This project is done by some students of Rajshahi University of Engineering & Technology(RUET), Bangladesh. Department of Mechanical Engineering...

1. LIGHT FOLLOWING ROBOT
HRIDOY BARUA ANIK(1502085),
MD.MAHMUDUL HASAN(1502092),
MD.SHAMIM MIAH(1502096)
DEPARTMENT OF MECHANICAL ENGINEERING, RUET

4. PRESENTATION DETAILS
 Objectives
 Introduction
 Description of apparatus
 Working principle(Mechanical part and Electrical part)
 Results
 Applications , Limitations and Further recommendations

5. OBJECTIVES
The objectives of “The Light Following Robot” project are
 To know the working principle of light following robot.
 To know the working procedure of the circuit diagram.
 To compare the results and resulting data with the standard results and graph.
 To run the project according to the principle.
 To know the applications of the light following robot.

6. INTRODUCTION
 “The Light Following Robot” is a robot that senses the light & follows it. A user
can shine a flashlight at its front and it will respond by following the light source.
 The light following robot depends on the intensity of light. If the transistor, sense
the light in which intensity is high than other, the robot will move on that
direction of the sensing phototransistor.
 If the both transistors sense the same amount light then the robot will move in
the forward direction.

7. DESCRIPTION OF APPARATUS
 Phototransistor: A phototransistor is a light-sensitive transistor. It has two
sides: one is collector and the other is emitter .In the circuit, two
phototransistors are used .One is left phototransistor and the other is right
phototransistor.
 BC548 transistor: It is the transistor which is used in the circuit in order to
control the movement speed of the motor according to light intensity .It can
take maximum 30v supply.
 Breadboard: It is also known as protoboard. Test connections are made on
this .we have used it to make the connection.

8.  DC Motor: Two motors are used to rotate the wheel of the light
following robot .Each motor rotates with 400 RPM .Motors are
parallel connected to save the power .For this type of
motor can rotate separately and robot can follow light in every
direction.
 Battery: Batteries are used in this connection to supply power
.Two 9v battery is connected in series in order to achieve
power.

9. WORKING PRINCIPLE
Figure: Schematic diagram of Light Following Robot

10. Mechanical Part
 Mechanical parts of this robot are motors, wheels and a support cluster wheel. The motor
pair support maximum weight of the robot. It drives wheels which eventually drive the robot.
The wheels are made of rubber to ensure friction which helps to move the robot. The cluster
wheel at the front support a portion of weight of the robot. It can move in all direction unlike
the wheels attached to motors.
 The right motor is controlled by the phototransistor at the left and vice versa. When left
phototransistor gets much light than right phototransistor, the robot is meant to move at left.
So right motor gets much power than the left, which produce more torque and the robot
tend to move left. Same principle works for the other phototransistor – motor pair.
Electrical Part (Circuit)
 The circuit of this robot is simple. It consists of 2 phototransistor, 2 BC548 transistor, wires, 2
motors and batteries.
 There are phototransistor in the circuit. Light falls on the phototransistor’s base and emitter
emits electron flow, which is a signal to send power to motors from batteries.
 But the phototransistor do not have sufficient amplification to drive the motors directly and
so each phototransistor has a second transistor connected to it in an arrangement called a
Darlington-Pair. The BC548 transistor was used as second transistor.

11. RESULTS
Distance(m) Rotation(rpm)
0.25 384
0.51 360
0.76 324
1.02 276
1.27 228
1.52 192
0
50
100
150
200
250
300
350
400
450
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Rotation
Distance
Rotation vs Distance graph
According to the graph, the result can be say that, if distance is increased then the light intensity
which is fall into the phototransistors is decreased and the rotation of the motors as well as the
wheels is decreased. Again if distance is decreased then the light intensity which is fall into the
phototransistors is increased and the rotation of the motors as well as the wheels is increased.
Finally it can be said that, the rotation is inversely proportional to the distance.

12. APPLICATION
 This technology can be used in mining.
 It can determine the direction of sun.
 It can follow a light controlled closed track.so it can be used to carry useful
material in a closed area.
 Alarming devices
 It can also be used to measure light intensity for applications that require greater
precision.
 Cameras can use this technology to determine the proper exposure time.

13. LIMITATION
The LED torch light which used in this project can cover the linear distance of
3.5 m. After the limit the phototransistor stopped to capture the light and the
project stopped working. This is the important limitations of this project.
FURTHER RECOMMENDATIONS
If the light intensity will be more, then the
phototransistor will work from large distance. This project can be
used for large coverage areas in future if better light intensity can
be found. This project can be worked in closed track in future.

14. THANK
YOU