CRAZY ROBOTS: A LINE FOLLOWER ROBOT

A LINE FOLLOWER ROBOT

The purpose of this document is to help you build a Line Following Robot.
Starting with an overview of the system the document would cover implementation
details like circuits and algorithms, followed by some suggestions on improving the
design.

BACKGROUND:

The present condition in Industry is that they are using the crane system to carry the parcels from one place to another, including harbor’s .Some times the lifting of big weights may cause the breakage of lifting materials and will cause damage to the parcels too.The robot movement depends on the track. Use of this robot is to transport the materials from one place to another place in the industry.

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

Prerequisites:
Knowledge of basic digital and analog electronics.
(A course on Digital Design and Electronic Devices & Circuits would be helpful), C Programming

WORKING PRINCIPLE:

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 five 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 five 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 . 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.

overview of robot

Now we will discuss all blocks in detail..... and i 'll tell you the complete procedure to make all blocks separately and how to assemble them.

SENSOR ARRAY

We have used IR sensors for making sensor array. IR sensor consists of a transmitter and a receiver as shown in above photo. The transparent led is transmitter while the black one is receiver. IR transmitter will transmit infra-red radiation which will fall on the surface and the reflected radiation will be received by the receiver. The reflection of radiation will depends upon the colour of the surface.as shown in photo below.

the orientation of sensors should be as like as shown in above photo so that robot can detect a sharp as well as curve tuns.

Most of the radiations will be reflected back from white surface but it is just opposite in case of black surfaces as shown in diagram below.

working of ir sensors

circuit diagram of one pair of ir sensor

This circuit diagram is showing only one ir sensor. we need to make 5 sensors on PCB board as shown in 1st photo of sensor array.

2. COMPARATOR

We used comparators(OP_AMPs) to convert the analog signals received from sensors in to digital signals

The op-amp IC we used is LM324 to give square wave as a output by comparing the sensor signal with a reference signal provided by us.

Theory :-
As you all know that in the world of electronics all the microcontrollers and microprocessors works on DIGITAL SIGNAL, but from the sources like battery we get a ANALOG SIGNAL. So in embedded systems it is mandatory to convert the analog signal into digital signal.
So for converting the analog signal into digital signal we use operational amplifiers(OP-AMP). We use operational amplifiers as a voltage comparator . A op-amp is shown in figure below :-

We fix a voltage at negative input with the help of variable resistor of 10k ohm and at the positive input we give our analog signal. If the analog signal is grater than the fix voltage at negative input then we get 1 in output(means +5V) and if the analog signal voltage is less than the voltage at negative input then we get 0 at output(means 0V).
Note :- Set the negative input voltage with the help of variable resistor according to your requirement.
you can see a A to D converter in below fig.

There are several OP-AMP ICs are available like :- lm358, 741, lm324 etc.Here we use LM324 which have 4 op-amps in it.

The reference voltage will be given to inverting terminal(2,6,9,13) . The value of Vcc will be equal to 5v or 6v so that output of opamp shold be less than 5v only otherwise micro-controller will not read the signal from opamp.

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 2
using variable resistor.

· Large value of reference voltage – less sensitive.

· Small value of reference voltage – more sensitive.

3. MICRO-CONTROLLER

I am using ATMEGA 328 with ARDUINO UNO development board. it is very easy to programme and burn the same in to ur arduino.

Microcontroller board used :- ARDUINO UNO

Technical specification:-

Microcontroller:- ATmega328

Operating Voltage 5V

Input Voltage (recommended) 7-12V

Input Voltage (limits) 6-20V

Digital I/O Pins 14 (of which 6 provide PWM output)

Analog Input Pins 6DC

Current per I/O Pin 40 mA

DC Current for 3.3V Pin 50 mA

Flash Memory 32 KB of which 0.5 KB used by bootloader

SRAM 2 KB

EEPROM 1 KB

Clock Speed 16 MHz

4.MOTOR DRIVER

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.

PIN DIAGRAM OF LM293D

CODES FOR LINE FOLLOWER

the following code is left priority code ie if all sensors will detect black line then it will go for left line. you can change the priority order by jst making slight change in code.

int motorLEFTpin1 = 5; //define digital output pin no.

int motorLEFTpin2 = 6; //define digital output pin no.

int motorRIGHTpin1 = 10;

int motorRIGHTpin2 = 11;

int irl2=2;

int irl1=4;

int irc=7;

int irr1=8;

int irr2=12;

int il2=0;

int il1=0;

int ic=0;

int ir1=0;

int ir2=0;

void setup () {

Serial.begin(57600);

pinMode(irl2,INPUT);

pinMode(irl1,INPUT);

pinMode(irc,INPUT);

pinMode(irr2,INPUT);

pinMode(irr1,INPUT);

pinMode(motorLEFTpin1,OUTPUT); //set pin 5 as output

pinMode(motorLEFTpin2,OUTPUT); // set pin 6 as output

pinMode(motorRIGHTpin1,OUTPUT); // set pin 10 as output

pinMode(motorRIGHTpin2,OUTPUT); // set pin 11 as output

delay(100);

}

void loop()

{

int c=0;

int r=0;

il2=digitalRead(irl2);

il1=digitalRead(irl1);

ic=digitalRead(irc);

ir2=digitalRead(irr2);

ir1=digitalRead(irr1);

Serial.print("Raw Ratel2: ");

Serial.println(il2);

Serial.print("Raw Ratel1: ");

Serial.println(il1);

Serial.print("Raw Rateic: ");

Serial.println(ic);

Serial.print("Raw Rater2: ");

Serial.println(ir2);

Serial.print("Raw Rater1: ");

Serial.println(ir1);

Serial.println("\t");

if(ir2==LOW)

r=1;

if(ir1==LOW)

r=2;

if(ic==LOW)

c=3;

if(il2==LOW || il1==LOW)

lft();

else if(c>r)

st();

else if(r>c)

rt();

else if(il1==HIGH && il2==HIGH && ic== HIGH && ir1==HIGH && ir2==HIGH)

lft();

}

void st()

{

digitalWrite(motorLEFTpin1,HIGH);

digitalWrite(motorLEFTpin2,LOW);

digitalWrite(motorRIGHTpin1,HIGH);

digitalWrite(motorRIGHTpin2,LOW);

}

void rt()

{

digitalWrite(motorLEFTpin1,HIGH);

digitalWrite(motorLEFTpin2,LOW);

digitalWrite(motorRIGHTpin1,LOW);

digitalWrite(motorRIGHTpin2,LOW);

}

void lft()

{

digitalWrite(motorLEFTpin1,LOW);

digitalWrite(motorLEFTpin2,LOW);

digitalWrite(motorRIGHTpin1,HIGH);

digitalWrite(motorRIGHTpin2,LOW);

}

CRAZY ROBOTS

Pages

Thursday 28 March 2013

A LINE FOLLOWER ROBOT

A LINE FOLLOWER ROBOT

The purpose of this document is to help you build a Line Following Robot.
Starting with an overview of the system the document would cover implementation
details like circuits and algorithms, followed by some suggestions on improving the
design.

Most of the radiations will be reflected back from white surface but it is just opposite in case of black surfaces as shown in diagram below.