line follower which is part of robotics and embedded

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Line follower. IR

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YOU ARE HERE Line Follower

Line Follower

By b O t s k O O l - Posted on 2 1 A p r i l 2 0 0 9

The line follower is an autonomous bot that canfollow a specific colored line painted on asurface of different contrast, such as white onblack.

To start with first of all I will be discussing asmall concept of light. I believe you all know thatthe light that strikes any platform is reflected.The reflection and absorption coefficient of lightdepend upon material, color of platform and other factors. In simple words the blacksurface absorbs the light and the white surface reflects it, this is the basic concept

behind making a line follower.

So the line follower has an emitter and a reflector. The reflector receives the lightand generates a voltage proportional to the intensity of the light, if this voltage isabove a threshold it means SIGNAL=1 (logic one) else SIGNAL= 0 (logic zero).

Lets take up an example where we have to move our bOt on black surface havingwhite line. Suppose I have two Infra Red (IR) sensor pairs that are on differenthalves of a bOt with respect to geometrical central axis of the bOt. The sensors areplaced in such a way that the white line lies in between both the sensors when thebOt is placed on the white track painted on black surface to move. Now if the whiteline is between both the sensors while moving forward both the sensors will be onblack surface and the detectors/receivers will receive less amount of light since

black absorbs light and hence signal provided by both the infra red receivers will below.

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Now if the heading/direction of the white line changes one of the sensors will movein the region of white line and will start giving output signal as high. This

information can be used to turn the bOt and orient itself in the right direction. Forexample in the above figure if the bot is located in position 1, then bOt will moveforward and if the bOt is in position 2 it will have to turn left .

Lets move on and discuss everything step by step in detail. We wil l be discussingthe making of line follower under three heads:

1.) Chassis of robot { those familiar can skip this section}2.) Electronics/Hardware Designing3.) Programming/Software Designing

CHASSIS OF ROBOT

1.) Base of robot: The base or the material of the platform of robot can be made

with any easily avai lable material like switch board, wood, acrylic sheet orsteel sheet. As our robot will be very light, you dont have to think a lot onstrength and other such factors. We will just recommend you to make a smallsize and light weight bOt. Here we are using, steel base:

2.) Motors and Driving Mechanism: We will need a set of two motors that have same rpm (revolution per

minute). We will be using differential drive for maneuvering our bOt i.e. we

will have three wheels for our bOt, the front two will be powered andthe rear will be free wheel.

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22:56:48 hi06:38:18 any onefrom admin17:31:05 any1 frmadmin11:59:05 hii yaar11:59:42 can ugime a circuit for white linefollower12:01:55 any bdyhr12:45:06 post inforum

Post




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When the bot is moving straight both the motors should have equalspeed.

For turning, one of the motor is switched off. If we switch off the leftmotor, the bot will turn left and vice versa.

You can choose a motor of rpm around 100 and a torque of 1kg cm

3.) Coupling wheels & clamping motors: For clamping the motors you can usepipe clamps or make right angled clamps. The right angle c lamps ensuremore rigidness. To couple the motor ensure that the shaft of motor and holeof wheel have equal diameter (if you cant find one check the tutorial onwheels).




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ELECTRONICS

This is a flow chart that explains the working of the bOt in sequence:

The Infra Red sensors are used to interact with the environment. The emittersends a ray which is received by detector in the form of voltage and it then




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amplified by amplifier since the signals are weak (more on this later). Beloware the circuit diagrams of Infra red LED emitter and receiver.

Op Amplifier (LM324)If the rays received by the IR LED receiver are above a particular threshold thenan amplified signal is generated by the amplifier (LM324). Note that the sensorscannot directly send a signal to the microcontroller as the signal voltagegenerated by them is too low and even when sensors are on white surface signalgenerated by them will interpreted low by the microcontroller.

Microcontroller (AT89S52)




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The microcontroller receives the signal and responds accordingly. It takes thedecision based on input signal received by both the receiver LEDs. It will givecommand to motors through H bridge to move forward, or take a left turn or aright turn.

Hbridge (L293B)

The microcontroller sends a signal to the H bride that acts as a switch. If thesignal received by the H bridge is high it will rotate the motor or else it wont doso. Note that microcontroller only sends a signal to a switch which gives thevoltage required by the motor to rotate. Here we are using L293B which can beused to control two motors.

Pin connections for H bridge: En1 & En2 are given logic 1 from microcontroller or give 5V from outside

and are used to activate/deactivate one half of the H bridge. V is the voltage that you want to supply to the motor(s) : 9 or 12V Vcc is the logic 1 or 5V

The complete circuit diagram with all the integrated circuits required for makinga line follower is shown below:




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Here we are using pins P1.0 and P1.4 for taking inputs from the IR sensors afterbeing amplified by LM324.

P1.0 Input from left sensor

P1.4 Input from right sensor

There are six outputs from AT89S52 microcontroller to the H bridge.

Pins P0.0 and P0.4 are connected to enable pins of the H bridge. We can use themto deactivate/active the two halves of H bridge i.e. if pins are set to logic 1 thecorresponding half of the H bridge wil l be activated.

P0.1 will drive the left motor in forward direction

P0.2 will drive the left motor in reverse direction

P0.3 will drive the right motor in forward directionP0.5 will drive the right motor in reverse direction

Programming

Below is the code in C for the line follower.

C Code www.botskool.com

#include

/* Sensors input port - P1 P1_0 --- --- --> Left sensor P1_4 --- --- --> Right sensor

Motors output port - P0

P0_0 --------> Enable pin of the left half of the H-bridge P0_1 -- -- -- --> will drive the left motor in forward direction P0_2 --------> will drive the left motor in reverse direction P0_3 -- -- -- --> will drive the right motor in forward direction




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P0_4 -- -- -- --> Enable pin of the right half of the H-bridge P0_5 -- -- -- --> will drive the right motor in reverse direction*/

/*Delay function runs an idle loop to create a time delay. If the crystal used is of 11.0592 MHz then the argument passed in delay is in 'milliseconds'.*/void Delay (unsigned int itime)

{ unsigned int i,j; for(i=0;i


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P0_3=0; P0_5=0; Delay(50); /*50ms time delay*/ }

void main()

{/* The pins which are receiving inputs from the sensors should be initially set to logic1.*/ P1_0=1; /*Left sensor input*/ P1_4=1; /*Right sensor input*/

//main loop of the program while (1) {

if ((P1_0==0)&&(P1_4==1)) TurnRight();

else if ((P1_0==1)&&(P1_4==0)) TurnLeft(); else Forward();

}}

Download c program file linefollower.c

Download hex file linefollower.hex

Download AT89X52.h header file

Average:

Your ra ting: None Average: 4.9 (9 votes)

Login or register to post comments 2962 reads

Tags 8051

Wow!Submitted by Steven (not verified) on Tue, 04/21/20 09 - 19:49.

Hello! simply super resource

Login or register to post comments

superb!Submitted by Michelle (not verified) on Thu, 04 /23/2009 - 00:47.

simply mind boggling! very informative indeed!





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Hey guys, I am am final yearSubmitted by mecool.1988 on Wed, 04/29/2009 - 03:16.

Hey guys,

I am am final year student working on a l ine follower project and i need some

advice on how to implement PID for this robot. I am using 6 infrared photodetectors to detect the line. I am taking the analog data from the sensors and

using the ADC's to get the feedback infor for the PID control. Plz can you help me

out...


Please correct the IC no. toSubmitted by heloitsadi on Mon, 05/04/20 09 - 14:32 .

Please correct the IC no. to L293D instead of L239B


Xtra informationSubmitted by heloitsadi on Mon, 05/04/20 09 - 15:13 .

This command is wrong...

else if((P1_0==1)&&(P1_4==1))

It should be...

else if((P1_0==1)&&(P1_4==0))

Please correct it, and if I am wrong correct me.


Re: Please correct the IC no. toSubmitted by bOtskOOl on Mon, 05/04/2009 - 15:56.

Thank you for feedback. The IC being used here is L293B . It was misspelled as

L239B. It has been updated.


Re: Xtra informationSubmitted by bOtskOOl on Mon, 05/04/2009 - 16:01.

Thank you for pointing this line out. I had overlooked it. Yes obviously it will be

vice versa of previous condition in the code. It has been updated.





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Very good job.. Thanx for theSubmitted by heloitsadi on Mon, 05/04/20 09 - 21:44 .

Very good job.. Thanx for the immediate response.


I didn't heard about that IC,Submitted by heloitsadi on Mon, 05/04/20 09 - 21:46 .

I didn't heard about that IC, i have heard about L293D, L298 only.. i pointed out..

thanx for correcting me.


Its awesome guys!!!Submitted by Dark Knight (not verified) on Tue, 05/05/20 09 - 23:33 .

Its awesome guys!!!


programming in avrSubmitted by aashiqcoolguy21 on Tue, 06/02/2009 - 22:28.

Please can anybody post the code in AVR .. when Atmega 16 is used and l293d is

used. i.e. we are working on atmega 16 dev board and we are makin black line

follower... and how we can c hange the code to obtain .. obstacle detector and edge

follower please help me out.


very niceSubmitted by Guest (not verified) on Sat, 06/13 /2009 - 16:2 8.

This tutorial i s really very useful for a beginner.


@aashiqcoolguy...Submitted by heloitsadi on Sat, 06/13 /2009 - 18:1 2.

This code will basically do the job.. just change the case conditions as per the

sensors assembly and their count... Its simple to implement..

#include

void main(void)




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{

unsigned int k, h;

DDRA=0x00;

DDRD=0XFF;

while (1)

{

k =~PINA;

h=k & 0x0F;

switch (h)

{

case 0x0D:

{

PORTD=0x89;

break;

}

case 0x07:

{

PORTD=0x86;

break;

}

case 0x0B:

{

PORTD=0x85;

break;

}

case 0x09:

{

PORTD=0x8A;

break;

}

case 0x0A:

{

PORTD=0x00;

break;

}

case 0x0E:

{

PORTD=0x81;

break;

}

case 0x0C:




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{

PORTD=0x88;

break;

}

case 0x08:

{

PORTD=0x82;

break;

}

case 0x06:

{

PORTD=0x88;

break;

}

}

}

}


awesome tutzSubmitted by vandy on Sat, 06/27/2009 - 14:47.

hey this tutz is really kool..

but i have a doubt in the c ode for the mc...

Delay(50); /* Wait for 50 ms*/ P0_0=0; /*Motors are not running*/ P0_2=0; P0_4=0; P0_6=0; Delay(50); /*Delay of another 50 ms*/ } y is P0_2,P0_4,P0_6 made zero???i request for a reply n kindly excuse if my doubt is silly coz im a beginner..


Re: awesome tutzSubmitted by bOtskOOl on Sat, 06/27 /2009 - 17:3 8.

Hi vandy,

Thank you for your comment.

Regarding your doubt -

What we are doing is that we are powering up motors for 50 milli seconds and thenturning them off for next 50 milli seconds and we keep on doing this repeatedly so




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that our line follower bOt turns slowly and doesn't get out of control on a sharp

turn.

So for turning off motor you need to set all the logic lines to 0 which are going to

H-bridge from microcontroller and that is acheived by setting pins 0, 2, 4 and 6 of

port 0 (which are connected to the H-bridge) to zero for 50 milliseconds. H ope

this explanation wil l make everything clear. We are really glad that you posted yourdoubt.

If there is any further doubt please don't hesistate to ask us. Just post another

comment .

All the best


hey thankq 4 theSubmitted by vandy on Sat, 06/27/2009 - 21:38.

hey thankq 4 the reply...

i think the ports to be made zero are

either P0_1, P0_2, PO_3 , PO_5 (turning off the motors by making the input data

zero)

or

P0_0 AND P0_4 (turning off the motors by making enable inputs zero)

WHY IS PO_6 MADE ZERO WHEN IT IS NOT USED? i hope its not used!


Re: hey thankq 4 theSubmitted by bOtskOOl on Sat, 06/27 /2009 - 23:0 4.

Oh my God! That was a terrible mis-print (set of four pins 1,2,3 & 5 was

misprinted as 0,2,4 & 6). Just now noticed it. First of all I must really thank you for

pointing this out.

Thank you vandy .

Now everything has been corrected. And yes you definately turn off motors by

setting both the enable inputs zero i.e. P0_0 and P0_4. Here we have done this bymaking pins 1, 2, 3 and 5 of port 0 so that it is easy for beginners to grasp

everything. But yes it can be definately done by that also and its a much shorter

code. Even you don't need to set all the four pins of port 0 to logic 0

because at a time only two pins will have logic 1 out of pins 1,2,3 & 5 but it has

been done so just to make everything easy to understand.


watch out this fast line follower




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Submitted by DeAviator on Mon, 06/29 /2009 - 00:2 6.

watch it now


Thats really very fast... I sSubmitted by heloitsadi on Mon, 06/29/20 09 - 02:38 .

Thats really very fast... I s it designed by you.. if yes.. how many sensors are usedin this bot... and are you using PWM to maintain the sharp turn accurasy...


thankqSubmitted by vandy on Mon, 06/29/2009 - 22:13.

thankq for the prompt correction.

i request you to clear the following doubts also.

1. which of the following combination of sensors would be efficient in terms of

accuracy and immunity towards external light?

IR LED +photo transistor (or)

IR LED + IR reciever (or)

high intensity red led + photo transistor

2. is it possible to program a line follower with 3 sensors that can follow a

blackline on a white surface as well as whiteline on a black surface at the same

time with the same program? if so, will the following logic work ?

assuming p1_0,p1_1,p1_2 to be the inputs and p0_1,p0_2,p0_3,p0_5 to be the

outputs to the mc

blackline on white surface :

p1_0 p1_1 p1_2 p0_1 p0_2 p0_3 p0_5 action

1 0 1 1 0 1 0 forward

1 0 0 1 0 0 0 right

0 0 1 0 0 1 0 left

1 1 1 0 0 0 0 stop




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17/19

thanks for the comment, this is my line follower Shelby


Hey please give me theSubmitted by heloitsadi on Sun, 07/12/20 09 - 19:39 .

Hey please give me the details about how you increased the speed and the

accuracy upto that extent... WHat type of sensors and actuators are used by you...

Are you using PWM...?


if i connect the circuit as shown above...can i get output ?Submitted by palla.anilkumar on Tue, 07/14/2009 - 09:10.

is that circuit working?i need to execute that...so,i am asking whether that circuitis correct or not?pls..reply soon


line followerSubmitted by insopor1upiita on Tue, 07/14/2009 - 21:19.

Hello!

I use sensors QRD1114, and mosfet for the motors.

I have not tested the program or the circuit that comes on this page.

Saludos desde Mxico


if i connect the circuit as shown above...can i get output ?Submitted by bOtskOOl on Tue, 07/14/2009 - 21:55 .

This circuit is absolutely fine and yes it worksIf you have any doubt or if you face any problem during making line follower just

post your query.

Keep posted us of you progress

All the best


line followerSubmitted by nileshrockfire on Sun, 07/19 /2009 - 20 :29.

hi, i m new in the field of robotics ...........




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