A Mini Project Report On

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MOBILE PHONE CONTROLLED DTMF BASED ROBOT

INTRODUCTION:

“Mobile Phone Controlled DTMF Based Robot” is capable of receiving a set of command

(instructions) in the form of DTMF tones and performs the necessary actions. Here

DTMF stands for “Dual-tone multi-frequency”. We will be using a dedicated

modem/mobile at the receiver module i.e. with the robot itself and send the commands

using DTMF tones as per the required actions.

Description:

The mobile unit which is dedicated at the robot is interfaced with an intellectual

device called Microcontroller so that it takes the responsibility of decoding the tones

received and perform the corresponding predefined tasks such as move forward,

Backward , left or right directions etc.

The micro controller is also interfaced with few DC motors in order to move the

robot in different directions. The ON and OFF of the DC motors depends on the direction

it has to move which is the complete responsibility of the controller to take those

intelligent decisions. This project uses AT89S52 micro controller. Now when we dial the

numbers in the mobile phone from the controlling side then it automatically recognizes

which number has been recorded and it follows with the corresponding next step to be

taken This Project uses DTMF Decoder which is controlled by a battery and in turn is

connected to the mobile phone. This is controlled by the controller and is again connected

to the driver circuit for driving the motor. This project uses battery

The major building blocks of this project are:-

o Regulated Power Supply

o GSM Modem/Phone

o Microcontroller based Control Unit

o Robot Mechanical Assembly

o DTMF Drivers

o H-Bridge

DJR INSTITUTE OF ENGG.& TECH.

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BLOCK DIAGRAM

Mobile Phone controlled DTMF based Robot BLOCK DIAGRAM (1.1)


Head set

DTMF

Decoder

11.0592MHz Crystal Oscillator

Mobile Phone

AT89S52 MCU

Power – On Reset

Power Supply

H-Bridge Circuit

Motors

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BLOCK DIAGRAM EXPLANATION:

The current project is a prototype implementation of Mobile phone controlled

DTMF robot with direction controlling. It is based on the embedded microcontroller

(AT89S52) with DTMF receiver connected with headset of mobile phone and H-Bridge

to send the appropriate motions to the motors.

The main aim of this project is to fulfill the needs in absence of human

beings. “Mobile phone controlled DTMF robot with direction controlling” is capable of

receiving a set of command (instructions) in the form of DTMF tones and performs the

necessary actions. Here DTMF stands for “Dual tone multiple frequency”. We will be

using a dedicated modem/mobile at the receiver module i.e. with the robot itself and send

the commands using DTMF tones as per the required actions.

The mobile unit which is dedicated at the robot is interfaced with an intellectual

device called Microcontroller so that it takes the responsibility of decoding the tones

received and perform the corresponding predefined tasks such as move front or back, left

or right etc.

The micro controller is also interfaced with few DC motors in order to move the robot in

different directions. The ON and OFF of the DC motors depends on the direction it has to

move which is the complete responsibility of the controller to take those intelligent

decisions.


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CIRCUIT DIAGRAM:


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CIRCUIT DIAGRAM EXPLANATION:

The circuit diagram shows the wiring connections of the “MOBILE PHONE

CONTROLLED DTMF BASED ROBOT”

The supply given is the +5V D.C. The incoming power is 230V A.C.; there

is a need to convert it into +5V D.C.

The input A.C. supply is stepped down from 230V to 9-0-9V. The rectifier

consists of diodes D1 and D2 makes the supply D.C. that is, unidirectional

waveform. The output from rectifier is a URDC, whose value is 12.726V peak to

peak. The voltage regulator makes this URDC to RDC of +5V. The capacitor C1 is

used to maintain constant voltage between two consecutive positive cycles

whereas C2 is used to remove the fluctuations caused by regulator. Here we are

selecting 12.726V as a peak value. Because of fluctuations, the peak voltage may

decrease, then regulator cannot step up to +5V. If we select peak value, a higher

one, then the problem can be overcome.

Power Supply Circuit Diagram:

Fig : Block Diagram of R.P.S

A regulated power supply which maintains the output voltage constant

irrespective of A.C. mains fluctuations or load variations is known as regulated power

supply. A regulated power supply consists of an ordinary power supply and voltage

regulating device. The output of ordinary power supply is fed to the voltage regulator

which produces the final output. The output voltage remains constant whether the load

current changes or there are fluctuations in the input A.C. voltage.


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The rectifier converts the transformer secondary A.C. voltage into pulsating

voltage. The pulsating D.C. voltage is applied to the capacitor filter. This filter

reduces the pulsations in the rectifier D.C. output voltage. Finally, it reduces the

variations in the filtered output voltage

Need of RPS in an ordinary power supply, the voltage regulation is poor

i.e. D.C. output voltage changes with load current. Output voltage also changes

due to variations in the input A.C. voltage. This is due to the following reasons

Fig : Circuit Diagram of R.P.S

There are considerable variations in A.C. line voltage caused by outside

factors beyond our control. This changes the D.C. output voltage. Most of the

electronic circuits will refuse to work satisfactorily on such output voltage

fluctuations.

Fig : Input Wave Form of R.P.S

The internal resistance of ordinary power supply in relatively large.

Therefore, output voltage is markedly affected by the amount of load current

drawn from the supply. These variations in D.C. voltage may cause erratic


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operation of electronic circuits. Therefore, regulated D.C. power supply is the only

solution in such situations.

Fig3.5: Output Wave Form of R.P.S

VOLTAGE REGULATOR

LM 7805 SERIES VOLTAGE REGULATOR

The LM 7805 series of the three terminal regulations is available with

several fixed output voltages making them useful in a wide range of applications.

One of these is local on card regulation. The voltages available allow these

regulators to be used in logic systems, instrumentation and other solid state

electronic equipment. Although designed primarily as fixed voltage regulators,

these devices can be used with external components to obtain adjustable voltages

and currents. The LM7805 series is available in aluminum to 3 packages which

will allow over 1.5A load current if adequate heat sinking is provided. Current

limiting is included to limit the peak output current to a safe value. The LM 7805

is available in the metal 3 leads to 5 and the plastic to 92. For this type with

adequate heat sinking, the regulator can deliver 100mA output current.

The advantage of this type of regulator is, it is easy to use and minimize the

number of external components.


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The following are the features voltage regulators:

a) Output current in excess of 1.5A for 78 and 78L series

b) Internal thermal overload protection

c) No external components required

d) Output transistor sage area protection

e) Internal short circuit current limit.

f) Available in aluminum 3 package.

POSITIVE VOLTAGE REGULATOR

The positive voltage regulator has different features like

Output current up to 1.5A

No external components

Internal thermal overload protection

High power dissipation capability

Internal short-circuit current limiting

Output transistor safe area compensation

Direct replacements for Fairchild microA7800 series


Nominal

Output VoltageRegulator

5V uA7805C

6V uA7806C

8V uA7808C

8.5V uA7885C

10V uA7810C

12V uA7812C

15V uA7815C

18V uA7818C

24V uA7824C

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GSM Modem/Phone

GSM TECHNOLOGY:

GSM History:

In 1982, the European Conference of Postal and Telecommunications Administrations

(CEPT) created the Group Spécial Mobile (GSM) to develop a standard for a mobile

telephone system that could be used across Europe. In 1987, a memorandum of

understanding was signed by 13 countries to develop a common cellular telephone system

across Europe. Finally the system created by SINTEF lead by Torleiv Maseng was

selected. In 1989, GSM responsibility was transferred to the European

Telecommunications Standards Institute (ETSI) and phase I of the GSM specifications

were published in 1990. The first GSM network was launched in 1991 by Radiolinja in

Finland with joint technical

.

GSM Frequencies:

GSM networks operate in a number of different frequency ranges (separated into GSM

frequency ranges for 2G and UMTS frequency bands for 3G). Most 2G GSM networks

operate in the 900 MHz or 1800 MHz bands. Some countries in the Americas (including

Canada and the United States) use the 850 MHz and 1900 MHz bands because the 900

and 1800 MHz frequency bands were already allocated. Most 3G GSM networks in

Europe operate in the 2100 MHz frequency band The rarer 400 and 450 MHz frequency

bands are assigned in some countries where these frequencies were previously used for

first generation systems.

GSM-900 uses 890–915 MHz to send information from the mobile station to the

base station (uplink) and 935–960 MHz for the other direction (downlink), providing 124

RF channels (channel numbers 1 to 124) spaced at 200 kHz. Duplex spacing of 45 MHz

is used. In some countries the GSM-900 band has been extended to cover a larger

frequency range. This ‘extended GSM’, E-GSM, uses 880–915 MHz(uplink) and 925–

960 MHz (downlink), adding 50 channels (channel numbers 975 to 1023 and 0) to the

original GSM-900 band. Time division multiplexing is used to allow eight full-rate


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or sixteen half-rate speech channels per radio frequency channel. There are eight

radio timeslots (giving eight burst periods) grouped into what is called a TDMA

frame.

CDMA TECHNOLOGY:

Code division multiple access (CDMA) is a channel access method utilized by various

radio communication technologies. It should not be confused with the mobile phone

standards called cdma One and CDMA2000 (which are often referred to as simply

“CDMA”), this uses CDMA as an underlying channel access method. One of the basic

concepts in data communication is the idea of allowing several transmitters to send

information simultaneously over a single communication channel. This allows several

users to share a bandwidth of frequencies. This concept is called multiplexing. CDMA

employs spread-spectrum technology and a special coding scheme(where each transmitter

is assigned a code) to allow multiple users to be multiplexed over the same physical

channel. By contrast, time division multiple access (TDMA) divides access by time,

while frequency division multiple access (FDMA) divides it by frequency. CDMA is a

form of “spread-spectrum” signaling, since the modulated coded signal has a much higher

data bandwidth than the data being communicated. An analogy to the problem of multiple

access is a room (channel) in which people wish to communicate with each other. To

avoid confusion, people could take turns speaking (time division), speak at different

pitches (frequency division), or speak in different languages


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MICROCONTROLLER (AT89C52):

Description:

The AT89S52 is a low-voltage, high-performance CMOS 8-bit microcontroller

with 4K bytes of Flash programmable memory.

The device is manufactured using Atmel’s high-density nonvolatile memory

technology and is compatible with the industry-standard MCS-51 instruction set. By

combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89S52 is a

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

many embedded control applications.

In addition, the AT89S52 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 and interrupt system

to continue functioning. The power-down mode saves the RAM contents but freezes the

oscillator disabling all other chip functions until the next hardware reset


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FEATURES:

Compatible with MCS-51 Products.

8K Bytes of In-System Reprogrammable Flash Memory.

Endurance: 1,000 Write/Erase Cycles.

Fully Static Operation: 0 Hz to 24 MHz

Three-level Program Memory Lock.

Three 256 x 8-Bit Internal RAM.

32 Programmable I/O Lines.

Three 16-bit Timer/Counters.

Eight Interrupt Sources.

Programmable Serial Channel.

Low Power Idle and Power Down Modes


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Architecture:

Figure: Architecture of AT89C52 (Diagram)


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Pin Configuration:

The Micro Controller generic part number actually includes a

whole family of Micro Controllers that have numbers ranging from 8031to 8751

and are available in N-Channel Metal Oxide Silicon (NMOS) and Complementary

Metal Oxide Silicon (CMOS) construction in a variety of package types.

PIN DIAGRAM:

(Diagram)

Vcc

Pin 40 provides supply voltage to the chip. The voltage source is +5V.

GND:

Pin 20 is the ground.


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XTAL1 and XTAL2:

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier that

can be configured for use as an on-chip oscillator, as shown in Figure 11. Either a quartz

crystal or ceramic resonator may be used. To drive the device from an external clock

source, XTAL2 should be left unconnected while XTAL1 is driven, as shown in the

below figure. There are no requirements on the duty cycle of the external clock signal,

since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but

minimum and maximum voltage high and low time specifications must be observed.

Fig: Oscillator Connections

C1, C2 = 30 pF ± 10 pF for Crystals= 40 pF ± 10 pF for Ceramic

Resonators

Fig: External Clock Drive Configuration


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RESET

Pin9 is the reset pin. It is an input and is active high. Upon applying a high pulse to

this pin, the microcontroller will reset and terminate all the activities. This is often

referred to as a power-on reset.

EA (External access)

Pin 31 is EA. It is an active low signal. It is an input pin and must be connected to

either Vcc or GND but it cannot be left unconnected.

The 8051 family members all come with on-chip ROM to store programs.

In such cases, the EA pin is connected to Vcc. If the code is stored on an external

ROM, the EA pin must be connected to GND to indicate that the code is stored

externally.

Ports 0, 1, 2 and 3

The four ports P0, P1, P2 and P3 each use 8 pins, making them 8-bit ports. All the

ports upon RESET are configured as input, since P0-P3 have value FFH on them

Port 0:

Port 0 is an 8-bit open drain bidirectional I/O port. As an output port

each in can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can

be used as high impedance 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 pull-ups. Port 0 also receives the code

bytes during Flash programming, and outputs the code bytes during program

verification. External pull-ups are required during program verification.


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Port 1:

Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. 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 pull-ups 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 pull-ups. Port 1 also receives the low-order address bytes during Flash

programming and verification.

Port 2:





the internal pull-ups. Port 2 emits the high-order address byte during fetches from

external program memory and during accesses to external data memory that uses

16-bit addresses (MOVX @ DPTR). In this application it uses strong internal pull-

ups when emitting 1s. During accesses to external data memory that uses 8-bit

addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function

Register. Port 2 also receives the high-order address bits and some control signals

during Flash programming and verification.

Port 3:





the pull-ups. Port 3 also serves the functions of various special features of the

AT89C52 as listed below:


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Internal RAM:

The 256-byte internal RAM. The upper 128 bytes occupy a parallel

address space to the Special Function Registers. Instructions that use indirect

addressing access the upper 128 bytes of RAM. Stack operations are examples of

indirect addressing.

Internal Data Memory addresses are always one byte wide, which

implies an address space of only 256 bytes. However, the addressing modes for

internal RAM can in fact accommodate 384 bytes, using a simple trick. Direct

addresses higher than 7FH access one memory space and indirect addresses higher

than 7FH access a different memory space. Thus Figure shows the Upper 128 and

SFR space occupying the same block of addresses, 80H through FFH, although

they are physically separate entities.

The Lower 128 bytes of RAM are present in all 89C52 devices as

mapped in Figure. The lowest 32 bytes are grouped into 4 banks of 8 registers.

Program instructions call out these registers as R0 through R7.

ALE/PROG

Address Latch Enable is an 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. If desired, ALE operation can be disabled by setting bit 0 of

SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC

instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit

has no effect if the microcontroller is in external execution mode.


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PSEN (Program Store Enable)

It is the read strobe to external program memory. When the AT89S8252 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

external data 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. Note,

however, that if lock bit 1 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 when 12-volt programming is selected.

Programmable Clock Out:

A 50% duty cycle clock can be programmed to come out on P1.0. This pin, besides

being a regular I/0 pin, has two alternate functions. It can be programmed to input

the external clock for Timer/Counter 2 or to output a 50% duty cycle clock ranging

from 61 Hz to 4 MHz (for a 16-MHz operating frequency).


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Theory of DC Motor:

The speed of a DC motor is directly proportional to the supply voltage, so if we

reduce the supply voltage from 12 Volts to 6 Volts, the motor will run at half the

speed. How can this be achieved when the battery is fixed at 12 Volts? The speed

controller works by varying the average voltage sent to the motor. It could do this

by simply adjusting the voltage sent to the motor, but this is quite inefficient to do.

A better way is to switch the motor's supply on and off very quickly. If the

switching is fast enough, the motor doesn't notice it, it only notices the average

effect.

When you watch a film in the cinema, or the television, what you are actually

seeing is a series of fixed pictures, which change rapidly enough that your eyes

just see the average effect - movement. Your brain fills in the gaps to give an

average effect.

Now imagine a light bulb with a switch. When you close the switch, the bulb

goes on and is at full brightness, say 100 Watts. When you open the switch it goes

off (0 Watts). Now if you close the switch for a fraction of a second, then open it

for the same amount of time, the filament won't have time to cool down and heat

up, and you will just get an average glow of 50 Watts. This is how lamp dimmers

work, and the same principle is used by speed controllers to drive a motor. When

the switch is closed, the motor sees 12 Volts, and when it is open it sees 0 Volts. If

the switch is open for the same amount of time as it is closed, the motor will see an

average of 6 Volts, and will run more slowly accordingly. The graph below shows

the speed of a motor that is being turned on and off


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H-BRIDGE:

An H-bridge is an electronic circuit which enables DC electric motors to be run

forwards or backwards. These circuits are often used in robotics. H-bridges are

available as integrated circuits, or can be built from discrete

components.

The two basic states of a H-bridge.

The term "H-bridge" is derived from the typical graphical

representation of such a circuit. An H-bridge is built with

four switches (solid-state or mechanical). When the

switches S1 and S4 (according to the first figure) are closed

(and S2 and S3 are open) a positive voltage will be applied

across the motor. By opening S1 and S4 switches and

closing S2 and S3 switches, this voltage is reversed,

allowing reverse operation of the motor.

Using the nomenclature above, the switches S1 and S2

should never be closed at the same time, as this would

cause a short circuit on the input voltage source. The same

applies to the switches S3 and S4. This condition is known as shoot-through.


S1 S2 S3 S4 Result

1 0 0 1Motor moves

right

0 1 1 0Motor moves

left

0 0 0 0 Motor free runs

0 1 0 1 Motor brakes

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Operation

The H-Bridge arrangement is generally used to reverse the polarity of the motor,

but can also be used to 'brake' the motor, where the motor comes to a sudden stop,

as the motors terminals are shorted, or to let the motor 'free run' to a stop, as the

motor is effectively disconnected from the circuit. The following table summarizes

operation.

H-Bridge Driver:

The switching property of this H-Bridge can be replace by a Transistor or a Relay

or a MOSFET or even by an IC. Here we are replacing this with an IC named

L293D as the driver whose description is as given below.

Features:

600mA OUTPUT CURRENT CAPABILITY

PER CHANNEL

1.2A PEAK OUTPUT CURRENT (non repetitive)

PER CHANNEL

ENABLE FACILITY

OVERTEMPERATURE PROTECTION

LOGICAL "0" INPUT VOLTAGE UP TO 1.5 V

(HIGH NOISE IMMUNITY)

INTERNAL CLAMP DIODES

Description:

The Device is a monolithic integrated high voltage, high current four channel

driver designed to accept standard DTL or TTL logic levels and drive inductive

loads (such as relays solenoides, DC and stepping motors) and switching power

transistors.


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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 L293D is assembled in a 20 lead surface mount which has 8

center pins connected together and used for heatsinking.

BLOCK DIAGRAM


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ABSOLUTE MAXIMUM RATINGS

PIN CONNECTIONS


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DTMF Decoder

The CS9370 is a complete DTMF receiver integrating both the band split

filter and digital decoder functions. The filter section uses switched capacitor

techniques for high-and low-group filters and dial-tone rejection. Digital

counting

techniques are employed in the decoder to detect and decode all 16

DTMF tone-pairs into 4-bit code. External component count is minimized

by on-chip provision of a differential input amplifier, clock-oscillator and

latched 3-state

bus interface.

PIN CONFIGURATION:


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FEATURES:

o CMOS 5/3volt operation.

o Excellent performance with minimum board quality.

o Central office quality.

o Low power consumption.

o Power down mode.

o Inhibit mode.

o Packages DIP18,SOP18.


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CODING

#include<reg52.h>

#define dtmfdata P1

void stop(void);

void forward(void);

void left(void);

void right(void);

void backward(void);

void main()

{

dtmfdata=0xff;

P0=0;

P3=0;

while(1)

{

if(dtmfdata==0x0f)

{

while(dtmfdata==0x0f)

{

stop();

}

}

if(dtmfdata==0x0e)

{

while(dtmfdata==0x0e)

{

forward();

}

}

if(dtmfdata==0x0d)

{


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while(dtmfdata==0x0d)

{

left();

}

}

if(dtmfdata==0x0b)

{

while(dtmfdata==0x0b)

{

right();

}

}

if(dtmfdata==0x07)

{

while(dtmfdata==0x07)

{

backward();

}

}

}

}

void stop(void)

{

P0=0x00;

P3=0x00;

}

void forward(void)

{

P0=0xCA;

P3=0;

}

void left(void)

{

P0=0x42;


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//P3=0x42;

}

void right(void)

{

P0=0x88;

// P3=0x88;

}

void backward(void)

{

P3=0xCA;

P0=0;

}


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APPLICATIONS:

1. These kinds of robots are very useful in mining research applications.

2. It is also useful in extracting the samples from the places which can’t be

reached by the humans like volcanic erosion from which we can get the

samples of the lava that is deposited and forms a layer on the earth.

3. It can also be used as an inspecting element for judging a route if it is

suspected to have some uneven conditions.


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FUTURE SCOPE:


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CONCLUSION:

This project presents a Mobile phone controlled DTMF robot with direction controlling

and it is designed and implemented with Atmel 89S52 MCU. The robot is moved in

particular direction using DTMF Signals and it is based on the embedded microcontroller

(AT89S52) with DTMF decoder connected with headset of mobile phone and H-Bridge

for controlling the motors.

The main aim of this project is to fulfill the needs in absence of human

beings. “Mobile phone controlled DTMF robot with direction controlling” is capable of

receiving a set of commands (instructions) in the form of DTMF tones and performs the

necessary actions. Here DTMF stands for “Dual tone multiple frequency”. We will be

using a dedicated modem/mobile at the receiver module i.e. with the robot itself and send

the commands using DTMF tones as per the required actions.


1


REFERENCE:

Books

1. The 8051Microcontroller by Kenneth J. Ayala

2. The 8051 Microcontroller and Embedded Systems by Muhammad Ali Mazidi.

References

1. www.alldatasheets.com

2. www.microcontroller.com

3. www.8051microcontroller.com

4. www.wikipedia.com


http://www.wikipedia.com/

http://www.8051microcontroller.com/

http://www.microcontroller.com/

http://www.alldatasheets.com/

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Documents

A Mini Project Report On