What Is the L293D Motor Driver?

The L293D is a popular H-bridge motor driver integrated circuit (IC) widely employed to control DC motors and stepper motors. It serves as a bridge between low-power microcontrollers (such as Arduino) and motors, delivering the higher current and voltage levels motors need to operate. Featuring two built-in H-bridge circuits, the L293D allows independent control of two DC motors or a single bipolar stepper motor. Its straightforward design and ease of use make it a go-to option for hobbyists, students, and engineers working on basic robotics, automation, and motor-driven projects.

Key Features

• Dual motor control: Operate two DC motors separately with distinct speed and direction settings.
• Current capacity: Handles up to 600 mA per motor channel, with short bursts up to 1.2 A.
• Voltage range: Supports motor operation from 4.5V to 36V, accommodating a variety of motor types.
• Built-in diodes: Includes flyback diodes to shield the IC from voltage spikes caused by motor inductance.
• Logic compatibility: Works seamlessly with 5V logic signals from microcontrollers.

Pinout of the L293D

• Enable Pins (EN1, EN2): Turn motor channels on or off. Connect PWM signals here to fine-tune motor speed.
• Input Pins (IN1–IN4): Set motor direction by applying HIGH or LOW logic states.
• IN1 & IN2 control Motor A, linked to outputs OUT1 & OUT2.
• IN3 & IN4 control Motor B, linked to outputs OUT3 & OUT4.
• Output Pins (OUT1–OUT4): Connect directly to the motor terminals to deliver power.
• VCC1 (5V): Supplies power to the IC’s internal logic circuitry.
• VCC2 (5V–36V): Provides the voltage needed to drive the motors.
• Ground Pins (GND): Complete the circuit by connecting to a common ground.

How It Works

The H-bridge setup inside the L293D enables bidirectional control by switching the direction of current flow through the motor. Here’s how it operates:

• Forward Direction: Set IN1 = HIGH, IN2 = LOW to spin Motor A one way.
• Reverse Direction: Set IN1 = LOW, IN2 = HIGH to spin it the opposite way.
• Speed Control: Send PWM (pulse-width modulation) signals to the EN pins to adjust motor speed smoothly.
• Stop Mode: Set both inputs LOW or the enable pin to 0 to halt the motor.

The IC essentially acts like an electronic switch, directing power to the motor based on input signals while protecting the microcontroller from high current.

Arduino Example Code

Below is a simple code snippet to control a DC motor with the L293D using an Arduino:

#define EN1 9  // PWM pin for speed control  
#define IN1 8  // Direction pin 1  
#define IN2 7  // Direction pin 2  

void setup() {  
    pinMode(EN1, OUTPUT);  
    pinMode(IN1, OUTPUT);  
    pinMode(IN2, OUTPUT);  
}  

void loop() {  
    // Spin motor forward at 50% speed  
    digitalWrite(IN1, HIGH);  
    digitalWrite(IN2, LOW);  
    analogWrite(EN1, 128);  // 50% duty cycle (0-255 range)  
    delay(2000);  

    // Stop motor  
    digitalWrite(IN1, LOW);  
    digitalWrite(IN2, LOW);  
    analogWrite(EN1, 0);  
    delay(1000);  

    // Reverse direction at full speed  
    digitalWrite(IN1, LOW);  
    digitalWrite(IN2, HIGH);  
    analogWrite(EN1, 255);  // 100% duty cycle  
    delay(2000);  

    // Stop again  
    analogWrite(EN1, 0);  
    delay(1000);  
}

This code demonstrates basic motor control: spinning forward, stopping, and reversing.

Practical Tips

• Power Supply: Use a dedicated power source for VCC2 (motors) and a separate 5V supply for VCC1 (logic) to minimize electrical noise and ensure stable operation.
• Heat Management: Add a heatsink to the L293D if running motors close to its 600 mA limit, as it can overheat during prolonged use.
• Diode Protection: Double-check motor wiring to prevent damage from back electromotive force (EMF), though the built-in diodes help mitigate this.
• Decoupling Capacitors: Place a 0.1 µF capacitor across VCC2 and ground to smooth out voltage fluctuations.
• Testing: Start with low PWM values to confirm motor behavior before ramping up speed.

Common Applications

• Small robots: Powers wheels in projects like line-following robots, obstacle-avoidance bots, or mini rovers.
• DIY gadgets: Drives motorized mechanisms in fans, toy cars, conveyors, or camera sliders.
• Educational tools: Teaches core concepts of motor control, H-bridge functionality, and microcontroller interfacing.
• Prototyping: Useful for quick experiments in automation or basic mechanical systems.

Limitations

• Current restriction: Unsuitable for motors exceeding 600 mA continuous draw or requiring high torque over long periods.
• Voltage drop: The IC introduces a small voltage loss (about 1.2V–2V), reducing efficiency slightly.
• External components: May need capacitors or resistors in noisy setups to maintain reliability.
• No advanced features: Lacks built-in current sensing or over-temperature protection found in newer motor drivers.

Expanding Functionality

For more complex projects, pair the L293D with additional hardware:

• Sensors: Add encoders to track motor speed or position.
• Shields: Use an Arduino motor shield with the L293D for simplified wiring.
• Upgrades: Consider the L298N for higher current needs or modern drivers like the DRV8833 for better efficiency.

Why It’s Popular

The L293D strikes a balance between simplicity, affordability, and functionality, making it ideal for beginners and small-scale projects. By connecting it to an Arduino or similar platform, you can quickly build and test bidirectional motor systems while gaining hands-on experience with electronics, programming, and robotics principles.