Introduction

A DC Motor Speed Controller is an electronic system used to control the speed of a DC motor according to user requirements. Speed control is an essential feature in many industrial, domestic, and robotic applications where precise motion control is required.

This project demonstrates how the speed of a DC motor can be varied using electronic techniques such as voltage control and Pulse Width Modulation (PWM).

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Objective of the Project

The main objectives of this project are:

• To control the speed of a DC motor smoothly.
• To understand PWM (Pulse Width Modulation) technique.
• To design an efficient motor control circuit.
• To reduce power loss compared to traditional methods.

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Working Principle

There are two main methods to control DC motor speed:

1. Analog Method (Using Potentiometer)

• The voltage supplied to the motor is varied using a potentiometer.
• Higher voltage → higher motor speed.
• Lower voltage → lower motor speed.

2. Digital Method (Using PWM – Arduino)

• PWM controls motor speed by rapidly switching the motor ON and OFF.
• The average voltage applied to the motor depends on the duty cycle.
• Higher duty cycle → faster motor speed.
• Lower duty cycle → slower motor speed.

PWM is more efficient and widely used in modern motor controllers.

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Components Required

Basic DC Motor Speed Controller

• DC Motor
• Potentiometer (10kΩ)
• Transistor (TIP122 / BC547) or MOSFET
• Diode (1N4007 – flyback protection)
• Resistors
• Power Supply (9V–12V)
• Breadboard & wires

Arduino-Based DC Motor Speed Controller

• Arduino Uno
• DC Motor
• Motor Driver (L298N / L293D) or MOSFET
• Potentiometer (10kΩ)
• Jumper wires

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Circuit Diagram

Basic Circuit (Without Arduino)

 +Vcc ---- Motor ---- Collector (Transistor)
                    Emitter ---- GND

Potentiometer ---- Base (via resistor)
Diode across motor (Reverse biased)

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Arduino-Based Circuit

Potentiometer ---- A0
Motor Driver ENA - Arduino PWM Pin (9)
Motor Driver IN1/IN2 - Direction Control
Motor ------------ Motor Driver Output

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Arduino Code for DC Motor Speed Controller

int potPin = A0;
int motorPin = 9;

void setup() {
  pinMode(motorPin, OUTPUT);
}

void loop() {
  int potValue = analogRead(potPin);
  int motorSpeed = map(potValue, 0, 1023, 0, 255);
  analogWrite(motorPin, motorSpeed);
}

Code Explanation

• Potentiometer value is read using analogRead().
• The value is mapped to PWM range (0–255).
• PWM signal controls motor speed using analogWrite().

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Advantages

• Smooth and precise speed control
• Energy efficient
• Simple and low-cost design
• Easy to upgrade and modify

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Applications

• Robotics and automation
• Fans and pumps
• Conveyor belts
• Electric vehicles (basic models)
• Industrial motor control

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Conclusion

The DC Motor Speed Controller is a highly practical electronics project that demonstrates efficient motor control techniques. By using PWM, this project achieves smooth speed variation with minimal power loss. It is an ideal project for students and serves as a foundation for advanced motor control and robotics applications.