This document outlines a semester project to build a line-following robot. It will use discrete electronic components like light dependent resistors and transistors to sense a white line on a black surface and motors to maneuver along the line. The project will have modules for mechanical design, motor control, and light sensing. It provides details on the components, circuit design, team responsibilities, timeline and potential risks.

1. Electronics-I
Semester Project

2. Farooq Saeed 2009-NUST-BE-EL-25

3.  To design a small autonomous
machine which can track a white
line over a black background.

4.  A line follower robot is basically a machine
designed to follow a path predetermined by
the user.
 The path maybe as simple as a straight or a
curved line or it maybe as complex as a 90
degree turn and junction counting capabilities.
 In our semester project, we will concentrate on
simple tasks.

5.  Line follower robot can detect bright light
using specific sensors, and define it’s motion
accordingly.
 Line follower senses the line using it’s sensors
(LDR’s) and maneuvers the mechanical
structure to stay on course while constantly
correcting wrong moves.

7.  This project can be done using following ways:
1. Using Micro-controller circuit.
2. Using Discrete Electronic Components.

8.  For our project we will be using discrete
electronic circuitry.
 Because its cheap, simple and
hard wired.

9.  We have divided the project into following
modules:
 Mechanical Design.
 Motor Speed and Direction Control.
 Light sensing Mechanism.

10.  The mechanical design should be light weight
and stable.
 It should be able to support the circuit and
motors while maintaining the balance during
operation.
 It should be able to freely move in any
direction without any structural hindrances.

11.  Motor Placement:
The motors should be positioned in the
mechanical structure so as to allow maximum
power transfer and torque. (We might use 2 or 3
motors depending upon the final design and
situation.)
 Direction:
Possible methods may include varying
the motor speed or PWM.

12.  We will use LDR’s or photo-transistors for the
light sensing mechanism.
 The intensity of light reflected from the surface
will determine the resistance of LDR or the
amount of current flowing from collector to
emitter in the photo-transistor.
 This changed resistance or current will
determine the speed of motors.

13.  The correct positioning of the sensors presents
a feasible controlling strategy for complex as
well as simple tasks.
 A robot will know when to turn depending on
the location of the sensors.
 Number of sensors determines the smooth
movement of the robot.
 Optimum distance between the sensors
depends on number of sensors, width of
straight line and the logic applied.

14. Left motor will be connected to the right
sensor and vice versa. As long as the
sensors remain on the white tape, it
continues to move in the straight direction.
But when the sensor detects the black
surface, the infra red light gets absorbed
and LDR resistance or photo transistor
current remains low and subsequently the
robot adjusts its direction by varying the
motor speed.

17.  Photo-transistors
 Light Dependent Resistors
 Comparators
 BJTs
 Diodes
 Resistors
 Motors
 Gates
Note: Components usage depending upon circuit requirement.

18.  Sensor Circuit:
This circuit will be designed using either photo-
transistors or LDRs.
 Photo-transistors allow current to pass from
collector to emitter depending upon the intensity
of light falling on collector-base junction.
 Light Dependent Resistors vary their values of
resistances depending upon light intensity
reflected from the path.

19.  Comparators:
Operational Amplifiers are used as comparators.
It compares two voltages and switches its voltage
to indicate which voltage is larger.

20. Components
Photo-transistors
Light Dependent Resistor

21.  D1: Submission of Project Proposal
(12-11-2010)
 D2: Working Circuit (Breadboard) (Week 12)
 D3: Mechanical Structure (Week 14)
 D4: Full Project Demo (Week 15)
 D5: Project Report (Week 16)
 D6: Poster (SPEX ‘11)

22.  Project Proposal:
Adil Khurram
Farooq Saeed
 Working Circuit:
Adil Khurram
Farooq Saeed
Haider Ali
 Mechanical Structure:
Adil Usman
Javed Khan

23.  R1: Failure of the proposed circuit.
 R2: Low Time Frame
 R3: Faulty Components
 R4: Unavailability of Components
 R5: Failure of synchronization between the
working circuit and mechanical structure.

24.  This project if successfully completed will give
us insight into practical applications of our
Electronics-I course.
 This project will also inculcate in us the ability
of solving real life technical problems using
simplest of electronics components.