LINE FOLLOWER ROBOTUSING

Micro-Controllers

WALCHAND INSTITUTE OF TECHNOLOGY,SOLAPUR

Robo Club

BY

WASI QAZI

What is a uC ?

In simple words -- a single chip Computer

Introduction

Computer

• uP• RAM• HDD• Clock• Ports (Serial/USB)• Ports (Parallel)• Mic/Headphone Jack (ADC/ DAC)• Power Supply Unit• Reset• Mother-board

uC

• uP• Flash Memory• EEPROM• Clock Unit• SPI / UART Controllers• Digital I/O Ports• ADC• Power Supply Unit• Reset• IC

Introduction

THE BLOCK DIAGRAM

Microcontroller H - BridgeDC Motor Control

LeftMotor

Right Motor

Clock12Mhz Main Power

SupplyMotor Power

Supply

HEX Inverter

Sensor Array

Analog Comparators

Threshold Voltage

Priority Encoder

NOR Gate

Sensors

• A sensor is a device which measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument.

• They are used to provide feedback from the external environment

IR Sensor Pair

Transmitter (Tx)

Receiver (Rx)

IR sensor PairObject / Line

Transmitter = LED( Light Emitting Diode)

Receiver = Photodiode

Principle of Operation

R1< R2

WHITE surfaceMaximum reflectionT1 is turned ONVout is LOW

BLACK surfaceMinimum or No ReflectionT1 is turned OFFVout is HIGH

ADC BY OP-AMP:

GND

+5v

Line Follower : Design

The bot has two IR sensors facing downwards (towards the floor).

The separation between the sensors is such that in normal (correct) position of the bot , both the sensors are on white surface. ie separation > strip width

The bot is driven by two wheel differential drive ie the two back wheels are driven by independent motors.

SleftSright

Line Follower : Algo

When the bot is in correct pos, both sensors are on white & read LOW. The robot should move forward in this case.

Sleft Sright Movement

LOW LOW Forward

SleftSright

Line Follower : Algo

When the bot is over line from right side, left sensor is on white & reads LOW whereas right sensor is on black & reads HIGH The robot should take a right turn in this case to come back in correct pos.

Sleft Sright Movement

LOW HIGH Right Turn

SleftSright

Line Follower : Algo

When the bot is over line from left side, right sensor is on white & reads LOW whereas left sensor is on black & reads HIGH The robot should take a left turn in this case to come back in correct pos.

Sleft Sright Movement

HIGH LOW Left Turn

Sleft

Sright

Line Follower

Sleft Sright Movement Left Motor Right Motor

LOW LOW Forward Forward Forward

LOW HIGH Right Turn Forward Back

HIGH LOW Left Turn Back Forward

Atmega16L : An Overview

8-bit Micro-cotroller

40-pin DIP

32 Programmable I/O Lines

Operating Voltages 2.7 - 5.5V

Speed Grades 0 - 8 MHz

16K Bytes of In-System Self-programmable Flash program memory

512 Bytes EEPROM

Two 8-bit Timer/Counters with Separate Prescalers and Compare Modes

One 16-bit Timer/Counter with Separate Prescaler, Compare Mode, and Capture Mode

8-channel, 10-bit ADC

Programmable Serial USART

Master/Slave SPI Serial Interface

Programmable Watchdog Timer with Separate On-chip Oscillator

On-chip Analog Comparator

Pin diagram

Block Daigram

Simplified Diagram

4 8bit Parallel Input-Output ports through which you can i/p or o/p digital data.

Power Supply

Port Architecture

PORTA

DDRA

PINA

uC External world

Complete Program

A program to o/p 33 (hex) on PortD and configure and read pins 2 and 7 of Port A

#include <mega16.h>

void main( ){unsigned int x,y;

DDRD=0xFF; // all pins o/pDDRA=0b01111011; // pin 7 & 2 i/p rest immaterial

PORTD=0x33;x=PINA.2;y=PINA.7;}

L298N Motor Driver

Similarly other 2 o/p are connected /disconnected by I/p 3 & I/P 4

All the O/p’s operate independently, ie if all I/p 1-I/p 4 are 1, all O/p1 – O/p4 will be connected to +VPP

L298 can provide 1A current / Output channel , therefore total of 4A. But heat sinks should be installed for such high currents .

VPP can be anything in the range 2V- 46V , therefore any motor can be driven even though Atmega provides only 0/5 V.

ATMEGA

MOTORDRIVER

MOTOR

4 Inputs 4 Outputs

I/p 1 ( O/p from uC)

I/p 2

I/p 3

I/p 4O/p 4

O/p 3

O/p 2

O/p 1

If uC send ‘1’ to I/p 1, O/p is conn to + VPPGND

+VPP

If uC send ‘0’ to I/p 1, O/p is conn to GND

Working of Motor Driver

I/p 1 ( O/p from uC)

I/p 2

I/p 3

I/p 4O/p 4

O/p 3

O/p 2

O/p 1

If uC send ‘1’ to I/p 2, O/p is conn to + VPPGND

+VPP

If uC send ‘0’ to I/p 1, O/p is conn to GND

Working of Motor Driver

Working of Motor

H-BRIDGE MOTOR CONTROL

H-BRIDGE MOTOR CONTROL

H-BRIDGE MOTOR CONTROL

H-BRIDGE USING TRANSISTOR

I/p 1 ( O/p from uC)

I/p 2

I/p 3

I/p 4O/p 4

O/p 3

O/p 2

O/p 1

If uC send ‘1’ to I/p 2, O/p is conn to + VPPGND

+VPP

If uC send ‘0’ to I/p 1, O/p is conn to GND

Motor Connection for Clockwise:

I/p 1 ( O/p from uC)

I/p 2

I/p 3

I/p 4O/p 4

O/p 3

O/p 2

O/p 1

If uC send ‘1’ to I/p 2, O/p is conn to + VPPGND

+VPP

If uC send ‘0’ to I/p 1, O/p is conn to GND

Motor Connection for Anti-Clockwise:

SPEED CONTROL BY PWM