Line Follwer Using l293d

7/28/2019 Line Follwer Using l293d

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Line Following Robot Using L293D

Introduction:

The name line follower itself clear its meaning that it is a robot which traces or follows a specific

path .The principleof the line follower is based on sensing the background surface by making use of

IR sensor. Basically IR sensor takes input by detecting the reflection of the IR rays from the surface

and accordingly gives its output to the motors. The output of the sensors are not directly fed to the

motors instead a L293D IC is used in between the sensors output and motors input. The sensors

output is given to the input pin of L293D and the output pin of L293 IC is connected to the motors.

The L293D IC is having two H-bridges which is capable to rotate motor in bidirectional.

DC Gear Motors:

In our line follower dc gear motors are used.

WHY DC MOTOR?

Easy to control

Require only two signals

For change the direction of rotation just reverse the polarity

Speed can be controlled by the voltage

USE OF GEARS

To provide enough torque.

Increases the torque on the expense of speed.


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IR Sensors:

Sensors are basically electronic devices which are used to sense the changes that occur in their

surroundings. The change may be in color, temperature, moisture, sound, heat etc. They sense thechange and work accordingly. In IR sensor the there is emitter and detector. Emitter emits the IR rays

and detector detects it.

The IR sensor basically consists ofthree components:

IR LED (emitter)

Photodiode (detector)

Op-Amp

IR LED:

Fig. 1

IR LED is a light emitting diode which emits the IR radiations. The basic function of the emitter is to

convert electricity into light. It works on the principle of recombination of the electron-hole pair. As

in the conduction band of a diode, electrons are the majority carrier and in the valence band, holes

are majority carrier. So when an electron from a conduction band recombines with a hole of valance

band, some amount of energy is released and this energy is in the form of light. The amount of

energy released is depends upon the forbidden energy gap. The IR Led has two legs, the leg which is

longer is positive and other leg is negative.


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Photo Diode:

Photodiode PIN Photodiode

Fig. 2

The photodiode is a p-n junction diode which is connected in reverse bias direction. The basic

function of the detector is to convert light into electricity. As its name implies that it works

effectively only when the certain number of photon or certain amount of light falls on it. When there

is no fall of light on the photodiode it has an infinite resistance and act as an open switch but as the

light starts falling on the photodiode, the resistance becomes low and when the full intensity of light

fall on the photodiode then its resistance becomes zero and it starts act like a closed switch.

Basicallytwo typeof photodiodes:

PIN type P stand for p-type semiconductor.

I stand for intrinsic semiconductor.

N stand for n-type semiconductor.

Avalanche type


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Op-Amp:

Op-Amp stands for operational amplifier. It is a DC-coupled high gain amplifier with differential

inputs and single output. Typically the output of the op-amp is controlled by either negativefeedback or positive feedback. Due to the fact that it performs several operations like addition,

subtraction, multiplication, integration etc, it is named as operational amplifier. It has two inputs,

inverted (Pin 2) and non-inverted input (Pin3). The signal which is applied to the inverted input gives

output 180 degree out of phase with input whereas in the non-inverted input gives output in phase

with that of input. Op-amp has a variety of uses in different electronics devices. In the line follower

it is used in the comparator mode. The op-amp IC which is used here is LM358 IC, which is an 8-pin IC

having two inbuilt op-amps. In the comparator mode, the reference voltage is set at the inverted

input pin and then it is compared with the input at non inverted pin. As the voltages at two input

pins of op-amp is compared, as the voltage at Pin 3 exceeds the reference voltage at Pin 2 the output

of the comparator becomes high (5 V) otherwise it becomes low (0 V). The reference voltage at Pin 2is set with the help of variable resistor.

Types of Op-amp:

1. General purpose op-amp.

2. Special purpose op-amp.

Fig 3. Internal block diagram of LM358 IC


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Working:

Fig 4. Circuit diagram of IR sensor

We know that the white surface reflects all the radiations falls on it whereas the black color absorbs

them. When the supply is given to IR sensor, LED starts emitting light radiations. If the surface is of

white color then it reflects all the radiations. As these radiations starts falling on the photodiodewhich is connected in reverse bias, the resistance of the photodiode starts decreasing rapidly and the

voltage drop across the diode also decreases. The voltage at Pin 3 starts increases, as it reaches just

beyond the voltage of Pin 2 the comparator gives high output. In case of the black surface, LED emits

light but it is not reflected by the surface, so the photodiode detects nothing and its resistance

remains infinite. Hence the comparator gives low output.

White surface Comparator output is high.

Black surface Comparator output is low.


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Sensitivity of IR sensor:

The sensitivity of sensor means that how much effectively the sensor senses the change that is

occurring in its surrounding. The sensitivity of the IR sensor is controlled by reference voltage at pin 2using variable resistor.

Large value of reference voltage less sensitive.

Small value of reference voltage more sensitive.

MOTOR DRIVER IC (L293D)

L293D IC is a dual H-bridge motor driver IC. One H-bridge is capable to drive a dc motor in

bidirectional. L293D IC is a current enhancing IC as the output from the sensor is not able to drive

motors itself so L293D is used for this purpose. L293D is a 16 pin IC having two enables pins which

should always be remain high to enable both the H-bridges. L293B is another IC of L293 series having

two main differences with L293D.

Difference between L293D and L293B:

1. L293D can run a motor up to 600 mA whereas L293B can run up to 1 A.

2. L293D has protection diode whereas L293B doesnt have any such protection diode. Need to

add the protection diode manually.

NOT gates are usually used as buffers in the H-bridge to strengthen the signal and also used as

repeaters.


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Fig 5. Pin diagram of L293D IC

Block diagram of Working Model:

Fig 6. Connetion Diagram of Working Model


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IR Sensors

Photo DiodeIR LED


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Front View of Working Model

Thank You

By: Meetinder Singh BajwaExecutive, Robosapiens India

Mail to: [email protected]

Website: http://www.robosapiensindia.com
http://www.robosapiensindia.com/mailto:[email protected]

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Line Follwer Using l293d