Final Report11

Mobile Controlled Robot 2013-14
DEPT. OF ELECTRONICS & COMMUNICATION, SIT, TUMKUR 1
CHAPTER 1
INTRODUCTION
This project involves the idea to couple the potential of mobile with microcontroller to
operate the robot. The functioning of mobile controlled robot is similar to the radio
frequency remote system which consists of a transmitter and a receiver unit. Therefore,
two mobile phones are used for effective transmission and reception of signals. The robot
is controlled by the mobile phone held by the user, which communicates with the mobile
phone attached to the robot. In the course of a phone call, if any button is pressed, a tone
corresponding to the button pressed is heard at the receiver end, which is called „Dual
Tone Multiple frequency‟ (DTMF) tone. The robot receives these tones via the receiver
mobile phone which is on the board. The received tone is processed by the
microcontroller with the help of DTMF decoder IC. The microcontroller communicates
with the motor driver which drives the robot in forward, reverse, right and left direction
according to the key pressed on the transmitter mobile. Wireless camera is attached to
the robot to realize the physical aspects of real world and its surrounding.
1.1 Motivation
Using wireless communication to monitor robot employs radio frequency (RF), which
has a drawback of limited working range, limited frequency range. By using a mobile
phone, for controlling robot can overcome these limitations. It provides the advantage of
working range as large as the area of coverage of service provider. Although the
appearance and the capabilities of every robot vary drastically, all robots share some
common feature of mechanical, movable structure under some form of control [4].The
control of the robot involves three distinct phases: direction, processing and action.
Generally, the direction is given by the user who is monitoring the robot, processing is
done by the on-board microcontroller or processor, and action is performed by motors
and wireless camera.
1.2 Objective
The objective of the project is to design a mobile controlled robot that has working range
as large as the area of coverage of service provider. For seeing the obstacles in the path

and a physical aspect of the real world, a wireless camera is mounted on the robot that
will transmit the audio and video signals to the output screen.
1.3 Organization of the report
This report is divided into 5 chapters. Chapter 1 discusses about the radio frequency
remote system and their drawbacks. It also focuses on the objective of the project to
overcome these drawbacks. Chapter 2 presents the block diagram of mobile controlled
robot with brief description of each block. Chapter 3 describes about the hardware
implementation of the project. Chapter 4 describes about the software description, flow
chart and the program code to operate the robot. Chapter 5 describes about the result,
application, limitation, conclusion and future enhancement of the project.

CHAPTER 2
BLOCK DIAGRAM DESCRIPTION
In this chapter, the block diagram of mobile controlled robot is discussed as shown in Fig
2.1.1.
2.1 Block Diagram
Fig 2.1.1 Block diagram of mobile controlled robot
Mobile controlled robot consists of transmitter mobile, receiver mobile, DTMF decoder
IC, microcontroller, motor driver IC, dc motor, wireless camera, modulated receiver and
output screen as shown in fig 2.1.This system requires +5V and +12V power supply.
When a key is pressed on the transmitter mobile, then DTMF tone is transmitted to the
receiver mobile. DTMF decoder will convert the tone frequencies into binary equivalent
digital form and passes it to microcontroller which runs the dc motor in clockwise and
anticlockwise direction to achieve forward, backward, right and left motion. Wireless
camera will transmit the audio and video signals to the output screen through modulated
receiver.
2.2 Transmitter Mobile
It is used to make a call to the receiver mobile. User can give the direction of movement

to the robot by using transmitter mobile.
2.3 Receiver Mobile
It takes the input from the transmitter mobile and transmits the message to the DTMF
decoder IC.
2.4 DTMF Decoder
In this project, DTMF decoder HT9170B is used which converts the DTMF tone
received from the receiver mobile into binary equivalent digital form and latches it into
microcontroller.
2.5 Microcontroller
In this project, AT89S52 microcontroller is used which has been programmed to rotate
the dc motor in clockwise and anti-clockwise direction.
2.6 Motor Driver
In this project, L293D motor driver is used which is used to amplify the current received
from microcontroller and thus runs the DC motor.
2.7 DC Motor
It is used to achieve the forward, backward, rightward and leftward movement of the
robot
2.8 Wireless Camera
It is used to transmit the audio and video signals to the modulated receiver.
2.9 Modulated Receiver
It receives the signal from the wireless camera and transfers it to output screen.
2.10 Output Screen
It is used to see the video and audio output on the screen such as T.V.

CHAPTER 3
HARDWARE DESCRIPTION
Circuit diagram description includes the hardware components which are used for
building the overall system. The circuit diagram of mobile controlled robot is as shown
in Fig.3.1.1
3.1 Circuit Diagram Description
The circuit diagram of mobile controlled robot consists of HT9170B DTMF decoder,
AT89S52 microcontroller, L293D motor driver and DC motor.
Fig 3.1.1 Circuit diagram of Mobile controlled robot
In order to operate the robot, a call is made through transmitter mobile to the receiver
mobile which is kept in auto answering mode for receiving the call. Receiver mobile is
connected to the DTMF decoder through the earphone plug outlet. When a certain key

such as 2 is pressed, a set of frequencies is produced which is transmitted to the receiver
mobile. Since, microcontroller works on the digital logic, so these analog signals should
be converted into digital form. For this purpose, DTMF Decoder is used which converts
the frequencies into binary equivalent digital form.
Through tip and ring of earphone, inverting and non-inverting input is applied to the
operational amplifier. Operational amplifier will adjust the input signal w.r.t to gain
when signal is weak. From there it is passed to band split filter which will split it into
high and low frequency group. From there it is passed to frequency detector which
identifies the high and low frequency. Then, the identified frequency is passed to code
detector which converts the frequency into binary equivalent form. Code detector counts
the no of cycles of a given reference clock contained in a period of the input signal and
thus produces binary equivalent form. From there, it is passed to the latch buffer which
latches the binary equivalent code onto the port 2 of the micro-controller.
Microcontroller receives the input from DTMF decoder. Then, output is provided to the
motor driver from port 0 which acts as an output port. Since the output current from the
controller is of the order of µA, it can‟t be used to drive the DC motor. So, Motor driver
like L293D is required to amplify the current and drive DC motor.
Microcontroller is programmed to produce movement action i.e. when a key 2 is pressed,
both motor will run in clockwise direction and robot will have forward motion. When a
key 8 is pressed, then both motor will run in anticlockwise direction and robot will have
backward motion. When a key 5 is pressed, then low logic will be provided to both
motor and there will be stop motion. When a key 4 is pressed, then motor A will move in
anticlockwise direction and motor B will move in clockwise direction to produce left
turn. When a key 6 is pressed, then motor B will move in anticlockwise direction and
motor A will move in clockwise direction to produce right turn.
3.2 Transmitter Mobile
It acts as a remote control to the robot. It remains with the user who monitors the robot.
Its purpose is to generate the dual tone multiple frequencies corresponding to the number
pressed on its keypad and transmit it through the mobile wireless network.

3.3 Receiver Mobile
It receives the DTMF tone transmitted by the transmitter mobile and forwards the
message to the DTMF decoder. It is connected to the DTMF decoder through earphone
plug outlet. The earphone plug outlet has two parts which are tip and ring. The tip of the
jack is called as tip and the rest part behind the tip after the black strip is called as ring.
3.4 Power Supply
Lead Acid Battery of +12V is used to supply the power to the Robot. Battery is used
instead of power-supply because the robot need to be wireless for larger coverage area.
3.5 DTMF Decoder
The block diagram of DTMF decoder is shown in Fig 3.5.1. It consists of operational
amplifier, filter, frequency detector, code detector, latch & output buffer, steering control
circuit and crystal oscillator.
Fig 3.5.1.Internal Block Diagram of HT9170B
Operational Amplifier: It is built-in to adjust the input signal depending upon gain
select.
Filter: Pre-filter reduces the dialling tone noise and separates to low group and high
group filter. The low group filter which filters the low group frequency and high group

filter filters the high group frequency signal.
Frequency Detector: It is used to detect the frequency that has been passed from high
group and low group filter.
Code Detector: It converts the frequency into binary equivalent form. Code detector
counts the no of cycles of a given reference clock contained in a period of the input
signal and thus produces binary equivalent form. From there, it is passed to the latch
buffer.
Latch & Output Buffer: It latches the binary equivalent code onto the port 2 of the
micro-controller.
Steering Control Circuit: It controls frequency detector, code converter and output
latch to convert 16 DTMF tone-pairs into a 4-bit code as shown in Fig 3.2.
Internal Clock Circuit: The internal clock required by HT9170B is providedby 3.579545
MHz crystal.
Filter Section: The HT9170B consist of three band pass filters and two digital decoder
circuits to convert DTMF tone signal into digital code output.
Steering Control Circuit: The steering control circuit is used for measuring the
effective signal duration and for protecting against drop-out of valid signals.
Power-down and Inhibit Mode: When a logic high is applied to pin 6 (PWDN), then
it will place the device into standby mode to minimize power consumption.
Working
When key 2 is pressed from “Touch Tone Pad” then, it will send a tone made by
adding 697 Hz and 1209 Hz to the other end of the line. The tones and assignment
in a DTMF system[4] is as shown in Table 3.5.1.

Table 3.5.1– Touch Tone Pad
3.6 AT89S52 Microcontroller
Microcontrollers are intelligent electronic devices used inside robots. They deliver
functions similar to those performed by a microprocessor (CPU) inside a personal
computer. Microcontroller are slower and can address less memory than CPUs, but are
designed for real-world control problems.
This Project uses AT89S52 (MCU) which is a low-power, high-performance CMOS
micro-controller.
There are four basic aspects of a microcontroller -
1. Speed
Speed is designated in clock cycles, and is usually measured in millions of cycles per
second (MHz).The crystal frequency required for AT89S52 is 11.0592MHz.
2. Size
Size specifies the number of bits of information that MCU can process in one step.
AT89S52 can process 8 bit data at a time.

3. Memory
AT89S52 has 8K bytes in-system programmable Flash Memory and 256 bytes of
RAM to store and process data. The on-chip Flash allows the program memory to be
reprogrammed in-system by a memory programme.
4. Others
a) A microcontroller takes input from the device like DTMF Decoder and controls it
by sending signals to different components like L293D Motor.
b) It has 32 I/O lines for various applications.
By combining the basic aspects of AT89S52 with in-system programmable Flash on a
monolithic chip, the Atmel AT89S52 provides a highly-flexible and cost-effective
solution to many embedded control applications.
Port 0: Port 0 pins are used to provide output to the L293D Motor Driver. It will send
the binary equivalent output (0 & 1) to the L293D motor driver.
Port 2: Port 2 pins are used to take digital input from the DTMF decoder. Then, this is
processed by the micro-controller as per the coding done to produce required output.
Others:
1. Lead Acid Battery will provide +12V supply to the micro-controller development
board. Since micro-controller requires +5V supply, so +12V will be converted to +5V
by 7805 regulator. The voltage regulator converts unused power to heat. So, heat sink
is used to lower the temperature of 7805 IC.
2. Bridge rectifier is also used in micro-controller board which allows the circuit to work
with a DC power supply regardless of the jack‟s polarity. Whether the input line is
positive or negative, the four diodes in bridge rectifier ensure that the DC output line
is always positive and the bottom line is always negative. So, it doesn.t matter which
polarity is used, it will correct the polarity as required.

3.7 Motor Driver
The current from the microcontroller is of the order of 1 µA which is not sufficient to
drive the motors. Therefore, motor driver is used which act as current amplifier. They
take a low-current signal from micro-controller and provide a higher-current signal
which is used to drive the motors.
L293D is a dual H-Bridge motor driver as shown in Fig.3.7.1. It means that with one IC
we can interface two inductive loads which can be controlled in both clockwise and anti-
clockwise direction It is designed to provide bidirectional drive current of up to 600-mA at
voltage ranging from 4.5 V to 36 V. L293D has two channels and each channel is used
for one motor.
Channel 1 - Pin 1 to 8
Channel 2 - Pin 9 to 16
Enable Pin is used to make a channel active. Drivers are enabled in pairs, with drivers 1
and 2 enabled by 1,2EN and drivers 3 and 4 enabled by 3,4EN.When a channel is active,
then their outputs are in phase with the input. When a channel is not active, then their
outputs are off and in the high-impedance state.
Fig.3.7.1. L293D Motor Driver Circuit

Input to motor driver is given by micro-controller at pin no 2 & 7 for channel 1 and pin
no 10 & 15 for channel 2.Then, L293D amplifies the current and provides it to the geared
DC motor for running action through pin 3 & 6 for channel 1 and pin 11 & 14 for
channel 2.A supply voltage of +12V is also supplied to Motor Driver to run geared DC
motor.
Table 3.7.1- Motor Driving Table
MOTION LEFT MOTOR A RIGHT MOTOR B
FORWAD CLOCKWISE CLOCKWISE
BACK ANTI-CLOCKWISE ANTI-CLOCKWISE
LEFT ANTI-CLOCKWISE CLOCKWISE
RIGHT CLOCKWISE ANTI-CLOCKWISE
STOP STOP STOP
Table 3.7.1 depicts the running action of the robot. For instance, for forward movement,
both motor should move in clockwise direction etc. For backward movement, both
should run in anti-clockwise direction. For Left motion, left motor should run in anti-
clockwise direction and right motor should run in clockwise direction. For right motion,
left motor should run in clockwise direction and right motor in anti-clockwise direction.
For stopping the motor, input to both motor should be made low.
3.8 DC Motor
DC geared motor has been used which requires a dc voltage of +12 V. The speed of DC
motor can be controlled by changing the voltage applied to the armature or by changing
the field current. It provides an output power of 0.0082-0.0134 Hp.
3.9 Wireless Camera
It is used to project the real world surrounding into an output screen. It works on the
principle of RF and has limited range of about 50-100m. It requires a +9V DC Voltage to
operate. It transfers the video and sound to receiver, from where it is transferred to output
screen.
3.10 Modulated Receiver
It receives the input signal from wireless camera. From there, it is transferred to output

screen using audio and video cable. It operates on +9V Dc supply. RF Antenna is
connected to receiver to communicate with the camera in the prescribed range. With the
help of tuner knob, the output on the screen can be seen.
3.11 Output Screen
Audio and Video output line from receiver is connected to the audio and video plugin of
the output screen to see the output on screen such as T.V. If the output screen like laptop,
LCD monitor does not have audio and video plugin, then T.V Tuner card must be used
for seeing the output on the screen. T.V Tuner card is an external hardware which has the
audio and video plugin to receive the audio and video signals. After receiving it, it
transfers the audio and video signal to the output screen like laptop, LCD monitors etc.

CHAPTER 4
SOFTWARE DESCRIPTION
In this chapter, the software that is used to implement this project is discussed. Software
description includes the Keil µvision3 software explanation, flowchart explanation and
program code. The flowchart is explained in fig.4.3.1 which describes the functionality
of mobile controlled robot.
4.1 Keil µVision 3 (Microcontroller Programming & simulation)
The program is written in C language using Keil µvision3. Keil µvision is an integrated
development environment which allows the program to be written either in assembly or
C language and simulated on a computer before being loaded onto the microcontroller.
To create a new project in µVision3:
1. Select Project – New Project.
2. Select a directory and enter the name of the project file.
3. Select Project – Select Device and select a device from Device Database. When the
target device is selected from the Device Database, all-special options are set
automatically.
4. Create source files to add to the project.
5. Select Project – Targets, and Files. Add/Files, select Source Group1, and add the
source files to the project.
6. Select Project menu – Options and set the tool options.
7. Select Target Tab- Change XTAL(MHz) frequency to 11.0592
8. Select Output Tab-Click on create hex file check box.
9. Click Ok button.
10. Select Project – Rebuild all target files or Build target.
11. In the Build Window, it should report „0 errors(s), 0 warnings.
4.2 Flash Magic
It is a software used to burn hex codes generated by the Keil µvision3 onto the
microcontroller placed on the development board.

4.3 Flow Chart
A flowchart is type of diagram representing a process using different symbol containing
information about steps or a sequence of event. Each of these symbols is linked with
arrow to illustrate the flow direction of process. The flowchart is as shown in Fig.4.3.1
which describes the functionality of the mobile control robot.
Fig.4.3.1 Flow Chart

4.4 Program Code
#include<reg52.h>
sbit rightfront=P0^0;
sbit rightback=P0^1;
sbit leftback=P0^2;
sbit leftfront=P0^3;
sbit D0=P2^0;
sbit D1=P2^1;
sbit D2=P2^2;
sbit D3=P2^3;
void main(void)
{
P0=0x00;
P2=0xff;
while(1)
{
If (D3==0 && D2==0 && D1==1 && D0==0) //front
{
Rightfront= 0;rightback=1;leftback=1;leftfront=0;
}
else if(D3==0 && D2==1 && D1==0 && D0==0) //left
{
rightfront=0;rightback=1;leftback=0;leftfront=1;
}
else if(D3==0 && D2==1 && D1==1 && D0==0) //right
{
}
else if(D3==1 && D2==0 && D1==0 && D0==0) //back
{
}

else //stop
{
}
}
}

CHAPTER 5
RESULT AND CONCLUSION
RESULT:
The mobile controlled robot designed in this project is a prototype model as shown in
Fig.5.1.1, which demonstrates the movement of a robot with the help of two mobiles,
used as receiver and transmitter. During the course of a call, if any button is pressed, tone
corresponding to the button is heard at the receiver side. This DTMF tone is decoded
with the help of decoder.
Fig.5.1.1 Mobile Controlled Robot
Micro-controller AT89S52 and DTMF decoder HT9170B requires +5 V power supply to
run. So, a voltage regulator IC 7805 is used to convert +12V supply from Lead Acid

Battery to +5 V. Input at pin no.1 of IC 7805 is found to be around +12V and output at
pin no.3 of IC 7805 is found +5 V respectively. Inverting and non-inverting input from
mobile is fed at pin 1 & 2 of HT9170B respectively. Corresponding output at pin no.
11,12,13,14 is found to be around 2.6 V. Then, outputs from these pins are fed to micro-
controller at pin no 24,23,22,21. Then, again output at pin no. 36,37,38,39 of micro-
controller is checked which is found to be around 1.4 µA. So, L293D motor driver is
used to amplify the current up to 1.2 mA to run the DC geared motor. Thus, as a result of
which, user is able to run the robot. When the key „2‟ is pressed, the robot moves
forward. When the key „8‟ is pressed, robot moves in backward direction. When the key
4„‟ is pressed, robot moves in left direction. When the key „6‟ is pressed, robot moves in
right direction. If a key other than 2, 4, 6, and 8 is pressed, robot stops its respective
movements.
Applications
1. It can be used for spying purpose.
2. Mobile robots can be used to reach inaccessible areas such as nuclear power plants. It
can be used in nuclear environments with high levels of radiation, particularly during a
disaster or threat of disaster.
3. It can be used to collect information from mines.
4. It can be used at the border for disposing hidden land mines.
Limitation
1. If mobile robot goes underground or areas of low connectivity like subway tunnels,
control of the robot could be lost and there may be physical damage to the robot.

CONCLUSION
The aim of the project, ”Mobile Controlled Robot” is to develop a real time wireless
robot through which user can monitor what is happening in its surrounding. The working
range of mobile controlled robot is as large as the area of service provider coverage. So,
robot can be operated up to larger distance. It can be used in various applications ranging
from the mining industry to the defence purpose.
Future Scope
1. IR sensors can be mounted to automatically detect & avoid obstacles if the robot goes
beyond the line of sight. This avoids damage to the vehicle if it is monitored from a
distant place.
2. GPS Modules can be incorporated in robot system to discover the status and location
of the robot.
3. Sensors like bomb detector, metal detector or gas detector can be mounted on the
robot for avoiding the man-made disasters.
4. Heart-Beat sensor can be mounted on the robot and it can be used for military
purposes. When this robot will be send into the war-field, then it will detect heart-
beat. If the soldier is alive then defence force can send their rescue team for saving
their warrior lives.
5. GPS camera can be incorporated in robot system to increase its working range.

REFERENCES
1. The 8051 Microcontroller,3e, Kenneth Ayala,2010
2. The 8051 Microcontroller and Embedded Systems Using Assembly and C, 2e.By
Muhammad Ali Mazidi, Janice Gillispie Mazidi and Rolin D. Mckinlay,2009
3. A2Z Control System- DTMF Control System, Vol 10, No 11 (2010)
Er. Zatin Gupta, Payal Jain, Monika
4. An Interactive Control Architecture For Mobile Robots,Chia-How Lin and Kai-Tai
Song(10.2316/Journal,206,2013.1.206-3601)

APPENDIX
A PIN CONFIGURATION OF AT89S52 :-
Fig A.1 Pin Configuration of AT89S52
PIN DESCRIPTION
VCC: It requires a +5v DC supply voltage from battery or power supply to run.
GND: Ground connection (0 V).Generally, It is named as Vss.
Port 0 (P.0 to P.7): Port 0 pins may serve as inputs, outputs, or, as a bidirectional
low order address and data bus for external memory interface. It is of 8-bit size. By
writing 1 to port 0 pins, the pins can be used as input. By writing 0 to Port 0, it can be

configured as output & external pull-up resistor will be needed to supply logic high.
Port 1(P1.0 to P1.7): Port 1 pins have no dual functions. When 1s are written to Port
1 pins, they are pulled high by the internal pull-ups and can be used as inputs. By writing
0, it can be used as output port.
Port 2 (P2.0 to P2.7): Port 2 is an 8-bit bidirectional I/O port with internal pull-ups.
When 1s are written to Port 1 pins, they are pulled high by the internal pull-ups and can
be used as inputs. By writing 0 to port, it can be used as output port. It has same function
as that of port 0 but it differs in 1 respect that it is used to supply a high order address
byte in conjunction with the port 0 low order byte to address external memory.
Port 3(P3.0 to P3.7): Port 3 is an 8-bit bidirectional I/O port with internal pull-ups.
When 1s are written to Port 1 pins, they are pulled high by the internal pull-ups and can
be used as inputs. By writing 0 to port, it can be used as output. Pins of port 3 can also be
programmed individually to be used as either I/O.
Reset: Reset pin is used to set the 8051 microcontroller to its initial values, while the
microcontroller is working or at the initial start of application. The RESET pin must be
set high for 2 machine cycles.
ALE (Address Latch Enable): It is a type of control signal which is used for
external memory interfacing. It is used for latching the address on port 0 so that it can be
used as data bus.
EA (External Enable): It is used to enable or disable external memory interfacing.
If there is no external memory requirement, this pin is pulled high by connecting it to
VCC. If the programmer wants to fetch instruction from external memory only, then he
must connect External Access (EA) pin to ground.
Program Store Enable: It is used to read signal from external program memory.
XTAL1 & XTAL2 (Crystal Input): It is used for interfacing an external crystal to
provide system clock [1 & 2].

B H BRIDGE CIRCUIT
H Bridge is an electronic circuit that enables voltage to be applied across load in either
direction of motor. These circuits are often used in robotics application and other
applications where motor needs to be rotated in both backward and forward directions.
FIG B.1 H-Bridge Circuit
H bridge is consists of four switches. When switches s1 and s4 are closed then positive
voltage is applied across the motor. Motor rotate in right direction. When switch s2 and
s3 is closed, negative voltage is applied across motor and motor rotate in left direction.
Switch s1 and s2 should never be closed at the same time, if so, this will cause short
circuit on input voltage source. The same condition apply to switches s3 and s4. When
switches s1 and s3 are closed, then motor suddenly stops. Same thing happen when
switches s2 and s4 are closed.
Table B.1.1: Motor Running description using H bridge
S1 S2 S3 S4 Result
1 0 0 1 Motor moves right
O 1 1 0 Motor moves left
0 0 0 0 Motor free runs
1 0 1 0 Motor brakes
0 1 0 1 Motor brakes
1 1 0 0 Shoot through

C HT9170B DTMF Decoder
Circuit Diagram
Fig.C.1 HT9170B Circuit Diagram
PIN DESCRIPTION

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