How to run a motor using L293D (double H-bridge) and interfacing it with the Arduino

Motor drivers are needed because the pins of a micro-controller cannot source the required current to run a motor.
The arduino can provide a maximum 200mA per pin and can sink a total of 400mA current.

You will damage the micro - controller or pins if you try to draw more current. A motor cannot run on such small current. Thus an amplifier circuit or a relay is needed. To drive the motor in both directions , an H-bridge is needed.

Lo and behold ! Let me present to you L293D. It is a transistor implementation of both an amplifier and an H-bridge , in other words , the solution to our problem.

This is what an h-bridge looks like:

 

This is the pin layout of L293D:

It can run two motors.

Vss needs to be connected to 5v for either h-bridge to run.

Enable1, if connected to 5v enables the left h- bridge.

Enable2, is for right H- bridge.

Gnd pins go to ground. 

Vs  is the voltage you want to give the motor.

 WIRE IT UP


Created Using Fritzing

THE PROGRAM

#define M1pin1 9  
#define M1pin2 10
void setup()
{
pinMode(M1pin1, OUTPUT);
pinMode(M1pin2, OUTPUT);
}
void loop()
{
 Clockwise();  // motor turns in clockwise direction
 delay(2000);  // Arduino sleeps for 2 seconds
 AntiClockwise(); // motor turns in anticlockwise direction
 delay(2000);
}

void Clockwise()
{
    digitalWrite(M1pin1, HIGH); // digitalWrite is a predefined function to control pin state.
    digitalWrite(M1pin2, LOW);
}  
void AntiClockwise()
{
 
    digitalWrite(M1pin2, HIGH);
    digitalWrite(M1pin1, LOW);
}

If You Are looking for speed control :
// You need to connect input wires to a pmw enabled pins on Arduino. These are identified by ~ sign on the arduino board. Notice 9 has a ~ before it on the board.

#define M1pin1 9       
#define M1pin2 10
int pmw=128;
void setup()
{
pinMode(M1pin1, OUTPUT);
pinMode(M1pin2, OUTPUT);
}
void loop()
{
 Clockwise();  // motor turns in clockwise direction
 delay(2000);  // Arduino sleeps for 2 seconds
 AntiClockwise(); // motor turns in anticlockwise direction
 delay(2000);
}

void Clockwise()
{
    analogWrite(M1pin1, pmw); // analogWrite is a predefined function to control pin state.
    digitalWrite(M1pin2, LOW);
}  
void AntiClockwise()
{
 
    analogWrite(M1pin2, pmw);
    digitalWrite(M1pin1, LOW);
}

//pmw can take values between 0 and 256. At 256, it will run at max speed. At 128, it will run at half the speed.