Line follower is an autonomous robot which follows either black line in white area or white line in black area. Robot must be able to detect particular line and keep following it.

For special situations such as cross over’s where robot can have more than one path which can be followed, predefined path must be followed by the robot.

Line following is a task in which robot has to follow the line. It must be capable of taking various degrees of turns to follow the curved lines also.

Fig. 1: Prototype of LM324 IC based Line Following Robot

Image: Line Follower Robot without Microcontroller

The Line following Robot moves to follow a line drawn on the floor. This Robot follows the black line which is drawn over the white surface .The line sensors are used to sense the line. When the signal falls on the white surface, it gets reflected and if it falls on the black surface, it is not reflected this principle is used to scan the Lines for the Robot.

The Robot should be capable of taking various degrees of turns and must be insensitive to environmental factors such as lighting and noise.

Principal of Operation

Principal of operation

Fig. 2: Block Diagram of LM324 IC based Line Following Robot

 

Explanation of block diagram

 

Stage 1  

Line sensor plate

Reflection of light

This stage consists of reflection of light phenomena in which light reflect from the plane surface.

LED:

LEDs are used as indicator lamps in many devices and are increasingly used for general lighting.

Long leg is positive.

Fig. 3: Image showing polarity of LED

Short leg is negative.

LDR: 

A photoresistor light dependent resistor (LDR) or is a resistor whose resistance decreases as with increasing incident light intensity.

Fig. 4: Typical Image of Light Dependant Resistor (LDR)

Reflection of light on any plane surface 

Fig. 5: Image showing mutual assembly of LED and LDR Sensor against a plane surface

Reflection of light on white surface is More.

Reflection of light on black surface is Less.

Line sensor

Line sensor is a combination of LDR (Light Dependent Resistor) and LED (Light Emitting Diode) which works on phenomenon of Reflection and Absorption.

White color surface reflects the most of the color falling on them while Black color surface absorbs all the light  falling on them.

So, a major part of light emitted by LED is reflected by white surface and so, LDR detects it.

Image of line sensor

Fig. 6: Image of Line Sensor built using LED and LDR on a PCB

Stage 2

Logic circuit Section

Logic circuit consists of LM324 ic which is used for to generate logic signal. It take input from the line sensor and generate the output signal which is used for to drive the motors.

LM324 IC

LM324 is a 14pin IC consisting of four independent operational amplifiers (op-amps) compensated in a single package. Op-amps are high gain electronic voltage amplifier with differential input and, usually, a single-ended output. The output voltage is many times higher than the voltage difference between input terminals of an op-amp.

Pin Diagram

Fig. 7: Pin Diagram of LM324 OPAMP IC

Pin Description: 

Pin No	Function	Name
1	Output of 1st comparator	Output 1
2	Inverting input of 1st comparator	Input 1-
3	Non-inverting input of 1st comparator	Input 1+
4	Supply voltage; 5V (up to 32V)	Vcc
5	Non-inverting input of 2nd comparator	Input 2+
6	Inverting input of 2nd comparator	Input 2-
7	Output of 2nd comparator	Output 2
8	Output of 3rd comparator	Output 3
9	Inverting input of 3rd comparator	Input 3-
10	Non-inverting input of 3rd comparator	Input 3+
11	Ground (0V)	Ground
12	Non-inverting input of 4th comparator	Input 4+
13	Inverting input of 4th comparator	Input 4-
14	Output of 4th comparator	Output 4

Logic inverter circuit section

In this logic inverter circuit section 74HC04D IC is used for to invert the logic. The logic is  given to it ’s input terminal in the form of logic 0 and logic 1.

74HC04 IC

This IC is used for to invert the logic. The input are given from the output of LM324 IC and this IC output are used for to drive the motor. It also provide buffering that is amplification for the motor driver IC.

Fig. 8: Pin Diagram of LM7404 Logic Inverter IC

Stage 4

Motor Driving Stage

In this stage the motor driver l293D IC is used for to drive the motor. As the signal comes from the inverter IC it drives the motor according to signals comes.

L293D IC

L293D is a dual H-bridge motor driver integrated circuit (IC). Motor drivers act as current amplifiers since they take a low-current control signal and provide a higher-current signal. This higher current signal is used to drive the motors.

L293D contains two inbuilt H-bridge driver circuits. In its common mode of operation, two DC motors can be driven simultaneously, both in forward and reverse direction. The motor operations of two motors can be controlled by input logic at pins 2 & 7 and 10 & 15. Input logic 00 or 11 will stop the corresponding motor. Logic 01 and 10 will rotate it in clockwise and anticlockwise directions, respectively.

Enable pins 1 and 9 (corresponding to the two motors) must be high for motors to start operating. When an enable input is high, the associated driver gets enabled. As a result, the outputs become active and work in phase with their inputs. Similarly, when the enable input is low, that driver is disabled, and their outputs are off and in the high-impedance state.

Fig. 9: Pin Diagram of L29D Motor Driver IC

Truth table for robot Movement

Sr.No	IN1	IN2	IN3	IN4	Movement of robot
1	1	0	0	1	Forward
2	0	1	1	0	Backward
3	0	1	0	1	Left
4	1	0	1	0	Right

Note

You can exchange the motor wire with output pins to make the above respective movement.

Accessories Required to make line follower robot

Sr.No.	Component Name	Quantity
1.	Double AA batteries cell holder	1
2.	Chassis  ( Robotic  Platform)	1
3	Breadboard	1
4	Nipper	1
5.	Stripper	1
6.	One  core wire	1
7.	Nose pliers	1
8	Screw driver	1

Mechanical assembly of robotic chassis

 

Step 1:

Take a robotic chassis.

Fig. 10: Representational Image of Main Chassis of Robot

Step 2:

Take the BO motor as shown in the diagram.

Step 3:

Take a M2.5 (25) screw to fit the BO motor on the chassis. Fit the motor in upward direction as shown in the figure. Here the last hole of the chassis are used to fit the motor.

Fig. 11: Image showing motor attachment to robot’s chassis

Note

Here kept the motor screw M2.5 (25) in the separate polyethene and also don’t mix it with other screw.

Fig. 12: Image showing motor attachment on both sides of robot’s chassis

Step 4

Fit the both wheel on the both motor shaft as shown in figure. Fix the motor with self tapping red wheel screw.

Fig. 13: Image showing attachment of wheels to motors on robot’

Step 5 

Take the caster wheel and caster wheel strip as shown in the diagram.

Fig. 14: Representational Image of Caster Wheel and Strip for Robot

Step 6

Inset three M3 -10 screw into the caster wheel. Now fit the caster wheel into the caster wheel strip in the outward direction as shown in the figure.

Fig. 15: Image showing attachment of Caster Wheel to Strip for Robot

Step 7

Now fit the caster wheel strip on the middle position of the chassis as shown in the diagram by using two M3-10 screw.

Fig. 16: Image showing attachment of Caster Wheel strip to Chassis of Robot

Now your robotic platform is ready to be used.

Breadboard Connection

Breadboard Connection  

Fig. 17: Image showing rows and columns of breadboard

·         Give positive +5 volt supply in first row.

·         Connect the GND in the second row of the breadboard.

·         Connect + 5 volt  upper row with the below row to make below line +5 volt . 

·         Connect the upper gnd line with the lower gnd line to make the below row gnd line.

·         Short the below middle rows as connect the +5 volt to +5volt line and gnd line with the gnd line.

Fig. 18: Typical image of Breadboard

Construction of line follower robot on breadboard

·         Power Supply

·         Motor Driver

·         Logic sensor ( Comparator + Line sensor plate)

·         Inverter IC section

Power Supply

General Description

Power supply is used for to give power to the whole circuit assembly. The below component are used for to make power supply section.

Component list for power supply

Sr.No.	Component Name	Component list
1	DC jack	1
2	7805 voltage regulator IC	1
3	3 mm Led	1
4	Resistor  (220 ? ) (Red, Red, Black, Black )	1

Explanation of component

Make the below connection for power supply as given in below image.

DC jack

Fig. 19: Typical Image of DC Jack

7805 Connection pin diagram

Sr .No	7805 Pin No	7805 Pin name
1	Pin 1	+12 volt (Given by battery)
2	Pin 2	Gnd
3	Pin3	+ 5 (output to give whole circuit )

By referring below images you can make the power supply circuit.

1.      Breadboard Image

Fig. 20: Representational Image of Power Supply Circuit on Breadboard

2.      Schematic Diagram for  power supply

Fig. 21: Circuit Diagram of Power Supply for Robot

3.      Actual image of  power Supply

Fig. 22: Image of Power Supply Circuit designed on Breadboard

Testing of power Supply Section

If  the led will be glow it means the power supply circuit connection is correct. and  now you can able to give power to whole the assembly.

Motor Drive Section

General Description

Now you have make a motor driver section which is used for to drive the motor. Here to drive the motor you have use L293D IC.

Component List for Motor Driver Section

Sr No	Component Name
1.	L29D3 IC Section
2.	One core wire

Designing of motor driver section

By referring below images and table  you can make and test the motor driver section.

L293D pin connection

Sr.No	L293 D pin	Supply voltage
1	Pin no 1	+5 volt
2	Pin no 9	+5 volt
3	Pin no 16	+5 volt
4	Pin no 8	+12 volt
5	Pin no 4 &  5	Gnd
6	Pin no 12 & 13	Gnd

Connection of Motor with L293D IC

Sr. No.	Output pins	Motor Wire
1	o/p1	First wire of  first  motor
2	o/p2	Second wire of first motor
3	o/p3	First wire of second motor
4	o/p4	Second wire of second motor

Breadboard Image

Fig. 23: Representational Image of Motor Driver Circuit on Breadboard

Schematic image of motor driver section

Fig. 24: Circuit Diagram of L293D IC based Motor Driver

Actual  image of  motor driver section

Fig. 25: Image of L293D Motor Driver circuit on Breadboard

Give the below supply at input terminal of L293d IC to test the motor 

Sr.No.	Pins Name	Given supply
1	In1	+5
2	In2	Gnd
3	In3	+5
4	In4	Gnd

Note

·         Short 4  (gnd) and 5 (gnd) pin with the jumper. Jumper can be taken from the wire.

·         In the same way also short  pin no  12 (gnd) and 13(gnd) of the l293D IC.  

Testing of motor driver section

Fig. 26: Representational Image of Motor Driver Circuit on Breadboard

Step 1

Connect one wire of  first motor with the o/p1 pin of L293D IC. And second one is with second o/p2 of L293D IC.

The motor should be rotate in clockwise direction from your front side. If the motor rotate in anticlockwise direction than make it in clockwise direction by exchanging it’s wire with L293 o/p pins.    

Step 2

Connect one wire of  second  motor with the o/p3 pin of L293D IC. And second one with second o/p4 of L293D IC.

Now the motor should be rotate in anticlockwise direction from your front side. If the motor rotate in clockwise direction than make it in anticlockwise direction by exchanging it’s wire with L293D o/p pins.   

Now the chassis should be moves in the forward direction.

Logic Circuit

General Discription

This section consists of  two parts one is comparator section and another one is line sensor plate section.

Part 1

Comparator Section

Comparator LM324 IC  is used to generate logic which is used to drive the motor and led. Here the comparator IC is used to perform comparison between the reference voltage which is set at it’s non inverting input terminal and it’s inverting terminal voltage.

Component required to make logic circuit is as given below table.

Sr.No.	Component Name	Quantity
1.	LM324 IC	1
2.	20 k preset (Metallic)	2
3.	Led ( 3mm )	2
4.	10 k ? ( Brown, Black ,Black, Red)	4

Component Explanation

20 k preset

Fig. 27: Image showing pin connections for 2K Preset

Here two potentiometer are used to set reference voltage at the non inverting terminal of pcb.

Note:

You can exchange the 5 volt and Gnd pin with each other.

LM 324 IC section

Sr.No	Pin no	Component Connection
1	1 (Output pin)	Negative terminal of led
2	2 (Inverting pin)	o/p  of  LDR sensor 1  from zero pcb
3	3 (Non inverting terminal)	o/p pin of potentiometer 1
4	4  (vcc)	+5 volt
5	11	GND
6	14(Output pin)	Negative terminal of led
7	13 (Inverting pin)	o/p  of  LDR sensor 2  from zero pcb
8	12 (Non inverting terminal)	o/p pin of potentiometer 2

Make also below connection

·         Connect the positive terminal of both  led with the  one terminal of 10 k ? resistance  and another terminal of resistance with the +5 volt.

·         Connect the  one terminal of 10 k?  resistance with the  pin no 2 & pin no 13 of the LM324 ic and another terminal of both resistance with the + 5volt.

·         Also insert the 220 ? resistance in breadboard where it’s one terminal is connected to +5 volt and another will be connected with the Zero pcb +5 volt pin. 

1.      Breadboard image of  logic section

Fig. 28: Representational Image of LM324 based Logic Circuit for Robot

2. Schematic layout of logic section

Fig. 29: Circuit Diagram of LM324 based Line Follower Logic Controller

3.  Actual Image of comparator Section 

Fig. 30: Image of LM324 based Line Follower Logic Controller

Part 2

Sensor plate section

Sensor plate section consists of two LDR sensor and two led. Make the positive terminal of led and ldr are common and negative terminal of led and LDR are common.

Note

You can connect the LDR are sensor in any way in any direction. You can use ten core wire to make connection.

Component list for sensor plate

Sr.No.	Component Required	Quantity
1	3mm led	2
2	LDR	2
3	Ten core wire	As per use

Note

Please make the connection on the zero pcb.

Breadboard image of sensor plate

Fig. 31: Representational Image of Sensor Plate

Schematic  layout for sensor plate.

Fig. 32: Circuit Diagram of Sensor Plate

Actual image of  sensor plate  

Fig. 33: Image of Sensor Plate used on Line Following Robot

Calibration of line sensor 

          Take a line sensor plate and make connection with the LM324 IC as given below.

·         Here one +5 volt pin of line sensor will be connected through the 220 ? resistance on breadboard and gnd pin will be connected through gnd pin on breadboard.

·         Two signal pin which are coming from two ldr sensor o/p (B & C) will be connected through lM324 pin ( 2 & 13 ).

·         Now take a white paper and stretch black tape on it.

·         Put the line sensor above the white sheet and perform calibration on it.

·         Set the both preset in this way that  both output led’s of LM324 IC  will becomes on  at the black surface and will becomes off on white surface as the sensor comes on the white sheet.

Note

You can set the preset by revolving it through screw driver.

·         Try the above step number of times until the both led will becomes on at the black surface and remains off at the white surface.   

Sr.No.	Color	Logic generate at LM324 output pin
1	Black	0
2	White	1

Check your calibration step from below table as output generate on color.    

Sr.no	LDR_sensor1 On	LDR_ sensor 2 On	Led1 of LM324 IC	Led 2 of LM324 IC
1	White	White	Off	Off
2	Black	White	On	Off
3	White	Black	Off	On
4	Black	Black	On	On

Inverting IC stage

Inverting IC stage of (HD74LS04) IC

General Description

This section is used for to drive the motor by converting signal into the it’s invert form. If you have give 1 on it than it’s outcome will be 0 and if you have give 0 than it’s outcomes will be 1.

Component list

Sr.No.	Component Name	Quantity
1	HD74LS04  inverting IC	1

Make connection as given below in the table and as image given below

Short the inverter( HD74LS04) IC pin with each other as given in below table    

Sr. No.	Pin of inverting  IC	Pin of inverting  IC
1	Pin no 1	Pin no 5
2	Pin no 2	Pin no 3
3	Pin no 14	Pin no 9
4	Pin no 12	Pin no 11

Breadboard Image of inverter section

Fig. 34: Representational Image of Inverter Section

 Schematic image of inverter section

Fig. 35: Circuit Diagram of Inverter Section

Actual image of inverter section

Fig. 36: Image of Inverter Section used on Line Following Robot

Fully connected circuit for line follower robot

First make the connection of inverting IC with the L293D IC

Inverter IC connection with L293D IC

Sr. No.	Pin of inverting IC	Pin of L293D IC
1	Pin no 4	Pin no 3
2	Pin no 6	Pin no 7
3	Pin no 10	Pin no 14
4	Pin no 8	Pin no 10

Inverter IC connection with comparator IC

Sr.No	Output pin of LM324 IC	Inverting pin ic no
1	LM 324 o/p pin 1 ( pin no 16)	Pin no 1
2	LM 324 o/p pin 2  ( pin no 1)	Pin no 13

Breadboard and Schematic Layout

Breadboard image of complete assembly

Fig. 37: Representational Image of complete breadboard circuit for Line Follower Robot

Schematic layout of complete image

Fig. 38: Circuit Diagram of Line Following Robot

Actual Image of Complete Circuit

Fig. 39: Image of LM324 based Line Follower Logic Controller

Now connect the Motor with the L293D as given below in table.

Connection of Motor with L293D IC

Sr. No.	Output pins	Motor Wire
1	o/p1	First wire of  first  motor
2	o/p2	Second wire of first motor
3	o/p3	First wire of second motor
4	o/p4	Second wire of second motor

Movement of robotic platform

Sr.No.	LDR_Sensor 1	LDR_Sensor 2	Output
1	White	White	Forward Movement
2	White	Black	Left /Right Movement
3	Black	White	Right/Left Movement
4	Black	Black	Backward Movement

Complete Assembly of Line Follower Robot

·         Now take the robotic platform to fit the zero line sensor PCB on the robotic platform.

Fig. 40: Representational Image of Robot Chassis

·         Take the M-60 screw and bolts to fit the zero pcb with the robotic platform.

Fig. 41: Image of screws used to fit wheels on Robot

·         Take the line sensor zero pcb and make drill on it’s corner point.

Fig. 42: Image of Sensor Plate used on Line Following Robot

·         Now take a robotic platform and fit the zero pcb on the robotic platform with the M-60 screw driver. The sensors direction should be in downward direction.

·         Also fit the breadboard on the robotic platform. The complete assembly of the line robotic platform as given below.

Fig. 43: Image showing complete prototype of Line Follower Robot

·         Also take a battery cell holder and put it on the robotic platform.

Fig. 44: Image showing Line Follower Robot in action

 

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Filed Under: Electronic Projects
Tagged With: line follower robot, robot, robotics
 

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