how to run a PSU fan using usb connection?

tatsu99 · Dec 7, 2016

hi
im trying to run a 90mm fan that i took out from a PSU, it needs the following power thingy:
12VDC, 0.12A, 1.44W
right now i have connected it to a usb wire which was previously a usb 2.0 extension cable. the red and black wires are connected and the fan is running but it isnt giving much airflow as it is running at only 5V from the usb port. how can i give it more voltage and make it run faster? any ideas?

getochkn · Dec 7, 2016

Can't. USB is 5v. Can't make it more

tatsu99 · Dec 7, 2016

getochkn :

can i add another two red and black cables from another usb cable from another port so that the power gets increased to 10V?

getochkn · Dec 7, 2016

No. Technically putting another USB would only double the amount of AMPS available to the fan, but the same voltage as it would be wired in parallel. You would need to wire in series, so Red-1 to Black 2 together and then Black 1 and Red 2 to the fans, but I would avoid this. It's not good electrical practice. Find another way to wire the fan. Why are you trying to run it from USB by the way?

tatsu99 · Dec 8, 2016

getochkn :

right now im using it as a cooler for my pavilion g6 laptop(as exhaust)
actually im trying to make a vacuum cleaner using a 2L bottle,its my science project. i need the fan for suction so im just testing how fast the fan can run at 12V. if the fan can run very fast then i will place it in the bottle. i am also searching for a alternative power source, can i use two 9V batteries in the series way you suggested?

sizzling · Dec 8, 2016

9v batteries are unlikely to deliver the current you need and if they did would die quickly. You would be best to find a 12v supply, maybe from an old toy or gadget. If not they can be found really cheap. You want 12v with at least 300mha

AppleGwava · Dec 8, 2016

if you have the skills,get a boost converter from china

tatsu99 · Dec 8, 2016

sizzling :

AppleGwava :

i tried connecting the wires to my PSU's molex connector's black and red wires but then the fan would not spin at all

ex_bubblehead · Dec 8, 2016

tatsu99 :

That's because the red wire isn't 12v, it's +5v, and you likely connected in reverse. The yellow wire is +12v. You also have to make sure to connect the + side of the motor to the + side of the supply.

tatsu99 · Dec 10, 2016

okay so i tried the serial method, the fan is spinning at the same speed. ill just stick with a normal 1$ motor+fan you find at the electrical store. ill try connecting the psu fan to my wall socket, is it compulsory to connect the +ve wire to the +ve pinout of the wall socket or will it be fine? ill connect a fuse to the positive wire for safety.

ex_bubblehead · Dec 10, 2016

If you are talking about connecting to the mains voltage (120 or 240) this is a spectacularly BAD idea, unless the fan is specifically built for this. My patented Troll Detector just pegged.

madmatt30 · Dec 10, 2016

Good god man , plugging a 12v fan to a mains supply !!!!
Just NO .

Whats wrong with a 12v battery exactly ??

tatsu99 · Dec 10, 2016

ex_bubblehead :

ok so will i need a resistor? and of how many volts? will the normal 1$ motor work fine without a resistor?

tatsu99 · Dec 10, 2016

madmatt30 :

i connected a PSU fan to a usb cable , the fan worked but not fast enough. then i tried using two usb wires in serial but even then the speed was same. ill go to the electrical shop and ask for a 12V battery
edit: i havent tried a 12V battery yet

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