What is a line follower?Line follower is a machine that can follow a path. The path can bevisible 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 manoeuvring the robot to stay on course, whileconstantly correcting wrong moves using feedback mechanismforms a simple yet effective closed loop system. As a programmeryou get an opportunity to teach the robot how to follow the linethus giving it a human-like property of responding to stimuli.

Practical applications of a line follower : Automated cars runningon roads with embedded magnets; guidance system for industrialrobots moving on shop floor etc.

Sensor systems Data input systems; Data capture information of outside world

Microcontroller Systems to interpret input signals and take action

Drive systems Output systems of the machine; Motor driver circuit implements the

signals from the motor controller

Micro Controller

Sensor

Sensor

Motor 1

Motor 2

Photo resistors

Phototransistors

Photodiodes

Resistance is inversely proportional to the light levels

Cheapest of the three types of photoconductive devices

Have the slowest reaction rate of all photo detectors

Current is sourced in the presence of light

Moderately priced

Response about 1000 times faster than photo resistors

Cost less than photodiodes

Have better reaction time than Photo resistors

Current is sourced in the presence of light

Most expensive class of photoconductors

Respond about 1000 times faster than photo resistors

Vout

+Vcc

-Vcc

OP AMPS

Algorithm

Programmable logic device

Microcontroller

Robot direction is determined by what the robot sees If line is centered in front of robot, go forward

If line is left of center, turn left

If line is right of center, turn right

If no line is detected, circle until line is found

Straight Left Right

Centre

When nodes are encountered

Relatively inexpensive

Can easily implement finite state automata

Has limited program capacity

Has limited program capabilities

Costlier than PLD

Relatively easy to program

Memory can be expanded, if needed

Arduino UNO or Arduino Duemilanove are microcontroller boards based on Atmega 328 can be used

Use Pulse Width Modulation Change the duration of the time for which the signal is high, in a given time period.

DC motor

Stepper motor

Servo motor

Abundant and cheap Easy to implement Provides no feedback regarding

motor speed or position

Expensive Require special circuitry to implement Provide no feedback regarding motor

speed or position

Affordable

Will be run continuously

Does not need advanced features of servo

Motor Driver Pin Diagram

Design Considerations

1. Weight

2. Moment of inertia about central axis.

3. Height of center of mass

Chassis

A common line follower robot follows a single path

In grid follower, many junctions are created due to number of continuous horizontal and vertical lines crossing one another

So, two sensors fitted on the side of middle sensors

Sensors

5 sensors are used

3 sensors will be primarily used for line following

The other two sensors would be used for detection of the intersections or nodes i.e. points where two lines intersect perpendicularly.

Sensor 1:- extreme leftSensor 2:- left sensorSensor 3:- center sensorSensor 4:- right sensorSensor 5:- extreme rightSensor on white surface = high output

Sensor on black surface = low outputThe middle three sensors are placed at a gap

of 15 mm from each other while the extreme sensors 1 and 5 are at a distance of 20 mm from sensor 2 and 4 respectively.

At the junction, two side sensors sense it

These sensors sends feedback signal to microcontroller

Now microcontroller examine it and decide where to turn according to program stored into the memory of microcontroller

For better controls it is suggested to use 3 sensors for line following robot

100rpm motors should be used, which suited ideally for our program. Motors with higher rpm may cause problem as the junction can be missed due to speed.

A small amount of delay is included after each turn of robot to prevent false input to be taken by robot while turning.