How to Use the L293D Motor Driver Shield: Beginner’s Guide

What is the L293D Motor Driver Shield?

The L293D motor driver shield is an expansion board that allows you to control DC motors, stepper motors, and servos directly with an Arduino. This shield is widely used in robotics projects because it simplifies motor control by providing the necessary power and signal interface between your motors and Arduino. It can drive up to two DC motors at a time, making it ideal for basic projects such as driving wheels on a small robot.

Why Use L293D Motor Driver Shield?

Controlling motors directly from Arduino is not recommended because the board cannot supply enough current or handle the voltage spikes motors generate. The L293D motor driver shield solves this by acting as an intermediary, managing the high current and voltage required by motors while letting the Arduino handle logic-level signals.

How L293D Motor Driver Shield Works

The L293D motor driver shield is based on the H-Bridge concept, which allows for bi-directional control of motors. This means you can control both the direction (forward or backward) and speed of each motor connected to the shield. The H-Bridge uses four switches (transistors) to enable the current to flow in either direction across the motor, making it possible to reverse the motor’s direction.

Controlling the Speed of Two DC Motors

To control the speed of two DC motors, the shield uses PWM (Pulse Width Modulation) signals. The PWM signal is sent to the enable pins on the motor driver to control the speed, while the direction of rotation is determined by digital signals sent to the input pins.

We’ll use the Adafruit Motor Shield Library (AFMotor) to make it easier to control the motors with code.

Wiring Diagram

Here’s a general setup of how to wire two DC motors to the L293D motor driver shield:

1. Plug the L293D shield on top of the Arduino board.
2. Connect Motor 1 to the M1 terminal and Motor 2 to the M2 terminal on the motor shield.
3. Provide an external power source for the motors by connecting a battery or power supply to the Vin and GND terminals on the motor shield.
4. Ensure the Arduino itself is powered separately through a USB cable or a separate power supply.

Important: It’s crucial to power the motors with a separate power supply if they require more current than the Arduino can provide. This prevents potential damage to the Arduino due to excessive current draw.

Arduino Code

Here is a sample Arduino code to control two DC motors using the AFMotor library:

#include <AFMotor.h>

AF_DCMotor motor1(1);  // DC motor on channel 1
AF_DCMotor motor2(2);  // DC motor on channel 2

void setup() {
  Serial.begin(9600);  // Initialize serial communication
  motor1.setSpeed(255);  // Set initial speed (255 is the max)
  motor2.setSpeed(128);  // Set motor 2 to half speed
}

void loop() {
  Serial.println("Moving forward");
  
  motor1.run(FORWARD);  // Move motor 1 forward
  motor2.run(FORWARD);  // Move motor 2 forward
  delay(2000);  // Run motors for 2 seconds

  Serial.println("Moving backward");
  
  motor1.run(BACKWARD);  // Move motor 1 backward
  motor2.run(BACKWARD);  // Move motor 2 backward
  delay(2000);  // Run motors for 2 seconds

  Serial.println("Stopping");
  
  motor1.run(RELEASE);  // Stop motor 1
  motor2.run(RELEASE);  // Stop motor 2
  delay(2000);  // Pause before repeating
}

Explanation of code:

• We include the AFMotor library, which simplifies motor control.
• We define two motors, motor1 on channel 1 and motor2 on channel 2.
• In the setup(), the speed of both motors is set using the setSpeed() function. This function takes a value between 0 (stop) and 255 (full speed).
• The loop() function demonstrates forward and backward movement for 2 seconds each, followed by stopping the motors.

Conclusion

The L293D motor driver shield is an essential tool for beginners in robotics and motor control, enabling you to drive multiple motors with minimal wiring and effort. Understanding its H-Bridge-based functionality allows you to control motor direction and speed. With the AFMotor library, you can simplify the coding part of your project, making it easy to add motor control to your Arduino projects.

For future projects, try expanding to control stepper motors or experiment with different PWM speeds to see how varying the signal affects motor behavior.