Modding Which Fans from USB?

I am looking into building a Laptop cooler and I want to run 2 fans from USB. I know that USB can give out 5V and 500mA. All fans I have at home need more amps, so I would like to know if somebody knows of fans who run with about 200mA each.
Thanks

 

you can use resistor .
the formula is V=R*I . V=5 I=0.5 . V=voltage R=resistor I=current .
5=0.5R . R=10 ohm . buy
very simple electronic . you dont need to spend your money on new fans .
just take a look of electronic guides before .

 

Hang on don't fans need 12 V?

 

They can work at lower voltages, which is how you can make fans run more quietly. But 5V is a bit low for undervolting fans and they risk of stalling.

 

Thanks for the reply`s guys.

I know that 5V is a bit low as most fanbus use 7V as low setting. Thing i was wondering is which kind of fans Zalman & co use in there cooler which run of USB. Or do they use a transformer to get the higher voltage?

 

THEY JUST USE REALLY SMALL FANS oops if you manually spin them they won't stall lol

 

They use 5v fans, and yes they are typically smaller... I remember seeing a mod on a site, i think it was an undervolting guide, but he made up a circuit that rev'd the fans up a bit every so often to avoid stalling, this uncluded upon startup aswell (when they are most likely not to start up)

Cant find the link now

 

i have made one of these to cool my external hdds

most 25mm wide fans will runs at 5v but a fan at around 300mA works best

i have found it hard to find fans that need more than 500mA (what fans are you looking at) thermaltake 80mm fans only use 480mA at 4800rpm which is really fast

i have found that most 80mm fans use between 140-300mA

 

get some 120mm delta focus flow fans underneath lol then you will be able to easily hear whether they have started up or not...

 

Depends on the fan. I know that sunon, evercool, and adda's mid-speed offerings will usually spin up at 5v.

 

I thought about Cooltek fans as i get them cheap in a shop around the corner. And it seems like there fans use only 100mA, just dont know if the work good with 5V

 

just try them if they are cheap
You will never know unless you try.

 

A 12v fan should normally run on a voltage as low at 5v with a low speed and virtually no noise. Just be aware of how much air it is actually pushing at such a low setting.

You can find tons of small 5v ones that are around 40mm, get 2 or 3 of those at various locations and that should be all the airflow you need.

 

The silence freaks at SPCR often run their fans on 5V but as said, not all fans will start reliably. Nexus Silent won't, I think they're already under-volted.

The other point is, a 200mA @ 12V fan will draw under half that current at 5V once running, but there is a starting surge.

 

How much damage can I do to my laptops USB ports if the fans need more power then they can handle? Burn them out or would the fans just not work?

 

it should come up with a warning saying this usb port has overloaded due to a power surge etc.....

 

Interesting, i've got 3 Papst (L1As?) running at 5v in mine, have been for well over a year, with no problems!