Line Following Robot – DIY (Simple)

Line Following Robot ? We all have heard or seen one. Let’s build one in this tutorial.

If this is the first time you are building a Line Following Robot or LFR, as it is commonly known, this will be a comprehensive guide.

To keep matters simple, we’ll not be using any microcontroller/processor or programming and anyone can make it in a couple of hours. 

BRIEF INTRODUCTION

Line follower or Line following robot is an autonomous robot which follows either black line on a white area (or a white line on a black area).

Robot must be able to detect particular line using sensors and keep following it. The paths can be complicated and in such cases a microcontroller is required to navigate the path.

However, we’ll be keeping it very simple for beginners and won’t be using any programming/microcontroller for this robot.

LINE FOLLOWING ROBOT – PRINCIPLE OF OPERATION

Any line follower uses sensors, which can be a combination of LED & LDR or IR LED & IR Receiver. Both work on similar principle but we’ll be using IR sensor for our robot. You must be knowing that the light that strikes any platform is reflected.

The reflection and absorption coefficient of light depends upon material, color of platform and other factors.
In simple words the black surface absorbs the light and the white surface reflects it,  and this is the basic concept behind making a line follower.Our robot’s sensor has two parts which are emitter/transmitter and receiver.

The emitter continuously emits the infrared light and the receiver absorbs it after getting reflected from the black or white surface. The voltage across the receiver is directly proportional to the reflected light it absorbs.

So for white surfacemaximum reflection occurs and the reverse happens for the black surface. This change in signal voltage is used to drive a LFR.

ir-sensor-working

LINE FOLLOWING SENSOR CIRCUIT

For this simple LFR, we need two sensors to sense either sides of the line. A single sensor can be made using IR LED, IR Receiver and IC LM358, LED, few resistors and a 10k potentiometer.

Please follow the circuit diagram for exact connections. You can also buy a sensor module as shown in the video/link.

This sensor gives a logic low (0 V) on detecting white surface and logic high (5 V) on detecting black surface. 

lm358-ir-sensor

 

LM358 is used as a comparator here. We give a reference voltage to its input using a 10k pot.

When the voltage across the receiver is less than this reference voltage, the comparator gives low output and when the voltage is more than the reference point, the comparator gives a high output.

In our circuit this output will be directly connected to the motor driver IC L293D which will drive the motors.

MOTOR DRIVER CIRCUIT

L293D is a typical Motor driver or Motor Driver IC which allows DC motor to drive on either direction. It is a 16-pin IC which can control a set of two DC motors simultaneously in any direction. It means that you can control two DC Motor with a single L293D IC.

It works on the concept of H-bridge. H-bridge is a circuit which allows the voltage to be flown in either direction. As you know voltage need to change its direction for being able to rotate the motor in clockwise or anticlockwise direction, Hence H-bridge IC are ideal for driving a DC motor.

l293d motor driver module

In a single L293D chip there are two h-Bridge circuit inside the IC which can rotate two dc motor independently. Due its size it is very much used in robotic application for controlling DC motors. 

Please check the circuit diagram of motor driver circuit given here

Read more about L293D Operation here
Credits & References

Components required :
1) 1 x Robot Chassis with Caster Wheel (Buy here) + 2 x DC Geared Motors (Buy here) + 2 x Tyres (Buy here)
2) 2 x IR sensor Modules (Buy here
3) 1 x General Purpose PCB (Buy here) or 1 x Mini Breadboard (Buy here) + Jumper Wires (Buy here)
4) L293D Motor Driver Module with IC (Buy here)
5) 1 x 7805 Based Power Supply Circuit Components (Buy here)
6) Tools (Buy here)

Download Schematic from here.

Please follow the video for an easy step by step guide. In case of any questions or queries, feel free to post below.

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