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.

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.

This neat little chip can easily be used to help provide cooling or ventilation to your next project. 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.

Delivered to you on our custom Stemma QT form factor PCB, the Adafruit EMC2101 breakout is ready to help you integrate a fan into your project by making it easy to use with a range of devices. A voltage regulator and 5V tolerant pins allow you to use it with 3.3V or 5V microcontrollers or single-board computers. The included SparkFun qwiic compatible STEMMA QT connectors for the I2C bus allow you to make easy solderless connections to your controlling device, and the standard headers make breadboard prototyping easy. QT Cable is not included, but we have a variety in the shop.

Our libraries, wiring diagrams, and example code for Arduino, CircuitPython, and Python complete the package. How fan-tastic!