Overview
Adafruit EMC2101 I2C PC Fan Controller and Temperature Sensor makes it much easier to add smart cooling to your project without tying up PWM and counter resources on your microcontroller. The EMC2101 handles fan control and tachometer monitoring over I2C, making it a practical choice for embedded systems, enclosures, SBC projects, and custom electronics that need active cooling.
This breakout supports 3-pin and 4-pin PC fans, with a programmable PWM output for fan speed control and a tach input for monitoring fan RPM. It also includes both an internal temperature sensor and connections for an external temperature sensing diode, allowing temperature-aware fan control with up to 1°C accuracy on the external channel.
Built on Adafruit's STEMMA QT form factor, the board includes qwiic-compatible STEMMA QT connectors for fast solderless I2C hookup, plus standard headers for breadboard prototyping. An onboard regulator and 5V-tolerant pins make it compatible with both 3.3V and 5V microcontrollers or single-board computers. Note: fan power is routed separately, and a QT cable is not included.
Specification
Technical details for Adafruit EMC2101 I2C PC Fan Controller and Temperature Sensor.
| Specification | Details |
|---|---|
| Interface | I2C / SMBus-compatible fan controller with temperature monitoring |
| Fan control | Programmable PWM output with tachometer input |
| Temperature sensing | Internal sensor plus external temperature diode connection |
| Accuracy | External temperature channel accuracy up to 1°C |
| Fan support | Suitable for 3-pin or 4-pin PC fans |
| Logic compatibility | Works with 3.3V or 5V microcontrollers and SBCs |
| Board features | STEMMA QT / qwiic-compatible connectors, standard header footprint, onboard voltage regulator, 5V-tolerant pins |
| Software support | Libraries, wiring guides, and example code available for Arduino, CircuitPython, and Python |
| In the box | Breakout board only; QT cable not included |
Pinout
| Pin | Type | Description |
|---|---|---|
| VIN | Power input | 3V to 5V input for the onboard regulator; power this to match your controller logic level |
| 3Vo | Power output | 3.3V output from the onboard regulator, available for light auxiliary use |
| GND | Power | Common ground for logic and power |
| SCL | I2C | I2C clock line for communication with your microcontroller or SBC |
| SDA | I2C | I2C data line for communication with your microcontroller or SBC |
| FAN | Output | Fan control output for 3-pin or 4-pin fans; defaults to PWM output |
| TACH | Input | Tachometer input used to monitor fan speed; shared with alert function via board jumper configuration |
| DP / DN | Sensor input | Connections for an external temperature sensing diode |
Applications
Use the EMC2101 to build automatic cooling systems, quieter fan profiles, or temperature-based ventilation control in custom electronics. When used with an external temperature sensor, the chip can apply a configurable lookup table to automatically change fan speed as temperature rises.
Important: do not route the fan's supply voltage through the breakout logic pins. Fan power must be wired separately as shown in the supplier guide.
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