Metal Detecting Robot

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Metal Detecting Robot

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CONTENT

1. INTRODUCTION 2. DESIGN PRINCIPLE 3. CIRCUIT DESCRIPTION

A. Metal detector B. Signal conditioning C. Mother Board D. IR Transmitter E. IR Receiver F. Relay driver G. Bidirectional DC motor H. Bidirectional DC motor driver I. Buzzer Driver

4. FUTURE EXPANSION 5. 6. CONCLUSION

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INTRODUCTION

The present scenario of technology, research and development primarily focused

on the defense activity. The Anti Tank mine detector is a robotic instrument which

can be used as a mine detector to protect the Tank. This is very much useful and

advantageous to protect the tanks moving on the war field. The ANTI-TANK

MINE DETECTOR is an automated robotic vehicle which moves on the earth

surface and scans the area on which it moves. This project is designed with an

intension to design a pilot robot which can guide the tank fleet. The Pilot robot is

designed to find out a safe path for the tanks. This robot is known as Anti Tank

Mine Detector. The Anti Tank Mine Detector move on a surface and detect

obstacles and mines and finds safe path for the tank fleet. The pilot robot is a

intelligent path finder which finds a safe and effective path for the tanks in the

war field. This robot can be used in defense and also used as path finder for

explosive detector. This is basically a robotic vehicle which has certain

inelegancy to under stand the obstacle and mine etc also this robot is having

memory to remember the obstacle position so that it will not enter into a vicious

loop.

The word "robot" originates from the word for forced labor, Basically a robots consists of:

A mechanical device, such as a wheeled platform, arm, or other

construction, capable of interacting with its environment

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Sensors on or around the device that are able to sense the environment

and give useful feedback to the device

Systems that process sensory input in the context of the device's current

situation and instruct the device to perform actions in response to the

situation

In the manufacturing field, robot development has focused on engineering robotic

arms that perform manufacturing processes. In the space industry, robotics

focuses on highly specialized, one-of-kind planetary rovers. Unlike a highly

automated manufacturing plant, a planetary rover operating on the dark side of

the moon -- without radio communication -- might run into unexpected situations.

At a minimum, a planetary rover must have some source of sensory input, some

way of interpreting that input, and a way of modifying its actions to respond to a

changing world. Furthermore, the need to sense and adapt to a partially unknown

environment requires intelligence (in other words, artificial intelligence).

From military technology and space exploration to the health industry and

commerce, the advantages of using robots have been realized to the point that

they are becoming a part of our collective experience and every day lives.

They function to relieve us from danger and tedium:

Safety: Robotics have been developed to handle nuclear and radioactive

chemicals for many different uses including nuclear weapons, power

plants, environmental cleanup, and the processing of certain drugs.

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Unpleasantness: Robots perform many tasks that are tedious and

unpleasant, but necessary, such as welding or janitorial work.

Repetition and precision: Assembly line work has been one of the

mainstays of the robotics industry. Robots are used extensively in

manufacturing and, more glamorously, in space exploration, where

minimum maintenance requirements are emphasized.

Robot,defined

"A re-programmable, multifunctional manipulator designed to move material,

parts, tools, or specialized devices through various programmed motions for the

performance of a variety of tasks."

-- From the Robot Institute of America, 1979

Robots have become important over a wide range of applications--from

manufacturing, to surgery, to the handling of hazardous materials. Consequently,

it's important to understand how they work, and what problems exist in designing

effective robots. This project will address one of those problems: positional

control.

Anti Tank Mine Detector is an autonomous robot with certain amount of

artificial intelligence, which is one of the evolving fields of application, in the

present scenario of robotics. There are different technologies used for design of

this type of robots. This is an application where the concept of embedded

processor to wireless communication is being used for a practical application.

These types of applications are very much useful for the industries engaged in

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hazardous process and places where the access of human being is difficult.

Specifically, the if the path of the robot is quit complicated and not suitable for

laying cable then there is the only solution exists that is to provide autonomy or

artificial intelligence to the robot. The Anti Tank Mine Detector is one of such

application realized using embedded micro-controller. The basic advantage of

embedded technology is compact size and reliable operation. The micro

controller used in this project is AT89C51. The micro controller receives the

signal from the sensors connected and takes the decision as per the program

algorithms

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THEORY AND DESIGN PRINCIPLE

Theory:

Mechanical platforms -- the hardware base

A robot consists of two main parts: the robot body and some form of artificial

intelligence or control system. Many different body parts can be called a robot.

Articulated arms are used in welding and painting; gantry and conveyor systems

move parts in factories; and giant robotic machines move earth deep inside

mines. One of the most interesting aspects of robots in general is their behavior,

which requires a form of intelligence. The simplest behavior of a robot is

locomotion. Typically, wheels are used as the underlying mechanism to make a

robot move from one point to the next. And some force such as electricity is

required to make the wheels turn under command.

Motors

A variety of electric motors provide power to robots, allowing them to move

material, parts, tools, or specialized devices with various programmed motions.

The efficiency rating of a motor describes how much of the electricity consumed

is converted to mechanical energy. Let's take a look at some of the mechanical

devices that are currently being used in modern robotics technology.

DC motor: Permanent magnet, direct-current (PMDC) motors require only two

leads, and use an arrangement of fixed- and electro-magnets (stator and rotor)

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and switches. These form a commutator to create motion through a spinning

magnetic field.

AC motor: AC motors cycle the power at the input-leads, to continuously move

the field. Given a signal, AC and DC motors perform their action to the best of

their ability.

Stepper motor: Stepper motors are like a brush less DC or AC motor. They

move the rotor by applying power to different magnets in the motor in sequence

(stepped). Steppers are designed for fine control and will not only spin on

command, but can spin at any number of steps-per-second (up to their maximum

speed).

Servomotors: Servomotors are closed-loop devices. Given a signal, they adjust

themselves until they match the signal. Servos are used in radio control airplanes

and cars. They are simple DC motors with gearing and a feedback control

system.

Driving mechanisms

Gears and chains: Gears and chains are mechanical platforms that provide a

strong and accurate way to transmit rotary motion from one place to another,

possibly changing it along the way. The speed change between two gears

depends upon the number of teeth on each gear. When a powered gear goes

through a full rotation, it pulls the chain by the number of teeth on that gear.

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Pulleys and belts: Pulleys and belts, two other types of mechanical platforms

used in robots, work the same way as gears and chains. Pulleys are wheels with

a groove around the edge, and belts are the rubber loops that fit in that groove.

Gearboxes: A gearbox operates on the same principles as the gear and chain,

without the chain. Gearboxes require closer tolerances, since instead of using a

large loose chain to transfer force and adjust for misalignments, the gears mesh

directly with each other. Examples of gearboxes can be found on the

transmission in a car, the timing mechanism in a grandfather clock, and the

paper-feed of your printer.

Power supplies

Power supplies are generally provided by two sources, either from battery of from

rectified and regulated power supply source. The motors and the controller can

be operated from any source of power. Where as the wireless communication

devices are requiring low ripple power supply. The most reliable source for this

type of power is 3v and 9v batteries. While designing wire less communication

devises a special care must be taken for low power consumption.

Microcontroller systems

Micro controllers (MCUs) are intelligent electronic devices used inside robots.

They deliver functions similar to those performed by a microprocessor (central

processing unit, or CPU) inside a personal computer. MCUs are slower and can

address less memory than CPUs, but are designed for real-world control

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problems. One of the major differences between CPUs and MCUs is the number

of external components needed to operate them. MCUs can often run with zero

external parts, and typically need only an external crystal or oscillator.

There are four basic aspects of a microcontroller: speed, size, memory, and

other. Speed is designated in clock cycles, and is usually measured in millions of

cycles per second (Megahertz, MHz). The use of the cycles varies in different

MCUs, affecting the usable speed of the processor. Size specifies the number of

bits of information the MCU can process in one step -- the size of its natural

cluster of information. MCUs come in 4-, 8-, 16-, and 32-bits, with 8-bit MCUs

being the most common size. MCUs count most of their ROM in thousands of

bytes (KB) and RAM in single bytes. Many MCUs use the Harvard architecture,

in which the program is kept in one section of memory (usually the internal or

external SRAM). This in turn allows the processor to access the separate

memories more efficiently.

The fourth aspect of micro controllers, referred to as "other", includes features

such as a dedicated input device that often (but not always) has a small LED or

LCD display for output. A microcontroller also takes input from the device and

controls it by sending signals to different components in the device. Also the

program counter keeps track of which command is to be executed by the

microcontroller.

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Design and operation principle:

Mechanical Design:

In this project there are four Wheels in of an robotic vehicles driven by four servo

motors. The Microcontroller AT 89C51 is programmed to drive the servo motors

in either direction to control the movement of the robotic vehicle. The program

which is executing to drive the robot reserve the memory area to keep the

status of movement if the last movement is found to be defective then

automatically the controller select another path to move the robot.

The obstacle detector is a photo reflective type sensor. There is a IR source and

receiver .The receiver output is feed to the microcontroller to detect the obstacle.

A metal detector is used for detecting the Anti Tank Mine. The out put of the

metal detector is feed to the interrupt input of the micro controller for alarm and

wait until get cleared.

CIRCUIT DESCRIPTION

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A. METAL DETECTOR

Metal detectors use electromagnetic induction to detect metal. Uses include de-

mining (the detection of land mines), the detection of weapons such as knives

and guns, especially at airports, geophysical prospecting, archaeology and

treasure hunting. Metal detectors are also used to detect foreign bodies in food,

and in the construction industry to detect steel reinforcing bars in concrete and

pipes and wires buried in walls and floors.

In its simplest form, a metal detector consists of an oscillator producing an

alternating current that passes through a coil producing an alternating magnetic

field. If a piece of electrically conductive metal is close to the coil, eddy currents

will be induced in the metal, and this produces an alternating magnetic field of its

own. If another coil is used to measure the magnetic field (acting as a

magnetometer), the change in the magnetic field due to the metallic object can

be detected.

The metal detector circuit is consisting of basically three sections. There is a

colpit oscillator with split capacitors and single inductance coil. The C1 and C2

are the capacitance of the capacitor and L is the inductance of the inductor. A

Colpitts oscillator is the electrical dual of a Hartley oscillator. In the Colpitts

circuit, two capacitors and one inductor determine the frequency of oscillation.

The feedback needed for oscillation is taken from a voltage divider made by the

two capacitors, where in the Hartley circuit the feedback is taken from a voltage

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divider made by two inductors (or a tapped single inductor). (Note: the capacitor

can be a variable device by using a varactor)

A simplified version of the formula is this:

In this case when metal or mine is detected then the inductance l changes so the

oscillation frequency decreases. And the change of frequency is the vital concept

of mine or metal detector. The Transistors T1, T2, Capacitor C1, C2, and

Inductor L form the oscillator section. The next section is a tuned oscillator which

varies its gain with frequency. The transistor T3, T4, capacitor C3, C4 and

Resistance R1 forms a filter network and a amplifier. The frequency signal feed

to the filter and amplifier is rectified by a diode so the amplifier output is a DC.

The C3 acts as a high pass capacitor so when the metal is detected the

frequency decreases and the capacitor attenuate the signal and diode and

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capacitor filter the signal and convert into DC. This signal is feed to the amplifier

T3. In this condition (metal or mine detected) the T3 output is high ( at the base

of T4 appears with Vcc.). The transistor T4 is in ON condition so current flow in

the LED and LED glows. When the coil is normal condition(no metal or mine

detected) the frequency is higher the pass capacitor C3 allow signal and the

output of the amplifier transistor T3 is low as the transistor T3 is ON. Which in

turn Off the Transistor T4 so the LED is in OFF condition.

The next stage is a signal conditioning or high gain amplifier stage which

converts the output of the amplifier into a TTL compatible signal to feed further

section. The Transistors T5 and T6 are designed to operate in cutoff and

saturation region. This signal is feed to the next sections for further processing.

.

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56

k

15k

56

k

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Vcc=+12V

BC547

27

0p

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Vcc=+5V

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B. SIGNAL CONDITIONING

The output form the input signal i.e. comparator or any other external circuit must

be compatible with the -controller, because the -controller can takes 5V as

input voltage and gives a 5V as output voltage. That for we need a signal

conditioning circuit as given in the below figure.

BC5471.5k

10k

(1:0)

VCC= +5vVCC= +5v

(1:1)

INPUT

1.5k

SIGNAL CONDITIONING

OUTPUT

10kOUTPUT

BC547

INPUT

fig..1:1

In the fig1: 1, whenever the base voltage is HIGH the transistor

comes to saturation condition i.e. the collector current flows to the emitter which

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gives a high voltage at the output corresponding to Vcc given at the collector.

The output is taken from the emitter junction through a current limiting resistance

and the output signal is given to the - controller or any other circuit which needs

a compatible (5V) voltage. Similarly, whenever the base voltage is LOW the

emitter current flows from the emitter junction of the transistor, which gives a low

voltage at the output corresponding to GND. The output is taken from the emitter

junction through a current limiting resistance and the output signal is given to the

- controller or any other circuit which needs a compatible (5V) voltage.

fig..1:0

In the fig1: 0, whenever the base voltage is HIGH the transistor comes to

saturation condition i.e. the emitter current flows to the collector which gives a

low voltage at the output corresponding to GND. The output is taken from the

collector junction through a current limiting resistance and the output signal is

given to the - controller or any other circuit which needs a compatible (5V/0V)

voltage. Similarly, whenever the base voltage is LOW the collector current flows

from the collector junction of the transistor, which gives a high voltage at the

output corresponding to Vcc. The output is taken from the emitter junction

through a current limiting resistance and the output signal is given to the -

controller or any other circuit which needs a compatible (5V/0V) voltage.

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C. MOTHER BOARD

The motherboard of this project is designed with a MSC 51 core compatible

micro controller. The motherboard is designed on a printed circuit board,

compatible for the micro controller. This board is consisting of a socket for micro

controller, input /output pull-up registers; oscillator section and auto reset circuit.

Micro controller core processor:

Introduction

Despite its relatively old age, the 89C51 is one of the most popular Micro

controller in use today. Many derivatives Micro controllers have since been

developed that are based on--and compatible with--the 8051. Thus, the ability to

program an 89C51 is an important skill for anyone who plans to develop products

that will take advantage of Micro controller.

Many web pages, books, and tools are available for the 89C51 developer.

The 89C51 has three very general types of memory. To effectively program

the8051 it is necessary to have a basic understanding of these memory types.

The memory types are illustrated in the following graphic. They are: On-Chip

Memory, External Code Memory, and External RAM.

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On-Chip Memory refers to any memory (Code, RAM, or other) that physically

exists on the Microcontroller itself. On-chip memory can be of several types, but

we'll get into that shortly.

External Code Memory is code (or program) memory that resides off-chip. This

is often in the form of an external EPROM.

External RAM is RAM memory that resides off-chip. This is often in the form of

standard static RAM or flash RAM.

Code Memory

Code memory is the memory that holds the actual 8051 program that is to be

run. This memory is limited to 64K and comes in many shapes and sizes: Code

memory may be found on-chip, either burned into the Microcontroller as ROM or

EPROM. Code may also be stored completely off-chip in an external ROM or,

more commonly, an external EPROM. Flash RAM is also another popular

method of storing a program. Various combinations of these memory types may

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also be used--that is to say, it is possible to have 4K of code memory on-chip and

64k of code memory off-chip in an EPROM.

When the program is stored on-chip the 64K maximum is often reduced to 4k, 8k,

or 16k. This varies depending on the version of the chip that is being used. Each

version offers specific capabilities and one of the distinguishing factors from chip

to chip is how much ROM/EPROM space the chip has.

However, code memory is most commonly implemented as off-chip EPROM.

This is especially true in low-cost development systems and in systems

developed by students.

Programming Tip: Since code memory is restricted to 64K, 89C51 programs

are limited to 64K. Some assemblers and compilers offer ways to get around this

limit when used with specially wired hardware. However, without such special

compilers and hardware, programs are limited to 64K.

External RAM

As an obvious opposite of Internal RAM, the 89C51 also supports what is called

External RAM.

As the name suggests, External RAM is any random access memory which is

found off-chip. Since the memory is off-chip it is not as flexible in terms of

accessing, and is also slower. For example, to increment an Internal RAM

location by 1 requires only 1 instruction and 1 instruction cycle. To increment a 1-

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byte value stored in External RAM requires 4 instructions and 7 instruction

cycles. In this case, external memory is 7 times slower!

What External RAM loses in speed and flexibility it gains in quantity. While

Internal RAM is limited to 128 bytes (256 bytes with an 8052), the 8051 supports

External RAM up to 64K.

Programming Tip: The 8051 may only address 64k of RAM. To expand RAM

beyond this limit requires programming and hardware tricks. You may have to do

this "by hand" since many compilers and assemblers, while providing support for

programs in excess of 64k, do not support more than 64k of RAM. This is rather

strange since it has been my experience that programs can usually fit in 64k but

often RAM is what is lacking. Thus if you need more than 64k of RAM, check to

see if your compiler supports it-- but if it doesn't, be prepared to do it by hand.

On-Chip Memory

As mentioned at the beginning of this chapter, the 89C51 includes a certain

amount of on-chip memory. On-chip memory is really one of two types: Internal

RAM and Special Function Register (SFR) memory. The layout of the 89C51's

internal memory is presented in the following memory map:

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As is illustrated in this map, the 8051 has a bank of 128 bytes of Internal RAM.

This Internal RAM is found on-chip on the 8051 so it is the fastest RAM available,

and it is also the most flexible in terms of reading, writing, and modifying its

contents. Internal RAM is volatile, so when the 8051 is reset this memory is

cleared.

The 128 bytes of internal ram is subdivided as shown on the memory map. The

first 8 bytes (00h - 07h) are "register bank 0". By manipulating certain SFRs, a

program may choose to use register banks 1, 2, or 3. These alternative register

banks are located in internal RAM in addresses 08h through 1Fh. We'll discuss

"register banks" more in a later chapter. For now it is sufficient to know that they

"live" and are part of internal RAM.

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Bit Memory also lives and is part of internal RAM. We'll talk more about bit

memory very shortly, but for now just keep in mind that bit memory actually

resides in internal RAM, from addresses 20h through 2Fh.

The 80 bytes remaining of Internal RAM, from addresses 30h through 7Fh, may

be used by user variables that need to be accessed frequently or at high-speed.

This area is also utilized by the Microcontroller as a storage area for the

operating stack. This fact severely limits the 8051s stack since, as illustrated in

the memory map, the area reserved for the stack is only 80 bytes--and usually it

is less since this 80 bytes has to be shared between the stack and user

variables.

SFR Descriptions

There are different special function registers (SFR) designed in side the 89C51

micro controller. In this micro controller all the input , output ports, timers

interrupts are controlled by the SFRs. The SFR functionalities are as follows.

This section will endeavor to quickly overview each of the standard SFRs found

in the above SFR chart map. It is not the intention of this section to fully explain

the functionality of each SFR--this information will be covered in separate

chapters of the tutorial. This section is to just give you a general idea of what

each SFR does.

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P0 (Port 0, Address 80h, Bit-Addressable): This is input/output port 0. Each bit

of this SFR corresponds to one of the pins on the Microcontroller. For example,

bit 0 of port 0 is pin P0.0, bit 7 is pin P0.7. Writing a value of 1 to a bit of this SFR

will send a high level on the corresponding I/O pin whereas a value of 0 will bring

it to a low level.

Programming Tip: While the 8051 has four I/O port (P0, P1, P2, and P3), if your

hardware uses external RAM or external code memory (i.e., your program is

stored in an external ROM or EPROM chip or if you are using external RAM

chips) you may not use P0 or P2. This is because the 8051 uses ports P0 and P2

to address the external memory. Thus if you are using external RAM or code

memory you may only use ports P1 and P3 for your own use.

SP (Stack Pointer, Address 81h): This is the stack pointer of the

Microcontroller. This SFR indicates where the next value to be taken from the

stack will be read from in Internal RAM. If you push a value onto the stack, the

value will be written to the address of SP + 1. That is to say, if SP holds the value

07h, a PUSH instruction will push the value onto the stack at address 08h. This

SFR is modified by all instructions which modify the stack, such as PUSH, POP,

LCALL, RET, RETI, and whenever interrupts are provoked by the Microcontroller.

Programming Tip: The SP SFR, on startup, is initialized to 07h. This means the

stack will start at 08h and start expanding upward in internal RAM. Since

alternate register banks 1, 2, and 3 as well as the user bit variables occupy

internal RAM from addresses 08h through 2Fh, it is necessary to initialize SP in

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your program to some other value if you will be using the alternate register banks

and/or bit memory. It's not a bad idea to initialize SP to 2Fh as the first instruction

of every one of your programs unless you are 100% sure you will not be using

the register banks and bit variables.

DPL/DPH (Data Pointer Low/High, Addresses 82h/83h): The SFRs DPL and

DPH work together to represent a 16-bit value called the Data Pointer. The data

pointer is used in operations regarding external RAM and some instructions

involving code memory. Since it is an unsigned two-byte integer value, it can

represent values from 0000h to FFFFh (0 through 65,535 decimal).

Programming Tip: DPTR is really DPH and DPL taken together as a 16-bit

value. In reality, you almost always have to deal with DPTR one byte at a time.

For example, to push DPTR onto the stack you must first push DPL and then

DPH. You can't simply plush DPTR onto the stack. Additionally, there is an

instruction to "increment DPTR." When you execute this instruction, the two

bytes are operated upon as a 16-bit value. However, there is no instruction that

decrements DPTR. If you wish to decrement the value of DPTR, you must write

your own code to do so.

PCON (Power Control, Addresses 87h): The Power Control SFR is used to

control the 8051's power control modes. Certain operation modes of the 8051

allow the 8051 to go into a type of "sleep" mode, which requires much, less

power. These modes of operation are controlled through PCON. Additionally, one

of the bits in PCON is used to double the effective baud rate of the 8051's serial

port.

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TCON (Timer Control, Addresses 88h, Bit-Addressable): The Timer Control

SFR is used to configure and modify the way in which the 8051's two timers

operate. This SFR controls whether each of the two timers is running or stopped

and contains a flag to indicate that each timer has overflowed. Additionally, some

non-timer related bits are located in the TCON SFR. These bits are used to

configure the way in which the external interrupts are activated and also contain

the external interrupt flags which are set when an external interrupt has occurred.

TMOD (Timer Mode, Addresses 89h): The Timer Mode SFR is used to

configure the mode of operation of each of the two timers. Using this SFR your

program may configure each timer to be a 16-bit timer, an 8-bit auto reload timer,

a 13-bit timer, or two separate timers. Additionally, you may configure the timers

to only count when an external pin is activated or to count "events" that are

indicated on an external pin.

TL0/TH0 (Timer 0 Low/High, Addresses 8Ah/8Ch): These two SFRs, taken

together, represent timer 0. Their exact behavior depends on how the timer is

configured in the TMOD SFR; however, these timers always count up. What is

configurable is how and when they increment in value.

TL1/TH1 (Timer 1 Low/High, Addresses 8Bh/8Dh): These two SFRs, taken

together, represent timer 1. Their exact behavior depends on how the timer is

configured in the TMOD SFR; however, these timers always count up. What is

configurable is how and when they increment in value.

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P1 (Port 1, Address 90h, Bit-Addressable): This is input/output port 1. Each bit




it to a low level.

SCON (Serial Control, Addresses 98h, Bit-Addressable): The Serial Control

SFR is used to configure the behavior of the 8051's on-board serial port. This

SFR controls the baud rate of the serial port, whether the serial port is activated

to receive data, and also contains flags that are set when a byte is successfully

sent or received.

Programming Tip: To use the 8051's on-board serial port, it is generally

necessary to initialize the following SFRs: SCON, TCON, and TMOD. This is

because SCON controls the serial port. However, in most cases the program will

wish to use one of the timers to establish the serial port's baud rate. In this case,

it is necessary to configure timer 1 by initializing TCON and TMOD.

SBUF (Serial Control, Addresses 99h): The Serial Buffer SFR is used to send

and receive data via the on-board serial port. Any value written to SBUF will be

sent out the serial port's TXD pin. Likewise, any value which the 8051 receives

via the serial port's RXD pin will be delivered to the user program via SBUF. In

other words, SBUF serves as the output port when written to and as an input port

when read from.

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P2 (Port 2, Address A0h, Bit-Addressable): This is input/output port 2. Each bit




it to a low level.

Programming Tip: While the 8051 has four I/O port (P0, P1, P2, and P3), if your

hardware uses external RAM or external code memory (i.e., your program is

stored in an external ROM or EPROM chip or if you are using external RAM

chips) you may not use P0 or P2. This is because the 8051 uses ports P0 and P2

to address the external memory. Thus if you are using external RAM or code

memory you may only use ports P1 and P3 for your own use.

IE (Interrupt Enable, Addresses A8h): The Interrupt Enable SFR is used to

enable and disable specific interrupts. The low 7 bits of the SFR are used to

enable/disable the specific interrupts, where as the highest bit is used to enable

or disable ALL interrupts. Thus, if the high bit of IE is 0 all interrupts are disabled

regardless of whether an individual interrupt is enabled by setting a lower bit.

P3 (Port 3, Address B0h, Bit-Addressable): This is input/output port 3. Each bit

of this SFR corresponds to one of the pins on the Micro controller. For example,



it to a low level.

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Auto reset Circuit:

RST10uF

22pF

22pF

8.2k

4 - 12Mhz

VCC=+5vdc

AT89C51

9

1819

2930

31

12345678

2122232425262728

1011121314151617

3938373635343332

RST

XTAL2XTAL1

PSENALE/PROG

EA/VPP

P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7

P2.0/A8P2.1/A9

P2.2/A10P2.3/A11P2.4/A12P2.5/A13P2.6/A14P2.7/A15

P3.0/RXDP3.1/TXD

P3.2/INT 0P3.3/INT 1

P3.4/T0P3.5/T1

P3.6/WRP3.7/RD

P0.0/AD0P0.1/AD1P0.2/AD2P0.3/AD3P0.4/AD4P0.5/AD5P0.6/AD6P0.7/AD7

MICROCONTROLLER

The auto reset circuit is a RC network as shown in the mother board circuit

diagram. A capacitor of 1-10mfd is connected in series with a 8k2 resister the R-

C junction is connected to the micro controller pin 9 which is reset pin. The reset

pin is one when ever kept high( logic 1) the programme counter (PC) content

resets to 0000h so the processor starts executing the programme. from that

location. When ever the system is switched ON the mother board gets power and

the capacitor acts as short circuit and the entire voltage appears across the

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31

resistor, so the reset pin get a logic 1 and the system get reset, whenever it is

being switched ON.

Pull-UP Resisters:

AT89C51

9

1819

2930

31

12345678

2122232425262728

1011121314151617

3938373635343332

RST

XTAL2XTAL1

PSENALE/PROG

EA/VPP

P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7

P2.0/A8P2.1/A9

P2.2/A10P2.3/A11P2.4/A12P2.5/A13P2.6/A14P2.7/A15

P3.0/RXDP3.1/TXD

P3.2/INT 0P3.3/INT 1

P3.4/T0P3.5/T1

P3.6/WRP3.7/RD


10k

PORT-0

VCC=+5V

The PORT0 and PORT2 of the MCS-51 architecture is of open collector type so

on writing logic 0 the pins are providing a perfect ground potential. Where as on

writing logic 1 the port pins behaves as high impedance condition so putting a

pull-up resister enables the port to provide a +5volt(logic 1). Port1 and Port3 are

provided with internal pull-ups. A pull-up resister is normally a 10K resistance

connected from the port pin to the Vcc (+5) volt.

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Crystal Oscillator

The 8051 family microcontroller contains an inbuilt crystal oscillator, but the

crystal has to be connected externally. This family of microcontroller can support

0 to 24MHz crystal and two numbers of decoupling capacitors are connected as

shown in the figure. These capacitors are decouples the charges developed on

the crystal surface due to piezoelectric effect. These decoupling capacitors are

normally between 20pf to 30pf. The clock generator section is designed as

follows,

The Microcontroller design consist of two parts

1) Hardware.

2) Software.

HARDWARE:

The controller operates on +5 V dc, so the regulated + 5v is supplied to pin no.

40 and ground at pin no. 20. The controller is used here need not required to

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handle high frequency signals, so as 4 MHz crystal is used for operating the

processor. The pin no. 9 is supplied with a +5V dc through a push switch. To

reset the processor .As prepare codes are store in the internal flash memory the

pin no. 31 is connected to + Vcc

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RST

OBSTACKLE

AT89C51

9

1819

2930

31

12345678

2122232425262728

1011121314151617

3938373635343332

RST

XTAL2XTAL1

PSENALE/PROG

EA/VPP

P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7

P2.0/A8P2.1/A9

P2.2/A10P2.3/A11P2.4/A12P2.5/A13P2.6/A14P2.7/A15

P3.0/RXDP3.1/TXD

P3.2/INT0P3.3/INT1

P3.4/T0P3.5/T1

P3.6/WRP3.7/RD


22pF

22pF

4M

Hz

8.2k

BUZZER DRIVER

MOTOR START

DC MOTOR DRIVER

10uF

Vcc =+5V

MOTHER BOARD

MINE-DETECTOR

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E.IR TRANSMITTER The IR LED is also light emitting diode but the junction is made out of such

material that the transition of electron between the bands emits quanta of energy(

E=h) having a particular frequency which is having a particular characteristic.

When a diode emits a particular characteristic signal having frequency in the

range of infrared then, that diode is called a infrared emitting diode. The IR data

transmitter is a high intensity IR signal transmitter. There are two diodes

connected in parallel to increase the intensity to avoid data corruption.

In this section our aim is to protect the zone/door/almira etc. from the

unauthorized entry or interruption, for that we need some element that should not

be visible to the unauthorized person. For that we have taken elements as IR

LED as a source and photo diode as a destination. Generally, we have taken IR

because IR is invisible to the eye, where as in case of LASER, which is easily

visible to the human eye by which will, alert the unauthorized person. That is why

we have taken IR as a transmitter which will transmit a continuously IR signal. At

the receiver end the photodiode will receive the IR signal. if somebody tries to

interrupt the IR signal at the transmitter end, the receiver will decide the absence

of the IR signal at the receiver end.

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10K

IR RECEIVER/DETECTOR

200K

15k

10k

VCC=+12V

BC547

150E/2W

TO NAND GATE

PHOTO

DIODE

10k

10K

1kVCC=+12V

U1A

LM393

1

3

2

84

OUT

+

-

VC

CG

ND

IR TRANSMITTER

IRDIODE

Operation:

Whenever the base voltage (12v) is high which is connected through a base

resistance Rb (1k-10k), the transistor (BC547/BC548) comes to saturation

condition (ON state) thus emitter current starts flowing towards the collector

junction which is connected through a collector resistance Rc (150E/2) and

connected to Vcc. Which makes an IR LED as a forward biased thus transmit a

continuous IR signal.

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F.IR RECEIVER Introduction:

If a convectional silicon diode is connected in reverse biased ckt in fig., negligible

current will flows through the diode and zero voltage will develop across R.

R

VCC

D1 Vout

D1

Vout

Fig.1

R

VCC

Fig.2

If the diode casing is now carefully removed so that the diode semiconductor

junction is revealed, and the junction is then exposed to the visible light in the ckt

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fig.1, the diode current will rise, possibly to as high as 1mA,producing a

significant output across R. In use, the photodiode is reversed biased and the

output voltage is taken from across a series-connected load resistor. This resistor

may be connected between the diode and ground as in fig.1, or between the

diode and the positive supply as in fig.2. Photodiodes have a far lower light

sensitivity than cadmium-sulphide LDRs, but give a far quicker response to

change in light level. Generally, LDRs are ideal for the use in slow acting direct-

coupled light- level sensing application, while photodiodes are ideal for the use in

fast-acting AC-coupled signaling applications.

Application: IR beam switches and alarm ckt, and photographic flash slave

circuits, etc.

Operation:

In our project in the data receiving section, the photodiode is used as signal

(data) detector purpose to detect the IR signal (data) from the IR transmitter LED

section. Whenever the signal is transmitted from the IR transmitter LED, the

signal is received at the photodiode receiving section. The receiving signal is

very weak in strength, for that we used an amplifier. The output of the photodiode

is given as input to the amplifier (Op-amp LM351) through a filtering capacitor

(0.01uF) which is configured as an inverting amplifier and the non-inverting is

grounded and the gain is adjusted with a variable resistor (1ME) to amplify the

weak signal. Thus the amplified output is obtained at the output. That output

signal is not compatible with the Microcontroller because of the high current; that

output from the Op-amp is given to the signal conditioning i.e. the signal is given

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to the base of the transistor through a base resistance (1.5k) and the collector is

connected to Vcc and the output is taken from the emitter through a (10k)

resistance which is connected to ground. Thus the output signal is compatible

with the Microcontroller and that signal is connected to the RxD pin of the

Microcontroller. Thus the transmitted data is received at the receiving section.

The transmitted signal must fall pin pointed to the photodiode junction in order to

receive the correct data at the receiver end without any interference or

malflacuation.

G.RELAY DRIVER

The relay driver is design by using a BC547 transistor .The relay used here

having the specification as follows

Coil resistance =400ohm

Coil voltage=12Vdc

Contact capacity=230V, 7A

The above specification indicates that the coil requires 12V dc and 200mA

current dc. The Microcontroller cant supply more then 10mA current. So driver

section is very much required. BC547 has a typical current gain of 200 and

maximum current capacity of 1A. So a typical base current of 200 A can trigger

to on the relay.

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ELECTRO MAGNETIC RELAY

These are varying much reliable devices and widely used on field. The

operating frequency of these devices are minimum 10-20ms.That is 50Hz

100Hz.The relay which is used here can care 25mA currents continuously. The

electromagnetic relay operates on the principle magnetism. When the base

voltage appears at the relay driver section, the driver transistor will be driver

transistor will be driven into saturation and allow to flow current in the coil of the

relay, Which in turn create a magnetic field and the magnetic force produced

due to that will act against the spring tension and close the contact coil.

Whenever the base voltage is withdrawn the transistor goes to cutoff .So no

current flow in the coil of the relay. Hence the magnetic field disappears so the

contact point breaks automatically due to spring tension. Those contact points

are isolated from the low voltage supply, so a high voltage switching is possible

by the help of electromagnetic relays.

The electromagnetic relays normally having 2 contact points. Named as normally

closes (NC), normally open (NO). Normally closed points will so a short CKT path

when the relay is off. Normally open points will so a short CKT path when the

relay is energized.

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H. DC MOTOR

The motor being dissected here is a simple PMDC electric motor that is typically

find applications in robotics and control systems also used for techo generator in

the industries.

This is a small motor, about as big around as a coin. From the outside the body

of the motor is shown in the picture along with its axle and two battery leads. If

the motor is connected to the battery then , the axle will spin. If the leads are

reversed then, it will spin in the opposite direction. Here are two other views of

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the same motor. (Note the two slots in the side of the steel can in the second

shot -- their purpose will become more evident in a moment.)

e nylon end cap is held in place by two tabs that are part of the steel can. By

bending the tabs back, end cap can be free and removed. Inside the end cap

are the motor's brushes. These brushes transfer power from the battery to the

commutator as the motor spins:

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The axle holds the armature and the commutator. The armature is a set of

electromagnets in this case three. The armature in this motor is a set of thin

metal plates stacked together, with thin copper wire coiled around each of the

three poles of the armature. The two ends of each wire (one wire for each pole)

are soldered onto a terminal, and then each of the three terminals is wired to one

plate of the commutator. The figures below make it easy to see the armature,

terminals and commutator:

The final piece of any DC electric motor is the field magnet. The field magnet in

this motor is formed by the can itself plus two curved permanent magnets:

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One end of each magnet rests against a slot cut into the can, and then the

retaining clip presses against the other ends of both magnets.

An electromagnet is the basis of an electric motor. You can understand how

things work in the motor by imagining the following scenario. Say that you

created a simple electromagnet by wrapping 100 loops of wire around a nail and

connecting it to a battery. The nail would become a magnet and have a north and

south pole while the battery is connected.

Now say that you take your nail electromagnet, run an axle through the middle of

it and suspend it in the middle of a horseshoe magnet as shown in the figure

below. If you were to attach a battery to the electromagnet so that the north end

of the nail appeared as shown, the basic law of magnetism tells you what would

happen: The north end of the electromagnet would be repelled from the north

end of the horseshoe magnet and attracted to the south end of the horseshoe

magnet. The south end of the electromagnet would be repelled in a similar way.

The nail would move about half a turn and then stop in the position shown

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I. DC MOTOR DRIVER

The D.C. Motor used in this project operates at 12 volt and carries approximately

400mA of current. The motor driver is designed to inter face the motor with micro

controller. The micro controller out put is +5volt and can maximum give a current

of 5mA. The driver stage changes the current and voltage level suitably to drive

the motor. The driver stage not only drives the motor but also helps to control

the direction of rotation. As the output current (Ic) is large the driver section

requires a Darlington pair to switch the load. The Darlington pair I.C. TIP 122 is

used here for designing. There are four ICs used here but two of those switched

for one direction and other two will be switched for opposite direction rotation of

the D.C. motor. The design principle of the driver section is as follows.

The motor takes approximately 400mA at 12 volt D.C., The power transistors can

have amplification factor maximum 60 to 70 as per this assumption the base

current required to switch on the transistor is approximately

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Ib= (Ic/beta) =400mA/60 =6.7 mA

This current is too high to supply as a base current, more over the Microcontroller

can not supply that much current to drive the transistor so, a darling ton pair is

required to limit the base current with in 100 micro amp. To 2 mA.

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Vcc =+12v

BC547

BC547

1.5k

Vcc =+12v

10u

F

RE

LA

Y

+

-

1N

4007

RE

LA

Y

1.5k

DC MOTOR DRIVER- 01

M

Vcc =+12v

10u

F

1N

4007

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Vcc =+12v

BC547

BC547

1.5k

Vcc =+12v

10

uF

RE

LA

Y+

-

1N

40

07

RE

LA

Y1.5k

DC MOTOR DRIVER- 02

M

Vcc =+12v

10

uF

1N

40

07

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J. BUZZER DRIVER

This section interfaces one audible piezo electric buzzer with the controller. The

controller activates the buzzer whenever there is any fault appears in any of the

channel.

PIEZO ELECRTIC BUZZER:

It is a device that converts electrical signal to an audible signal (sound signal).

The Microcontroller cannot drive directly to the buzzer, because the

Microcontroller cannot give sufficient current to drive the buzzer for that we need

a driver transistor (BC547), which will give sufficient current to the buzzer.

Whenever a signal received to the base of the transistor through a base

resistance (1.5k) is high, the transistor comes to saturation condition i.e. ON

condition thus the buzzer comes to on condition with a audible sound. Similarly,

whenever the signal is not received to the base of the transistor, thus the

transistor is in cut-off state i.e. is in OFF state thus the buzzer does not gets

activated.

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FUTURE EXPANSION

This project has a vast field for expansion. The robot is designed with latest

technology of communication and control. This project is designed with constraint

of time and cost. This project can be modified and expanded in the following

fields,

1. The robot can be interfaced with GPS sensor to send back the

information to the base station to indicate the detection of mine at the

particular location.

2. The robot can be programmed remotely through a GPRS or GSM

network to control its movement.

3. The system may have a robotic arm and gripper to diffuse the mine .

4. The robo can be designed with a web cam to send the snap shots of

the location.

CONCLUSION

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This project is designed as a concept to control a robotic vehicle with automated

control system. The control system is having feed back and the response is quit

fast and accurate.

The project performs satisfactorily in the laboratory condition. The accuracy and

performance is quite accurate and the errors observed are well bellow the

tolerance level.

Documents

Metal Detecting Robot