Guide: Variable Speed Fan Controller

[bigal]

damnit, thught i could of got out of a hole there ¬_¬

Oh well, thanks anyway!

[triccas]

Hi,

I followed with interest the forums of a variable speed fan controller. I would like to first suggest a little mod to the circuit diagram.
As the load for the LM317 regulator chip is not resistive, but more likely inductive (coils) a certain amount of back EMF is developed when the motor is powered down. This might result in the destruction of the IC. The mod actually quenches any reverse voltages. Simply connect a IN4002 diode across the input/output pins of the IC. Connect the + side of the diode to the input; the - side to the output pin. The + side is clearly marked on the diode by a continious white line.

Now something about RPM sensing. Has any of you tried to connect the RPM sensing wire to the mobo?

[bigal]

no, buy that would work. If you have a chassis fan connector with RPM pin, connect the RPM wire to that and the Mobo will detect it.

[FRAGMAN_BOB]

someone flush the toilet cuz dat's the sh*t

[cloran]

is there anyway you can guide me to a schematic with just 7-off-12, instead of being variable? Or even tell me the resistance needed

[I LOVE ED]

here you go:

http://www.fanbus.com/thelab/Schematics/dv_712_bicolor.jpg

[cloran]

Is there a link that doesn't use 5 volt rail. and uses a voltage regulator

[I LOVE ED]

Is there a link that doesn't use 5 volt rail. and uses a voltage regulator

well, you can use the same schematic as on the guide since it uses a voltage regulator, only a "programmable" one, and, it only uses the 12v line of a molex.  Then, just keep the potentiometer close to the circuit (as opposed to be available for user setting outside the case) and then set it's resistance so that the output voltage would go 7v.  Then just keep it at that so when you set your switch, you'll be choosing between 12v, 7v and off.  It is better to keep using a potentiometer than a resistor so you'll have control over the other mode.

[Spork]

Nice job btw. I want to do something like but go another way. I just want my switches to control some fans, lights, and the water pump. As if that that enough I want the computer in off mode to run these when I flip the switches, that in turn will make a red LED light up. Then I turn a key switch which will make the red LED's turn green (if thats not possible have a set of red ones and a set of green ones) or have the red LED's turn off and the green LED's turn on. At that point I would like to be able to press the power button and turn on the computer. The key switch must be turned on and all the switches must be in the on position in order to give power to the power button. If you need to know how much is going into this project it is 8 SPST Military switches, 2 LED for each switch (1 green, 1 red), 4 knobs for the fans, and the key switch.

[Skylined]

I got some noisy 120mm x 38mm fans, and to make them even quiter I had to drop the minimum voltage, so I've changed two resistors.
Now this thing goes from 4V to 10.5V, more or less.

Just change this:
1K2 > 1K
4K7 > 2K2