Stepper L 293 H Bridge

Initial report by Carlyn?, 08, March, 2006

This report is designed to allow you to create a reusable module for Bi-Polar Stepper applications based on a L293D H-Bridge. This report draws heavily from Tom Igoe’s Intro to Physical Computing resources.

Applications and Background

Stepper Motors are used when percision motor control is required. The L293D is a standard Quadruple Half-H Driver and it is used in the case of a bi-polar stepper motor to reverse the polarity of the current. It can be easily replaced with the SN754410.

More general disscussion of stepper motors

http://tigoe.net/pcomp/motors.shtml
http://www.tigoe.net/pcomp/code/archives/picbasic_pro/000245.shtml
http://www.cs.uiowa.edu/~jones/step/
http://www.doc.ic.ac.uk/~ih/doc/stepper/
http://www.shinano.com/xampp/stepping_motors.php

Datasheets for L293D and SN754410

http://focus.ti.com/docs/prod/folders/print/l293d.html
http://focus.ti.com/docs/prod/folders/print/sn754410.html

Circuit Diagram

Breadboard Style

http://flickr.com/photos/pcomp/sets/72057594070996918/

Perfboard Style

Printed Board Style

Code

PicBasic Pro code:

start:
    High PORTB.0

' set variables:
x VAR BYTE
steps VAR WORD 
stepArray VAR BYTE(4)
clear

TRISD = %11110000
PORTD = 255
input portb.4
Pause 1000

stepArray[0] = %00001010
stepArray[1] = %00000110
stepArray[2] =%00000101
stepArray[3] = %00001001


main:
    if portb.4 = 1 then
        steps = steps + 1
    else
        steps = steps - 1
    endif

    portD = stepArray[steps //4] 
    pause 2

GoTo main

Wiring Code (for Arduino board):

/*
 Stepper Motor Control
 by Tom Igoe

 This program moves a stepper motor 100 steps in one direction,
 then 100 steps in the opposite direction, indefinitely.

 Created 21 October 2005
 Updated 

 */

int motorStep[4];        // array to hold the stepping sequence
int thisStep = 0;        // which step of the sequence we're on

//  function prototypes:
void stepMotor(int whatStep, int speed);
void blink(int howManyTimes);


void setup() {
  /*
     save values for the 4 possible states of the stepper motor leads
   in a 4-byte array.  the stepMotor method will step through 
   these four states to move the motor. This is a way to set the 
   value on four pins at once.  The  digital pins 8 through 13 are 
   represented in memory as a byte called PORTB. We will set
   PORTB to each  of the values of the array in order to set 
   digital pins 8, 9, 10, and 12 at once with each step.

   We're representing the numbers as hexadecimal values below, but
   it'd be nicer to represent them as binary numbers, so that the 
   representation shows us visually which pins of PORTB we're 
   affecting.
   */
  motorStep[0] = 0x0A;   //  in binary: 0000_1010;
  motorStep[1] = 0x06;   //  in binary: 0000_0110;
  motorStep[2] = 0x05;   //  in binary: 0000_0101;
  motorStep[3] = 0x09;   //  in binary: 0000_1001;

  /*
   The DDRB register is the Data Direction Register.  It sets whether
   the pins of PORTB are inputs or outputs. a 1 in a given position 
   makes that pin an output.  A 0 makes it an input.
   */

  // set the last 4 pins of port b to output:
  DDRB = 0x0F; //0b0000_1111;

  // set all the pins of port b low:
  PORTB = 0; //0b0000_0000;

  // start  program with a half-second delay:
  delay(500);  

  // blink the reset LED 3 times:
  blink(3);
}

void loop() {
  int i = 0;    // a counter

  /*
  move motor forward 100 steps. 
   note: by doing a modulo operation on i (i % 4), 
   we can let i go as high as we want, and thisStep 
   will equal 0,1,2,3,0,1,2,3, etc. until the end 
   of the for-next loop.
   */
  for (i = 1; i<= 100; i++) {
    thisStep = i % 4;
    stepMotor(thisStep, 10);
  }

  // move motor backward    
  for (i = 100; i >=1; i--) {
    thisStep = i % 4;
    stepMotor(thisStep, 10);
  }
}

//Step the motor forward one step:
void stepMotor(int whatStep, int speed) {
  // sets the value of the eight pins of port c to whatStep
  PORTB = motorStep[whatStep];

 // vary this delay as needed to make your stepper step:
  delay(speed); 
}

// Blink the reset LED:
void blink(int howManyTimes) {
  int i;
  for (i=0; i< howManyTimes; i++) {
    digitalWrite(13, HIGH);
    delay(200);
    digitalWrite(13, LOW);
    delay(200);  
  }
}