Stepper motor driver using ULN2803

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Please read http://www.triindia.co.in/resources/?p=40 if you are handling the stepper motor for the first time.

Example describes stepper motor driver using ULN2803. In this example code two stepper motors are driven by a single timer. Code is written for ATmega16/32 running at 8MHz, for serial baudrate of 19200 and winavr platform.

Circuit description:

It is a simple unipolar drive. Circuit for a single stepper is shown same circuit is used for other stepper also. A B A’ B’ of first motor are connected to PORTB0-PORTB3. and other motor is connected to PORTD4-PORTD7.

Program description:

Include uart.h and makefile in your project folder and name your main program as main.c.

Stepper motors run by interrupt of Timer 0. Timer 0 is configured in CTC mode(refer datasheet) with pre-scalar of 1024. Every time interrupt is executed motors move by one step. Delay between the steps can be controlled by OCR0. To increase the speed of motor lower the value of OCR0 and do reverse to decrease the speed.

I use serial port of PC to configure speed and number of steps to rotate, this program runs without serial connection but motors will rotate only 100 steps each time it is switched ON. Connect a RS232 to TTL level converter like MAX 232 between TX and RX pin of uC and PC serial port.

Please read http://www.triindia.co.in/resources/?p=35 to configure your hyperterminal to be able to communicate with your robot through PC serial port.

Uart.h enables us to use C functions printf , scanf with controller. printf (“string”); writes specified string on hyperterminal screen and scanf can be used to take input from hyperterminal.

I have tested this circuit and program and it works fine but, There may be some bug introduced while writing this article so please post your comments to find the bug if any.

Downlaod stepper.zip from http://www.swapniljariwala.co.nr/upload.php

It contains main.c and uart.h.

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