Adafruit Industries EMC2101 - I2C PC Fan Controller Temperature Sensor

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.?

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.

Four pin PC fans have a power and ground pin (those are red and black) and then two more pins. One of those extra pins, the PWM pin, allows you to set the speed of the fan. The last TACH pin is for a tachometer output that allows the EMC2101 to monitor the speed of the fan to make sure it's working as expected. Instead of using a PWM output and counter input on your microcontroller, this chip will take care of that all for you, all over every-day I2C.

In addition to allowing you to control a fan, the EMC2101 includes an internal temperature sensor, as well as connections for an external temperature sensing diode. If you use an external temperature sensor, you can even configure a lookup table (LUT) that allows you to set different fan speeds depending on the temperature, and the EMC2101 will automatically adjust the speed depending on the temperature.

You might even be able to use it to help quiet down an existing project or hack a noisy piece of electronics that has a loud fan. By allowing you to run a fan at slower speeds when cooling needs are moderate, the EMC2101 can help ease the vibration noise caused by fans running at full speed.