1 1. Introduction:- 1.1. About The Project: For my final project, I decided to make a line-follower robot. This simple robot is designed to be able to follow a black line on the ground without getting off the line too much. The robot has two sensors installed underneath the front part of the body, and two DC motors drive wheels moving forward. A circuit inside takes an input signal from two sensors and controls the speed of wheels’ rotation. The control is done in such a way that when a sensor senses a black line, the motor slows down or even stops. Then the difference of rotation speed makes it possible to make turns. For instance, in the figure on the right, if the sensor somehow senses a black line, the wheel on that side slows down and the robot will make a right turn. What is a line follower? Line follower is a machine that can follow a path. The path can be visible like a black line on a white surface (or vice-versa) or it can be invisible like a magnetic field. Why build a line follower? Sensing a line and maneuvering the robot to stay on course, while constantly correcting wrong moves using feedback mechanism forms a simple yet effective closed loop system. As a programmer you get an opportunity to ‘teach’ the robot how to follow the line thus giving it a human-like property of responding to stimuli. Practical applications of a line follower: Automated cars running on roads with embedded magnets; guidance system for industrial robots moving on shop floor etc.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
1. Introduction:-
1.1. About The Project:
For my final project, I decided to make a line-follower robot. This simple
robot is designed to be able to follow a black line on the ground without getting off
the line too much. The robot has two sensors installed underneath the front part of the
body, and two DC motors drive wheels moving forward. A circuit inside takes an
input signal from two sensors and controls the speed of wheels’ rotation. The control
is done in such a way that when a sensor senses a black line, the motor slows down or
even stops. Then the difference of rotation speed makes it possible to make turns. For
instance, in the figure on the right, if the sensor somehow senses a black line, the
wheel on that side slows down and the robot will make a right turn.
What is a line follower?
Line follower is a machine that can follow a path. The path can be visible like a black
line on a white surface (or vice-versa) or it can be invisible like a magnetic field.
Why build a line follower?
Sensing a line and maneuvering the robot to stay on course, while constantly
correcting wrong moves using feedback mechanism forms a simple yet effective
closed loop system. As a programmer you get an opportunity to ‘teach’ the robot how
to follow the line thus giving it a human-like property of responding to stimuli.
Practical applications of a line follower: Automated cars running on roads with
embedded magnets; guidance system for industrial robots moving on shop floor etc.
2
Block Diagram:
Fig.1 Block diag. Of Track Follower Robot
1.2. DESCRIPTION OF BLOCK DIAGRAM
TRACK FOLLOWER
SENSOR:-We used Infrared Emitter-Sensor pair for sensing the track. When
the emitter passes over the white surface the light from it is reflected back to
the sensor whereas on black surface light doesn’t reflect back and thus
resistance of sensor goes high which intern switches off the motor.
AMPLIFIER- In this we used NPN transistor BC548 as the amplifier circuit. It
amplifies the low intensity sensor signal and provides it to the input of the
motor driving circuit.
CALIBRATION CIRCUIT- A preset or variable resistor of value 500K is
used to adjust the sensitivity of the sensor.
MOTOR DRIVEN CIRCUIT- L293D is used as motor driving circuit which
responses accordingly to the low input signal provided by the amplifier circuit.
MOTOR-In this we used the DC MOTORS which are used to move the
follower ahead.[1]
3
1.3. Circuit diagram
Fig. 2 Circuit Diagram of Track follower
4
1.4. Explanation of the Circuit
Introduction to Track follower:
Track follower is a machine that can follow a path. The path can be visible like a
black line on a white surface (or vice-versa) or it can be invisible like a magnetic
field. For many TRUE robotics competitions, which require an autonomous vehicle, a
track-follower is a pre-requisite. And unbelievably, a line-follower can be constructed
without using any microprocessor/controller and is a mere game of two sensors, a
comparator IC, and DC motors to move your vehicle [1]
.
The Circuit explanation:-
The robot uses a combination of IR Photo diode and IR-LEDs to sense the presence to
a line. An IR Photo diode is a resistor whose resistance is proportional to the light
falling on it- greater the light, lesser the resistance and visa-versa. The basic principle
underlying this project is that objects light in colour radiate the light falling on them
while dark coloured objects don’t. So when the sensors are above the black line the
light emitted by the IR- LED is not radiated by the floor, hence the resistance of the
Photo-diode increases. The opposite happens when the robot back on the white
surface.
In our robot the IR Photo diode is used part of a voltage divider circuit. The circuit
diagram of the voltage divider used in this project is given below
The resistor whose value is 500K is a potentiometer. A potentiometer (pot or preset)
whose resistance can be changed. In our project, we will be using 500k presets, that
is, we will use presets whose resistance can be changed from 0K to 500K.
5
When the robot is on white surface the
light emitted by the IR LEDs fall on the
IR Photo diode and decreases its
resistance. This in turn reduces the
voltage at Vout. When the robot is on
the black line, the light emitted by he
IR- LEDs does not reach the IR Photo
diode, hence its resistance increases.
This in turn increases the voltage at Vout. Fig. 3 Sensor Circuit
During both the cases it is necessary to adjust the 500K preset in such a way that, when
the robot is on white surface, voltage at Vout is <0.8V (so that the voltage at the emitter
of the transistor is LOW) and when the sensor is on the black line the voltage is >0.8V
(so that the voltage at the emitter of the transistor is HIGH). For controlling the two DC
motors, I have used the L293D motor driver. The reason I used this is that it has high
noise immunity (that is, it considers voltages up to 1.7V as LOW), perfect for a robot
which deals with analog signals.[2]
The pins 4, 5, 12 and 13 are connected to ground. Pin 8 is the motor power supply pin
and is connected to Vcc (9V) along with Pins 1, 16 (the two enable pins) and Pin 9.
The left and right motors are connected to Pins 3, 6 and Pins 14, 11 respectively. Pin 2
(Input A), Pin 7 (Input B) and Pin 15 (Input A), Pin 10(Input B) are the input pins for
controlling the left and right motor respectively. The truth table for controlling the
motors is given below
6
Fig.4 Sensors mounted on Robot.
Fig.5 schematic of track follower on PCB
7
WORKING OF THE CIRCUIT:
In both the sides of the robot two sensors are used to sense the presence the line. The
output of both the sensors of each side are connected together and connected to an
LED. So that, the LED glows even when one of the sensors detects the line. The
output of the left sensor is connected to Input A (Pin 2) of the left motor and the right
sensor to Input A (Pin 15) of the right motor. When the robot is on white surface only
one (Pin 7 and 10) input pin in each channel is high. The Pins 2 and 15 are low as the
sensors are on white surface. Hence this makes the robot move forward. When the left
sensor is on the line, Pin 2 is high. But Pin 7 is also high. Hence the left motor is
switched off as both the inputs are HIGH (refer to the truth table above).But the right
motor is still turning forward. This brings the robot Back on the white surface.
Similarly when the right sensors are on the line, the right motor is switched off until
the robot is back on the white surface.[3]
This circuit works fine for black line following and using the robot as a photovore and
obstacle avoider, for following white line and for using the robot as a photophobe,
there is a slight change in the circuit. The left sensor output is connected to Pin 7 and
right sensor output to Pin 10. Pins 2 and 15 remain unconnected.
The rest of the circuit remains unchanged. When the robot is on black surface (when
following white lines), the input pins 2 and 15 are high. This makes the motors turn
forward. When the left sensors are on the line the output goes low and stops the motor
until the sensors are back on the black surface. Similarly, when the right sensors are
on the line, the right motor is stopped.
8
Fig.6 Track Follower
Fig. 7 Views of Line follower/Track Follower
9
2. Description of Components:
2.1. LIST OF COMPONENT:
S.No. Equipment’s name Rating Manufacturer Quantity Cost per
unit
Total
cost
1 Resistor 100k +4
2 L293D 1 3 3
3 Capacitor 2 2 .50 1
4 IC Socket 4 4 3 12
5 Zero PCB 10*10 1 35 35
6
7
8
Total 998 908 90
10
2.2. Components Description:
2.2.1. Capacitor:
A capacitor or condenser is a passive electronic component consisting of a pair of
conductors separated by a dielectric. Capacitors store electric charge in them. They
are used with resistors in timing circuits because it
takes time for a capacitor to fill with charge. They are
used to smoothly vary DC supplies by acting as a
reservoir of charge. They are also used in filter
circuits because capacitors easily pass AC (changing)
signals but they block DC (constant) signals. An
ideal capacitor is characterized by a single constant
value, capacitance, which is measured in farads.
Fig.8 Capacitor
This are of different types which includes- multilayer ceramic, ceramic disc,