THE HEATSINK GUIDE: Info about connectors
The power supply plug contains a +12V
wire (yellow), two ground wires (black), and one +5V wire. Since most fans
run with 12V, you will have to connect the red fan wire to the yellow PS
wire, and the black fan wire to the black PS wire; if you have a 5V fan,
connect red to red and black to black. See the image below for an illustration.
How to get 7V voltage without any additional electronic components...
If you have a 12V fan, and you find it too loud, the best solution is to build yourself a temperature control for it.
However, if you'd just like to reduce noise without adding a temperature control, there's
a simply trick how you can achive this.
The problem is that normally, you only
have the choice between two voltages: 12V and 5V, and most 12V fans will
not run at all if they're powered with only 5V. What many people don't
know is that you can get 7V from your power supply plug, without using
any resistors or other components. Almost all 12V fans will run very well
You can simply use the voltage difference
between the +12V and +5V lines to power your fan with 7V: Connect the fan's
+ wire (usually red) to the power supply's +12V wire (yellow), and the
fan's - wire (usually black) to the power supply's +5V wire (red).
Note: unlike some other electrical motors,
you cannot reverse the rotation direction of fans by reversing the polarity.
If the polarity is incorrect, the fan motor will not work at all, or might
even be damaged.
A word about the MOLEX (three-pin motherboard)
molex connector has three wires: + (usually 12V, usually red), GND (usually
black), and SIGNAL (usually yellow or white, but there are no clear standards).
Unless you are a board designer, only the + and GND wires are of interest
to you. (For the curious: The SIGNAL switches between NC and GND twice
per rotation, resulting in a square perioducal signal if you connect a
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