7 volt fan MOD!

[mettleh3d]

are there topics or articles that describe how to do a 7 volt fan mod? All i know about it is, well, its name. My friend told me about it and I have no idea what he was talking about.

Anyway, this would be cool to slow down fans without buying new slower fans, and i have some old ones to test on.

Thanks.

 

[Ricemarine]

All you do is switch the farthest right molex (if its facing forward... it should be like Y B B R), and replace it with the black next to the farthest level molex... So it should be like ( Y R B B)

What it does is since the 5v is now grounded, its now giving off 7v, but some PSU's don't like the mod. Most of em do though.

But... Its easier getting 3 pins, hooking em up to your mobo, and using speedfan to slow it down.

 

[Leros]

Basicaly when you combine the +12 & -5 you get +7

So, instead having just the +12, you have +12 & -5

 

[qbackin]

Originally posted by: JToxic
Basicaly when you combine the +12 & -5 you get +7

So, instead having just the +12, you have +12 & -5

Ding ding ding!

 

[Navid]

Originally posted by: JToxic
Basicaly when you combine the +12 & -5 you get +7

So, instead having just the +12, you have +12 & -5

It is +12 and +5.

+12 - (+5) = +7.

Edit:
http://www.bleedinedge.com/guides/7volt_mod/7volt_fan_mod.html

 

[mettleh3d]

thanks for the pictures. I really dont get the 12-7 + 5 / torque of circular motion - Voltage etc. Maybe I will if i tried to, but its late and my brain is at 50%.

 

[Navid]

Originally posted by: mettleh3d
thanks for the pictures. I really dont get the 12-7 + 5 / torque of circular motion - Voltage etc. Maybe I will if i tried to, but its late and my brain is at 50%.

There is 12 Volts between the yellow wire and the black wire. There is 5 Volts between the red wire and the black wire. Therefore, there is 12-5=7 Volts between the yellow wire and the red wire.

So, if you hook up your fan between the yellow wire and the red wire, you will have 7 Volts across your fan instead of the usual 12 Volts.

 

[mettleh3d]

having 7 volts will "slow" the fan down? That's primarily my concern, to slow it down. Whats the resulting speed? the Article has a DANGER disclaimer. Will my PSU choke? (Antec 430w True Power)

Sorry for the ugly listing.

 

[Varun]

Yes it will slow it down

Simple electric theory, Ohm's Law

Let's say your 12V 92mm case fan draws 1.0Amps at full load.

V=I*R where V = Volts, I = Amps, R = resistance
therefore R = V/I, R=12/1 = 12 Ohms
Also, P=V*I where P = power in watts, 12*1 = 12 watts of power

change it to 7, resistance is constant therefore
I=7/12 = .583 Amps
Power = 4.08watts

So the power of your fan at 7 volts is about 1/3 the power at 12 volts, therefore it will turn slower. How much slower depends on the construction of the fan.

I've also just run fans between Red and Black (+5V to ground) although some fans won't have enough power to spin up since in the above example it will only have 2 watts, or 1/6 the original power.

I guess some power supplies wouldn't like the 12V to 5V (net 7V difference) since you would be putting current back into the 5V line rather than to ground. The actual amount of current is pretty low though. If you are seriously worried about it just purchase a fan speed controller which will give you much more control over the fan speeds, from full blast to as low as you want. It is also a much safer way to do it if you don't know much about electrical systems as there is no cutting, soldering, or moving wires in connectors.