This document describes the design of a line-following robot that uses an ATMega8 microcontroller. The robot uses IR sensors to detect a black or white line and follow it, taking turns automatically. It includes IR sensors, a comparator IC, motor driver IC, DC motors, and a microcontroller board to process sensor input and control the motors accordingly to follow the line. The robot is able to detect the line with the IR sensors, send the sensor signals to the microcontroller via comparators, and have the microcontroller turn the appropriate motor on or off to steer the robot along the line.

1. With ATMega8 μc

2. Introduction
This robot is designed to continuously
follow a black line painted on a bright
surface or a white line on a dark surface
and take the turns along with the line
automatically.

3. Hardware Components Required
 Microcontroller development board (ATMega8)
 IR Sensor
 Comparator (LM358)
 DC motor
 Motor driver IC (L293D)
 Wheels
 Power adopter

4. ATMega8 Development Board

5. IR Sensors
 IR sensors give output by receiving the reflected rays
transmitted by the transmitting diode.
 If the surface is black, the transmitted
ray will be absorbed and will not be
received and if the surface is white then
receiver will get the reflected ray and generate output.

6. IR Sensor Circuit

7. Motor Driver IC (L293D)
 It is required to supply sufficient
current to motors as microcontrollers
can’t supply that much current.
 It is a dual H-Bridge motor
means it can drive two DC
motors simultaneously in both
clockwise and anticlockwise
direction.
 Its input terminals are controlled
by the microcontroller.
It also includes the protection
circuit against back EMF.

8. Block Diagram
IR Sensor 1
IR Sensor 2
Variable DC
voltage
Compar
ator
Compa
rator
Variable DC
voltage
Microcont
roller
Motor
with
wheel
Motor
with
wheel
Motor
Driver IC
(L293D)

9. Overview
AT Mega8 μc
Chassis Board
IR sensors
Comparator
(LM358)
Voltage
regulator IC
Wheel
attached
with motor
shaft
DC Motor

10. Description
 It works with the signal generated by the sensors.
To follow black line, sensors are mounted in front
of robot keeping black line in between them.
 Each sensor has a motor associated with it. If it
gets the reflected light(means sensors are facing
bright background), the comparator sends logic 1
to microcontroller and vice versa.

11. CONTI….
 The program loaded into microcontroller takes the
decision of switching any motor ON or OFF
according to the inputs coming from the
comparators connected after each sensor.
 The robot turns in the direction of the sensor
detecting the black line, for this microcontroller
turns ON only the motor opposite to that sensor.