Inexpensive 12V-OFF-7V Modification Fanbus Wiring Diagram

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Khaos

King Kretin

694 Posts

25 Oct 2003, 5:14am

Inexpensive 12V-OFF-7V Modification Fanbus Wiring Diagram

I was bored so I whipped this up. 12V-OFF-7V switches are one of the most useful system mods one can do. This wiring diagram should make it simple enough for anybody to wire. I am also planning to create a more advanced schematic demonstrating the most efficient way to safely wire multiple fans to the fan bus. Why pay $50 when it can be done for $5?

P.S. I decided to do this because the only other decent schematic I've seen was sloppy (Is Snap To really that hard to master?) and everybody should know how to do this.

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GHoosdum edited : 23 Mar 2006 at 3:32pm .

Khaos

King Kretin

694 Posts

25 Oct 2003, 5:41am

Here's the more advanced schematic. As you can see, all of the wires can be conjoined EXCEPT the ground from each fan MUST go to a separate switch. It is much easier to build than it is to scheme. Normally all the switch posts line up in the fan bus, so you just take a length of wire, strip a section for each post, and run it the length of the row... Soldering as you go. Use some non-corrosive RTV to seal the solder joints with the posts.

Be careful not to exceed the wire's current capabilities when putting multiple fans on a single wire. Anything larger than 20AWG should work fine no matter how many fans you are wiring. I don't recommend using 22AWG or 24AWG, such is found in most fan tails.

Any questions, just PM me and I will try to answer the question in revised schematics or the accompanying text.

And for those who REALLY don't know what this is all about, lowering the supplied voltage to a fan makes it spin slower, which in turn lowers its air output and most importantly, noise output. 7V is the ideal low setting because all 12V fans should run comfortably at 7V, however, some fans will burn up at lower voltages.

It is inadvisable to run small, high speed fans on anything less than 10V. For instance, 60mm Delta screamers simply stop spinning around 9.5V, which can severely damage the fan's motor.

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Khaos edited : 26 Oct 2003 at 6:31pm .

Khaos

King Kretin

694 Posts

25 Oct 2003, 5:41am

Forgot the image.

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fatcat

sasquatch wannabe

3,990 Posts

26 Oct 2003, 1:18am

nice!...me likes, althou i run my 120mm fans 9v mod style. good diagram for the newbies tho

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Khaos

King Kretin

694 Posts

26 Oct 2003, 6:41pm

Cool. Just in case anybody is wondering, to run roughly 9V to your fans, all you need to do is substitute +3.3V for +5V in the diagrams.

FatCat, did you 9V your fans using the potential method, or by adding resistors? I'd personally prefer the resistance method, since the only +3.3V available from most PSUs is in the ATX connector, but this can get to be a pain in the butt since all fans have different current draws.

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Shorty

Sniping teh enterpwise!

9,543 Posts

26 Oct 2003, 6:53pm

Whoah.. now that's useful

Thanks Khaos

You just gained a sticky (or whatever it's called at the moment

)

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fatcat

sasquatch wannabe

3,990 Posts

26 Oct 2003, 6:58pm

i used the orange wires from the extra p4 power connector im never gonna use off the power supply. they give you 2 3.3v wires and i got 2 120mm fans.

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Khaos

King Kretin

694 Posts

26 Oct 2003, 7:49pm

Ahhh, I see, I see.

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Khaos

King Kretin

694 Posts

20 Feb 2006, 8:53pm

Re: Khaotic 12V-OFF-7V Wiring Diagram

Wow, I completely forgot about this thread.

2003! Hahaha, now that's some O L D S T U F F! This mod is just as relevant today as it has ever been. If anybody has questions about fan modding or electrical mods in general, please feel free to shoot me a PM. I check fairly regularly while I'm at work and would be happy to help with your project.

Another thing to note is that all modern PSUs now have auxilliary 3.3V lines, so if you're not using the P4 AUX connector you can safely and easily use one of the 3.3V cables to power your fan bus, thus yielding the 9V setting like FatCat has done.

Certain fans, most notably the high powered fans like Vantec Tornados and Deltas, do not perform well at 7V. They will spin, but their motors are such that a 7V feed causes excessive current draw and can actually damage the fan motor, resulting in premature failure and potential damage to your valuable hardware. In cases like this, it is actually prefferable to run the fan at 12V or 9V, but not 7V.

Personally, I prefer using a potentiometer and a small LED voltage meter for a system-critical fan so that you can fine tune the voltage to get the best possible combination of reduced noise (When necessary) to voltage drop. You want to drop as little voltage as possible on system critical fans.

A really nice system, one which I have yet to build, would be a system-critical fan bus that has a potentiometer for each fan and also a LED readout with a multi-position switch that allows you to view the current voltage of whatever fan you are currently tweaking. Of course, when not tweaking it should probably be left on CPU.

Lastly, do not get discouraged:
I won't lie. I killed six 120MM fans while developing my fanbuses, four of them in one fell swoop. Fan buses involving lots of fans (Mine had controls for six fans each) can get complicated, and a reversed wire will quickly burn up motors and melt wiring. In some cases, you'll get real lucky and the insulation will catch fire, which is always exciting. It smells real nice when that happens. Proceed with caution!

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Khaos edited : 21 Feb 2006 at 7:22am .

Leonardo

F@H Reign of Terror is back!

14,701 Posts

21 Feb 2006, 3:45am

Re: Khaotic 12V-OFF-7V Wiring Diagram

Thanks for sharing your engineering with us. I hadn't seen this thread before. Good stuff.

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tmh88

Custom User Title

2,487 Posts

21 Feb 2006, 4:17am

Re: Khaotic 12V-OFF-7V Wiring Diagram

reminds me some of the crazy xbox wiring schemes I came up with for dual hd's, activating the case fan to run at 12 volts instead of the normal 5v, and a hard dive cooler.

I had 2 hd's in my xbox, and 2 toggle switches. When the first switch was on, it booted the normal stock xbox hd. When switch 2 was on, it booted the 2nd 120 gig hd with the upgraded dashboard on it. When switch 1 and 2 were on, I think i used an AND gate, it would turn only the 120 gig on, and raise the case fan to 12volts(push more air out), and turn on the hd cooler fan.

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Inexpensive 12V-OFF-7V Modification Fanbus Wiring Diagram

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