How to make a line follower Introduction

How to make a line follower

(c) Copyright, roboVITics club

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Introduction

What is a line follower?

• Line follower is a robot that can follow a

path. The path can be visible like a black

line on a white surface (or vice-versa).


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Hardware Components

• IR Sensors

• DC Geared Motors

• Robot Chasis

• Microcontroller development board

• Atmega 8 Microcontroller

• USB Programmer


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IR Sensor


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Block Diagram Every sensor has three terminals

•VCC – to power up the sensor

•GND – to provide a fixed negative reference

•OUTPUT – analog output of the sensor

VCC

Sensor

GND

OUTPU

T

Physic

al

Param

eters


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Working

• IR sensor works on the principle of emitting IR

rays and receiving the reflected ray by a receiver

(Photo Diode)


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IR Sensor circuit


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Types of resistor

• Fixed type resistor

• Variable type resistor


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LM358

• The LM358 IC consists of two independent

operational amplifiers which were

designed specifically to operate from a

single power supply over a wide range of

voltages.

• It have two op-amp

• Single power supply


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LM358 IC


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Internal circuit


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DC geared motors

• Motors having external

gear arrangement

attached with motor.

• It has a gearbox that

increases torque and

decreases speed.

• Most commonly used in

robotics as they are

having considerable

torque.


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DC Motors

• Motors which works on dc

current and gives a

rotating motion as an

output.

• In robotics applications,

they are preferred over

AC motors as the motor

and the complete circuit

require same kind of

supply i.e. DC supply.


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Chasis

• Provides a base to

the robot.

• Wheels, sensors

and controller

board are

attached to it.


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IC’s

• L293D

• LM358

• IC 7805(voltage controlled)


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IC 7805

• It is a voltage regulator integrated circuit.

• It designed to automatically maintain a

constant voltage level


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Features

• Output current range up to 1A

• Output voltage 5V

• Input voltage range up to 12V

• Short circuit protection


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Transistor

• Transistor are of two types:

1-> n-p-n

A straight switch

2-> p-n-p

A inverted switch


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n-p-n as a switch

• When base of n-p-n is connected with

logic high voltage then it short circuit

emitter and collector (SWITCH ON).

• When base of n-p-n is connected with

logic low voltage then it open circuit both

emitter and collector (SWITCH OFF).


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Circuit diagram to show a switching

RB

M

VCC

Logic 0

Logic 1

or

GND

Logic transisto

r

Motor

0 off stop

1 on run


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p-n-p as an inverted switch

• When base of p-n-p is connected with

logic high voltage then it open circuit

emitter and collector (SWITCH OFF).

• When base of p-n-p is connected with

logic low voltage then it short circuit both

emitter and collector (SWITCH ON).


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Controlling Motor Using H-Bridge

• Switches settings for

rotation:

S1&S4: ON and

S2&S3: OFF (for one

direction).

S2&S3: ON and

S1&S4: OFF (for other

direction).

• S1-S2: ON or S3&S4: ON

(can be used to stop the

motor).


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H-Bridge Operation

A B o/p

0 0 Stop

0 1 Clock wise

1 0 Counter clock

wise

1 1 Stop


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L293D IC

Vcc EN1

EN2

12V

EN1

12V


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Conti….

• 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

• If you have motor with fix direction of motion then you can make use of all the four I/Os to connect up to four DC motors.

• L293D has output current of 600mA.

• Moreover for protection of circuit from back EMF output diodes are included within the IC.


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Dual H-Bridge Motor Driver IC: L293D

Features:

• Capable of driving 2

motors at a time in

clockwise and anti-

clockwise direction

separately.

• Works as an interface

for controlling motors

using lower voltage

(5V) and running

motors on higher

voltage.


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Interface motor with IC L293D

EN1

EN2 12V

VCC


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What is a Microcontroller?

A microcontroller (sometimes abbreviated µC or MCU) is a small computer on a single IC containing a processor core, memory, and programmable input/output peripherals.

It is a decision making device used widely in embedded systems and all intelligent devices.


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Difference between Microcontroller

and Microprocessor

Microcontroller has I/O ports, Memory,

timers etc all integrated on chip itself

In Microprocessors, I/O ports, memory,

timer etc are to be connected externally


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Microcontrollers

• Full fledged PC!

• ROM, RAM, Flash,

CPU, ALU, on-chip

peripherals

• Lower resources

Microprocessors

• Separated units

• Higher resources

• MCU – (everything in

point 2)


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Typical MCU based solution

Microwave Oven


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MCU Ports • Ports contains pins of

the MCU

• Can be turned ON or OFF by the program

– ON = 1 (in TTL 5V)

– OFF = 0 (in TTL 0V)

• Input mode – values can be read

– Above threshold = ON

– Below threshold = OFF


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AVR ATmega8 Microcontroller


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How AVR ATmega8 got its

name? It was developed by Atmel Corporation

AVR implies it belongs to AVR family.

‘8’ in Atmega8 means this microcontroller

has 8Kb of flash memory


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TYPES OF PACKAGES

28-lead PDIP (Plastic Dual In-line

Package)

32-lead TQFP (Thin Quad film Package)


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How ATmega8 PDIP Package looks

like?


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How ATmega8 TQFP Package looks

like?


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Pinout of ATmega8


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PORT B(PB7-PB0)

It is a 8-bit bi-directional I/O port.

It can be used either as a input port or as

output port ( direction must be specified in

programming).


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PORT C(PC6-PC0)




programming).


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PORTD(PD7-PD0)




programming).


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Microcontroller development board

• Used to interface motors, sensors and various other devices with microcontroller.

• Components like resistors, capacitors, power supply are attached to the microcontroller via development board for its working.


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USB Programmer

• Used to burn code

from laptop to

memory of

microcontroller.


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Left

Sensor

Right

Sensor

Directi

on

Left

Motor

Right

Motor

0 0 Forwar

d

+12V +12V

0 1 Left -12V +12V

1 0 Right +12V -12V

Two sensor line follower


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Getting Started

Selecting Hardware

• PC / Mac

• In-System

Programmer (ISP)

• Target Board (MCU

Dev Board)

• Lastly, a MCU!!

Selecting Software

• OS – Windows / Mac

OS / Linux

• “Free” Compiler

• “Free” Programmer

Software


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Softwares needed

• AVR Studio – for programming

• Compiler – for compiling the code

• eXtreme Burner or avrloader – for buring

code generated to microcontroller.


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Step 1


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Step 2


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• Manufacturer gives information regarding the

product to its users

• Data given is in detail

• Features, Technical Specs, Design, Register

Summary, Expected Usage, Troubleshooting,

Pin details, etc.

• Best source of info!!

• All electronic components have a datasheet for

them

• Google them out!!

Datasheet


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Pin Configurations

Atmega8 Atmega16/32


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• Most popular C compiler for AVR

• Its official!

• Unlike other compilers/emulators, its totally

free

• The code written will be common to all AVR

mcu’s

• AVR Studio 4 has been used

• AVR Studio 5 beta and AVR Studio 6 has

been released

AVR Studio


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INTRODUCTION TO EMBEDDED SYSTEM

AND

EMBEDDED C


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What is Embedded C?

• Embedded C is nothing but a subset of C

language which is compatible with certain

microcontrollers.

• Some features are added using header files like

<avr/io.h>, <util/delay.h>.

• scanf() and printf() are removed as the inputs

are scanned from the sensors and outputs are

given to the ports.

• Control structures remain the same like if-

statement, for loop, do-while etc.


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Development process of Embedded C

projects • Write C programs in AVR Studio IDE(Integrated

Development Environment)

• Compile them into a .hex file using the AVR-GCC

compiler (which integrates into AVR Studio)

• Simulate the target AVR program and debug the code

within AVR Studio

• Program the actual chip using the USBasp device, which

is attached to our target board with a special 6-pin cable

• Once programmed, the chip runs the program in your

circuit


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Registers to Communicate with I/O

Ports

To communicate with the ports of

Atmega8, we use three registers:

PINx

PORTx

DDRx

Where x would be either B,C or D.


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DDRx Register

It stands for Data Direction Register.

It is used to define Port as Input or Output.

In order to make Port as Input Port:

DDRx=0x00 (In Hexadecimal)

DDRx=0b00000000(In Binary)

In order to make Port as output Port:

DDRx=0xFF (In Hexadecimal)

DDRx=0b11111111(In Binary)


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PORTx Register

If DDRx=0xFF(Output port)

Writing logic 1 to PORTx will make output

high i.e 5v for that particular pin.

Writing 0 to PORTx will make output low

i.e 0v for that particular pin.


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Continued..

If DDRx=Ox00(Input port):

If corresponding PORTx bit is set to 1, Internal pull up resistors are enabled i.e if we do not connect this pin to anything it still reads as 1.

If corresponding PORTx bit is set to 0, internal pull up resistors are disabled i.e the pin will enter a high impedance state and will become unpredictable.


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PINx Register

It reads data from the port pins.

If any/all bits of DDRx is set to 0(input)for

a particular pin, we can read data from

PINx

If any/all bits of DDRx is set to 1(output),

then reading PINx register gives the same

data which has been output on that

particular pin.


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Grid Follower


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maxEmbedded.com

For Details, visit

A guide to robotics and embedded electronics AVR Guide and Tutorials

Basics of Microcontrollers, Sensors, Timers, ADC, Serial Communication, etc


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maxEmbedded blog


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• store.extremeelectronics.co.in

• nex-robotics.com

• embeddedmarket.com

• rhydolabz.com

• thinklabs.in

• sparkfun.com

• ietestore4u.com

Online Stores


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That’s all for today

Suggestions and Doubts are welcome

For more info, visit Mayank bhaiya’s blog maxEmbedded.wordpress.com

© maxEmbedded 2013

Thank you


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Documents

How to make a line follower Introduction