3/9/13 Automated Line Following Robot

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M I C R O C O N T R O L L E R S

Automated Line Following Robot

Line-following robots with pick-and-placement capabilities are commonly used in manufacturing plants. These move on a

specified path to pick the components from specified locations and place them on desired locations.

Basically, a line-following robot is a self-operating robot that detects and follows a line drawn on the floor. The path to betaken is indicated by a white line on a black surface. The control system used must sense the line and manoeuvre therobot to stay on course while constantly correcting the wrong moves using feedback mechanism, thus forming a simpleyet effective closed-loop system.

Circuit description

Fig. 1 show the block diagram of the automated line-following robot. It consists of mainly four parts: twosensors, two comparators, one decision-making deviceand two motor drivers. The robot is built usingmicrocontroller AT89C51 (used as the decision-makingdevice), motor driver L293D, operational amplifier LM324(comparator), phototransistor (sensor) and a fewdiscrete components.

In the circuit, the sensors (phototransistors) are usedto detect the white strip on a black background. The sensor output is fed to the microcontroller, which takes the decisionand gives appropriate command to motor driver L293D so as to move the motor accordingly. Sensor. The sensor senses the light reflected from the surface and feeds the output to the comparator. When the sensoris above the white background the light falling on it from the source reflects to the sensor, and when the sensor is abovethe black background the light from the source doesn’t reflect to it. The sensor senses the reflected light to give anoutput, which is fed to the comparator. Comparator. The comparator compares the analogue inputs from sensors with a fixed reference voltage. If this voltage isgreater than the reference voltage the comparator outputs a low voltage, and if it is smaller the comparator generates ahigh voltage that acts as input for the decision-making device (microcontroller).

Microcontroller. The microcontroller is programmed to make the robot move forward, turn right or turn left based on theinput coming from the comparator. The outputs of the microcontroller are fed to the motor driver. Motor driver. The current supplied by the microcontroller to drive the motor is small. Therefore a motor-driver IC is used.It provides sufficient current to drive the motor.

Fig. 2 shows the circuit of the automated line-following robot. When light falls on thephototransistor (say, T1), it goes into saturation and starts conducting. When no lightfalls on the phototransistor, it is cut-off. A white LED (LED2) has been used to

3/9/13 Automated Line Following Robot

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falls on the phototransistor, it is cut-off. A white LED (LED2) has been used toilluminate the white path on a black background. Phototransistors T1 and T2 are usedfor detecting the white path on the black background. Collectors of phototransistors T1 and T2 are connected to the inverting inputs ofoperational amplifiers A2 and A1. The signal voltage at the inverting input of theoperational amplifier is compared with the fixed reference voltage, which is formed by apotential divider circuit of 5.6-kilo-ohm resistor and 10-kilo-ohm preset. This referencevoltage can be adjusted by changing the value of the 10-kilo-ohm preset. When sensor T2 is above the black surface, it remains cut-off as the black surfaceabsorbs virtually all the light falling from LED2 and no light is reflected back. Thevoltage at the inverting input (pin 2) of operational amplifier A1 is higher than thereference voltage at its non-inverting input (pin 3) and therefore the amplifier outputat pin 1 becomes zero. When sensor T2 is above the white line, the light gets reflected from the white surfaceto fall on phototransistor T2. Phototransistor T2 goes into saturation and conducts.The inverting input (pin 2) of operational amplifier A1 goes below the reference voltageat its non-inverting input (pin 3) of operational amplifier A1 and therefore output pin 1goes high. This way, the comparator outputs logic ‘0’ for black surface and logic ‘1’ forwhite surface. Similarly, comparator A2 compares the input voltage from phototransistor T1 with afixed reference voltage. The outputs of operational amplifiers A1 and A2 are fed to microcontroller AT89C51.The AT89C51 is an 8-bit microcontroller having 4 kB of Flash, 128 bytes of RAM, 32 I/Olines, two 16-bit timers/ counters, a five-vector two-level interrupt architecture, on-

chip oscillator and clock circuitry. A 12MHz crystal is used for providing the basic clock frequency. All I/O pins are reset to‘1’ as soon as RST pin goes high. Holding RST pin high for two machine cycles while the oscillator is running resets thedevice. Power-on reset is derived from resistor R5 and capacitor C1. Switch S2 is used for manual reset. Themicrocontroller, based on the inputs from sensor T1 (say, left) and sensor T2 (say, right), controls the motor to make therobot turn left, turn right or move forward. Port pins P2.0, P2.1, P2.2 and P2.3 are connected to pins 15, 10, 7 and 2 of motor driver L293D. Port pins P2.0 and P2.1are used for controlling the right motor, while port pins P2.2 and P2.3 are used for controlling the left motor. Three wheelscan be used for this robot—one on the front and two at the rear. Front wheel can rotate in any direction as specified bythe rear wheel. To make the robot turn left, the left-side motor should stop and the right-side motor should rotate in theclockwise direction. Similarly, to make the robot turn right, the right-side motor should stop and the left-side motor shouldrotate in clockwise direction. For forward motion, both the motors should rotate in clockwise direction.

Working

An actual-size, single-side PCB for the automated line-following robot isshown in Fig. 3 (View as PDF) and its component layout in Fig. 4 (View asPDF). Fig. 5 shows the path of the line-follower robot, where ‘L’ is the leftsensor and ‘R’ is the right sensor. At the start, when the robot is at point ‘A,’ sensors T1 and T2 are abovethe black surface and port pins P3.0 and P3.1 of the microcontroller receivelogic ‘0.’ As a result, the robot moves forward in straight direction.

At point ‘B,’ a leftturn is encountered,and the left sensorcomes above thewhite surface,whereas the rightsensor remainsabove the blacksurface. Port pinP3.0 of themicrocontrollerreceives logic ‘1’

from the left sensor and port pin P3.1 receives logic ‘0’ from the right sensor. As a result, the left motor stops and theright motor rotates, to make the robot turn left. This process continues until the left sensor comes above the blackbackground. Similarly, at point ‘C,’ where a right turn is encountered, the same procedure for right turn is executed. When both thesensors are at the white surface, the robot should stop. The output of the microcontroller (IC2) depends on the inputsreceived at its port pins P3.0 and P3.1 as shown in table.

3/9/13 Automated Line Following Robot

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5

61 26 7 Post Comment | 36 Comments

Shree Harsha 304 days ago

Good one.But need more information... Reply 1 Reply

Efy Admin 303 days ago

Software

The source program for the project is written in Assembly languageand assembled using Metalink’s ASM51 assembler, which is freelyavailable on the Internet for download. It is well commented for easyunderstanding and works as per the flow-chart shown in Fig. 6. Thehex file ‘robot.hex’ is to be burnt into the microcontroller.

ROBOT.ASM

$MOD51 ORG 0000H LJMP MAIN ORG 0030HMAIN: SETB P3.0 ;Input for left sensor SETB P3.1 ;Input for right sensorAGAIN: JB P3.0,NEXT JB P3.1,GO CLR P2.0 SETB P2.1 CLR P2.2 SETB P2.3 SJMP AGAINGO: CLR P2.0 SETB P2.1

CLR P2.2 CLR P2.3 SJMP AGAINNEXT: JB P3.1,GO1 CLR P2.0 CLR P2.1 CLR P2.2 SETB P2.3 SJMP AGAINGO1: CLR P2.0 CLR P2.1 CLR P2.2 CLR P2.3 SJMP AGAINHERE: SJMP HERE END

Download actual-size, single-side PCB layout.

Download PCB component layout.

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3/9/13 Automated Line Following Robot

www.electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=491&title = Automated+Line+Following+Robot&id=4679&article_type=2&b_type=… 4/6

Efy Admin 303 days ago

What kind of information do you think can be added? Reply 2 Replies

akash 279 days ago

sir i want to make a project over wireless remote controlled switching of lights onoff. please help me out... as soon aspossible..

Reply

EZHIL 253 days ago

sir i need set of vlsi projects Reply

agile 296 days ago

This ckt is not working.is it tested ckt or not?? Reply 2 Replies

Efy Admin 295 days ago

All our circuits are tested before publishing. What is the problem you are facing? Reply 1 Reply

Kart 295 days ago

seems to be awsome can i implement in my companyif possible send me more details to my mail.Thanks Reply

akash 279 days ago

hey ..ece branch or what? Reply

agile 295 days ago

motor is not working..... Reply 1 Reply

RP 225 days ago

MY MOTOR IS WORKING BUDDY Reply 1 Reply

Akash Patel 126 days ago

how many voltage you gave to it.because my motor is not working with 5-6V. Reply

agile 274 days ago

ckt is now workingcan we ust 7805 regulator with controller? Reply 1 Reply

XYZ 259 days ago

OFCOURSE.. U can use but use it along with the transformer Reply

rupam kalita 273 days ago

can give more details about the ckt? Reply

avishek ghosh 267 days ago

how do we burn the code in the microcontroller..???? Reply

abc 260 days ago

Sir I havee to build a line tracer using IR sensors7.Can i get some circuitry related to that? Reply

VrOon 256 days ago

@Admin Im a student of Diploma EXTC last year i need some good and innovative project for my last year.. PLzz mail me assoon as possible..thanking you

Reply

3/9/13 Automated Line Following Robot

www.electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=491&title = Automated+Line+Following+Robot&id=4679&article_type=2&b_type=… 5/6

mahesh 247 days ago

sir can you plz load the c file here for the same project... Reply

akash dhiman 244 days ago

please can any body give the codes for this project.....???? Reply 1 Reply

Shirsha Ghosh 231 days ago

I have build this using AVR ATMega8 uC. This is the code for that#includeavrio.hvoid main DDRC0x00 DDRD0xf0PORTD0x00 while1 switchPINC&0x03 case 0x03 PORTD0x00 break case 0x02 PORTD0x10 break case 0x01 PORTD0x40break case 0x00 PORTD0x50 break

Reply

bhaumik 240 days ago

what is the rpm of motor Reply

cubertron 227 days ago

May I have the hex file ? Reply

RAK 225 days ago

Hi can any one help developing a module which transmits signal to a distance of 3 km range.. plzzz do soo i am in need.. Reply

inertia 216 days ago

the flow diagram is incorrect at 4 level i think because it saysright motor stops and robot turns rightit should be right motorstops and robot turns left.My main question is that the program of this robot can run in avr studio and proteus or not?

Reply

mangesh 216 days ago

i like the info given Reply

vivek 196 days ago

@admin efy ...sir i want to do this project can you send me the componnents.....motors ....ics....pcb layout.....all requiredmaterials for this project???.....what will be the total cost.....and how much time it will take for delllivery....how can i place theorder for this....

Reply

soumya 195 days ago

I need project of socially relevant Reply

richy 195 days ago

hey i need some iit projects ...... is ther anybody to helpmailtatrach127@gmail.com Reply

janardhana 168 days ago

sir i want to do this project can you send me the componnents.....motors ....ics....pcb layout.....all required materials for thisproject???.....what will be the total cost.....and how much time it will take for delllivery....how can i place the order for this....

Reply

karthick 153 days ago

Can u plzzz post the hex coding for black line follower .. Reply

Akash Patel 127 days ago

sir Can we apply 12V to the circuit instead of 6V? because my DC MOTOR50rpm is running very very slowly with 5-6V. Reply

surendar 58 days ago

please write programs in c languge Reply

surendar 58 days ago

3/9/13 Automated Line Following Robot

www.electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=491&title = Automated+Line+Following+Robot&id=4679&article_type=2&b_type=… 6/6

surendar 58 days ago

where do i fix the photo transistor? is both transistors near? or....one in right side and another one is left side?if i fixed theseare seperatelyis both transistor absorb properly?

Reply

Nidhish 56 days ago

Would U tell mewhat ll be the cost of this project. Reply

vikash 46 days ago

@admin efy ...sir i want to do this project can you send me the componnents.....motors ....ics....pcb layout.....all requiredmaterials for this project???.....what will be the total cost.....and how much time it will take for delllivery..is it available at yourokhla branch?pls replly me asap.

Reply

JAIPRAKASH SHARMA 10 days ago

SIR ... I WANT TO MAKE A DISPLAY SYSTEM ON LCD USING MICROPROCESSOR 8085.... PLZ HELP ME.... Reply

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