Cooling fans...They're everywhere, and they serve the important purpose of keeping things cool, generally electronics. One might rightfully think: "these fans are pretty good at moving air to keep things cool; maybe I can use one of these neat computer fans to keep my widget frosty" followed closely by throwing up one's hands in confusion at the sight of a 3 or even 4-pin connector. OK, power takes two pins but what are these other pins for and how do I use them to convince this fan to keep my things chilly?The EMC2101 from Microchip/SMSC is a fan controller with temperature monitoring, and it will take care of all of that for you. Programmable PWM output and tachometer input, with both internal and external temperature sensing, with a 1°C accuracy, it's a perfect friend for any 3 or 4-pin PC fan you may find.