I have studied about the logic of controlling unipolar stepper motors.
Can anybody tell me how to control them using ATMEL microcontrollers?
Plz help me in writing the code for the same.
There is a chip L296/L297.This is used for driving stepper motors.Just download the datasheets and it will give a very easy way to interface your avr micro to a stepper motor.
You can use four bipolar transistor and one look up table and one delay routine.
L297/L298 is expensive solution comared to four trasistors and few lines code.
you will need to use a chip called L298 which is a bridge called H-bridge
it is expensive it is about 25L.E , and only works with bidirectional stepper motors