Interfacing DC motor to Atmega32

In a past tutorial, we saw how to control a servo using AVR. This tutorial will aim at interfacing a DC geared motor with the ever popular ATMEGA series. For the sake of simplicity we will just learn a way to interface DC motor and not controlling it’s speed. DC Motors are small, inexpensive and powerful motors used widely in robotics for their small size and high energy out. A typical DC motor operates at speeds that are far too high speed to be useful, and torque that are far too low. Gear reduction is the standard method by which a motor is made useful .Gear’s reduce the speed of motor and increases the torque.


Choosing a DC Motor depends upon the application. Prefer following:

  • DC-Motor with Gear head
  • Operating voltage 12V
  • Speed

It has two wires or pins. When connected with power supply the shaft rotates. You can reverse the direction of rotation by reversing the polarity of input. As the MCUs PORT are not powerful enough to drive DC motors directly so we need some kind of drivers. A very easy and safe is to use popular L293D chips. It is a 16 PIN chip. The pin configuration is as follows.


This chip is designed to control 2 DC motors. Three pins are needed for interfacing a DC motor (A, B, Enable). If you want the o/p to be enabled completely then you can connect Enable to VCC and only 2 pins needed from controller to make the motor work. The connections are as follows.


The next figure shows the direction of motor control with respect to the input given


H-Bridge Circuit using transistors for bidirectional driving of DC motor. H-Bridges in IC’s to reduce the drive circuit complexity.L293D is a dual H-Bridge motor driver, So with one IC we can interface two DC motors which can be controlled in both clockwise and counter clockwise direction and if you have motor with fix direction of motion the you can make use of all the four I/Os to connect up to four DC motors. L293D has output current of 600mA and peak output current of 1.2A per channel. Moreover for protection of circuit from back EMF ouput diodes are included within the IC. The output supply (VCC2) has a wide range from 4.5V to 36V, which has made L293D a best choice for DC motor driver.


Source Code:

#include <avr/io.h>
#include <util/delay.h>
int main(void)
DDRD=0xFF; //PORTD declared as output
DDRB=0×00; //PORTB as input
//Pin 0 of PORTB high,then Moves Clockwise
//Pin 0 of PORTB Low,then Moves AntiClockwise

Circuit Diagram


Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *