ULN2003 driving stepper motors

INDEX

MY EXPERIENCE IN AUTONOMOUS ROBOTICS

Motor Drving Circuit(H bridge)
H bridge Basics
H bridge Ciruit
H bridge Circuit continued
H bridge for high voltages
H bridge links
H bridge IC-L293d
Troubleshooting L293D

L298
Stepper motor driving with ULN2003
Stepper motor diriving with L293D
Another motor driving circuit

DRIVING STEPPER MOTORS

There are two different circuits required for driving stepper motors. First let's start with unipolar stepper motors. You can use ULN2003,L293D and L298 to drive unipolar stepper motors. For ULN2003 this circuit is nice

The sequence to apply (a,b,c,d) – (1,0,0,0), (0,1,0,0),(0,0,1,0),(0,0,0,1), the motor rotates in one direction if we apply (1,0,0,0),(0,0,0,1) then motor will rotate in other direction. A good parallel port circuit diagram is in the link
http://electronics-diy.com/stepper_motors.php
A sample program
vary the delay in the program and see the variations in torque of the motor and see whether it losses the sequence. Change delay(4) to delay(50) and see the torque at the rotor. The following program exits when u press ESC key.
#include<dos.h>
#delay D delay(4);
void main()
{

int i=1;
do
{
Do
outportb(0x378,i);
i*=2;
if(i>8) i=1
ch=getch()
while(ch!=27);
}
here is another circuit
http://home.cogeco.ca/~rpaisley4/Stepper.html