MOBILE CONTROLLED ROBOT

This is the robot whose actions can be controlled by a mobile

phone from all over the world using the DTMF signaling.

Use of mobile phones for robotic controls provides working range

as large as the coverage area of the service provider and no

interference with other controllers.

Block diagram

Mobile Controlled Robot

PROJECT OVERVIEW

In this project, the robot is controlled by a mobile phone that makes a

call to the mobile phone attached to the robot. In the course of a call,

if any button is pressed, a tone corresponding to the button pressed is

heard at the other end of the call. This tone is called DTMF (dual-

tone-multiple-frequency).The robot perceives this DTMF tone with

the help of the phone stacked in the robot. The received tone is

processed by the (ATmega8) microcontroller with the help of DTMF

decoder IC (MT8870). The decoder decodes the DTMF tone into its

equivalent binary digit and this binary number is sent to the

microcontroller. The microcontroller is programmed to take a

decision for any given input and outputs its decision to motor drivers

in order to drive the motors in forward direction or backward

direction or turn. The mobile phone that makes a call to mobile phone

stacked in the robot act as a remote.

DTMF

DTMF (Dual tone multi frequency) as the name suggests uses a

combination of two sine wave tones to represent a key dialed on a

pushbutton or DTMF keypad.

These tones are called row and column frequencies as they

correspond to the layout of a telephone keypad.

DTMF keypad layout

A DTMF keypad (generator or

encoder) generates a sinusoidal

tone which is mixture of the row

and column frequencies. The

row and column frequencies

corresponding to a DTMF keypad have been indicated in the above

figure.

DTMF tones are able to represent one of the 16 different states or

symbols on the keypad.

Hardware components required and their purpose:

1. A microcontroller (ATMega8)

2. Transmitter and receiver mobile phones

3. DTMF decoder IC (MT8870)

4. DC motor

5. Motor driver IC (L293D)

6. Wheels

7. Power adopter

Microcontroller (ATMega8): This is the brain of this robot in

which the program is loaded to do the required functioning and

is interfaced with sensors and the motor driver to make the

system work as required.

Transmitter and receiver mobile phones: Here the transmitting

phone is working as a remote and the receiving phone is

attached to the robot which receives the DTMF signals which

are then fed to decoder IC after converting them to electrical

form through audio jack.

DTMF decoder IC (MT8870)

The decoder decodes the DTMF tone into its equivalent binary

digit and this binary number is sent to the microcontroller.

DTMF decoder IC (MT8870)

On pressing any key say key 1, a combination of frequencies

1209 and 697 Hz will be generated by keypad which is fed to

IC through sound converter

which in turn produce the

output 0001 (Q1, Q2, Q3,

Q4). Following table shows

output of remaining keys.

DC Motor: This motor is

controlled with DC voltages and can move in forward and

backward direction according to the polarity of the voltage

applied.

Motor driver IC (L293D): Microcontrollers can’t supply the

current required by DC motor to run. So, to fulfill this

requirement these motor driver ICs are used.

MT8870 output

DC motors with Driver IC

Power adopter: This is used to give appropriate dc power

supply to microcontroller, driver IC sensors and the other

passive components of the robot.

Wheels: In it three wheels are employed, two at rear end and one

at front end. Rear wheels are attached with the motors and also

control the steering of robot. Front wheel is the loose steered

wheel which moves in the direction of the pressure applied to it.

Overview:

Top view of robot

Description

The robot is controlled by a mobile phone that makes call to the

mobile phone attached to the robot and in the course of the call, if

any button is pressed the corresponding DTMF freq. will be heard

at the other end.

DTMF assigns a specific frequency (consisting of two separate

tones) to each key that it can easily be identified by the electronic

circuit. The signal generated by the DTMF encoder is the direct

algebraic submission, in real time of the amplitudes of two

sine(cosine) waves of different frequencies, for example: pressing

key5 will send a tone made by adding 1336hz and 770hz to the

other end of the mobile.

The received tone is processed by the atmega8 microcontroller

with the help of DTMF decoder (MT8870). The decoder decodes

the DTMF tone in to its equivalent binary digit and this binary

number is send to the microcontroller.

The microcontroller is preprogrammed to take a decision for any

given input and outputs its decision to motor drivers in order to

drive the motors for forward or backward motion or a turn.

Programming I/O port of ATMega8:

Each port has three i/o registers associated with it which are

designated as DDRx, PORTx, PINx.

Port Registers in ATMega8

DDRx register:

It stands for data direction register. This register is of 8 bits. Value of this

register decides whether the port will act as input port or as output port.

To make any port as input port, the contents of the associated DDRx

register are made 0x00 and to make any port as output port, the contents

of the associated DDRx register are made 0xff.

PORTx register:

This register is responsible for outputting any data to the port. Data to be

outputted to any port is loaded to the corresponding PORTx register after

making the direction of that port as output.

For example:

To send 0x14 to PORTA:-

DDRA=0xFF;

PORTA=0x14;

PINx register:

This register is responsible for inputting data from any port. Data to be

inputted from any port is taken from the corresponding PINx register

after making the direction of that port as input.

For example:

To get data from PORTB:-

DDRA=0x00;

var=PINB; //’var’ is a character type variable