I noticed that the media furniture where I have most of my media related devices (bluray-player,gaming consoles, etc.) was getting very warm whenever I was using one of these.I felt the urge to "geek-out" on this to make a something that is both fun and at the same time practical.
The system is divided in 2 sub-circuits; 5V and 12V.
I am using a 5V relay that is connected to the Raspberry Pi to control the higher voltage system where the fan is connected.
The Raspberry Pi reads its data from a temperature sensor that is placed inside the media furniture. This sensor is pulled for new data at a constant interval and will activate the high voltage circuit when the temperature becomes too hot.