Driving a Unipolar Stepper Motor

     If your stepper requires a higher current than the L293 can provide (600 mA for the L293D), you can use the SN754410 chip that handles up to 1 amp. For current up to 2 amps, you can use the L298 chip.A simple way to connect an L298 to Arduino is to use the SparkFun Ardumoto shield (DEV-09213). This plugs on top of an Arduino board and only requires external connection to the motor windings; the motor power comes from the Arduino Vin pin. In1/2 is controlled by pin 12, and ENA is pin 10. In3/4 is connected to pin 13, and ENB is on pin 11. Make the following changes to the code to use the preceding sketch with Ardumoto:

/*

* Stepper_bipolar sketch

* stepper is controlled from the serial port.

* a numeric value followed by '+' or '-' steps the motor

* http://www.arduino.cc/en/Reference/Stepper

*/

#include <Stepper.h>

// change this to the number of steps on your motor

#define STEPS 24

// create an instance of the stepper class, specifying

// the number of steps of the motor and the pins it's

// attached to

Stepper stepper(STEPS, 12,13);

int steps = 0;

void setup()

{

pinMode(10, OUTPUT);

digitalWrite(10, LOW); // enable A

// set the speed of the motor to 30 RPMs

stepper.setSpeed(30);

Serial.begin(9600);

pinMode(11, OUTPUT);

digitalWrite(11, LOW); // enable B

}

void loop()

{

if ( Serial.available()) {

char ch = Serial.read();

if(ch >= '0' && ch <= '9'){ // is ch a number?

steps = steps * 10 + ch - '0'; // yes, accumulate the value

}

else if(ch == '+'){

stepper.step(steps);

steps = 0;

}

else if(ch == '-'){

stepper.step(steps * -1);

steps = 0;

}

}

}