L293D Motor Driver

Published March 13, 2020

Controlling a motor from an Arduino using the L293D H-bridge

Driving a Motor with Arduino

A good way to control a motor is to use an H-bridge. This is a type of circuit that allows you to reverse the current flow of the motor, therefore giving you direction control.

An H-bridge contains four switches and a motor at the center, forming an H-like shape. Turning any two of the switches on reverses the motor's current, which can change its direction.

The L293D has two of these H-bridges inside it, allowing you to control up to two DC motors or one stepper motor.

L293D Pinout

The pins with names containing the same numbers form a single channel in the L293D that can control one motor.

Each pin type has a specific function:

• Enable pins turn the motor on/off and control its speed.
• Input pins control the direction of the motor.
• Output pins connect to the motor to drive it.
• GND pins are ground connection pins.
• Pin 8 is the motor power connection.
• Pin 16 is the IC power connection.

Controlling L293D

The Enable pins turn their motors on/off. A HIGH state enables the motor; a LOW state disables it. You can also send PWM signals to control motor speed. A duty cycle of 0% stops the motor; a duty cycle of 100% runs the motor at full speed.

The input pin pairs of the H-bridge control the direction of their motor. If input A is high and input B is low, the motor spins one direction. If input A is low and input B is high, the motor spins in the opposite direction. If the inputs' states are the same, the motor stops.

Schematic

Example

// Define pin constants
#define EN  5
#define IN1 4
#define IN2 3

boolean isReversed = false;

void setup() {
  // Configure pins as output
  pinMode(EN,  OUTPUT);
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
}

void loop() {
  for (int i = 0; i < 256; i++) {
    // Increment the speed from 0 to 255
    setMotorSpeed(i, isReversed);
    delay(10);
  }

  delay(3000); // Run at full speed for 3 seconds

  for (int i = 255; i > 0; i--) {
    // Decrement the speed from 255 to 0
    setMotorSpeed(i, isReversed);
    delay(10);
  }

  // Stop the motor and wait a little bit
  stopMotor();
  delay(2000);
  isReversed = !isReversed; // Reverse the motor
}

// Motor control functions

void setMotorSpeed(int speed, boolean reverse) {
  // Set the speed of the motor.
  analogWrite(EN, speed);
  digitalWrite(IN1, reverse);
  digitalWrite(IN2, !reverse);
}

void stopMotor() {
  // Stop the motor.
  analogWrite(EN, 0);
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, LOW);
}