How to make a Line Follower Robot

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).

(c) Copyright, roboVITics club 2012 2

Hardware Components
• IR Sensors
• DC Geared Motors
• Robot Chasis
• Microcontroller development board
• Atmega 8 Microcontroller
• USB Programmer


IR Sensor


Block Diagram
Every sensor has three
terminals
VCC •VCC – to power up the
sensor
•GND – to provide a
fixed negative
reference
Physical
Parameters
Sensor OUTPU •OUTPUT – analog
T output of the sensor

GND

Working
• IR sensor works on the principle of emitting IR
rays and receiving the reflected ray by a receiver
(Photo Diode)


IR Sensor circuit


Types of resistor
• Fixed type resistor

• Variable type resistor


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


LM358 IC


Internal circuit


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.


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.


Chasis
• Provides a base
to the robot.
• Wheels, sensors
and controller
board are
attached to it.


IC’s
• L293D
• LM358
• IC 7805(voltage controlled)


IC 7805
• It is a voltage regulator integrated circuit.
• It designed to automatically maintain a
constant voltage level


Features
• Output current range up to 1A
• Output voltage 5V
• Input voltage range up to 12V
• Short circuit protection


Transistor
• Transistor are of two types:
1-> n-p-n
A straight switch

2-> p-n-p
A inverted switch


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).


Circuit diagram to show a switching
VCC

Logic transisto Motor
r

0 off stop
1 on run
Logic 1
or RB
Logic 0

M

GND

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).


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).

H-Bridge Operation

A B o/p
0 0 Stop
0 1 Clock wise
1 0 Counter clock
wise
1 1 Stop


L293D IC

EN1 EN1 Vcc

12V EN2

12V


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.


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.

Interface motor with IC L293D

EN1 VCC

12V EN2


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.

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


Microcontrollers Microprocessors
• Full fledged PC! • Separated units
• ROM, RAM, Flash, • Higher resources
CPU, ALU, on-chip • MCU – (everything in
peripherals point 2)
• Lower resources


Typical MCU based solution

Microwave Oven


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


AVR ATmega8 Microcontroller


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


TYPES OF PACKAGES

 28-lead PDIP (Plastic Dual In-line
Package)

 32-lead TQFP (Thin Quad film Package)


How ATmega8 PDIP Package looks
like?


How ATmega8 TQFP Package looks
like?


Pinout of ATmega8


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).


PORT C(PC6-PC0)
programming).


PORTD(PD7-PD0)
programming).


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.


USB Programmer
• Used to burn code
from laptop to
memory of
microcontroller.


Two sensor line follower

Left Right Directi Left Right
Sensor Sensor on Motor Motor
0 0 Forwar +12V +12V
d
0 1 Copyright, roboVITics club 2012
(c)
Left -12V +12V 44

Getting Started
Selecting Hardware Selecting Software
• PC / Mac • OS – Windows / Mac
• In-System OS / Linux
Programmer (ISP) • “Free” Compiler
• Target Board (MCU • “Free” Programmer
Dev Board) Software
• Lastly, a MCU!!


Softwares needed
• AVR Studio – for programming
• Compiler – for compiling the code
• eXtreme Burner or avrloader – for buring
code generated to microcontroller.


Step 1


Step 2


Datasheet
• 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!!

AVR Studio
• 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


INTRODUCTION TO EMBEDDED SYSTEM
AND
EMBEDDED C


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.

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


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.

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)
(c) Copyright, roboVITics club 2012
60

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.


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.


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.

For Details, visit

maxEmbedded.com
A guide to robotics and embedded electronics
AVR Guide and Tutorials
Basics of Microcontrollers, Sensors, Timers, ADC, Serial Communication, etc


maxEmbedded blog


Online Stores
• store.extremeelectronics.co.in
• nex-robotics.com
• embeddedmarket.com
• rhydolabz.com
• thinklabs.in
• sparkfun.com


Suggestions and Doubts are welcome
That’s all for today
Thank you

24 hour helpline
9566758862

P.S. Its not toll-free! For more info, visit Mayank’s blog
maxEmbedded. com
(c) Copyright, roboVITics club 2012 © maxEmbedded68 2012

How to make a Line Follower Robot

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