This document describes an edge-detecting robot that uses an ATMega8 microcontroller. The robot has IR sensors on the left and right sides that detect edges and cause the robot to turn in the opposite direction. When an edge is detected, the appropriate motor is turned on via a motor driver IC to turn the robot away from the edge. The IR sensors send signals to comparators and then the microcontroller which controls the motor driver IC and decides which motor to power based on sensor input.

1. With ATMega8 μc

2. INTRODUCTION
This 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.

3. Hardware Components Required
A microcontroller (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
Microcontr
oller
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 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.

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 opposite of the sensor
detecting the edge, for this it turns ON only the motor
associated with that sensor.