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anyway to make a fan go faster?

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batboy

Senior Moment
Joined
Jan 12, 2001
Location
Kansas, USA
Ok, I'm obviously not an electrical engineer. How do I make a standard 12v computer fan run faster (high RPM)? I know we can use 5v or 7v with a fan controller to run them slower. I know the PSU only goes up to 12v. So, does this require a transformer?
 
One way to do it without a transformer is to utilize the negative rail of a powersupply. There is a negative 3.3, a negative 5 and a negative 12v rail, you can utilize these the same way you can do the 7v mod. Of course, the amerage isn't too high on these rails so you wouldn't be able to put too many fans on them, but you can get up to 24 volts of power.
 
i'd say the above are most likely correct. to get the fans to go faster you need a bigger voltage difference that has the amperage to move it. your fan's prbly won't last too long though since they are only made to take 12 volts.

this comming from an still learning EE major :D
 
Ok, thanks for the response. I don't see a -3.3v line looking at the power supply schematics. I see -5v, -12v, +3.3v, +5v, and +12v. Combining -5v with +12v for 17v total is too much in my opinion. Oh well, was just a thought.
 
couldnt you make a 13.7V line with 12+5-3.3V?
would it work with putting the red wire on the 12V and the 5V line simultaneously and also connecting the black wire to the 3.3V line?
 
Most 12V fans are good to around 13-14V or so - most of them have the limit either on the back of the fan, or if not there, on the manufacturer's spec-sheet.

As for providing that voltage, you can either overvolt your +12VDC rail (which is a very, very bad idea past ~12.5V or so), or purchase a dedicated +12VDC PSU for fans alone, and overvolt it. A ~100W dedicated +12VDC PSU can be found on eBay, or at a good electronics store, for fairly cheap.


Ultimately though, if you want more fan power, it's far easier to just buy a more powerful fan. :-/

EDIT: There is no -3.3VDC :(
 
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I am an EE and I happen to know a few things about fans so let me put in my 2 cents.

While you could buy a DC to DC Converter they are not cheap (start at around $70 or so.) So this alone is not an option. Using the minus lines on your PSU while it looks to be a good idea there are downsides and risks, capacity being one but you also run the risk of injecting noise from the fan in the lines since you are technically not using a ground, add to this that the -5 VDC connects directly to your MB making this even more of a risk especially if you overload the line. While you could a filter inline and watch your wattage draw you are back again talking about cost and benefit. So in the end I recommend you follow Felinusz advice and just buy a more powerful fan. By pure happenstance I may know of a few to recommend. ;) LOL
 
if you did ^^that, you might end up with this:
SingleFan-BurntBldg.jpg
 
felinusz

Most 12V fans are good to around 13-14V or so - most of them have the limit either on the back of the fan, or if not there, on the manufacturer's spec-sheet.


Just thought I'd add that this information which I posted earlier is only correct to a certain degree.



I just learned today that manufacturer's fan spec sheets are made with fan lifetime in consideration - the manufacturer's "maximum voltage" spec is only accurate as it relates to the fan working for it's rated MTBF.

A very knowledgeable electrician I am aquanted with by the name of Greenman100 informed me that almost all +12VDC fans will operate up to around 24V for semi-long term use.

Life expectantcy at these voltages is decreased dramatically however; at 24V a +12V fan can be expected to survive around 1 or 2 weeks (depending on the quality of the fan) !

At 15V, Greenman told me that a high quality (Such as a high end Delta) fan will operate nicely for about a year.

The reason extreme overvoltage kills fans, is the drastically increased heat output (wattage) that goes with overvoltage.
 
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