DC Motor Interfacing With Micrcontroller

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 on application.Prefer following:

• DCMotor with Gear head
• Operating voltage 12V
• Speed

Drive basics of DC Motor

Red wire	Black wire	Direction of rotation
Positive	Negative	Clock wise
Negative	Positive	Anti clock wise

Logic	Logic	Direction
1	0	Clock
0	1	Anti clock

Direction	Pulse to
Clock wise	A and C
Anti Clock wise	B and D

Bi-Direction control of DC Motor

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.

As you can see in the circuit, 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.

**To Move the motor Clockwise And Anticlockwise,Must be use two separate Power source,one for microcontroller and another for driving motor with Driver IC.

Here,i have used ATMEGA32 micrcontroller and  Code is written in C  using AVR Studio 5.0.

Source Code

/*
* DCMotorControl.c
*
* Created: 4/1/2011 12:08:10 AM
*  Author: sfg
*/

#include <avr/io.h>
#include <util/delay.h>

int main(void)
{
DDRD=0xFF; //PORTD declared as output
PORTD=0x00;
DDRB=0x00; //PORTB as input
while(1)
{

//Pin 0 of PORTB high,then Moves Clockwise
//A–1–PD0
//B–0–PD1
//Enable–1–PD2
if(PINB==0x01)
{
PORTD=0x05;
//_delay_ms(5000);
}
//Pin 0 of PORTB Low,then Moves AntiClockwise
//A–0–PD0
//B–1–PD1
//Enable–1–PD2
else
{

PORTD=0x06;
//_delay_ms(5000);
}
}
}

Circuit Diagram

Led blinking program with 8051 Microcontroller and Keil uVision4

The first “Hello World!” project I prefer for Microcontroller is LED Blinking. I have used ATMEL’s 89C51 (40-pins DIP) 8051 architecture microcontroller which is ideal for first time learning MCU Chip.  The program is very simple and straight forward, that uses a delay procedure  loop based software delay.

Source Code

Here,i have  written code  in C using Keil uVision4.

#include <REGX51.H>
void msdelay(unsigned int );
void main(){

P2=0x00;  //all pin of PORT2 declared as output
//infinite loop
while(1){

P2=0xFF;   //all pin high
msdelay(250);    //delay
P2=0x00;   //all pin low
msdelay(250); //delay

}
}

//delay function
void msdelay(unsigned int value){

unsigned int x,y;
for(x=0;x<value;x++)
for(y=0;y<1275;y++);
}

In C programs you cannot be sure of delay, cause  it depends on compiler how it optimize the loops as soon as you make changes in the options the delay changes.

you will have to use Timers for making exact delays….. it does not matters whether u need delays of ms , us or even seconds…

below is a function of 1 second using timers…..

// the idea is to make a 50ms delay and run it 20 times as 20x50ms= 1000ms= 1sec

delay_1s() // timer of 1 sec
{
int d;
for(d=0;d<=20;d++)
{
TMOD=0x01;
TL0=0xFD;
TH0=0x04B;
TR0=1; // start timer.
while(TF0==0); // run until TF turns to 1
TR0=0; // stop timer
TF0=0; // reset the flag
}
}

Circuit Diagram

Led blinking with 8051 microcontroller