Interfacing Bipolar Stepper motor using L293D

Bipolar Stepper motor

Bipolar motors have a single winding per phase. The current in a winding needs to be reversed in order to reverse a magnetic pole, so the driving circuit must be more complicated, typically with an H - bridge arrangement (however there are several off-the-shelf driver chips available to make this a simple affair). There are two leads per phase, none are common.Dithering the stepper signal at a higher frequency than the motor can respond to will reduce this "static friction" effect.
Because windings are better utilized, they are more powerful than a unipolar motor of the same weight. This is due to the physical space occupied by the windings. A unipolar motor has twice the amount of wire in the same space, but only half used at any point in time, hence is 50% efficient (or approximately 70% of the torque output available). Though a bipolar stepper motor is more complicated to drive, the abundance of driver chips means this is much less difficult to achieve.

Components Required

• ATmega32 microcontroller
• AVR programmer board
• Crystal
• Capacitors
• Bipolar Stepper Motor
• L293D
• +5 V Supply
• Battery Equivalent to the voltage rating of the motor
• Breadboard
• Connecting wires 

Circuit Diagram

For details on L293D IC go to 

http://rickruling.blogspot.in/2013/10/interfacing-dc-motor-with-atmega32.html

Description

• PB0 to PB3 are connected to the four inputs of the L293D IC.
• Both the enable pins are separately connected to Vcc.
• A crystal is connected to the XTAL1 and XTAL2 pins to provide the clock pulse.
• Reset is connected to +5 volt

Control Logic

To control the bipolar motor,apply voltage to each of the coils in a specific sequence. The sequence would go like this:

Source Code

/* This code will make the stepper motor to run continously */ 

#include <avr/io.h>

#include <util/delay.h>

#ifndef F_CPU

#define F_CPU 1000000UL         // frequency of external crystal

#endif

int main()

 { 

DDRB = 0xFF;                   //All pins of PORTB as output

PORTB = 0x00;                 //Initially all pins as output high

while(1)

{

PORTB = 0x01;          //0001

_delay_ms(10);

PORTB = 0x04;          //0100

_delay_ms(10);

PORTB = 0x02;          //0010

_delay_ms(10);

PORTB = 0x08;          //1000

_delay_ms(10);

}

return 0;

}

Source Code for controlled Rotation

/* This code will make the stepper motor to run for a specific angle */ 

#include <avr/io.h>

#include <util/delay.h>

#ifndef F_CPU

#define F_CPU 1000000UL         // frequency of external crystal

#endif

int main()

 {

         /*Calculate x by the minimum step angle of your motor and required rotation angle*/

         int x = 200;

         DDRB = 0xFF;                   //All pins of PORTB as output

 PORTB = 0x00;                 //Initially all pins as output high

while(x)                              //will loop till x is not equal to zero

{

PORTB = 0x01;          //0001

_delay_ms(10);

PORTB = 0x04;          //0100

_delay_ms(10);

PORTB = 0x02;          //0010

_delay_ms(10);

PORTB = 0x08;          //1000

_delay_ms(10);

                x--;                             //decrement x by 1

}

return 0;

}

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