The idea here is to produce a small box which should alter the voltage of the fans with some switches. The fans are those that cause most of the noise in a computer, so decreasing their voltage causes a decrease in revolutions per minute, and therefore a reduction of noise. The efficiency is also decreased, but this is taken in consideration by allowing the user to switch between levels of voltage.

Let's start off with a list of required parts.

I happened to find a box in the just right size to hold the connections within itself. I got two 3-state switches from SPeletroniikka, 8mk (~1.3 USD) a piece, and some connectors that we here in Finland call as sugarcubes. They costed 8.50mk (~1.4 USD), if I recall correctly. Also, a quick connector package for speaker cords - about 9mk (~1.5 USD). The picture doesn't have the LEDs which are 3mm, red, and cost about nothing.

A closeup of the switch. The middle connector is shared for both of the left and right connectors. The switch has three positions, centered is OFF.
And then off to the box to make holes for the connector package. Draw the positions with a pen and off for the column drill
As a result, holes which are neat, and just in the right places. Attatch the connector of the package with superglue(tm). Not a very bright move if you want to use the connectors in some other project, but you can always buy some more ;)
In the mean time, I finished a splitter for the power cord so our gadget would get its electricity. As a base, I used the fan of some old P90 processor, and snagged the splitter and put the required additional cord into the +5 v line.
An artist's view of how the connection should be with one switch. The switch combines the +12 v line with either the +5 v, ground or into nothing, which gives us the voltages +12 v if it's connected to the ground, +7 v (= +12 v minus +5 v) and 0 v. The LED is here to indicate if the fans get electricity. On the side of the LED, you'll install a 500 ohm resistor. You'll find 470 ohm resistors from the shelf.
And then off to the already hooked-up box. The LEDs and switches will come to the box with their own flat cables and the connections are made with the sugar cubes if you easily want to modify the wirings. The switches and the leds are already installed in their places on the front panel.
The connection from a bit closer which shows the resistor which drop the voltages for the LEDs to appropriate levels.
The LEDs are attached to their holes with the oh-so-wonderful superglue(tm) :). A smarter way would be of course using LED headers which would enable you to chance the LEDs conveniently.
The box is closed and the whole system is starting to be ready for a test.
The fans are connected and the power is all set. The switches are centered so nothing happens yet.
Heureka! It works. I supply the fans with +12 v and the rpm increases. I try to lower the voltage down to +7 v and notice the fan to spin elegantly slowly and silently, but still supplying almost the same efficiency as with it would with +12 v. (Because of the poor quality of the digicam, the LEDs aren't as red as they should be)

Time for the summary. The building itself was quite straightforward. The connection isn't that complex and the profit should be pleasing for the overclockers. During this project, I used only two switches which allow you to control two separate fans. Nothing stops you from connecting several fans paralelly, which enables you to control several fans with one switch. It shouldn't be that much of a problem to add more switches, either. Just use the same technique. Some of you might want to use two colored LEDs or two different LEDs to indicate wether +7 v or +12 v is active. You will need to get yourself a bit more expensive switch which has two pairs of connectors paralelly. The fancy word for this was parallel switch, i suppose :) So, the bottom has 6 connectors instead of 3.

Well, this was the project this time. Go and check more hardware mods that I have succeeded to document.

Questions, comments?
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31.01.2001 - ©Japala    28.12.2001 translated to English by Henrik Paul

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