Fan Controller

This is a 5V PWM fan controller built around an ESP32 microcontroller.

Features:

• Integrable with Home Assistant.
• Fan speed control.
• Fan RPM sensor.
• Temperature sensors.
• Supports connecting other I2C devices, like a screen to display the controller information or additional sensors.
• Physical button to toggle the fan.

Future features:

• Physical buttons to adjust the fan speed.
• Alarm LED.

It also exposes 8 additional GPIO pins for future extensibility.

Build your own

• Download the Gerber file and order the PCB to the manufacturer of your choice. ⚠️ Currently (5 April 2023) I'm waiting for the PCB to arrive. Until I've tested it I cannot confirm the Gerber file doesn't have any problem.
• Download the BOM file and order the components.
• Assemble the board.
• Install the latest firmware. Visit the last release page to see what's changed.
  • Using the web installer.
  • Download the latest firmware and upload it to the ESP32 with ESP Tool.
• Integrate in Home Assistant.
• Aditionally: add the device to the ESPHome dashboard.

Modify the design

The schematics and the PCB design are available in the hardware directory:

• Schematics
  
• PCB design
  

I used EasyEDA, which is a free of charge tool, for their design.

The ESPHome YAML file to build the firmware can be found in the firmware directory. It has been tested with ESPHome v2023.3.2.

A bit of history

This is a hobby project aimed to build a device able to control a small fan which can easily be integrated with Home Assistant.

I build it because I wanted to hide my NAS inside a cabinet and some kind of ventilation was required to avoid overheating. I also wanted to be able to monitor temperature inside the cabinet and to change the speed of the fan. I hate noise and I also have a very fine earing: for me a 2000 RPM fan is too noisy at night. And I wanted to do it from my phone or from an automation in Home Assistant.

So, the initial design requirements were:

• The fan speed MUST be adjustable.
• It MUST have a temperature sensor.
• It MUST be integrable with Home Assistant.
• It MIGHT have a display to show the speed and the temperature.
• It MIGHT have physical buttons.
• It SHOULD work with an old phone charger as the power supply (I have lots I want to give them some use).

It was clear that the project would require a microcontroller and I preferred to use wifi for communications so an ESP32 (successor of the ESP8266) was a natural choice.

While investigating the easyest way to integrate an ESP32 in Home Assitant I found ESPHome, also from Nabu Casa. Using ESPHome to build the controller firmware also meant that less coding would be required.

As the fan I decided to use a Noctua NF-A12x25 5V PWM because it was quiet, its speed could be controlled with a PWM signal and it could also be powered by the same 5V power supply I was planning to use to power the microcontroller.

The last piece missing was a way to generate the PWM signal. I knew the ESP32 could generate it but while looking for different solutions I found the Adafruit EMC2101 which also included the required temperature sensor. The Adafruit EMC2101 is an I2C fan controller and temperature sensor to which the ESP32 can off-load the PWM signal generation and a tachometer as a bonus. But it was not supported by ESPHome 😞. At this point I needed to decide between:

• Develop all the firmware code from scratch.
• Add support for the Adafruit EMC2101 to ESPHome.

I decided that the latter was much less work, I could contribute to a wonderful project and some other people could benefit of my work. Also I found this feature request to add support for the Adafruit EMC2101 to ESPHome.

Because the Adafruit EMC2101 worked at 5V and the ESP32 at 3.3V, a 2-bit bidirectional voltage-level shifter fast enough for the I2C bus would be required and I decided to use a module with a Texas Instruments TXS0102.

I assembled all the components in a breadboard and started coding an ESPHome external component to add support for the Adafruit EMC2101. When I got it all working, the breadboard was replaced by a perfboard and the whole contraption was mounted on the cabinet.

With the external component working fine for a few months, on May 29, 2022 I created a draft pull request. But life is unpredictable and I needed to pause the whole project: I could not even send the PR for review. On 24 Feb 2023 the github-actions bot closed it, and, just a couple days later I was able to work again on the project and created a new pull request.

I also designed a PCB to replace the perfboard and decided to publish the PCB schematics, PCB design, BOM and firmware as Open Source Hardware in this repository. You can find them in the hardware and firmware directories.

All the files are released under a Creative Commons Attribution ShareAlike 4.0 license.

It've been a very fun project 😆.