This document describes a mobile controlled robot that can be operated from any location via a mobile phone. The robot contains a mobile phone that receives DTMF tones corresponding to buttons pressed on the controlling phone. These tones are decoded by a microcontroller that directs motors for movement. When buttons are pressed, unique frequency combinations are generated and received by the robot phone. The microcontroller then controls motors via motor drivers to move the robot forward, backward or turn based on the decoded DTMF signals from the controlling phone.

1. 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

2. 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.

4. 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

5.  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

6. 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
MT8870 output
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.

7. 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.

8. 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

9. 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.

10. 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:

11. 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