Hey gang, I think I know the answer but I want to make sure before I burn down my apartment. I've got a spare Wii power supply: INPUT: AC 120V 52W 60HZ OUTPUT: DC 12V 3.7A CLASS 2 POWER SUPPLY FOR USE WITH Wii ONLY ( ) I plan on using this : SilenX Corporation - iXtrema Pro Fans Specifications 18 DBA\t 120mm 1400 RPM 90 cfm Operating voltage: 8-14v Current draw: 0.24A Power consumption: 2.88w Using the Wii supply would be fine, yes? Theoretically I could run about fourteen fans on this, right? A bit excessive perhaps but it's lying around. I want to make sure my math is correct. What about an iPhone charger? If it's a 12V output and the wires match up, all I have to do is make sure that the amps add up correctly, right? 1.0 Amp power supply could handle two .5 Amp fans.
In your case you will be pulling 0.24A per fan because this fan is more than likely a computer fan designed to run on a 12V system. With power supplies you sometimes get fluxes in power so you want to leave some leeway incase this happens. I would say you are safe to run up to three of these fans off of this power supply and not worry about overheating your power supply. If you want to figure out your power usage try the West Virginia Formula: Watts= Volts X Amps; Amps=Watts / Volts; Volts= Watts / Amps; (/)= divide.
also that powersupply will put all of those amps into that fan so you are going to need some resistors or something to take up that extra amperage. Could use more fans yes. Just remember this otherwise that fan will go 100,000rpm and then burn out.
And lower voltage runs them slower? Because amps are the size of the pipe while volts is the water running through it, right? 50,000V with minimal amps is survivable while just a few volts with high amps can be lethal?
For a water pipe analogy, Voltage would be the pressure (psi) of the water, Amps would be the flow rate (gal/hr) and the electrons are the water... -Loki
Though you can find pot switches for a 12 volt system your best bet to control the speed is with a household dimmer switch.this will keep your fan speed where you like it and you are able to control the speed better. You do want to watch how fast you go because as the speed picks up (especialy with computer fans) when the speed gets higher the life of the fan (especialy the bearings) goes down significantly. The 12 volt fans that are in most computers are built pretty cheaply and can break down fast with high speeds or alot of dust/dirt. I did some dumpster diving around town and campus and found a few 120V fans that are larger (4"-10" are common in Server racks or exhaust fans) and they have stronger housings (usualy metal instead of plastic) and better bearings so they can handle higher speeds.
a old style dimmer switch is basically just a potentiometer. but new dimmers won't work on DC power. a cheap potentiometer will work just fine to adjust speed. just make sure its rated for the amperage you are going to use.