About Devolopment Board

1. 1.AVR Development board with All ICs
2. 2.Microcontrollers: Atmega16, Atmega8
3. 3.LCD 16x2
4. 4. Seven Segments 4 numbers
5. 5. RTC battery
6. 6. Buzzer
7. 7. Two Relays
8. 8. Eight DIP Switch
9. 9. Eight 5mm LEDs
10. 10. 4 x 4 Keypad
11. 11. Two Serial Ports
12. 12. Temperature Sensor LM35
13. 13. Power adapter 12V, 1A
14. 14. Single pin female connectors: 20 
15. 15. Serial Cable
16. 16. USB Cable
17. 17. AVR USB Programmer

DC MOTOR CONTROL By IR-Remote using PWM AtMega8

Note:-click to-AtMega 8 datasheet

Introduction

To control the speed of DC motor where precision and protection are essence, we use a technique called PWM (pulse width modulation) to control the speed of DC motor.We can achieve speed control of DC motor using mechanical or electrical techniques but they require large size hardware to implement but Micro controller based system provides easy way to control the speed of DC motor.We will use ATmega8 controller to produce PWM wave. By varying the width of this PWM wave, we can control the speed of DC motor. In ATmega8 controller, timer1 and timer2 have PWM mode. 

PWM Based DC Motor Speed Control using Microcontroller Circuit Principle:

The heart of this project is ATmega8 controller. These controllers 

consist of 2 PWM modes. Now we will see   how to generate 

PWM wave using timer2 PWM mode.

Before writing the program to the PWM mode we need to know 

the register description of all the registers that are used for PWM mode.

TCCR2 (Timer Counter Control Register):

In Timer 2, we have different modes like CTC mode, normal mode,

phase correct PWM mode, Fast PWM 

mode,etc.Among all of these modes, we have to select FastPWM mode.

From the above figure, it is clear that

For Fast PWM mode,

            WGM21=1    WGM20=1

To select PWM mode

TCCR2 |= (1<<WGM21)| (1<<WGM20);

Again in PWM mode we have two modes one INVERTING and 

other is NON – INVERTING.

To select non-inverting mode,

    COM21=1     COM20=0

    TCCR2 |= (1<<COM21);

 To select inverting mode,

COM21=1,    COM20=1

TCCR2 |= (1<<COM21)| (1<<COM20);

After that we have to select prescaler value.

            CS22        CS21       CS20                Description

               0              0               0                    No clock source

               0              0               1                     clk/1

              0              1                0                     clk/8

              0              1                1                     clk/32

              1              0               0                      clk/64

              1              0               1                      clk/128

              1              1               0                      clk/256

              1              1               0                      clk/1024

   To set the prescaler to 8,

CS22=0     CS21=1       CS20=0
TCCR2|= (1<<CS21);

OCR2 (Output Compare Register):

            OCR2 register contains an 8 bit value that is continuously compared with counter value.

PWM Program:

//********************************************************

// *********** PWM DC MOTOR CONTROL with IR *************

//********************************************************

//Controller: ATmega8 (1MHz internal Crystal)

//Compiler: ICCAVR

//Author: bidyut das, Chennai

//Date: FEB 2013

//********************************************************

//this program uses two of the three PWM channels (OC1A & OC1B)

//of the ATmega8, for controlling speed & direction of DC motor

//The remote of Sony TV was used for sending IR codes

#include <iom8v.h>

#include <macros.h>

#include "PWM_main.h"

//*********************************************************************

//   Initializing functions for ports, timer0 & timer1

//*********************************************************************  

void port_init(void)

{

 PORTB = 0x00; 

 DDRB  = 0x06; //PWM pins OC1A & OC1B defined as outputs

 PORTC = 0x00; 

 DDRC  = 0x20; //LED for IR detection indication

 PORTD = 0x00; 

 DDRD  = 0x01; //LED, for testing purpose

}

//timer0 init

void timer0_init(void)

{

    //8-bit timer for measuring delay between IR pulses

TCCR0 = 0x03; //CLK / 64

TCNT0 = 0; //reset the timer

}

//TIMER1 initialize - prescale:1

//PWM Frequency: 1KHz

void timer1_init(void)

{

 TCCR1B = 0x00; //stop

 TCNT1H = 0xFC; //setup

 TCNT1L = 0x18;

 OCR1A  = COUNTER_LOWER_LIMIT;

 OCR1B  = COUNTER_LOWER_LIMIT;

 ICR1H  = 0x03;

 ICR1L  = 0xE8;

}

/**************************************************************************

* Interrupt Service Routine for INT0

* Executed whenever a remote code is detected

**************************************************************************/

#pragma interrupt_handler int0_isr:2

void int0_isr(void)

{

unsigned char count, code, address;

unsigned int IR_input;

TCNT0 = 0;

while(!(PIND & 0x04));

count = TCNT0;

if(count < 30)  //to verify start pulse (2.4 ms long)

{

 delay_ms(20);

 ENABLE_INT0;

 return;

}

 

PORTC |= 0x20;

IR_input = read_IR ();

code = (unsigned char) ((IR_input & 0xff00) >> 8);

address = (unsigned char) (IR_input & 0x00ff);

motorControl ( code, address );

PORTC &= ~0x20;

delay_ms(250);

}

//*********************************************************************

//Function to read IR message from the detector

//Return value contains code in upper byte and address in lower byte

//*********************************************************************  

unsigned int read_IR (void)

{

    unsigned char pulseCount=0,  code = 0, address = 0, timerCount;

unsigned int IR_input;

 

while(pulseCount < 7)

{

  while(PIND & 0x04);

  TCNT0 = 0;

  

  while(!(PIND & 0x04));

  pulseCount++;

 

  timerCount = TCNT0;

 

  if(timerCount > 14)

     code = code | (1 << (pulseCount-1));

  else

 code = code & ~(1 << (pulseCount-1));  

}

pulseCount = 0;

while(pulseCount < 5)

{

  while(PIND & 0x04);

  TCNT0 = 0;

  

  while(!(PIND & 0x04));

  pulseCount++;

 

  timerCount = TCNT0;

 

  if(timerCount > 14)

     address = address | (1 << (pulseCount-1));

  else

 address = address & ~(1 << (pulseCount-1));  

}

 

IR_input = (((unsigned int)code) << 8) | address;

 

return(IR_input);

}

//****************************************************************************

//Function to control motor speed & direction depending onthe IR code rceived

//Argumets are the code and address values received from IR detector

//****************************************************************************  

void motorControl (unsigned char code, unsigned char address)

{

static unsigned char counter, dir, dir1;

 

if (address != 1) //detect only TV remote, other signals rejected

  return;

if((code == 16) || (code == 17)) //Channel+ or Channel- button is pressed

     {

        if(code == 16)  //Channel+

       dir = 0;

    else    //Channel-

       dir = 1;

 

      if(dir != dir1)  //change direction

      {

         STOP_MOTOR;

      delay_ms(500);

  

  if(dir == 0)

         set_FORWARD;

  else

     set_REVERSE;

    

      START_MOTOR;

  dir1 = dir;

         }  

     }  

 

 if(code == 18) //Volume- button pressed

     {

         if(counter >= COUNTER_UPPER_LIMIT) //if speed is already maximum, don't do anything

            counter = COUNTER_UPPER_LIMIT;

    else

   counter += STEP_SIZE;   //increase speed by a fixed step

     

    OCR1A = counter;

    OCR1B = counter;

     }

 

if(code == 19) //Volume+ button pressed

     {

         if(counter <= COUNTER_LOWER_LIMIT) //if speed is already minimum, don't do anything

            counter = COUNTER_LOWER_LIMIT;

    else

   counter -= STEP_SIZE;   //reduce speed by a fixed step

     

    OCR1A = counter;

    OCR1B = counter;

     }

 

     if(code == 9)  //'0' button pressed

     {

         OCR1A  = COUNTER_LOWER_LIMIT;

         OCR1B  = COUNTER_LOWER_LIMIT;

    STOP_MOTOR;  

     }

 

 if(code == 0)  //'1' button pressed

     {

         OCR1A  = COUNTER_LOWER_LIMIT;

         OCR1B  = COUNTER_LOWER_LIMIT;

 

TCCR1A = 0x81;

    START_MOTOR;  

     }

}

//************************************************************

//*** call this routine to initialize all peripherals

//************************************************************

void init_devices(void)

{

 //stop errant interrupts until set up

 CLI(); //disable all interrupts

 port_init();

 timer0_init();

 timer1_init();

 MCUCR = 0x02;

 GICR  = 0x40;

 TIMSK = 0x00; //timer interrupt sources

 SEI(); //re-enable interrupts

 //all peripherals are now initialized

}

//************************************************************

//***** FUNCTION FOR SOFTWARE DELAY OF 1 mSEC (appx.) ******* 

//************************************************************

void delay_ms(int miliSec)  //for 1 Mhz crystal

{

  int i,j;

  

  for(i=0;i<miliSec;i++)

    for(j=0;j<100;j++)

{

 asm("nop");

 asm("nop");

}

}

//*******************************************************

// ************  MAIN FUNCTION  *************

//*******************************************************  

void main(void)

{

 init_devices();

  

 while(1); //infinite loop, waiting for interrups from IR detector

}

//******************************  END  ***************************************

Circuit Diagram:

           

Model Car

Some Experiments with the help of Multimeter

LED when exposed to light,it generate DC voltage:-

Now switch multimeter to the lowest DC voltage range available, and touch the meter's test probes to the terminals (wire leads) of the light-emitting diode (LED). An LED is designed to produce light when powered by a small amount of electricity, but LEDs also happen to generate DC voltage when exposed to light, somewhat like a solar cell. Point the LED toward a bright source of light with your multimeter connected to it, and note the meter's indication.

Motor Acts As Generator:-

Another source of voltage through energy conversion a generator. The small electric motor specified in the "Parts and Materials" list functions as an electrical generator if its shaft is turned by a mechanical force. Connect voltmeter (multimeter, set to the "volt" function) to the motor's terminals just as connected it to the LED's terminals, and spin the shaft with fingers. The meter should indicate voltage by means of needle deflection (analog) or numerical readout (digital).

If it difficult to maintain both meter test probes in connection with the motor's terminals while simultaneously spinning the shaft with fingers, one may use alligator clip "jumper" wires.

Multimeter  fuse checking:-

One may test the condition of a multimeter's fuse by switching it to the resistance mode and measuring continuity through the test leads (and through the fuse). On a meter where the same test lead jacks are used for both resistance and current measurement, simply leave the test lead plugs where they are and touch the two probes together. On a meter where different jacks are used, this is how one insert the test lead plugs to check the fuse.

Bread board continuity:-

Although multimeter is capable of providing quantitative values of measured resistance, it is also useful for qualitative tests of continuity: whether or not there is a continuous electrical connection from one point to another. For instance, test the continuity of a piece of wire by connecting the meter probes to opposite ends of the wire and checking to see the the needle moves full-scale. What would we say about a piece of wire if the ohmmeter needle didn't move at all when the probes were connected to opposite ends?

Digital multimeters set to the "resistance" mode indicate non-continuity by displaying some non-numerical indication on the display. Some models say "OL" (Open-Loop), while others display dashed lines.

Use meter to determine continuity between the holes on a breadboard: a device used for temporary construction of circuits, where component terminals are inserted into holes on a plastic grid, metal spring clips underneath each hole connecting certain holes to others. Use small pieces of 22-gauge solid copper wire, inserted into the holes of the breadboard, to connect the meter to these spring clips so that one can test for continuity.