Color Changing Digital PC Fan Controller

Step 11 Test and Install

Now it's time to see how it works.  Plug the serial port into the PC, plug the power cord into your power supply (make sure you orient it right on both ends, +12V goes on the LEFT looking at the board from the top), plug the fan in (so that the tabs face towards the center of the board) and plug in the fan LED's (so that the ground pin goes on the RIGHT).  Turn on the power.

You'll need your AVR programmer now.  The first thing you want to do is change the frequency of the internal oscillator.  By default, ATMega168's come with the clock/8 internal prescaler enabled.  This causes the chip to run too slow for this application and the LED's will just flash without glowing solid (or at least  appearing to using PWM).  You need to reprogram the fuse bits to turn off the prescaler.

Using AVRdude, this is accomplished by the options:

-U lfuse:w:0xe2:m -U hfuse:w:0xdf:m -U efuse:w:0xf9:m

After applying these, the lights should fade smoothly and serial communication at 19200 baudrate should work using the supplied Windows or Linux GUI program (download at the end of this Instructable).  If so, the board works fine and you can install it.  This depends on your case, so just install the fan as usual and mount the controller board however you can (I used tape, it's basic but it works).  Also remember to insulate the board so it doesn't short out against the case frame.