How to Control Motor Speed Using Arduino: Simple Guide

You can control motor speed using Arduino by sending PWM signals to the motor driver or motor pin. Use the analogWrite(pin, value) function where value ranges from 0 (stop) to 255 (full speed) to adjust speed smoothly.

Syntax

The main function to control motor speed with Arduino is analogWrite(pin, value).

• pin: The Arduino pin connected to the motor driver or motor control input.
• value: A number from 0 to 255 representing the speed (0 = stop, 255 = full speed).

This function sends a PWM (Pulse Width Modulation) signal to control the motor speed.

arduino

analogWrite(pin, value);

Example

This example shows how to control a DC motor speed connected to pin 9 using PWM. The motor speed increases from 0 to full speed gradually.

arduino

const int motorPin = 9;  // PWM pin connected to motor driver

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

void loop() {
  // Increase speed from 0 to 255
  for (int speed = 0; speed <= 255; speed++) {
    analogWrite(motorPin, speed);  // Set motor speed
    delay(20);  // Wait 20ms for smooth change
  }
  // Decrease speed from 255 to 0
  for (int speed = 255; speed >= 0; speed--) {
    analogWrite(motorPin, speed);
    delay(20);
  }
}

Output

Motor speed smoothly increases from stop to full speed and then back to stop repeatedly.

Common Pitfalls

• Using digitalWrite instead of analogWrite: digitalWrite only turns the motor fully ON or OFF, no speed control.
• Wrong pin selection: Only PWM-capable pins (marked with ~ on Arduino Uno) support analogWrite.
• Not using a motor driver: Arduino pins cannot supply enough current; always use a motor driver or transistor.
• Ignoring motor power supply: Motor should have its own power source, not just Arduino 5V pin.

arduino

/* Wrong way: No speed control */
digitalWrite(9, HIGH);  // Motor runs full speed only

/* Right way: Speed control with PWM */
analogWrite(9, 128);    // Motor runs at half speed

Quick Reference

Remember these tips when controlling motor speed with Arduino:

• Use analogWrite on PWM pins only.
• Value range: 0 (stop) to 255 (full speed).
• Use a motor driver or transistor to handle current.
• Provide separate power supply for the motor.

Key Takeaways

Use analogWrite(pin, value) with PWM pins to control motor speed smoothly.

Value 0 stops the motor; 255 runs it at full speed.

Always use a motor driver or transistor to protect Arduino pins.

Provide a separate power source for the motor to avoid damage.

Avoid digitalWrite for speed control as it only turns motor fully on or off.