This document is a project report on a GSM based robotic vehicle. It was submitted by 4 students - Nipun Nair, Abir Bose, Sayam Roy, and Shashi Bhushan - in partial fulfillment of their Bachelor of Engineering degree in Electrical and Electronics Engineering from St. Peter's University. The report includes an abstract, introduction to embedded systems, description of the project block diagram, list of hardware components used, schematic diagram, coding, testing procedures, results, and conclusion.

1. 1
A PROJECT REPORT ON
GSM BASED ROBOTIC VEHICLE
Submitted by
NIPUN NAIR (SP09EEU024)
ABIR BOSE (SP09EEU302)
SAYAM ROY (SP09EEU308)
SHASHI BHUSHAN (SP09EEU309)
In partial fulfillment for the award of the degree
Of
BACHELOR OF ENGINEERING
IN
ELECTRICAL AND ELECTRONICS ENGINEERING
St. PETER’S UNIVERSITY
St. Peter’s Institute of Higher Education and Research
(Declared Under Section 3 of the UGC Act, 1956)
AVADI, CHENNAI – 600 054
TAMIL NADU
APRIL 2013

2. 2
St. PETER’S UNIVERSITY
St. Peter’s Institute of Higher Education and Research
(Declared Under Section 3 of the UGC Act, 1956)
AVADI, CHENNAI – 600 054
TAMIL NADU
BONAFIDE CERTIFICATE
Certified that this project report “GSM BASED ROBOTIC VEHICLE”
is the bonafide work of Nipun Nair (Reg No: SP09EEU024), Abir Bose (Reg
No: SP09EEU302), Sayam Roy (Reg No: SP09EEU308), Shashi Bhushan
(Reg No: SP09EEU309) who carried out the project work under my
supervision.
SIGNATURE SIGNATURE
Prof. R. JAYARAMAN, M.Sc.(Engg), Mrs. M. VASUGI
Head of the Department
Professor & Head Of the
Department of EEE Department of EEE
St. Peter’s University, St. Peter’s University,
Avadi, Chennai – 600 054 Avadi, Chennai – 600 054
Certified that the candidate was examined in the viva-voce examination held
on__________.
INTERNAL EXAMINER EXTERNAL EXAMINER

3. 3
ACKNOWLEDGEMENT
The satisfaction and euphoria that accompany the successful completion of any task
would be incomplete without the mentioning of the people whose constant guidance and
encouragement made it possible. We take pleasure in presenting before you, our project,
which is result of studied blend of both research and knowledge.
With deep sense of gratitude and immense pleasure, we would first like to thank our
Vice Chancellor Dr. D.S. RAMACHANDRA MURTHY, B.E, M.Sc(Engg.), Ph.D. (Offg.) for his
support.
A particular department of gratitude to Prof R. JAYARAMAN, M.Sc.(Engg), Head of
the Department, Electrical and Electronics Engineering for having instilled in us the
confidence to complete our project in time.
We express our earnest gratitude to our internal guide Mrs. M. VASUGI, ,
Electrical and Electronics Engineering, our project guide, for his constant support,
encouragement and guidance. We are grateful for his cooperation and his valuable
suggestions.
Finally, we express our gratitude to all other members who are involved either directly
or indirectly for the completion of this project.

4. 4
TABLE OF CONTENTS
TOPIC PAGE NO
Bonafide Certificate 2
Acknowledgement 3
Table of Contents 4
List of Figures 6
1. Abstract 7
2. Introduction to Embedded Systems 8
3. Project block Diagram 12
4. Hardware Requirements 13
4.1 Voltage Regulator 14
4.2 Microcontroller AT89S52 15
4.3 Push button 19
4.4 DTMF Decoder 20
4.5 MOTOR DRIVER IC L293D 22
4.6 DC MOTOR 25
4.7 INVERTER IC 7404 26
4.8 LED 27
4.9 1N4007 DIODE 28
4.10 Resistors 29
4.11 Capacitors 30
4.12 Battery 31

5. 5
CONTENTS PAGE NO
5. Schematic Diagram 32
5.1 Description 33
5.2 Operation Explanation 35
6. List of Materials 38
7. Coding 39
8. Hardware Testing 41
8.1 Continuity Test 41
8.2 Power on Test 41
9. Result 42
10. Conclusion 45
11. Bibliography 46

6. 6
LIST OF FIGURES
Figures Page No
2(a). Embedded System design Calls 8
2(b). V Diagram 9
3. Project block diagram 12
4.1(a) Block diagram of Voltage Regulator 14
4.2(a) Pin diagram AT89S52 15
4.2(b) Oscillator Connections 16
4.2(c) External clock drive Configuration 16
4.2(d) Block diagram of AT89S52 17
4.3(a) Push on Button 19
4.4(a) Frequency Group of DTMF Decoder 20
4.4(b) DTMF Decoder IC MT8870D 21
4.4(c) DTMF Generated signal 21
4.5(a) Block Diagram of L293D 23
4.5(b) Pin Diagram of L293D 23
4.6(a) DC MOTOR 25
4.7(a) INVERTER IC 7404 26
4.8(a) Types of LED 27
4.8(b) Symbol of LED 27
4.9(a) 1N4007 DIODE 28
4.9(b) PN Junction DIODE 28
4.10 Different Resistors 29
4.11 Different Capacitors 30
5.1(a) L293D Working circuit 34
5.2(a) DTMF Decoder Circuit 36
9.1 Voltage of pin Without IC 42
9.2 Voltage of pin With IC 43
9.3 Project photo 44

7. 7
1. ABSTRACT
The project is designed to develop a robotic vehicle that is controlled by a GSM based
cell phone. DTMF commands from a GSM device (cell phone) are sent to another GSM
device (cell phone) which is mounted on the robot. These commands are fed to a
microcontroller of 8051 family to operate the vehicle movement through motor interface.
The main scope of project is to send commands from one GSM device to be received
by another GSM device mounted on the robot to receive the DTMF (Dual Tone Multi
Frequency) mode commands which are then decoded by a DTMF decoder. The
corresponding codes are then fed to a microcontroller, programmed to recognize those codes
to operate 2nos DC motors through motor driver IC for any direction movement as per the
sent commands from sender’s mobile. The motors are controlled using motor driver IC which
is interfaced to the microcontroller. It uses microcontroller from 8051 family and a battery for
power source.
In this we aim to develop the GSM based robotic vehicle with successful movement
of the vehicle in the direction required. Further the project can be enhanced by interfacing it
with additional motors for multipurpose activity, with camera and sensors for remote
movement of vehicle by avoiding obstacle. For example, spy robot, obstacle sensing robot,
war fighter, pick and place robot used in industry works etc.

8. 8
2. INTRODUCTION TO EMBEDDED SYSTEMS
What is embedded system?
An Embedded System is a combination of computer hardware and software, and
perhaps additional mechanical or other parts, designed to perform a specific function. An
embedded system is a microcontroller-based, software driven, reliable, real-time control
system, autonomous, or human or network interactive, operating on diverse physical
variables and in diverse environments and sold into a competitive and cost conscious market.
An embedded system is not a computer system that is used primarily for processing,
not a software system on PC or UNIX, not a traditional business or scientific application.
High-end embedded & lower end embedded systems. High-end embedded system - Generally
32, 64 Bit Controllers used with OS. Examples Personal Digital Assistant and Mobile phones
etc .Lower end embedded systems - Generally 8,16 Bit Controllers used with an minimal
operating systems and hardware layout designed for the specific purpose
.
SYSTEM DESIGN CALLS:
FIG 2(a): Embedded system design calls

9. 9
EMBEDDED SYSTEM DESIGN CYCLE:
FIG 2(b) “V Diagram”
Characteristics of Embedded System:
• An embedded system is any computer system hidden inside a product other than a
computer.
• They will encounter a number of difficulties when writing embedded system software
in addition to those we encounter when we write applications
– Throughput – Our system may need to handle a lot of data in a short period of
time.
– Response–Our system may need to react to events quickly
– Testability–Setting up equipment to test embedded software can be difficult
– Debugability–Without a screen or a keyboard, finding out what the software is
doing wrong (other than not working) is a troublesome problem
– Reliability – embedded systems must be able to handle any situation without
human intervention
– Memory space – Memory is limited on embedded systems, and you must
make the software and the data fit into whatever memory exists

10. 10
– Program installation – you will need special tools to get your software into
embedded systems
– Power consumption – Portable systems must run on battery power, and the
software in these systems must conserve power
– Processor hogs – computing that requires large amounts of CPU time can
complicate the response problem
– Cost – Reducing the cost of the hardware is a concern in many embedded
system projects; software often operates on hardware that is barely adequate
for the job.
• Embedded systems have a microprocessor/ microcontroller and a memory. Some
have a serial port or a network connection. They usually do not have keyboards,
screens or disk drives.

11. 11
APPLICATIONS
1) Military and aerospace embedded software applications
2) Communication Applications
3) Industrial automation and process control software
4) Mastering the complexity of applications.
5) Reduction of product design time.
6) Real time processing of ever increasing amounts of data.
7) Intelligent, autonomous sensors.
CLASSIFICATION
 Real Time Systems.
 RTS is one which has to respond to events within a specified deadline.
 A right answer after the dead line is a wrong answer.
RTS CLASSIFICATION
 Hard Real Time Systems
 Soft Real Time System
HARD REAL TIME SYSTEM
 "Hard" real-time systems have very narrow response time.
 Example: Nuclear power system, Cardiac pacemaker.
SOFT REAL TIME SYSTEM
 "Soft" real-time systems have reduced constrains on "lateness" but still must operate
very quickly and repeatable.
 Example: Railway reservation system – takes a few extra seconds the data remains
valid.

12. 12
3. PROJECT BLOCK DIAGRAM

13. 13
4. HARDWARE REQUIREMENTS

14. 14
HARDWARE COMPONENTS:
1. VOLTAGE REGULATOR
2. MICROCONTROLLER (AT89S52)
3. PUSH BUTTONS
4. DTMF DECODER
5. L293D MOTOR DRIVER
6. DC MOTOR
7. INVERTER IC 7404
8. LED
9. 1N4007
10. RESISTORS
11. CAPACITORS
12. BATTERY
4.1 VOLTAGE REGULATOR 7805

15. 15
Features
• Output Current up to 1A
• Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V
• Thermal Overload Protection
• Short Circuit Protection
• Output Transistor Safe Operating Area Protection
Description
The LM78XX/LM78XXA series of three-terminal positive regulators are available in
the TO-220/D-PAK package and with several fixed output voltages, making them useful in a
Wide range of applications. Each type employs internal current limiting, thermal shutdown
and safe operating area protection, making it essentially indestructible. If adequate heat
sinking is provided, they can deliver over 1A output Current. Although designed primarily as
fixed voltage regulators, these devices can be used with external components to obtain
adjustable voltages and currents.
Here we use the voltage regulator to provide a constant 5v Dc output voltage.
Internal Block Diagram
FIG 4.1(a): BLOCK DIAGRAM OF VOLTAGE REGULATOR
4.2 MICROCONTROLLER AT89S52

16. 16
The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with
8K bytes of in-system programmable Flash memory. The Atmel AT89S52 is a powerful
microcontroller which provides a highly-flexible and cost-effective solution to many
embedded control applications. The AT89S52 provides the following standard features: 8K
bytes of Flash, 256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-
bit timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-
chip oscillator, and clock circuitry. In addition, the AT89S52 is designed with static logic for
operation down to zero frequency and supports two software selectable power saving modes.
Pin Configurations of AT89S52
FIG 4.2(a): PIN DIAGRAM OF AT89S52
Oscillator Characteristics:

17. 17
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier
which can be configured for use as an on-chip oscillator. 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 Figure 4.2.
FIG 4.2(b): Oscillator Connections
FIG 4.2(c): External Clock Drive Configuration
Block Diagram of AT89S52:

18. 18
FIG 4.2(d): BLOCK DIAGRAM OF AT89S52
Operating Modes:

19. 19
1. Idle Mode
In idle mode, the CPU puts itself to sleep while all the on chip peripherals remain active.
The mode is invoked by software. The content of the on-chip RAM and all the special
functions registers remain unchanged during this mode. The idle mode can be terminated by
any enabled interrupt or by a hardware reset.
2. Power down Mode
In the power down mode the oscillator is stopped, and the instruction that invokes
power down is the last instruction executed. The on-chip RAM and Special Function
Registers retain their values until the power down mode is terminated. The only exit from
power down is a hardware reset. Reset redefines the SFRs but does not change the on-chip
RAM. The reset should not be activated before VCC is restored to its normal operating level
and must be held active long enough to allow the oscillator to restart and stabilize.
4.3 PUSH BUTTONS

20. 20
A push-button (also spelled pushbutton) or simply button is a simple switch mechanism for
controlling some aspect of a machine or a process. Buttons are typically made out of hard
material, usually plastic or metal. The surface is usually flat or shaped to accommodate the
human finger or hand, so as to be easily depressed or pushed.
Push to ON button:
FIG 4.3(a): Push on button
Initially the two contacts of the button are open. When the button is pressed they become
connected. This makes the switching operation using the push button.
Here we use the push button for the reset operation to clear the memory of the
microcontroller.
4.4 DTMF DECODER

21. 21
Introduction
Dual Tone Multiple Frequency (DTMF) decoder IC is used to decode the key strokes
like that of a telephone.
Telephone signalling is based on encoding keypad digits using two sinusoidal of
different frequencies, hence the name DTMF. Each digit is represented by a low frequency
and a high frequency sinusoid. The frequencies used were recommended by AT&T such that
no two frequencies are integral multiples of each other. This facilitates correct decoding even
in the presence of non-linearity of filters which cause higher harmonics to be present.
FIG 4.4(a). Frequency group of DTMF Decoder

22. 22
FIG 4.4(b): DTMF DECODER IC MT8870D
DTMF generated signal
FIG 4.4(c): DTMF generated signal
Each digit on the keypad is encoded as a DTMF tone, which is then transmitted over a
medium, and decoded at the receiving end. A keypad is usually used to generate the required
DTMF tone. Each key has associated with it a row frequency, and a column frequency. When
a key is pressed, the encoding circuitry mixes together these two frequencies, and transmits
the result. The receiver then decodes the tone back into its two respective frequencies, and
then the processing circuit will act accordingly.
Here we use the DTMF tone of keys 2, 4, 5, 6, 8 for vehicle movement. The DTMF tone of
other keys can be designed to control other advanced features if required.

23. 23
4.5 MOTOR DRIVER IC (L293D)
DESCRIPTION:
L293D is a dual H-bridge motor driver integrated circuit (IC). Motor drivers act as
current amplifiers since they take a low-current control signal and provide a higher-current
signal. This higher current signal is used to drive the motors.
L293D contains two inbuilt H-bridge driver circuits. In its common mode of
operation, two DC motors can be driven simultaneously, both in forward and reverse
direction. The motor operations of two motors can be controlled by input logic at pins 2 & 7
and 10 & 15. Input logic 00 or 11 will stop the corresponding motor. Logic 01 and 10 will
rotate it in clockwise and anticlockwise directions, respectively.
Enable pins 1 and 9 (corresponding to the two motors) must be high for motors to
start operating. When an enable input is high, the associated driver gets enabled. As a result,
the outputs become active and work in phase with their inputs. Similarly, when the enable
input is low, that driver is disabled, and their outputs are off and in the high-impedance state.
In the project pins 11 and 14 are used to drive the motors to move the vehicle forward
or backward and the pins 3 and 6 used to drive the motors to move the vehicle right or left.

24. 24
Block diagram:
FIG 4.5(a): BLOCK DIAGRAM OF L293D
Pin Diagram:
FIG 4.5(b): Pin diagram L293D

25. 25
Pin description:

26. 26
4.6 DC MOTOR
A DC motor is an electric motor that runs on direct current (DC) electricity. In any
electric motor, operation is based on simple electromagnetism. A current-carrying conductor
generates a magnetic field; when this is then placed in an external magnetic field, it will
experience a force proportional to the current in the conductor, and to the strength of the
external magnetic field. The internal configuration of a DC motor is designed to harness the
magnetic interaction between a current-carrying conductor and an external magnetic field to
generate rotational motion.
A 2-pole DC electric motor (here red represents a magnet or winding with a "North"
polarization, while green represents a magnet or winding with a "South" polarization).
FIG.4.6 (a) DC motor
Here we use two dc motors that are used to move the vehicle as required. The two
motors rotate together or individually as per the command given by the driver IC.

27. 27
4.7 INVERTER IC 7404
The 7404 is an inverting buffer, especially useful when the output of one circuit cannot sink
much current. It operates on the basic principle of NOT gate operation.
NOT GATE Logic-Rules:
The output is the inverse of the input, in other words if the input is HIGH then the output is
LOW and if the input is LOW the output is HIGH.
FIG 4.7: INVERTER IC 7404
Description:
The inverter IC is used here as a buffer to invert the binary output of the DTMF
decoder. For example for the pressed key ‘2’ output of the DTMF decoder is
‘0010’(D3D2D1D0) that is inverted to ‘1101’ by the inverter IC for easy operation of the
interfaced microcontroller.
APPLICATION:
 Logical inversion
 pulse shaping
 Oscillators

28. 28
4.8 LED
A light-emitting diode (LED) is a semiconductor light source. LEDs are used as
indicator lamps in many devices, and are increasingly used for lighting. When a light-
emitting diode is forward biased (switched on), electrons are able to recombine with holes
within the device, releasing energy in the form of photons.
This effect is called electroluminescence and the color of the light (corresponding to
the energy of the photon) is determined by the energy gap of the semiconductor. LEDs
present many advantages over incandescent light sources including lower energy
consumption, longer lifetime, improved robustness, smaller size, faster switching, and greater
durability and reliability.
Types of LED’S:
FIG 4.8(a): Types of LED
Light-emitting diodes are used in applications as diverse as replacements for aviation
lighting, automotive lighting as well as in traffic signals.
Electronic Symbol:
FIG 4.8(b): Symbol of LED

29. 29
4.9 1N4007 DIODE
Diodes are used to convert AC into DC these are used as half wave rectifier or full wave
rectifier. Three points must he kept in mind while using any type of diode.
1.Maximum forward current capacity
2.Maximum reverse voltage capacity
3.Maximum forward voltage capacity
FIG 4.9(a): 1N4007 diodes
Diode of same capacities can be used in place of one another. Besides this diode of
more capacity can be used in place of diode of low capacity but diode of low capacity cannot
be used in place of diode of high capacity.
FIG 4.9(b):PN Junction diode
Here we use the diode 1N4007 to get a voltage of approx. 5V.

30. 30
4.10 RESISTORS
A resistor is a two-terminal electronic component designed to oppose an electric current by
producing a voltage drop between its terminals in proportion to the current, that is, in
accordance with Ohm's law:
V = IR
FIG 4.10: Different Resistors
We use the resistors to limit the current in different applications. The value of
resistances used here are 330R, 330K, 10K, 100K, 22K.

31. 31
4.11 CAPACITORS
A capacitor or condenser is a passive electronic component consisting of a pair of conductors
separated by a dielectric. When a voltage potential difference exists between the conductors,
an electric field is present in the dielectric. This field stores energy and produces a
mechanical force between the plates. The effect is greatest between wide, flat, parallel,
narrowly separated conductors.
FIG 4.11: Different Capacitors
Capacitors are widely used in electronic circuits for blocking direct current while
allowing alternating current to pass, in filter networks, for smoothing the output of power
supplies, in the resonant circuits that tune radios to particular frequencies and for many other
purposes.
Value of capacitances used here are 470uF/35V, 10uF/63V, 33pF Ceramic, 0.1uF
Ceramic, 0.47uF (470nF) Polyester, 22pF Ceramic.

32. 32
4.12 BATTERY
An electrical battery is a combination of one or more electrochemical cells, used to convert
stored chemical energy into electrical energy. The battery has become a common power
source for many household and industrial applications.
Batteries may be used once and discarded, or recharged for years as in standby
power applications. Miniature cells are used to power devices such as hearing aids and
wristwatches; larger batteries provide standby power for telephone exchanges or computer
data centers.
In this project we use 4 pencil batteries (AA) each providing 1.5V in series. So a
total voltage of 6V is provided to the diode.

33. 33
5. SCHEMATIC DIAGRAM

34. 34
5.1 DESCRIPTION
POWER SUPPLY
This project uses a 6V battery for power supply. A silicon diode is used in series for
getting approximately 5V. One LED is connected of this 5V point in series with a resistor of
330Ω to the ground i.e., negative voltage to indicate 5V power supply availability.
STANDARD CONNECTIONS TO 8051 SERIES MICRO CONTROLLER
ATMEL series of 8051 family of micro controllers need certain standard
connections. The 4 set of I/O ports are used based on the project requirement. Every
microcontroller requires a timing reference for its internal program execution therefore an
oscillator needs to be functional with a desired frequency to obtain the timing reference as t
=1/f.
A crystal ranging from 2 to 20 MHz is required to be used at its pin number 18 and 19
for the internal oscillator to work. Typically 11.0592 MHz crystal is used. Two small value
ceramic capacitors of 33pF each is used as a standard connection for the crystal.
RESET
Pin no 9 is provided with a reset arrangement by a combination of an electrolytic
capacitor and a register forming RC time constant. At the time of switch on, the capacitor
gets charged, and it behaves as a full short circuit from the positive to the pin number 9. After
the capacitor gets fully charged the current stops flowing and pin number 9 goes low which is
pulled down by a 10k resistor to the ground. This arrangement of reset at pin 9 going high
initially and then to logic 0 i.e., low helps the program execution to start from the beginning.
In absence of this the program execution could have taken place arbitrarily anywhere from
the program cycle. A pushbutton switch is connected across the capacitor so that at any given
time as desired it can be pressed such that it discharges the capacitor and while released the
capacitor starts charging again and then pin number 9 goes to high and then back to low, to
enable the program execution from the beginning. This operation of high to low of the reset
pin takes place in fraction of a second as decided by the time constant R and C.

35. 35
For example: A 10µF capacitor and a 10kΩ resistor would render a 100ms time to pin
number 9 from logic high to low, there after the pin number 9 remains low.
External Access (EA):
Pin no 31 of 40 pin 8051 microcontroller termed as EA¯ is required to be connected to
5V for accessing the program form the on-chip program memory. If it is connected to ground
then the controller accesses the program from external memory. However as we are using the
internal memory it is always connected to +5V.
L293D MOTOR DRIVER
L293D has 2 set of arrangements where one set has input 1, input 2, output 1
and output 2 and other set has input 3, input 4, output 3 and output 4, according to
block diagram if pin no 2 & 7 are high then pin no 3 & 6 are also high.
If enable 1 and pin number 2 are high leaving pin number 7 as low then the
motor rotates in forward direction.
If enable 2 and pin number 10 are high leaving pin number 15 as low then the
motor rotates in forward direction.
If enable 1 and pin number 2 are low leaving pin number 7 as high then the
motor rotates in reverse direction.
If enable 2 and pin number 15 are high leaving pin number 10 as low then the
motor rotates in forward direction.

36. 36
FIG 5.1(a): L293D Circuit
5.2 OPERATION EXPLANATION
Connections:
1. The output of the power supply which is 5v is connected to the 40 pin of Microcontroller
and GND I connected to its 20th
pin.
2. Port 2.2, 2.3, 2.4 of Microcontroller are connected to pin number 9, 15, 10 of L293D i.e.,
Motor driver IC. Port 2.5, 2.6, 2.7 of Microcontroller are connected to pin number 7, 2, 1 of
Motor driver IC L293D.
3. Two motors M1 and M2 are connected to pin 3, 6 and 11, 14 of Motor driver IC L293D.
4. Port 3.0, 3.1, 3.2 of Microcontroller is connected to pin number 13, 12, and 11 of DTMF
MT8870. Port 3.3 of Microcontroller is connected to pin 10 of DTMF IC.
5. The output of the mobile earphone socket is connected to the pin 2 and 3 of the DTMF IC.
6. Crystal is connected to pin 7, 8 of the DTMF IC and pin 18, 19 of the Microcontroller.
7. Reset circuit is connected across 9, 31 pin of Microcontroller.

37. 37
Working:
DTMF DECODER
FIG 5.2: DTMF Decoder Circuit
After the call is answered by the mobile phone the tone command sent by the sender
is received at the ear phone socket which is fed to pin no 2 of DTMF decoder through
series resistor and capacitor. The project uses DTMF technology for decoding tone
commands by a DTMF decoder IC MT8870. This develops a 4 bit binary data
corresponding to the number related to the tone received at its pin 2 through a high
pass filter of 0.47 Microfarad and 1K resistor in series. The IC uses a crystal of 3.57
MHz for frequency reference such that input frequency is compared to develop digital
output. This 4 bit binary data is passed through an inverter for buffering purposes
before being connected to MC input at pin 3.1 to 3.3.The output from the
microcontroller drives the L293D for 2 motors as per the command to move forward,
backward, left, right, stop etc.

38. 38
Operation:
One mobile phone is used on the robotic vehicle with its audio output from the earphone
socket connected to pin 2 of DTMF IC in series with a high pass filter as noted above. The tip
and GND thus formed the input tone command to the DTMF decoder IC. So while a call is
established from a calling cell phone to an installed cell phone which is kept on auto answer
mode gets activated, as if the call is answered. Now any number by the sending cell phone is
pressed the corresponding tone is available at the receivers cell phone (which is connected to
the robot) thus forms an input tone to the DTMF decoder the output from which is fed to the
controller through inverter IC 7404. The program while executed makes the motor run
forward, backward, left, and right as per the command from the senders end. The commands
are 2 for forward, 8 for backward, 4 for left and 6 for right and 5 for stop. Thus the robot
operates as per the command given in the program.

39. 39
6. LIST OF MATERIALS
COMPONENT NAME QUANTITY
Resistors
330R 1
10K 5
330K 1
100K 1
22K 1
Capacitors
470uF/35V 1
10uF/63V 2
33pF Ceramic 2
0.1uF (104) Ceramic 1
0.47uF (470nF) Polyester 1
22pF Ceramic 2
Integrated Circuits
AT89S52 1
L293D 1
MT8870/HT9170 1
7404 1
IC Bases
40-PIN BASE 1
18-PIN BASE 1
16-PIN BASE 1
14-PIN BASE 1
DIODE
IN4007 1
Miscellaneous
CELL COVER 1
PENCIL CELL BATTERY (4 X 1.5V=6V) 4
CRYSTAL1 11.0592MHz 1
CRYSTAL2 3.57MHz 1
2 PIN PUSH BUTTON 1
MALE BURGE 2-PIN 3
MALE RELIMET 2-PIN 1
FEMALE RELEMENT 2-PIN ONE SIDE 4
MOBILE PHONE EARPHONE PIN 1
LED RED 1
VEHICLE BODY (INCLUDING 2 DC MOTORS) 1
PLAIN PCB 1
SCREW DRIVER 1
SOLDERING LED (50 gm)
CONNECTING WIRES
SCREW NUT SET 2
SPST SWITCH (ON/OFF) 1
CASTOR BALL 1
Z-Clamps 2
104PF 2
7. CODING
Algorithm
1. Start.
2. Assign integer variable h to Port 3 of the microcontroller.

40. 40
3. Use switch case as per the value of h.
4. For ‘2’ pressed Port 2=2B (Forward).
5. For ‘8’ pressed Port 2=35 (Backward).
6. For ‘4’ pressed Port 2=28 (Left).
7. For ‘6’ pressed Port 2=03 (Right).
8. For ‘5’ pressed Port 2=00 (Stop).
9. Stop
C Program
#include<mega61.h>
void main(void)
{ unsigned int h;
while(1)
{ h=PORT3; // binary input from DTMF IC
switch(h)
{
case 0x0D: // when 2 is pressed
{ PORT2=0x2B; //move forward
break; }
case 0x07: // when 8 is pressed

41. 41
{ PORT2=0x35; // move backward
break; }
case 0x0B: // when 4 is pressed
{ PORT2=0x28; // move left
break; }
case 0x09: // when 6 is pressed
{ PORT2=0x03; // move right
break; }
case 0x0A: // when 5 is pressed
{ PORT2=0x00; // stop
break; }
}
}
8. HARDWARE TESTING
8.1 CONTINUITY TEST:

42. 42
In electronics, a continuity test is the checking of an electric circuit to see if current
flows (that it is in fact a complete circuit). A continuity test is performed by placing a small
voltage (wired in series with an LED or noise-producing component such as a piezoelectric
speaker) across the chosen path. If electron flow is inhibited by broken conductors, damaged
components, or excessive resistance, the circuit is "open".
This test is the performed just after the hardware soldering and configuration has been
completed. This test aims at finding any electrical open paths in the circuit after the soldering.
Many a times, the electrical continuity in the circuit is lost due to improper soldering, wrong
and rough handling of the PCB, improper usage of the soldering iron, component failures and
presence of bugs in the circuit diagram. We use a multi meter to perform this test. We keep
the multi meter in buzzer mode and connect the ground terminal of the multi meter to the
ground. We connect both the terminals across the path that needs to be checked. If there is
continuation then you will hear the beep sound.
8.2 POWER ON TEST:
This test is performed to check whether the voltage at different terminals is according
to the requirement or not. We take a multi meter and put it in voltage mode. First of all check
the voltage across the battery terminal whether it is fully charged or not, the battery used in
this project is 12V, so touch the ‘red terminal’ of battery with ‘red probe’ of multi meter and
touch ‘black terminal’ of battery with ‘black probe’ of multi meter, if 12V is being displayed
on multi meter screen then we can proceed for next steps.
Now that the power supply is available, no IC should be inserted in the base, first
apply power and check whether proper voltage is reaching at ‘vcc’ and ‘gnd’ pins of each IC
base or not. If proper voltages appear at the supply pins of IC bases then insert IC and check
the required output.
9. RESULTS
9.1 Voltage at Pins Without IC:

43. 43
9.2 Voltage at Pins With IC:

44. 44
9.3 Project Photo

45. 45
10. CONCLUSION

46. 46
Thus our aim to develop a GSM based robotic vehicle with movement in the desired
direction as per the command given is successful.
The hardware tests provided successful results and the vehicle was fully implemented.
This project defines the preliminary development of a vehicular robot which can be further
applied to manufacture war fighter vehicle, pick and place vehicle in industry or any other
applications involving distance sensors, camera, and remote device operation etc.
11. BIBLIOGRAPHY

47. 47
TEXT BOOKS REFERED:
1. “The 8051 Microcontroller and Embedded systems” by Muhammad Ali Mazidi and Janice
Gillispie Mazidi , Pearson Education.
2. ATMEL 89S52 Data Sheets.
WEBSITES
 www.atmel.com
 www.beyondlogic.org
 www.wikipedia.org
 www.howstuffworks.com
 www.alldatasheets.com