adafruit learning system EMC2101 Fan Controller and Temperature Sensor Instruction Manual
- June 5, 2024
- adafruit learning system
Table of Contents
- adafruit -learning -system -EMC2101- Fan -Controller -and -Temperature
- Overview
- Pinouts
- Example Code
- Arduino Docs
- Python & CircuitPython
- Python Computer Wiring
- CircuitPython Installation of EMC2101 Library
- Python Installation of EMC2101 Library
- CircuitPython & Python Usage
- Example Code
- Python Docs
- Additional Features
- Look Up Table Support
- LUT Hysteresis
- Forcing a Manual Temperature
- PWM Tuning
- PWM vs DAC Output
- Fan Spinup Drive and Time
- Fan Minimum Speed
- Downloads
- Fab Print
- References
- Read User Manual Online (PDF format)
- Download This Manual (PDF format)
adafruit -learning -system -EMC2101- Fan -Controller -and -Temperature
-Sensor
Overview
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 fan controller with temperature monitoring and it will take care of all of that for you. With 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 often red and black)
and then two more pins. One of those extra pins, the PWM pin, allows you to
set a 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
everyday 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 look-up 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 quiet (https://adafru.it/Fpw) compatible STEMMA QT (https://adafru.it/Ft4) connectors for the I2C bus allow you to make easy solderless connections to your controlling device, and the standard headers make breadboard prototyping easy. Our libraries, wiring diagrams, and example code for Arduino, CircuitPython, and Python complete the package. How fantastic!
Pinouts
Power Pins
- VIN – this is the power pin. Since the sensor chip uses 3 VDC, we have included a voltage regulator on board that will take 3-5VDC and safely convert it down. To power the board, give it the same power as the logic level of your microcontroller – e.g. for a 5V microcontroller like Arduino, use 5V
- 3Vo – this is the 3.3V output from the voltage regulator, you can grab up to 100mA from this if you like
- GND – common ground for power and logic
I2C Logic Pins
- SCL – I2C clock pin, connect to your microcontroller I2C clock line. This pin is level shifted so you can use 3-5V logic, and there’s a 10K pullup on this pin.
- SDA – I2C data pin, connect to your microcontroller I2C data line. This pin is level shifted so you can use 3-5V logic, and there’s a 10K pullup on this pin.
- STEMMA QT (https://adafru.it/Ft4) – These connectors allow you to connect to dev boards with STEMMA QT or Qwiic connectors or to other things with various associated accessories (https://adafru.it/Ft6)
Other Pins
- TACH -Tachometer input for 4-pin fans or alert/interrupt pin
- ALERT – This is the same pin as TACH, it can also be used for interrupts
- FAN -The fan control output pin for 3 or 4 pin fans. Defaults to PWM output but can be configured to use a DAC to output a DC voltage
- DN – External temperature diode negative pin
- DP – External temperature diode positive pin
Jumpers
- FAN – Cut this jumper to disable the built-in pullup on the Fan pin when using the DAC/DC voltage output
- TACH – Cut this jumper to disable the pull-up on the Tach pin when using the Tach pin for alerts
Either jumper can be bridged with solder later to re-enable the pullup after cutting the jumper
Arduino
Using the EMC2101 with Arduino is a simple matter of wiring up the sensor to
your Arduino-compatible microcontroller, and installing the Adafruit EMC2101
(https://adafru.it/PeJ) library we’ve written, and running the provided
example code.
I2C Wiring
Use this wiring if you want to connect via the I2C interface. The I2C address
for the EMC2101 is 0x4C. Here is how to wire the sensor to a board using a
breadboard, using an NPN transistor as a makeshift temperature diode. The
examples show a Metro but the wiring will work the same for an Arduino or
other compatible board. Carefully check the fan connections. Accidentally
wiring the Fan V+ to the EMC2101 or Metro can permanently damage the
boards
- Connect board VIN (red wire) to Arduino 5V if you are running a 5V board Arduino (Uno, etc.). If your board is 3V, connect to that instead.
- Connect board GND (black wire) to Arduino GND
- Connect board SCL (yellow wire) to Arduino SCL
- Connect board SDA (blue wire) to Arduino SDA
- Connect board DP (orange wire) to Transistor Base
- Connect board DN (gray wire) to Transistor Emitter
- Connect transistor Collector (orange wire) to Transistor Base
- Connect board FAN to fan PWM input
- Connect board TACH to fan Tach output
- Connect DC jack positive pin to Fan V+ input
- Connect DC jack GND to Fan V-/GND input
- Connect DC jack GND to Arduino GND
Library Installation
You can install the Adafruit EMC2101 library for Arduino using the Library
Manager in the Arduino IDE.
Load Example
Open up File -> Examples -> Adafruit EMC2101 -> adafruit_emc2101_tes
After opening the demo file, upload to your Arduino wired up to the EMC2101. Once you upload the code, you will see the Internal and External Temperature, Fan speed and PWM duty cycle values being printed when you open the Serial Monitor (Tools->Serial Monitor) at 115200 baud, similar to this:
Example Code
Arduino Docs
Arduino Docs (https://adafru.it/OeX)
Python & CircuitPython
It’s easy to use the EMC2101 with Python or CircuitPython, and the Adafruit CircuitPython EMC2101 (https://adafru.it/PeK) module. This module allows you to easily write Python code that reads temperature and fan speed from the EMC2101 sensor, as well as setting the fan speed. You can use this sensor with any CircuitPython microcontroller board or with a computer that has GPIO and Python thanks to Adafruit_Blinka, our CircuitPython-for-Python compatibility library (https://adafru.it/BSN). We will show how to wire up the EMC2101 to a microcontroller and fan, along with a NPN Bipolar Junction Transistor (BJT) as a makeshift temperature diode. Carefully check the fan connections! Accidentally connecting Fan V+ to the EMC or Feather may damage the boards
CircuitPython Microcontroller Wiring
First wire up an EMC2101 to your board exactly as shown below. Here’s an
example of wiring a Feather M4 to the sensor with I2C using standard 0.100″
pitch headers to wire it up on a breadboard:
- Connect board VIN (red wire) to Feather 3V
- Connect board GND (black wire) to Feather GND
- Connect board SCL (yellow wire) to Feather SCL
- Connect board SDA (blue wire) to Feather SDA
- Connect board DP (orange wire) to Transistor Base Connect board DN (gray wire) to Transistor Emitter
- Connect transistor
- Collector (orange wire) to Transistor Base Connect board
- FAN (blue wire) to fan PWM input
- Connect board TACH (green wire) to fan Tach output
- Connect DC jack positive pin to Fan V+ input
- Connect DC jack GND to Fan V-/GND input
- Connect DC jack GND to Feather GND
Python Computer Wiring
Since there’s dozens of Linux computers/boards you can use, we will show the
wiring for Raspberry Pi. For other platforms, please visit the guide for
CircuitPython on Linux to see whether your platform is supported
(https://adafru.it/BSN).
Here is an example of how to wire up a Raspberry Pi to the EMC2101 and fan,
along with an NPN Bipolar Junction Transistor (BJT) as a makeshift temperature
diode.
- Connect board VIN (red wire) to RPi 3V
- Connect board GND (black wire) to RPi GND
- Connect board SCL (yellow wire) to RPi SCL
- Connect board SDA (blue wire) to RPi SDA
- Connect board DP (orange wire) to Transistor Base Connect board DN (gray wire) to Transistor Emitter Connect transistor Collector (orange wire) to Transistor Base Connect board FAN (blue wire) to fan PWM input
- Connect board TACH (green wire) to fan Tach output Connect DC jack positive pin to Fan V+ input
- Connect DC jack GND to Fan V-/GND input
- Connect DC jack GND to RPi GND
CircuitPython Installation of EMC2101 Library
You’ll need to install the Adafruit CircuitPython EMC2101 (https://adafru.it/PeK) library on your CircuitPython board. First make sure you are running the latest version of Adafruit CircuitPython (https://adafru.it/Amd) for your board. Next you’ll need to install the necessary libraries to use the hardware–carefully follow the steps to find and install these libraries from Adafruit’s CircuitPython library bundle (https://adafru.it/ENC). Our CircuitPython starter guide has a great page on how to install the library bundle (https://adafru.it/ABU). Before continuing make sure your board’s lib folder or root filesystem has the adafruit_EMC2101.mpy file as well as the adafruit_register and adafruit_bus_device folders. Next connect to the board’s serial REPL (https://adafru.it/Awz)so you are at the CircuitPython >>> prompt.
Python Installation of EMC2101 Library
You’ll need to install the Adafruit_Blinka library that provides CircuitPython support in Python. This may also require enabling I2C on your platform and verifying you are running Python 3. Since each platform is a little different, and Linux changes often, please visit the CircuitPython on Linux guide to get your computer ready (https://adafru.it/BSN)! Once that’s done, from your command line run the following command:
- sudo pip3 install adafruit-circuitpython-emc2101
If your default Python is version 3 you may need to run ‘pip’ instead. Just make sure you aren’t trying to use CircuitPython on Python 2.x, it isn’t supported!
CircuitPython & Python Usage
These examples assume the use of a standard 4-pin computer fan. 3-pin fans can
be used as well, but won’t be able to read the RPM of the fan due to the lack
of a Tach output from the fan. To demonstrate the usage of the sensor we’ll
initialize it to set and read the fan speed and read the external and internal
temperatures from the board’s Python REPL.
Run the following code to import the necessary modules and initialize the I2C
connection with the sensor:
- internal_temperature – The temperature of the EMC2101 itself, a value in degrees Celsius.
- external_temperature – The temperature measured by the external sensor, a value in degrees Celsius.
- manual_fan_speed – The speed of the fan when not controlled by the LUT
- fan_speed – The speed of the fan in Revolutions Per Minute (RPM)
Example Code
Python Docs
Python Docs (https://adafru.it/Of4)
Additional Features
Measurement Frequency
Depending on your application, you may not need to measure the temperature
continuously if for example it doesn’t change quickly. You can specify the
EMC2101’s temperature conversion/measurement rate which will affect the power
usage of the EMC2101; more frequent measurements will use more power.
- Python – Documentation (https://adafru.it/PfM)
- Arduino – Documentation (https://adafru.it/PfN)
- Arduino – Example (https://adafru.it/PfO)
Internal and External Temperature
The EMC2101 supports measuring both the temperature of the EMC2101 itself as
the internal temperature, as well as the temperature of an externally
connected “diode”.
I’ve put a diode in quotes above because we’ve only been able to successfully measure external temperature using an NPN BJT transistor with the collector and base tied together which acts like a diode. PNP BJTs should also work with the base and emitter connected. The diagram from the datasheet above shows how connecting the pins of a BJT lets it act as a diode.
- Python – Documentation (https://adafru.it/PfM)
- Python – Example Code (https://adafru.it/PfP)
- Arduino – Documentation (https://adafru.it/PfN)
- Arduino – Example (https://adafru.it/PfO)
Note: The DAC output is not meant to directly drive a Fan! The output current is limited to 1mA, well below what any fan will need. Instead, the DAC output should be used as an input signal to other control circuitry.
- Python – Documentation (https://adafru.it/PfM)
- Arduino – Documentation (https://adafru.it/PfN)
Look Up Table Support
As an alternative to adjusting the speed directly with your code, the EMC2101 allows you to set up a Look Up Table (LUT) that specifies how fast the fan should spin for a given temperature. One important note is that the LUT only works automatically based on the external temperature.
- Python – LUT Documentation (https://adafru.it/PfM)
- Python – LUT Example (https://adafru.it/PfP)
- Arduino – Documentation (https://adafru.it/PfN)
- Arduino – LUT Example (https://adafru.it/PfQ)
LUT Hysteresis
If the current temperature is very close to a LUT temperature, the fan may
“thrash” by changing the fan speed excessively as the temperature fluctuates
between above and below the LUT temperature.
To prevent thrashing, the EMC2101 applies a hysteresis value to the measured
temperature which is an additional number of degrees below the LUT temperature
that the measurement must be before switching to the lower LUT entry.
- Python – Documentation (https://adafru.it/PfM)
- Arduino – Documentation (https://adafru.it/PfN)
- Arduino – LUT Example (https://adafru.it/PfQ)
Forcing a Manual Temperature
For testing the LUT, the EMC2101 allows you to set a temperature that the LUT will use instead of the external temperature. Each time you set a forced/manual temperature, the EMC2101 will consult the LUT to find the corresponding fan speed. The keen-eyed may notice that you can use this to hack LUT support for other values than the external temperature sensor by regularly updating the forced temperature based on another measurement.
- Python – Documentation (https://adafru.it/PfM)
- Python – LUT Example (https://adafru.it/PfP)
- Arduino – Documentation (https://adafru.it/PfN)
Arduino – LUT Example (https://adafru.it/PfQ)
PWM Tuning
It can sometimes be necessary to adjust the PWM frequency to suit your application or prevent a motor from making audible noise. These features allow you to specify the base PWM clock, divisor and frequency.
- Python – Documentation (https://adafru.it/PfM)
- Python – PWM Example
- Arduino – Documentation (https://adafru.it/PfN)
- Arduino – Example (https://adafru.it/PfO)
PWM vs DAC Output
By default the EMC2101 sets the speed of the fan by outputting a PWM signal compatible with 4 and 3-pin fans. A transistor in the fan uses this signal to change the amount of its operating voltage. The EMC2101 can alternatively be configured to output a steady DC voltage instead of a pulsed signal, should your application require it. The voltage range is from 0 to approximately 3.24V with the same 6-bit resolution as the PWM output.
Fan Spinup Drive and Time
The EMC2101 allows you to specify how the fan should be started from a stop by specifying a spinup speed and time. Sometimes fans have to build up momentum before slowing down to a lower speed, and these settings help with that. Fortunately the default settings are good enough for most cases.
- Python – Documentation (https://adafru.it/PfM)
- Arduino – Documentation (https://adafru.it/PfN)
Fan Minimum Speed
This setting allows you to specify the minimum speed of your fan. 4-pin fans will often still report a small speed on their tach output when stopped, and this setting allows you to say “anything below this speed is off” so you don’t think the fan is still on when it is not.
- Python – Documentation (https://adafru.it/PfM)
- Arduino – Documentation (https://adafru.it/PfN)
- Arduino – Fan Tuning Example (https://adafru.it/PfR)
Downloads
Files
- EMC2101 Datasheet (https://adafru.it/PeL)
- EagleCAD files on GitHub (https://adafru.it/PeM)
- Fritzing object in the Adafruit Fritzing Library (https://adafru.it/PeN)
Schematic
Fab Print
References
- Adafruit EMC2101 Library: Adafruit EMC2101 Temperature monitor and fan controller
- CircuitPython Libraries | Welcome to CircuitPython! | Adafruit Learning System
- Installing CircuitPython | Welcome to CircuitPython! | Adafruit Learning System
- The REPL | Welcome to CircuitPython! | Adafruit Learning System
- Overview | CircuitPython Libraries on Linux and Raspberry Pi | Adafruit Learning System
- Libraries
- Qwiic Connect System - SparkFun Electronics
- What is STEMMA? | Adafruit STEMMA & STEMMA QT | Adafruit Learning System
- Adafruit Industries, Unique & fun DIY electronics and kits
- Adafruit EMC2101 Library: Adafruit EMC2101 Temperature monitor and fan controller
- Introduction — Adafruit EMC2101 Library 1.0 documentation
- GitHub - adafruit/Adafruit_EMC2101
- GitHub - adafruit/Adafruit_CircuitPython_EMC2101: CircuitPython driver for EMC2101 brushless fan controller
- adafru.it/PeL
- GitHub - adafruit/Adafruit-EMC2101-PCB
- Fritzing-Library/Adafruit EMC2101.fzpz at master · adafruit/Fritzing-Library · GitHub
- adafruit_emc2101 — Adafruit EMC2101 Library 1.0 documentation
- Adafruit EMC2101 Library: Adafruit_EMC2101 Class Reference
- Adafruit_EMC2101/adafruit_emc2101_test.ino at master · adafruit/Adafruit_EMC2101 · GitHub
- Simple test — Adafruit EMC2101 Library 1.0 documentation
- Adafruit_EMC2101/lut_test.ino at master · adafruit/Adafruit_EMC2101 · GitHub
- Adafruit_EMC2101/fan_tuning.ino at master · adafruit/Adafruit_EMC2101 · GitHub
- Adafruit EMC2101 Library: Adafruit_EMC2101 Class Reference
- Adafruit EMC2101 Library: Adafruit_EMC2101 Class Reference
- Adafruit EMC2101 Library: Adafruit_EMC2101 Class Reference
- Adafruit EMC2101 Library: Adafruit_EMC2101 Class Reference
- Adafruit EMC2101 Library: Adafruit_EMC2101 Class Reference
- Adafruit EMC2101 Library: Adafruit_EMC2101 Class Reference
- Adafruit EMC2101 Library: Adafruit_EMC2101 Class Reference
- Adafruit EMC2101 Library: Adafruit_EMC2101 Class Reference
- Adafruit EMC2101 Library: Adafruit_EMC2101 Class Reference
- Libraries
- Introduction — Adafruit EMC2101 Library 1.0 documentation
- adafruit_emc2101 — Adafruit EMC2101 Library 1.0 documentation
- adafruit_emc2101 — Adafruit EMC2101 Library 1.0 documentation
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