Project 1 - Controlling a DC motor using PWM and monitoring its Running status

Aim

The aim of this project is to implement a system on the simulator to control a DC motor using PWM with the L293 motor driver. The project also involves monitoring the running status of the DC motor and displaying it on an LCD screen.

Components Required

1. Atmega 32
2. Motor Driver - L293
3. DC Motor
4. Pushbutton(2)
5. Switch- ON & OFF
6. LCD Display - 16x2
7. Resistor - 2.2k ohm
8. Resistor - 10kohm
9. Fixed power supply - 5V

Code

#include

#define F_CPU 16000000L

#include "avr/interrupt.h"

#include

#define sw_dir (PIND & (1<<1>

#define pw (PINC & (1<<3>

//LCD connections & commands

#define lcd_port PORTB

#define RS_high PORTD |= (1<<5>

#define RS_low PORTD &= ~(1<<5>

#define EN_high PORTD |= (1<<6>

#define EN_low PORTD &= ~(1<<6>

//LCD specific commands

#define LCD_LINE_1 0x80

#define LCD_LINE_2 0xC0

unsigned char i; //Variable to store duty cycle

void lcd_cmd(char cmd) //function to send a command to the LCD

{

lcd_port=(cmd & 0xF0); //send higher 4 bits of the command

RS_low; //set RS pin as low(command mode)

EN_low; //set EN pin as low

_delay_ms(1); //delay to ensure command is processed

EN_high; //set EN pin as high to process command

lcd_port=((cmd<<4>

RS_low; //set RS pin as low(command mode)

EN_low; //set EN pin as low

_delay_ms(1); //delay to ensure command is processed

EN_high; //set EN pin as high to process command

}

void lcd_data(char data) //function to send data to the LCD

{

lcd_port=(data & 0xF0); //send higher 4 bits of the data

RS_high; //set RS pin as high(data mode)

EN_low; //set EN pin as low

_delay_ms(1); //delay to ensure data is processed

EN_high; //set EN pin as high to process data

lcd_port=((data <<4>

RS_high; //set RS pin as high(data mode)

EN_low; //set EN pin as low

_delay_ms(1); //delay to ensure data is processed

EN_high; //set EN pin as high to process data

}

void lcd_init() //function to initialize the LCD

{

 lcd_cmd(0x28); //initialize LCD in 4 bit mode with 2lines and 5x8 font size

 _delay_ms(5);

 lcd_cmd(0x02); //return cursor to home position

 _delay_ms(5);

 lcd_cmd(0x01); //clear display

 _delay_ms(5);

 lcd_cmd(0x0C); //display ON,cursor OFF

 _delay_ms(5);

}

void lcd_string(const char* str) //function to display a string on the LCD

{

while (*str)

{

lcd_data(*str++); //send each character of string to LCD

}

}

int adc_read(char channel) //function to configure the adc value

{

unsigned int a,result;

ADMUX=channel; //select ADC channel

ADCSRA=0x80; //enable ADC,start conversion,enable ADC interrupt

ADCH=0x00; //clear ADC high value

ADCL=0x00; //clear ADC low value

ADCSRA |=(1<<6>

while ((ADCSRA & 0x40) !=0) //wait for conversion to complete

a=ADCL; //read ADC low value

result=ADCH; //read ADC high value

result=result<<8>

result=result | a; //combine high and low values to get the result

return result;

}

int main(void) //main function 

{

    //set data direction for LCD and control pins

DDRB=0xFF; //all 8 pins of PORTB are set as output

DDRA |=((1<<0>

DDRD &= ~(1<<1>

DDRD &= ~(1<<2>

DDRD |= (1<<5>

DDRD |= (1<<6>

DDRC &= ~(1<<3>

PORTD |=(1<<2>

PORTC |=(1<<3>

i=64; //initialize i for 25% duty cycle

TCCR0 =0x61; //non inverting mode,PWM phase correct mode

GICR =(1<

MCUCR =0x02; //set interrupt INT0 to be triggered on falling edge

sei(); //enable global interrupt

lcd_init();

while (1) 

    {

while (pw == 0)

{

//continue till push button is released

if (sw_dir==0)

{

//set appropriate motor direction pins

PORTA=0b0000001;

lcd_cmd(LCD_LINE_1);

lcd_string("->Motor ON-CL  "); //display on LCD

}

else

{

//set appropriate motor direction pins

PORTA=0b0000010;

lcd_cmd(LCD_LINE_1);

lcd_string("->Motor ON-ACL  "); //display on LCD

}

OCR0=i;

}

PORTA=0x00; //turn off motor

lcd_cmd(LCD_LINE_1);

lcd_string("->Motor TURN OFF  "); //display on LCD

    }

}

ISR(INT0_vect)

{

i=i+22; //increase duty cycle when external interrupt occurs

}

Code Explanation

• The code starts by including necessary libraries and defining constants for the pins and commands used in the program.
• It then initializes the ADC and sets up the LCD display.
• The main function configures the ports and pins for motor control, external interrupt, and ADC.
• The main loop continuously monitors the push button state and the direction switch.
• When the push button is pressed, the motor starts running in the specified direction, and the duty cycle is adjusted based on the external interrupt.
• When the push button is released, the motor stops, and the LCD displays the status accordingly.

Explanation for Registers Used in Code

• DDRB, DDRA, DDRD, DDRC: Data Direction Registers for configuring the direction of PORTB, PORTA, PORTD, and PORTC pins.
• PORTD: Used for enabling internal pull-up resistors for D2 and D3 pins (push button and direction switch inputs).
• TCCR0: Timer/Counter Control Register for Timer0 configuration (PWM settings).
• GICR: General Interrupt Control Register for enabling external interrupts.
• MCUCR: MCU Control Register for configuring external interrupt behavior (trigger on falling edge).
• ADCSRA, ADMUX: ADC Control and Status Registers for configuring and starting ADC conversion.

OUTPUT

1. When the push button is pressed and the direction switch is in one position, the motor starts running in the specified direction with a duty cycle proportional to the external interrupt count. The LCD displays the running status.
   1. CLOCKWISE:
2. When the push button is pressed and the direction switch is in the other position, the motor starts running in the opposite direction with a duty cycle proportional to the external interrupt count. The LCD displays the running status.
   1. ANTICLOCKWISE:
3. When the push button is released, the motor stops, and the LCD displays the "Motor TURN OFF" message.</> </> <><>></> <>>