Windows 7 - Fan Speed Controller - Build your Own

While it may seem very daunting at first, this tutorial is actually extremely simple once you see what to do.




Items needed:

• Potentiometer
• Multimeter with Ohm measurement
• Computer fan (no longer need to cut the wire)
• 22 Gauge Wire
• 3 pin MALE fan connector
• 4 pin FEMALE (and male if you want) MOLEX connectors (to connect to PSU)
• Wire clippers
• Heat Shrink (optional, but highly recommended)
• Solder and Soldering Iron (or pliers and cable connectors if you don't mind it)
  • *This tutorial will assume that you know how to solder, and that is the method you will use. If you have any questions about soldering or using connectors, feel free to ask*

Set up:
Set up your Soldering station to your preference, and make sure you have wire (and connectors) and solder. I used 22 Gauge wire because it is about the same size as the wire used in the fan already. You will need your wire clippers to cut the fan wires. I also recommend you use a Test PSU to test this mod until you are sure it works.


The Potentiometer
This device is what will be controlling your fans, so you need to make sure it is the correct resistance (in Ohms). This will depend on a few things, such as the size of your fan, and how many you wish to control with it.
To start off, you need to know a few things (and some basic algebra)
Vf = Fan Voltage desired (5v in my example)
Vs = Power from the PSU (12V for the yellow wire, 5V for the red)
Rf = Fan Resistance (in Ohms)
Rr = Potentiometer Resistance needed (in Ohms)
Vf1 = Fan Voltage (12V, 7V, or 5V)
Va = Fan Amps (usually between .1 and .5)

Formula:
Rf = Vf1/Va
Rr = ((Vs*Rf)/Vf)-Rf

Now, most computer fans operate from the 5V to 12V range (though some can go higher). So we will assume that you use the yellow wire (which is default on your connectors, or high speed). Next, we will use 5V as the desired voltage, because going below this will turn the fan off, and that is pointless.
The next step is a little harder. We need to know the resistance in the fan. This is determined by the fan operating voltage and amps. For the fan I used in this tutorial, it is 12V and .1A(Amps). We use Ohm's Law to determine the resistance. This is simply Resistance = Voltage / Amps, or Rf = 12/.1
This gives us a resistance of 120 Ohms.

Now, we need to know what resistance potentiometer we need. Plug all the variables into the second equation, and solve for Rr:
Rr = ((12*120)/5)-120
Rr = 168 Ohms

This shows us that we need a 168 Ohm potentiometer, but we will have to go up to the next closest potentiometer offered, either a 200 Ohm or 250 Ohm.

If you need any help with this step, please post in the thread, or PM me.

EDIT:I have rewritten this tutorial using my new method, which makes a TON more sense. There will be no need to cut the fan wire this time, and the potentiometer connection will use a regular 3 pin fan connector for use with ANY fan without modification.

Step 1:
Cut your red, yellow, and black wires to the length you desire. I made the wire long enough to be the fan connector AND the molex connector, and simply cut the red wire at the point I wanted the potentiometer attached. (you can see this is my pictures)

Step 2:
Strip the ends on all three (just a little) and solder each wire to its appropriate connector.
The red wire is the 12V wire, and will be in the MIDDLE, the other 2 wires are ground wires and can go either way (but matching is more fun).
In this tutorial I have used a green wire in place of a yellow.


Optionally, you can also wrap each individual wire in heat shrink to make sure it stays insulated


Also, you can wrap the wires to keep them looking good.


Step 3:
Now we solder the wires to the potentiometer. The first 2 pins needs to be soldered together. I just bent the middle one over to the first and then hooked the wire into the holes on the end and soldered it, but you could also just solder a wire between them and not bend it.


I then wrapped the wires


Step 4:
The wire leading to the 12V psu connector now needs to be soldered to the potentiometer.


Step 5:
Strip the ends of the red, yellow, and black wires and crimp (I also soldered) the molex pins onto the ends.


Then simply push them up through the bottom of the molex connector until they click gently. You can also tug on the wires GENTLY to make sure they are secure.


Step 6:
Last of all, I wrapped the molex wire and it was complete.


The great part about this fan controller is that you can simply plug a fan into it and then plug it into the power supply. No need to cut fan wires, no need to cut power supply wires. It is just like an extra connection you plug in!

While it may seem very daunting at first, this tutorial is actually extremely simple once you see what to do.




Items needed:

• Fan Controller from Part 1
• Computer fan (no longer need to cut the wire)
• 4 pin FEMALE (and male if you want) MOLEX connectors (to connect to PSU)
• Wire clippers
• Drill and bits
• Metal Plate / Front drive cover
• Heat Shrink (optional, but highly recommended)
• Solder and Soldering Iron (or pliers and cable connectors if you don't mind it)
  • *This tutorial will assume that you know how to solder, and that is the method you will use. If you have any questions about soldering or using connectors, feel free to ask*

Setup:
If you use a metal plate like I did, then you need to make that to size yourself, I will not cover it here (it was too difficult to make into a simple tutorial).

Step 1:
Decide where you want to position your fan controller (and switches from part 5, your new start button from part 2, etc)

Step 2:
Determine the drill bit size needed (I tend to estimate, then use bigger and bigger sizes until it fits). Mark the location from step 1, and drill the hole.

Step 3:
Push the controller through from the back. Only the "knob" should stick out. Put the washer on, then the nut, and tighten (use a wrench).
Then add the nice knob (I made sure to get nice machined aluminum ones) to give it an easy turn and good look.

Step 4:
Push the controller plate into place (I also like to have it screwed in). Attach the fan at the 3 pin connector, and plug it into the PSU. Turn on the computer and test it out!

OPT Step 5:
Use the extra ground plug to add the fan light switch right next to the speed controller (needs its own hole) to have a really custom fan controller!

Here is my semi-completed project. I have utilized all 5 sections of this series. To the right is my keyed start switch (the key switch at bottom right and aircraft safety toggle switch). On the top is my cathode switch and my soon-to-be fan light switches. The bottom has 3 of my 4 potentiometer speed controllers.

Hope this helps out the modders!

~Lordbob