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Arduino Nano-Based Turbofan Speed Controller with LCD Display and Rotary Encoder

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Circuit Documentation

Summary

This circuit is designed to control a DC motor using an Arduino Nano and an L298N motor driver. The motor speed is controlled via a rotary encoder, and the speed and voltage are displayed on a 16x2 I2C LCD. A 12V power supply is used to power the motor driver and the motor.

Component List

  1. Arduino Nano

    • Description: A small, complete, and breadboard-friendly board based on the ATmega328P.
    • Pins: D1/TX, D0/RX, RESET, GND, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11/MOSI, D12/MISO, VIN, 5V, A7, A6, A5, A4, A3, A2, A1, A0, AREF, 3V3, D13/SCK

  2. L298N DC Motor Driver

    • Description: A dual H-Bridge motor driver that allows speed and direction control of two DC motors.
    • Pins: OUT1, OUT2, 12V, GND, 5V, OUT3, OUT4, 5V-ENA-JMP-I, 5V-ENA-JMP-O, +5V-J1, +5V-J2, ENA, IN1, IN2, IN3, IN4, ENB

  3. DC Motor

    • Description: A 12V DC motor.
    • Pins: pin 1, pin 2

  4. Rotary Encoder with Knob

    • Description: A rotary encoder used to control the motor speed.
    • Pins: no name yet

  5. 12V Power Supply

    • Description: A power supply providing 12V DC.
    • Pins: +, -

  6. 16x2 I2C LCD

    • Description: A 16x2 character LCD with I2C interface.
    • Pins: GND, VCC, SDA, SCL

Wiring Details

Arduino Nano

L298N DC Motor Driver

DC Motor

Rotary Encoder with Knob

12V Power Supply

16x2 I2C LCD

Documented Code

/*
    This program used an L298N motor driver with a 12VDC motor.
    The 20x4 LCD displays motor speed, turbofan speed, and motor voltage.
    An encoder is used to control the motor speed.
    BUTTON INPUTS TO THE ENCODER:
      Press the button to set speed back to zero.
      Hold the button for 2 seconds to set the Maximum Fan speed.
      Hold the button for 5 seconds to reset the Maximum Fan speed to be uncapped.
    Maximum speed set is remembered inside the program even after power down.

    Visit https://www.thingiverse.com/thing:4743929 for the project directory
    Visit https://github.com/nairck/TurbofanDriver for the Github directory

    Written and designed by Adam B Johnson
    in British Columbia, Canada
    V1 - 15 January 2021
    V2 - 19 November 2022
    V3 - 9 August 2024
       - changed moving average window filter for voltage measurement to single pole RC type low-pass filter (simpler/better).
       - bug fix when turning encoder from higher value to zero wouldn't work. Encoder can bounce still, but zeroing now works a lot better.
       - bug fix where maximum pwm input was equal to maximum allowed minus the deadband
       - bug fixs for EEPROM code, setting new value would reset initialization sometimes or not work at all.
       - Serial monitor will now show encoder position and measured voltage at the sample rate for debugging purposes. Does not affect program when not in use.
       - i2c scanner built into program now, screen address not needed - it will be automatically scanned and used every power up. Included Wire library
       - Updated motor voltage equation to match better

*/

//#######################################  Adjust these values if needed #######################################
//#######################################  Adjust these values if needed #######################################
//#######################################  Adjust these values if needed #######################################
#define chB 2                           //***pin B of the rotary encoder (channel B should be pin 2). Can be non-interrupt capable pin, but will have lower performance
#define chA 3                           //***pin A of the rotary encoder (channel A should be pin 3). Can be non-interrupt capable pin, but will have lower performance
#define pushButton 4                    //***Button pin           
#define motorPWM 6                      //***PWM pin to motor controller 
#define motorDir1 9                     //***motor direction forward pin to driver
#define motorDir2 10                    //***motor direction reverse pin to driver 
#define motorRPMperVolt (5000.0 / 12.0)         //***DC motor max RPM (4825) divided by max voltage (12VDC. Measure both paraments and adjust
//#######################################  End of adjustable parameters #######################################
//#######################################  End of adjustable parameters #######################################
//#######################################  End of adjustable parameters #######################################


// Libraries to include 
#include <Encoder.h>                //Might need to download this library. Tools > Manage Libraries > Search for 'Encoder'
#include <LiquidCrystal_I2C.h>      //Might also need to download this one in the same way.
#include <EEPROM.h>                 //This should have been included when you installed Arduino IDE. No download needed
#include <Wire.h>


// &&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&
// &&&&&&&&&&&&&&&&&&&&&&& PROGRAM CONSTANTS &&&&&&&&&&&&&&&&&&&&&&&
// &&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&

LiquidCrystal_I2C lcd(0x00, 20, 4);     // Place holder LCD screen object
Encoder myEncoder(chA, chB);            // Encoder object

const float sampleR = 0.5; // 500ms sample rate

int eeAddress = 0;
int eeAddressForInitialization = 100;
byte initializationConst = 0;
byte pwmMax = 255;
int pwmVal = 0;
bool setFlag = false;

const float gearRatio = 2.27;       //fixed gear ratio
int fanSpeed = 0;                   //speed of the turbofan in RPM
int mtrSpeed = 0;                   //speed of the motor in RPM
int deadBand = 30;                  //minimum PWM signal for the motor to move
float vout = 0.0;                   //Voltage out of the motor
float