7V Fan trick

nwbdan · Post by **nwbdan** » Wed Jun 23, 2010 1:20 pm

I have a power cord extension set to work as the 5V trick, but 5V doesn't reliably start my 140mm NoiseBlocker.
I read recently somewhere MikeC stating that with a modern PSU the 7V trick was OK to do.
Is this right?
I have a fairly recent (but quite cheap) NOX Urano II 630W PSU (actually, the only thing that's loud around here...

). Will I be OK doing that trick with this PSU? I'll be connecting the fan to the power cord extension set to 7V and then connect that to an available PSU power "thingie" (

...).

Cheers,
nwbdan

frostedflakes · Post by **frostedflakes** » Wed Jun 23, 2010 7:56 pm

Should be fine. I've actually never heard of the 7V trick causing problems with PSUs. I think the load is so small and they're robust enough that, for all practical purposes, it's not an issue.

m0002a · Post by **m0002a** » Wed Jun 23, 2010 7:58 pm

What happens if 7V is not quite enough, or if you can start your fan with 6 volts? Personally, I would just get a Fanmate.

sub · Post by **sub** » Thu Jun 24, 2010 12:03 am

Hi,

Or you can put 2 fans in parallel on the 12v to get 6v.

klankymen · Post by **klankymen** » Thu Jun 24, 2010 1:46 am

sub wrote:Hi,

Or you can put 2 fans in parallel on the 12v to get 6v.

Nope, has to be in series. With parallel only the current gets halved, not the voltage.

frostedflakes · Post by **frostedflakes** » Thu Jun 24, 2010 5:44 am

Also note that they'd have to be the same fan to ensure the voltage drop across the two is about equal. Otherwise you might end up with a situation where you get like 5V across one fan and 7V across the other.