Thermal Fan Controller

A 4-channel PWM fan controller based on Arduino Nano, designed for active thermal management with reduced noise levels and electrical consumption in mind. Built for the Institut Jožef Stefan (Ljubljana, 2026), as part of a University of Ljubljana, Faculty of Electrical Engineering (UL FE) internship project.

Features

• Controls up to 4 PWM fans across 2 independent channels
• Support for 1 or 2 DS18B20 temperature sensors
• Linear duty cycle curve between two temperature limits
• RPM monitoring via tacho signal for each fan
• Alarm output on high temperature or low fan RPM
• 16x2 I2C LCD display with real-time status
• Serial monitor output for debugging and sensor setup
• Watchdog timer for automatic recovery from lockups
• Fully configurable via #define parameters at the top of the Arduino sketch

Hardware

• Arduino Nano
• Up to 2x Dallas DS18B20 temperature sensors (1-Wire interface)
• Up to 4x 4-wire DC fans
• 16x2 LCD with I2C backpack
• Custom PCB (included in repository)
• Traco Power TEN 4-2411 DC/DC converter (24V → 5V)
• Reed relay for alarm output

Repository Structure

This repository contains two versions of the project:

• prototype/ — initial prototype version
• v1.0/ — first full version with custom PCB, includes all files listed below

/
├── prototype/
├── v1.0/
│   ├── firmware/          # Arduino sketch (.ino)
│   ├── libraries/         # All included libraries (source files)
│   │   ├── lib_I2CLCD/    # Modified I2C LCD library
│   │   ├── DallasTemperature/
│   │   └── OneWire/
│   ├── pcb/               # PCB design files
│   ├── case/              # 3D model files (.step)
│   └── photos/            # Photos of assembled board
└── README.md

Wiring / Pin Assignment

Function	Arduino Pin
Temperature bus	D2
PWM channel 1	D9
PWM channel 2	D10
Alarm output	D3
Fan 1 tacho	D4
Fan 2 tacho	D5
Fan 3 tacho	D6
Fan 4 tacho	D7
LCD	I2C (A4/A5)

Configuration

All user parameters are at the top of the sketch under USER SET PARAMETERS:

Parameter	Description
SERIAL_FREQ	Serial baud rate, set to 0 to disable
NUM_SENSORS	Number of connected temperature sensors (1 or 2)
FAN_MASK	Bitmask of occupied fan slots, e.g. 0b0111 for fans 1–3
PWM_FREQ	PWM frequency in Hz (typically 25000 for PC fans)
UPDATE_FREQ	Measurement interval in ms (minimum 800ms)
UPPER_LIM	Temperature at which fans run at 100%
LOWER_LIM	Temperature at which fans run at minimum duty
MIN_DUTY	Minimum duty cycle (0.0 to 1.0)
ALARM_TEMP	Temperature threshold for alarm
PULSE_COUNT	Tacho pulses per revolution (typically 2)
MIN_RPM	Minimum RPM before alarm triggers (0 to disable)

Fan Mask

FAN_MASK is a 4-bit mask where each bit represents a fan slot:

0b(fan4)(fan3)(fan2)(fan1)

Example: 0b0111 means fans connected in slots 1, 2 and 3, while slot 4 is empty.

Adding a New Temperature Sensor

1. Connect the sensor and open the serial monitor
2. At startup, the sketch prints the address of all detected sensors
3. Copy the address into sensor1 or sensor2 in the sketch

A separate Address_reader sketch is also included for convenience.

LCD Display

• Spinning icon in top-left indicates the system is running
• Temperature shown in °C, No Con. if sensor can't be found (check if address is correct in sketch)
• Duty cycle shown as percentage or MAX
• Fan icons blink when RPM is below MIN_RPM
• ! next to temperature when alarm threshold is exceeded

Alarm Output

Pin D3 outputs LOW when any of the following occur:

• Any monitored fan RPM drops below MIN_RPM
• Any sensor reads above ALARM_TEMP
• Any sensor is disconnected

Dependencies

All required libraries are included in the v1.0/libraries directory and can be installed manually into the Arduino libraries folder. Original sources:

• DallasTemperature
• OneWire
• lib_I2CLCD — modified version of Arduino-I2C-RW1063-0B-002 by JeffVi

Photos

Photos of the assembled board are in the v1.0/photos directory.

License

No license specified. All rights reserved unless stated otherwise.
Contact the author for usage permissions.