🔄 DC Motor Speed Controller

Control a DC motor from dead-stop to full speed using a potentiometer and PWM — the foundation of all motor drives.

📋 Overview

DC motors are everywhere — in fans, wheels, pumps, and drills. This project teaches you to control their speed using Pulse Width Modulation (PWM) and an L298N motor driver to safely handle higher currents.

Technical Insight: The L298N dual H-bridge driver accepts PWM signals from Arduino and controls motor voltage using power transistors rated at 2A peak. By varying the duty cycle of the PWM from 0% (stopped) to 100% (full speed), the average voltage to the motor changes proportionally, allowing smooth, continuous speed control.

In simple terms: The potentiometer knob is your 'throttle.' The Arduino reads it (0–1023), scales it to a PWM value (0–255), and sends that to the L298N, which drives the motor at exactly that speed fraction.

What you'll learn: L298N motor driver wiring, analogRead() + analogWrite(), motor speed-to-PWM mapping, direction control with H-bridge logic, and flyback protection.

Estimated time: 40-55 minutes. Difficulty: ⭐⭐ Easy.

🧩 Components Needed

Component	Specification	Qty	Notes
Arduino Uno R3	5V	1
L298N Motor Driver	2A, 5–35V	1	Dual H-Bridge module
DC Motor	6–12V, any small DC motor	1	Hobby motor, fan, or pump
Potentiometer	10kΩ Linear	1	Speed control knob
Power Supply	9V battery or 12V adapter	1	For L298N motor supply
Breadboard + Wires	Full-size	1

🗺️ Component Pin Mapping

📖 Step-by-Step Tutorial

Wire the L298N

L298N: ENA → Arduino pin 9 (PWM), IN1 → pin 7, IN2 → pin 8. Motor terminals to OUT1 and OUT2. Connect 12V supply to VS and GND to GND (share GND with Arduino).

Wire the Potentiometer

Left pin → 5V, Right pin → GND, Center (wiper) → Arduino pin A0.

Set Direction

IN1=HIGH, IN2=LOW for one direction. Reverse to go the other way. Upload and test.

Adjust Speed

Turn the potentiometer knob. Watch the motor go from full stop to maximum speed smoothly.

Add Reverse

Optional: add a push button to toggle IN1/IN2 logic and instantly reverse direction.

💡

Never connect the motor directly to Arduino pins — they can only supply 40mA, far less than even a small motor needs. The L298N acts as a power amplifier, taking tiny PWM signals and driving motors with full battery power.

💻 Arduino Code

dc_motor_speed_control.ino

INO

// DC Motor Speed Controller — Volt X
// Potentiometer on A0 controls speed via L298N ENA pin

const int ENA = 9;  // PWM speed control (must be ~ pin)
const int IN1 = 7;  // Direction pin 1
const int IN2 = 8;  // Direction pin 2
const int POT = A0; // Potentiometer

void setup() {
  pinMode(ENA, OUTPUT);
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  // Set forward direction
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  Serial.begin(9600);
}

void loop() {
  int potVal = analogRead(POT);            // Read 0-1023
  int speed  = map(potVal, 0, 1023, 0, 255); // Scale to 0-255
  analogWrite(ENA, speed);                 // Set motor speed
  
  Serial.print("Pot: "); Serial.print(potVal);
  Serial.print("  Speed PWM: "); Serial.println(speed);

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