick. This one is rather simple; LM7805 linear power regulators have a fixed 5V voltage output, while the input voltage may vary up to 35V. By taking the 78L05 type I was sure that the regulator would still output 5V even when the supply voltage would be as low as 6,2V. With this regulator hooked up to the regulated 12V line I now have the display led up whenever the PSU is in work.

Madshrimps (c)


Results, pictures & video

Time for some results, I used a car lamp to load the PSU with roughly 50W to see what impact it had on its functioning. I used the Velleman APS230 Advanced Personnel Scope to see the reflections of my modifications on the transient ripple at the regulated 12V line.

PSU regulated at 6V:
Madshrimps (c)
Madshrimps (c)
0 Watt Load
50 Watt Load


PSU regulated at 12V:
Madshrimps (c)
Madshrimps (c)
0 Watt Load
50 Watt Load


The results are quite satisfying, only when we use the PSU at maximum voltage with load applied then we see the AC ripple increase, but nothing to really start worrying about since the PSU is solely used to feed DC motors.

A final shot of the device put back together:

Madshrimps (c)


Video:



In the video you'll notice that the 12V line doesn't really regulate in a linear way, that's because we're using the feedback circuit to regulate, the circuit is in fact not build to use as regulator over such large output voltage range. The multi turn variable resistor is added for testing purposes, the final version of the PSU should get a one-turn variable resistor as that's all you need when regulating DC motors, it doesn't have to be that precise. Since this unit will be used for hooking up a whole lot of fans you may want to add a printed circuit board with 3-pin fan headers, and in general I agree that there is a lot left to improve.

The idea was to get a high power fan controller and that is what we got. Is it the best solution? Maybe not, but for its price there isn't a whole lot which comes close to it. The rest I leave up to the pc enthusiast who contacted me in the first place, hopefully we see something beautifully coming out of this.

For now I hope you all found something of interest in here, let me thank my father who added few words of wisdom here and there, with 30 years experience in electronics he has been of great help into understanding the way electronics work. Until next time, cheers!

Sources:
Elektuur n°476
System General SG6105 datasheet
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Comment from geoffrey @ 2008/11/01
On demand, a picture which shows how the Velleman digital panel meter is configured, P3 = open, P1 = open, P2 = closed

Comment from thenextgeek @ 2008/11/05
Hi there, it was me that made that request, and THANKS for helping me out, i really appreciate it. .

I have tried to hook the vIN/vOUT (your brown&white) wires to have a reading,
and I am unclear as to the proper way to do this.

(as with a Ammeter hook up, one runs a +Positive lead to one ammeter and then back out the other ammeter lead - to your device, and that works)

I have not had luck reading a steady voltage, or one that i would count as being accurate when trying to hook this LEDPM/5 Voltmeter up the same way.

Am I trying this correctly? or do i got something mixed up.. *Thanks!

(maybe if you could just tell me where you have your brown & white leads coming from your LEDPM/5 (vIN & vOUT) to/from your device? power? or ground? or both? ? ?

Thank you for taking your time to show this. .

Cheers,
thenextgeek
Comment from geoffrey @ 2008/11/05
Don't forget you have to add a resistor on the circuit, you can easily spot what I'm talking about, it is on the right side of the LCD controller

Brown/white is used to read voltages on my picture. What you do is connect the two in between a potential difference. For instance you can try reading a 9V battery by connecting the VIN pin to one of the battery terminals and the VOUT pin to the other battery terminal.
You can also read the supply voltage source, you can connect brown to red and white to white and read the voltage source voltage. In my PSU I connected brown with +12V (ATX: yellow) and white with ground (ATX: black).
Comment from thenextgeek @ 2008/11/05
AhhhhhHA! I bet that's the problem, I don't have that resistor on there!

hehe, sorry so newb at this, the unit i received (locally) had no manual, (or at least one that I could read so it has been kind of a trial and error,

until now..

THANKS a lot for taking the time, I will put a resistor on as your picture indicates it should be...



Cheers!
thenextgeek
Comment from thenextgeek @ 2008/11/06
Did you just remove (desolder) the small black square part that you put that resistor to? (#RA?) I circled it in red with an arrow for referral

Attachment 2176


Sorry I don't know the name of what that is.. I have that Resistor, but it *looks* like you removed the original part then put that resistor on?




Thanks again for all your help.



Cheers,
thenextgeek
Comment from thenextgeek @ 2008/11/11
Hey, sorry if i'm cluttering your forum here, you can feel free to delete the posts if it looks bad, not a problem...


The place you put the resistor (RA / RB) as described in the manual. .

I have put the resistor on there as yours shows, but it *looks* like you may have also cut the other circuit resistor (RB? - the other one). .


Is that so? I dont want to cut those little things, as i know i would NEVER be able to put it back on, way to small.. hehe

Ok, well thanks if you can make any suggestions, i appreciate it !

I am asking this detail, because i am getting "unstable", and usually what would appear to be "inaccurate" Voltage readings, ie; even from a fully charged 9volt batt., a DC Wall adapter (universal), etc... it dosen't seem to read, usually about 1-2 volts different, although, I can use a voltage adjuster and see the changes, they don't seem accurate enough...

afaik, i also used the correct resistor, but i'm willing to double check.. but pretty sure.


THANKS SO MUCH for your site, and your suggestions...

Cheers,
thenextgeek
Comment from geoffrey @ 2008/11/12
Quote:
Originally Posted by thenextgeek View Post
Did you just remove (desolder) the small black square part that you put that resistor to? (#RA?) I circled it in red with an arrow for referral
Yes that one is removed.

Quote:
Originally Posted by thenextgeek View Post
I have put the resistor on there as yours shows, but it *looks* like you may have also cut the other circuit resistor (RB? - the other one). .
Yes there is one, label: 106. I don't know if that is the original one or not.
Comment from thenextgeek @ 2008/11/19
wow, ok, somehow. . lucky you.

I talked to velleman, via email, they sent a diagram showing that RB is the one to be removed, and RA should *not* be removed (the one you have your resistor on). .

and of course the resistor/s "should" be inserted into the wholes located top and bottom on there, but I often have done it differently as well.

Anyways, I am seeing how to fix mine now.. heh I need to put the RA resistor (the little black one) back on it... *i think*, unless there's an easier way... hopefully Radio Shack has this part or something... i dunno.

Any ideas?

it almost *seems* that your RB resistor WAS the resistor that USE to be on RA.. #[106], because RB is [D] (or [O]), and RA on mine was [106]

Jfyi?..
did you buy yours first hand/new? Mine was a new unit.

Thanks,
thenextgeek
Comment from geoffrey @ 2008/11/19
New one here too, yes I remember resoldering one of these SMD's, use tweezers, it's not that hard.

 

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