obstacle detection robot

8/13/2019 obstacle detection robot

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OBSTACLE DETECTION ROBOT

Mini project

Submitted in partial fulfilment of the requirements for the award of the degree

of

Bachelor of technology

In

Electrical and Electronics Engineering

By

NAME ROLL NO

Anusree Nagendran B090121EE

K. Neetusha B090027EE

Radhika Krishnan B090229EE

Tara Elizabeth Thomas B090189EE

Under the guidance of

Dr.JEEVAMMA JACOB

Department of Electrical and Electronics Engineering

NATIONAL INSTITUTE OF TECHNOLGY,CALICUT


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CERTIFICATE

This is to certify that the report entitled OBSTACLE DETECTI ON ROBOT is a bona

fide record of the mini-project done byANUSREE NAGENDRAN (B090121EE), K.

NEETUSHA (B090027EE), RADHIKA KRISHNAN (B090229EE) and TARA

ELI ZABETH THOMAS (B090189EE) in partial fulfilment of the requirements for the

award of Degree of Bachelor of Technology in Electrical & Electronics Engineering from

National Institute of Technology Calicut for the year 2012.

Dr.Jeevamma Jacob Dr. Sreeram Kumar(Project Guide) Professor & Head

EED EED

Place: NIT CALICUT

Date: 3.5.2012


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ACKNOWLEGDEMENT

At the very outset, we give all thanks to God almighty, who blessed us with the strength to

do this project. We express our sincere gratitude to our guide, Dr.Jeevamma Jacob,

Professor, Department of Electrical and Electronics Engineering, for her guidance and

support throughout this endeavour. We thank Dr. Sreeram Kumar, Head of the

Department, for providing all the facilities required for the project in the Department. We

would like to extend our sincere thanks to Ananthakrishnan Sir, miniproject co-ordinator

for giving us an opportunity to work in this project area. We also express our gratitude to

Mr. Anand K.R(Lab Staff) and Mr. Somanath for their dedication and sincere interest in

our work without which this project would not have been successful.


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ABSTRACT

This project aims at building a basic model of an obstacle detection robot using 8051

microcontroller and infra red proximity sensors. The model uses a three wheeled

differential drive configuration, with castor wheel and is powered by a DC voltage source

of 12 Volts. The robot is designed so that as soon as it detects an obstacle directly in front

of it, it goes in the reverse direction and then turns and proceeds along a path with no

immediate obstacles. IR leds whose frequencies are modulated to 38 KHz with the help of

an astable multivibrator circuit using 555 timer IC emit the IR rays, which get reflected and

comes back if an obstacle is present in its path. TSOP 1738 senses these rays changes its

output voltage level from high to low. This is given as an external hardware interrupt to the

microcontroller, which decides the action to be taken as per the source code.


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CONTENTS

1. Introduction2. Objective3. System Model

3.1 AT89C51

3.1.1 General Description

3.1.2 Features

3.1.3 Pin Description of AT89C51

3.2 Infra Red Sensor Module

3.2.1 TSOP 1738

3.2.2 Astable Multivibrator Circuit for frequency modulation.

3.3 The Movement Control System

3.3.1 L293D

3.3.2 Two wheeled Differential Drive with Castor Wheel4. Source Code

5. Circuit Diagram

6. Results

7. Future Enhancements

8. Conclusion

9. References


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1. INTRODUCTION

With the increasing importance and popularity of autonomous machines in the global scenario,

robotics is a field that captures much attention and interest. This vast topic is built upon the

basics of electrical, electronics and mechanical engineering. The ability of to move smoothly,

avoiding the obstacle in its path is an essential need of any autonomous robot, irrespective of

its specific purpose. One of the most economical ways to implement obstacle avoidance is by

using IR radiations and corresponding sensors. In this mini project, we tried to develop a

miniature robot that has this quality, so that this basic model can be the foundation for variety

of specific purpose robots in future by incorporating additional sensors and by adding to the

code of the program.


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2. OBJECTIVEThis project aims to design and build a basic robot, which moves in a straight line till it detects

an obstacle. On detecting an obstacle in its path, using its IR proximity sensor, the robot

automatically turns and finds a path without an immediate obstacle and continues its motion till

the next obstacle is encountered.


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3. SYSTEM MODEL

3.1 AT89C51

3.1.1 General Description

The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of

Flash programmable and erasable read only memory (PEROM). The device is manufactured

using Atmels high-density nonvolatile memory technology and is compatible with the

industry-standard MCS-51 instruction set and pinout. The on-chip Flash allows the program

memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer.

By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a

powerful microcomputer which provides a highly-flexible and cost-effective solution to many

embedded control applications.

Figure 1: 89C51 Microcontroller

3.1.2 Features:

4K bytes of Flash 128 bytes of RAM 32 I/O lines Two 16-bit timer/counters A five vector two-level interrupt architecture 80C51 Central Processing Unit Speed up to 33 MHz Full static operation 4 level priority interrupt 6 interrupt sources Four 8-bit I/O ports

Automatic address recognition Programmable clock out


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Second DPTR register Asynchronous port reset Low EMI (inhibit ALE) 3 16-bit timers A full duplex serial port, on-chip oscillator and clock circuitry. Wake up from power down by an external interrupt In addition, the AT89C51 is designed with static logic for operation down to zero

frequency and supports two software selectable power saving modes.

The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port andinterrupt system to continue functioning.

The Power-down Mode saves the RAM contents but freezes Pin Description.

Figure 2: AT89C51 Pinout

3.1.3 Pin Description Of AT89C51

Port 0: Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can

sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as

highimpedance inputs. Port 0 may also be configured to be the multiplexed low order

address/data bus during accesses to external program and data memory . In this mode P0

has internal pullups. Port 0 also receives the code bytes during Flash programming, and

outputs the code bytes during program verification. External pullups are required during

program verification.


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Port 1:It is an 8-bit bi-directional I/O port with internal pullups. The Port 1 output buffers can

sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the

internal pullups and can be used as inputs. As inputs, Port 1 pins that are externally being

pulled low will source current (IIL) because of the internal pullups. Port 1 also receives the

low-order address bytes during Flash programming and verification.

Port 2:It is an 8-bit bi-directional I/O port with internal pullups.The Port 2 output buffers can

sink/source four TTL inputs.When 1s are written to Port 2 pins they are pulled high bythe

internal pullups and can be used as inputs. As inputs,Port 2 pins that are externally being pulled

low will sourcecurrent (IIL) because of the internal pullups. Port 2 emits the high-order address

byte during fetches from external program memory and during accesses to external data

memory that use 16-bit addresses (MOVX @DPTR). In this application, it uses strong internal

pullupswhen emitting 1s. During accesses to external data memory that use 8-bit addresses

(MOVX @ RI), Port 2 emits thecontents of the P2 Special Function Register. Port 2 also

receives the high-order address bits and some control signals during Flash programming andverification.

Port 3: It is an 8-bit bi-directional I/O port with internal pullups. The Port 3 output buffers can

sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled high by the

internal pullups and can be used as inputs. As inputs, Port 3 pins that are externally being

pulled low will source current (IIL) because of the pullups.Port 3 also serves the functions of

various special featuresof the AT89C51 as listed below: Port 3 also receives some control

signals for Flash programming and verification.

RST: A high on this pin for two machine cycles while the oscillator is running resets thedevice.

ALE/PROG: Address Latch Enable output pulse for latching the low byte of the address

during accesses to external memory. This pin is also the program pulse input (PROG) during

Flash programming. In normal operation ALE is emitted at a constant rate of 1/6 the oscillator

frequency, and may be used for external timing or clocking purposes.

PSEN: Program Store Enable is the read strobe to external program memory. When the

AT89C51 is executing code from external program memory, PSEN is activated twice each

machine cycle, except that two PSEN activations are skipped during each access to externaldata memory.

EA/VPP:External Access Enable. EA must be strapped to GND in order to enable the device

to fetch code from external program memory locations starting at 0000H up to FFFFH. If lock

bit1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for

internal program executions.This pin also receives the 12-volt programming enable voltage

(VPP) during Flash programming, for parts that require 12-volt VPP.

.XTAL1: Input to the inverting oscillator amplifier and input to the internal clock operating

circuit.

XTAL2:Output from the inverting oscillator amplifier.


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3.1.4 Modes of Operation

Idle Mode:In idle mode, the CPU puts itself to sleep while all the on chip peripherals remain

active. The mode is invoked by software. The content of the on-chip RAM and all the special

functions registers remain unchanged during this mode. The idle mode can be terminated by

any enabled interrupt or by a hardware reset. It should be noted that when idle is terminated by

a hardware reset, the device normally resumes program execution, from where it left off, up to

two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits

access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate

the possibility of an unexpected write to a port pin when Idle is terminated by reset, the

instruction following the one that invokes Idle should not be one that writes to a port pin or to

external memory.

Power-down Mode: In the power-down mode, the oscillator is stopped, and the instruction

that invokes power-down is the last instruction executed. The on-chip RAM and Special

Function Registers retain their values until the power - down mode is terminated. The

only exit from power-down is a hardware reset.

Figure 3: Block Diagram of AT89C51


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3.2

3.2.1 TSOP 1738

3.2.1.1 General Description

The TSOP17..series are miniaturized receivers for infrared remote control systems. PINdiode and preamplifier are assembled on lead frame, the epoxy package is designed as IR

filter.

The demodulated output signal can directly be decoded by a microprocessor. TSOP17.. is the standard IR remote control receiver series, supporting all major

transmission codes.

TSOP 1738 responds only to IR radiations modulated at 38KHz frequency.

Figure 3.1: TSOP 1738

3.2.1.2 Features

Photo detector and preamplifier in one package Internal filter for PCM frequency Improved shielding against electrical field disturbance TTL and CMOS compatibility Output active low Low power consumption High immunity against ambient light

Continuous data transmission possible (up to 2400 bps)

Figure 4: Block Diagram


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3.2.2 Astable Multivibrator using 555 Timer IC

The NE555 monolithic timing circuit is a highly stable controller capable of producingaccurate time delays or oscillation.

For astable operation as an oscillator, the free running frequency and the duty cycle areboth accurately controlled with two external resistors and one capacitor.

Figure 5: Block Diagram of 555 Timer IC

IR transmitter should be tuned to send signals of frequency of the range 38KHz. This frequency is generated by IC 555 operating in astable mode. Two such IR proximity sensors are used in the circuit in order to detect obstacles.

Figure 6: Astable Multivibrator using IC555


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3.3

3.3.1 L293D

The Device is a monolithic integrated high voltage, high current four channel driverdesigned to accept standard DTL or TTL logic levels and drive inductive load and

switching power transistors.

To simplify use as two bridges each pair of channels is equipped with an enable input. A separate supply input is provided for the logic, allowing operation at a lower voltage and

internal clamp diodes are included.

This device is suitable for use in switching applications at frequencies up to 5 kHz. The L293D is assembled in a 16 lead plastic packaage which has 4 center pins connected

together and used for heatsinking.

The L293DD is assembled in a 20 lead surface mount which has 8 center pins connectedtogether and used for heatsinking.

Figure 7: Block Diagram of L293D

3.3.2 Two Wheeled Differential Drive using Castor Wheels

In the differential drive left and right wheel are powered independently. Hence it is calledas differential drive.

Zero turning radius is the most important advantage of the differential drive. In thedifferential drive as left and right wheel are independent if left wheel is rotated in

anticlockwise and right wheel is turned clockwise robot will take turn in the left direction

with zero turning radius.

Easy to move when path to be followed is contoured and zigzag in nature. If we want to move along curved path we have to control left and right motors velocity

independently. Hence precision velocity control becomes difficult as actual velocity of therobot will be average of the both wheels.


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Figure 8: Three Wheeled Differential Drive

Table 3.1 The pin voltages of L293D for various movements


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4. SOURCE CODE

#include

#define motor_lp P2_4

#define motor_ln P2_5

#define motor_rp P2_6

#define motor_rn P2_7

#define irsensorl P3_2

#define irsensorr P3_3

void delay(unsigned int value)

{

unsigned int x,y,z;

for(z=0;z


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motor_ln=1;

motor_rp=0;

motor_rn=1;

}

void turn_left()

{

motor_lp=0;

motor_ln=0;

motor_rp=1;

motor_ln=0;

}

void turn_right()

{

motor_lp=1;

motor_ln=0;

motor_rp=0;

motor_rn=0;

}

void left_obstacle() interrupt 0

{

P2_0=0;

move_backward();

delay(1000);

turn_right();

delay(1000);


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P2_0=1;

}

void right_obstacle() interrupt 2

{

P2_1=0;

move_backward();

delay(1000);

turn_left();

delay(1000);

P2_1=1;

}

void main()

{

motor_lp=0; //setting all in output mode

motor_ln=0;

motor_rp=0;

motor_lp=0;

EA=1;

EX1=1;

EX0=1;

IT0=1;

IT1=1;

while(1)

{

move_forward();

}

}


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5. CIRCUIT DIAGRAM

Figure 9: The Circuit consisting of AT89C51 and LD293D


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6.RESULT

The infrared transmittter was the first circuit to be designed. It was designed using IC 555

timer.The resistors and capacitors connected in the timer circuit were chosen so as to generate

38khz frequency. The frequency was verified using digital CRO.

Next the circuit for TSOP1738 an infrared sensor was assembled. A capacitor was connected

across the ground and VCC pin to filter out any noise in the input. And the output pin was

connected to CRO for verification. It was observed that as soon as infrared light of 38khz

frequency fell on the TSOP1738 the output became instantaneously low.

So the code to be burned in the microcontroller was written to be based on edge triggering

interrupts. It was intended that the motors connected to the microcontroller through LM324

would rotate in a manner such that the robot moves forward. And on detecting an interrupt the

robot would first move backward and then using differential drive would change direction.

The code was successfully compiled.


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7.FUTURE ENHANCEMENTS

As this project implements only a very basic model of obstacle detection and avoidance, many

more modifications can be made to it, depending on the need. A few important possible

enhancements are:

A position encoder can be used to measure the speed of the robot, and we can display thisspeed and direction of motion on an LCD screen.

The robot can be equipped with a serial port so as to facilitate data transfer to a separatecomputer.

By using pulse width modulation, it is possible to have a speed control for the robot. A mechanism to calibrate the approximate distance of the obstacle from the robot, by

measuring the intensity of the reflected IR rays can be implemented.


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8.CONCLUSION

The project can be used as the basic model for all autonomous systems that require obstacle

avoidance.


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10.REFERENCES

1.The 8051 microcontroller and embedded Systems using Assembly and C, Muhammed Ali

Mazidi et al.

2.www.nex-robotics.com

3. www.8051projects.net

4.www.robotshop.com

5. Spark 3 Manual

6. Datasheets of AT89C51, IC 555, TSOP 1738, LD293D

7. Pulse, Digital and Switching Waveforms, Jacob Millman and Herbert Taub
http://www.nex-robotics.com/http://www.nex-robotics.com/http://www.nex-robotics.com/http://www.robotshop.com/http://www.robotshop.com/http://www.robotshop.com/http://www.robotshop.com/http://www.nex-robotics.com/

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obstacle detection robot