Heat operated fan controller.

First off, I would like to say,that I am not sure if this is in the right section, let alone the right forum. If it's not, please let me know and I will move kit to the appropriate location.

Now that is out of the way, I will state my situation.

A few months ago, I made a custom exhaust heat system for my home computer. It has quite a few fans in it. But, I only have full on or full off with this... Yes, I know I could use a potentiometer to control it manually, but I want this to be automatic.

I should mention that I have a gaming Laptop, and the way my setup is, It exhausts into a small desk/shelf area and the heat used to build up in the area. That's why I built the exhaust system to help
remove the heat from back there. It worked, and still works to this day. But the exhaust system is quite loud. (I will make a video and post to youtube and link it here when it is done.) And I don't need it to be on full except when I'm gaming, however, I sometimes need it running at a low speed, like when I'm video editing, There are some games that only need it to run a low-medium speed, such as Minecraft...Anyways, I think you get the point by now... I want to make this automatic. (It's fine if I still have to do some things with it, but, you hopefully get the point.

There are two way I want to do this.

Method one (This is what I really want to do):

I want to modify an open source hardware monitoring software to output the averaged temperature of the CPU and GPU directly to a serial (USB) port with an arduino on the output. The Arduino will then interpret the input into a preset amount of voltage fed to the fans...now here's the problem, the fans operate at 12 volts, while the arduino operates at 5/3.3 Volts.. I'm not worried about the voltage input, as it will be computer powered, but I'm worried about how I will boost the output voltage.

Method #2 (This is probably the easier option):
I mount a thermistor either directly to the heatsink of the CPU and GPU, and the arduino will average the two and convert it into a voltage output,or I have the thermistors sitting just outside of the heat outputs and it (my GPU and CPU are on separate outputs and heatsinks, however, they are cooled by a single fan.)

If I need to add any information, or I left something out, please let me know.

I basically want to know if this is possible, and then how hard will it be?

Thanks for your help and assistance.

Have you looked at :SpeedFan - Access temperature sensor in your computer.

Paul

if noise is the concern i would use liquid cooling