With ATMega8 µc

INTRODUCTIONThis is the robot which keeps moving on a

platform and as soon as it detects an edge, it

turns in opposite direction i.e. if it detects the

edge of platform in its front, it starts moving

backward, if it detects an edge in its left then it

turns to its right and vice versa.

Hardware Components RequiredA microcontroller (ATMega8)

IR Sensor

Comparator (LM358)

DC motor

Motor driver IC (L293D)

Wheels

Power adopter

ATMega8 Development Board

IR SensorsIR 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.

IR Sensor Circuit

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.

Block Diagram

IR Sensor 1

IR Sensor 2

Compar

ator

Compa

rator

Variable DC

voltage

Variable DC

voltage

Microcontr

oller

Motor

with

wheel

Motor

with

wheel

Motor

Driver IC

(L293D)

Overview

IR sensors

Chassis Board

AT Mega8 µc

Comparator(

LM358)

Voltage

regulator IC

Wheel

attached with

motor shaft

DC Motor

Description It works with the signal generated

by the sensors. To avoid the

edge of platform, sensors are

mounted in front of robot at

both left and right side.

Each sensor has a motor associated with it. If it gets

the reflected light(means there is still surface below

the sensor), the comparator sends logic 1 to

microcontroller and vice versa.

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 opposite of the sensor

detecting the edge, for this it turns ON only the motor

associated with that sensor.