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Fan Voltage.......HUH?

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Justin

Registered
Joined
May 25, 2001
Yeah most of my fans have those little power supply adapters that continue the circuit onto the hard drive or whatever....but i have two running on the three pin connectors on my mobo. now i have settings for these in asus probe...and i see 12v 5 and 3.3.....what are those for? can i increase the speed of my fans through these settings????
 

Timmæy

Registered
Joined
May 12, 2001
you can only increase the voltage to your fans by connecting the 5v- to the negatvie fan lead and the 12v+ to the possitive lead, this will give you 17v to your fan and thus increase rpm and cfm.
check out www.freezin.8m.com for some how to guides for building an easy effective fan bus that is 17v for all your fans.
Hope this helps.

Later
Tim
 

cjtune

Member
Joined
Dec 18, 2000
I don't think it's a good idea to increase fan speed by increasing voltage ABOVE the rated value. There is a chance that the fan will burn (most probably the cheap ones) or will have a reduced lifespan. Panaflo fans, for example, have operating voltages of between 7 to 13.8V for their 12V rated fans (check it out on their website). Why don't just get a extra fan (best it it rotates counter to your first fan) and fix it in series or just get a larger fan and adapt it to your heatsink?
 

anarki_gr

Member
Joined
Jun 14, 2001
Location
Athens - Greece
increasing voltage will increase fan speed and cfm but it is a big risk to run them out of their specifications since their life expectancy will be dramatically lowered. most good quality fans can handle up to 14.5 or even 15 volts but i don't recommend taking this risk...
 

GooGobbler

Member
Joined
Jun 1, 2001
I know I am late but....I have a question.
How do you make the fans run at 13.8 Volts??
What do you mean switching the wires around?
How do you switch them around? Do you just pull them out of the little plastic thingy
Which ones are the +12 and -5 and all that other stuff.
I see 1 red, 2 black in the center and 1 yellow?
If there are any pictures/diagrams showing how this is done it would help too, but if not, I think ill be fine ;)

Well, theres my questions.
 

BboySkid

Registered
Joined
Apr 16, 2001
hehe a couple days ago i was experimenting with increasing fan speed
i had an old 80mm from a very old AT power supply
i linked 4 9v batteries in series and connect it to the fan, 36v on a 12v fan, it was spinning pretty damn fast, pushing as much air as my 120mm at normal voltage
it lasted for 5 mintues, then i just disconnected it
i linked my new sunon 80mm up to it and it crapped out, destroyed the fan totally
guess they just dont make'em the way they used to
 

Hoot

Inactive Moderator
Joined
Feb 13, 2001
Location
Twin Cities
cjtune (Jun 18, 2001 02:19 a.m.):
-snip-
Why don't just get a extra fan (best it it rotates counter to your first fan) and fix it in series?
-snip

I found two no-name 80mm fans at the surplus outlet. Neither has a tachometer output, but they feel like maybe 36cfm units. They spin in opposite directions, so one boring evening, I strapped the together. I would guestimate the output went up to about 45cfm. Pretty nice synergy. The noise went up slightly also, but nothing like the Delta screamers. Very tolerable. Until I modded my case for 92mm case fans, I used that twin fan arrangement with great success on the front intake. The guys at the surplus outlet always laugh when they see me coming in, with my 12V lantern battery. :D

Hoot
 

cjtune

Member
Joined
Dec 18, 2000
GooGobbler (Jun 20, 2001 12:56 a.m.):
I know I am late but....I have a question.
How do you make the fans run at 13.8 Volts??
What do you mean switching the wires around?
How do you switch them around? Do you just pull them out of the little plastic thingy
Which ones are the +12 and -5 and all that other stuff.
I see 1 red, 2 black in the center and 1 yellow?
If there are any pictures/diagrams showing how this is done it would help too, but if not, I think ill be fine ;)

Well, theres my questions.

You can either get voltage higher than 12V from one of those AC/DC adapters or you can do some wiring. Then to get EXACTLY13.8V (why do want to do that?), you can attach a resistor in series with the fan's wiring to 'absorb' some voltage so that the fan gets exactly waht it need. Say you need 13.8V and you can get 17V from the PSU. You need to 'redirect' 17-13.8=3.2V. Look at the rated current of your fan. Say it is 0.14A. Then the resistance you need in R=V/I=3.2/0.14=22.86 Ohms. Get a resistor that is closest to the calculated value. But the resistor is also subject to I^2*R=(0.14)^2*(22.86)=0.45watts of heating/wasted power. Hope this helps... and I'm not responsible for anything you burn up as a result of this reply 8`)