First of all, sorry for my lack of knowledge in the subject. I have a Nidec TA450DC B35502-35 fan which I've installed in a large wooden cabinet where my computer and other electronics sit. This cabinet of course gets hot from all the electronics inside of it. The fan forces air in from the room and goes out through openings in the top of the cabinet. This fan has 4 wires: red (+12v), black (ground), and then blue and yellow. I'm using only red and black to give the fan full 12v power.
The problem is since it's at max speed, it is way too loud. I have a simple toggle switch to turn it on and off. What I would like to do is replace the toggle switch with a knob to adjust the speed. I don't know how to use the other two wires to control the speed.
What kind of knob do I need to get, and how should I wire it? The minimum setting of the knob should feed the fan with its minimum required power to spin at the lowest speed possible, and the highest setting should spin it at full possible speed.
I don't have any problem with soldering a small circuit board together for this project, I just have no idea what schematic I need to put together. I've played with electronics and their components all my life but don't know nearly enough to even begin understanding how to accomplish this. It should be simple, right? Should I be using one or both of the additional wires for this, or should I use some method of adjusting the voltage?