120mm fan wiring...

[leapinlew]

I have a 120mm fan in the back of my last cabinet that I need to wire. The fan was supposed to connect using a molex connection into a standard power plug from a PSU (like a hard drive power plug).

I used a laptop in this project and don't have access to a PSU style plug. I want to wire the fan directly to a wall wart. The problem is, the fan has a red, yellow and black wire. I know the red is 5, the yellow is 12 and the black is ground. What I am unsure of is how to wire the fan. Do I need power to both the 5 and 12?

Any suggestions? Here is a pic of the guts of my cab

There isn't a lot of room, and I need to get this fan working.

What I've done is connect a red wire to a 5 volt wall wart and when I turn it on, the fan won't spin. However, if I give the fan a little spin it will start turning. The 5v wall wart I'm using have an output of DC 5.3V 500ma. So I'm thinking the 12v also has to be plugged in as well...

Any help?

[northerngames]

use the 12 volt line instead

[Teebor]

Typical of fan manufacturers to complicate things.

Black is Ground
Yellow should be 12 volt
Red should be the sense wire (this is only used to sense the speed of the fan by a controller)

[Green Giant]

I may be wrong but I am pretty there is only one power wire for that fan, the 12V line.  The other wire should be the control line to help keep the fan quieter.  With just the 12V and ground, it should spin full speed all the time.  You can ignore the other wire and possibly drop a pot in there to control the speed if you want.

-edit- damn, beat me to it.

[leapinlew]

ah...

damn. Thanks for the info. That did it. I was really over complicating things.

[Shattered]

If you find that the fan is too loud you can try this little trick:  7-volt mod, you lose a it of cooling but the fan is a lot quieter. 

http://www.bleedinedge.com/guides/7volt_mod/7volt_fan_mod.html

[leapinlew]

I bought some really good fans. I appreciate the tip though.

[Green Giant]

If you find that the fan is too loud you can try this little trick:  7-volt mod, you lose a it of cooling but the fan is a lot quieter. 

http://www.bleedinedge.com/guides/7volt_mod/7volt_fan_mod.html

Of course if you are using a variable input wall wart, you can just adjust the voltage to vary the speed.

[Green Giant]

Can't you just swipe the power off the AC/DC inverter that you're using to power the laptop?

That would be extremely risky.  Depending on the pinout of the laptop cable, you would have to find a low power signal to send to the fans.  The laptop power would send way to much current and fry the fan.  The only way to get it to work would be either resistors which get really hot or a buck converter.