G.S.M CONTROLLED CAR KIT

GLOBAL SYSTEM MOBILE COMMUNICATION
CONTROLLED CAR KIT
7th
SEMESTER PROJECT REPORT
Submitted by:
Hemanta Kumar Saikia
Mriganka Das
Nabanita Medhi
Nabanita Baishya
Under the guidance and supervision of
Jyothirmoi Garapati
Faculty, Regional Institute of Science & Technology
DEPARTMENT OF
ELECTRONICS AND COMMUNICATION ENGINEERING
REGIONAL INSTITUTE OF SCIENCE & TECHNOLOGY
9th
MILE, RI-BHOI, MEGHALAYA (2012-13)
Affiliated to
NORTH EASTERN HILL UNIVERSITY

FORWARDING CERTIFICATE
This is to certify that the thesis entitled, ―GLOBAL SYSTEM MOBILE
COMMUNICATION CONTROLLED CAR KIT‖ submitted by the following students of 7th
semester, B.Tech., Electronics and Communication Department at Regional Institute of science
& Technology, Meghalaya is an authentic work carried out by them under my supervision and
guidance.
To the best of my knowledge, the matter embodied in the thesis has not been submitted to
any other University/Institute for the award of any Degree or Diploma.
Hemanta Kumar Saikia (EC-114/09)
Mriganka Das (EC-123/09)
Nabanita Baishya (EC-124/09)
Nabanita Medhi (EC-125/09)
Signature: Project Guide: Jyothirmoi Garapati
Date: Assistant Professor
Department of Electronics & Communication Engineering
Regional Institute of Science & Technology

CERTIFICATE OF APPROVAL
This is to certify that this project entitled ―GLOBAL SYSTEM MOBILE
COMMUNICATION CONTROLLED CAR KIT” submitted by
Hemanta Kumar Saikia (EC-114/09)
Belonging to Electronics & Communication Department, Regional Institute of Science &
Technology, Meghalaya in partial fulfilment for the award of degree of Bachelor of Technology
was done under the guidance and supervision of Jyothirmoi Garapati and is bona fide
presentation of the work done by them.
The matter presented in this dissertation has not been submitted for the award of any
other degree to any other Institute/University.
Signature: Mrs. Krishna Sharma
Date: Professor and HOD
Department of Electronics & Communication Engineering
Seal:

TOPICS
Acknowledgement………………………………………………………………………………...5
Abstract……………………………………………………………………………………………6
CHAPTER-1
1. Introduction…………………………………………………………………………………7-10
1.1 Dual-Tone Multi-Frequency ………………………………………………………….7
1.2 Decoder…………………….………………………………………………………..7-8
1.3 Motor Driver …………………………………………….…………………………8-9
1.4 Motor………………………………………………………………………………….9
1.5 Voltage Regulators…………………………………………………………………..10
1.6 Oscillator……………………………………………………………………………..10
CHAPTER-2
2. Global System for Mobile Communications………………………………………………11-13
2.1 Technical Details………………………………………………….………..……......11
2.2 GSM Carrier Frequencies………………….………………………………………...11
2.3 Network Structure……………………………………………………………………12
2.4 Strength of GSM……………………………………………………………………..13
2.5 Weakness of GSM…………………………………………………………………...13
CHAPTER-3
3. Circuit Elements and Description………………………………..…...……………………14-23
3.1 HT 9170: DTMF Decoder…………………………………………………..……14-16
3.1.1 PIN Description………………………………………………..………..…15
3.1.2 Circuit Diagram…………………………………...……………..…..…….16
3.2 L293D: Motor Driver……………………………………….………………...….16-18
3.2.1 L293D PIN Configuration and Input- Output Logic Function
Table……………………………………………………………………….18
3.3 Controlling DC Geared Motor……………………………………………………….19
3.3.1 Circuit Description………………………………………….……………...19
3.4 IC Voltage Regulators……………………………………………………...…….19-21
3.4.1 Fixed Voltage Regulators…………………………….…….…………..20-21
3.4.1.1 Positive Voltage Regulators……………………………………...20
3.4.1.2 Negative Voltage Regulators…………….………………….…...21
3.4.2 Variable Voltage Regulators…………………………………….…………21
3.5 Crystal Oscillator…………………………………………………………….………21
3.6 Registers……………………………………………………………………………...22
3.7 Capacitor……………………………………………………………………………..23
CHAPTER-4
4. Project…………………………………………………………………………...…………24-30
4.1 Project Overview………………………………………….…………………………24
4.2 Block Diagram………………………………….……………………………………25
4.3 Circuit Design with Description………………………………………………..……26

4.4 Verification of Digital Output…………………….….………………………………27
4.5 Assembling the DC Motors……….…….…………………….………………….27-28
4.6 Interfacing IC L293D with IC HT9170B……………………………………………28
4.7 Circuit Diagram…………………………………….………………………………..29
4.8 Working…………………………………..………….………………………………30
4.9 Results & Conclusion………………………………………………………………..31
4.10 Safety & Precautions………………………………………………………………..32
PHOTO GALLERY
CONCLUSION

ACKNOWLEDGEMENT
Perseverance, inspiration and motivation have always played a key role in any venture.
Irrespective of the amount of hard work and determination, it is inevitable to come across
hurdles to grasp the wide spectrum of topics and find a suitable tool to co-relate all the topics to
yield the desired result. At this point, the able guidance of a teacher provides a means to
accomplish the inconceivable.
Hence we take this opportunity to express our deep and heartfelt sense of gratitude and
thank our project guide Jyothirmoi Garapati, Faculty, Department of Electronics and
Communication Engineering, RIST for his invaluable guidance, innovative suggestion,
encouragement and never-ceasing faith and patience with which he handled the whole project.
Apart from them we would like to give our sincere thanks to one of our HOD, Mrs.
Krishna Sharma and our other faculty members who helped us a lot in the project wherever we
needed.
Finally, we express our gratitude to everybody involved, directly or indirectly to this
project for the successful completion of the project.
Date: Hemanta Kumar Saikia (EC -114/09)
Regional Institute of Science & Technology 5

ABSTRACT
This project involves the design and development of GLOBAL SYSTEM MOBILE
COMMUNICATION CONTROLLED CAR KIT. This kit can be used globally to communicate
by GSM network. It is a user friendly. The main motive to design this car is to help in any
detective spy related work (video calling, camera, message transfer etc.) as it can travel in any
remote place (coal mine, underground etc.) and one can operate it from anywhere through the
GSM network. Also it is cost efficient.
This project concentrates on the design of a car kit by implementing Decoder HT 9170B
based on Dual Tone Multi Frequency (DTMF) technique. DTMF IC is a kind of decoder that
takes analog tone/DTMF tone as input and produce 4 bit digital output. Highly accurate switched
capacitor filters are implemented to divide tone signals into low and high group signals. A built-
in dial tone rejection circuit is provided to eliminate the need for pre-filtering. The decoder
decodes the DTMF tone into its equivalent binary digit and this binary number is sent to the
motor driver in order to drive the motors in forward direction or backward direction or turn. The
mobile phone that makes a call to another mobile phone stacked in the robot act as a remote.
Hence this car is a necessity for a day-to-day life implemented by dint of technology.

CHAPTER 1
1. INTRODUCTION
1.1 Dual-Tone Multi-Frequency
Dual-tone multi-frequency (DTMF) signalling is used for telecommunication signalling over
analog telephone lines in the voice-frequency band between telephone handsets and other
communications devices and the switching centre. When you press the buttons on the keypad, a
connection is made that generates two tones at the same time. A "Row" tone and a "Column"
tone. These two tones identify the key you pressed to any equipment you are controlling. If the
keypad is on your phone, the telephone company's "Central Office" equipment knows what
numbers you are dialling by these tones, and will switch your call accordingly. If you are using a
DTMF keypad to remotely control equipment, the tones can identify what unit you want to
control, as well as which unique function you want it to perform.
Fig 1.1: Tone assignments in DTMF system
When digit 1 is pressed on the keypad, tones 1209 Hz and 697 Hz are generated.
Pressing the digit 2, tones 1336 Hz and 697 Hz can be generated.
The tone 697 is the same for both digits, but it take two tones to make a digit and the
decoding equipment knows the difference between the 1209 Hz that would complete the digit 1,
and a 1336 Hz that completes a digit 2.
1.2 Decoder
A decoder is a device which does the reverse operation of an encoder, undoing the encoding so
that the original information can be retrieved. The same method used to encode is usually just
reversed in order to decode. It is a combinational circuit that converts binary information from n
input lines to a maximum of 2n
unique output lines.
In digital electronics, a decoder can take the form of a multiple-input, multiple-
output logic circuit that converts coded inputs into coded outputs, where the input and output

codes are different, e.g. n to 2n
, binary-coded decimal decoders. Enable inputs must be on for the
decoder to function, otherwise its outputs assume a single "disabled" output code word.
Decoding is necessary in applications such as data multiplexing, 7 segment display and memory
address decoding.
The example decoder circuit would be an AND gate because the output of an AND gate
is "High" (1) only when all its inputs are "High." Such output is called as "active High output". If
instead of AND gate, NAND gate is connected then the output will be "Low" (0) only when all
its inputs are "High". Such output is called as "active low output".
Fig1.2: A 2-to-4 line Single bit decoder
A slightly more complex decoder would be the n to 2n
type binary decoders. These types
of decoders are combinational circuits that convert binary information from 'n' coded inputs to a
maximum of 2n
unique outputs. We say a maximum of 2n
outputs because in case the 'n' bit
coded information has unused bit combinations, the decoder may have less than 2n
outputs. We
can have 2 to 4 decoder, 3 to 8 decoder or 4 to 16 decoder. We can form a 3 to 8 decoder from
two 2 to 4 decoders (with enable signals).
Similarly, we can also form a 4 to 16 decoder by combining two 3 to 8 decoders. In this
type of circuit design, the enable inputs of both 3 to 8 decoders originate from a 4th input, which
acts as a selector between the two 3-to-8 decoders. This allows the 4th input to enable either the
top or bottom decoder, which produces outputs of D(0) through D(7) for the first decoder, and
D(8) through D(15) for the second decoder. A decoder that contains enable inputs is also known
as a decoder-demultiplexer. Thus, we have a 4 to 16 decoder produced by adding a 4th input
shared among both decoders, producing 16 outputs.
1.3 Motor Driver
The motor driver can control upto two DC motors at a constant current. Four input signals (IN1,
IN2, IN3 and IN4) can be used to control the motor in one of four function modes – clockwise
(CW), counter-clockwise (CCW), short-brake, and stop. Two motors with standard RPM
(revolution per minute) are used to maintain the speed. The two motor outputs can be separately
controlled.
Logic supply voltage (VCC) can be in the range of 2.7V – 5.5 V DC, while the motor

supply (VM) is limited to a maximum voltage of 12V DC.
Table for Motor Driver control :
IN1 IN2 IN3 IN4 RESULT
1 0 0 1 Motor moves right
0 1 1 0 Motor moves left
0 1 0 1 Motor breaks
0 0 0 0 Motor stops
Fig 1.3: Motor driver IC
1.4 Motor
An electric motor is an electromechanical device that converts electrical energy into mechanical
energy.
Most electric motors operate through the interaction of magnetic fields and current-
carrying conductors to generate force.
A DC Geared Motor is an electric motor that runs on direct current (DC) electricity. DC
motors were used to run machinery, often eliminating the need for a local steam engine or
internal combustion engine. DC motors can operate directly from rechargeable batteries,
providing the motive power for the first electric vehicles.
Fig1.4: DC geared motor

1.5 Voltage Regulators
The regulator may be constructed from a zener diode, and/or discrete transistors, and/or
integrated circuits. All voltage regulators must have a stable voltage reference source which is
provided by a special type of diode operated in reverse breakdown called a breakdown diode, or
zener diode.
The primary function of a voltage regulator is to maintain a constant dc output voltage.
However, it also rejects ac ripple voltage that is not removed by the filter. The regulator may also
include protective functions such as short-circuit protection, current limiting, thermal shutdown,
or over voltage protection.
1.6 Oscillator
An oscillator is the basic element of all ac signal sources and generates sinusoidal signals of
known frequency and amplitude. It is one of the basic and useful instruments used in electrical
and electronic measurements. Although we speak of an oscillator as ―generating‖ a sinusoidal
signal, it is to be noted that it doesn‘t create energy, but merely converts unidirectional current
drawn from a dc source of supply into alternating current of desired frequency. The function of
an oscillator is reverse of that of rectifier and, therefore, sometimes called inverter. However, we
generally think of oscillator circuits as providing an ac voltage signal.
For having a sinusoidal oscillator, we require an amplifier with positive feedback. The
idea is to use the feedback signal in place of an input signal. If the loop gain and phase are
correct, there will be an output ignal even though there is no external input signal. In other
words, an oscillator is an amplifier that is modified by positive feedback supply to its own input
signal. In an oscillator, the output frequency depends on the passive components employed in the
circuit and can be varied as per needs. Oscillator may provide fixed or variable frequency.
Output
Fig 1.6.: Block diagram of an oscillator
Oscillatory
circuit
Electronic
amplifier
Feedback
network

CHAPTER 2
2. GLOBAL SYSTEM FOR MOBILE COMMUNICATION
GSM (Global System for Mobile Communications) is a standard set developed by the European
Telecommunications Standards Institute (ETSI) to describe technologies for second generation
(2G) digital cellular networks. It was developed as a replacement for first generation (1G) analog
cellular networks, the GSM standard originally described a digital, circuit switched network
optimized for full duplex voice telephony. The standard was expanded over time to include first
circuit switched data transport, then packet data transport via GPRS (General Packet Radio
Services). Packet data transmission speeds were later increased via EDGE (Enhanced Data rates
for GSM Evolution) referred as EGPRS. The GSM standard is more improved after the
development of third generation (3G) UMTS standard developed by the 3GPP.
2.1 Technical details
GSM is a cellular network, which means that cell phones connect to it by searching for cells in
the immediate vicinity. There are five different cell sizes in a GSM network—
macro, micro, pico, femto and umbrella cells. The coverage area of each cell varies according to
the implementation environment. Macro cells can be regarded as cells where the base
station antenna is installed on a mast or a building above average roof top level. Micro cells are
cells whose antenna height is under average roof top level; they are typically used in urban areas.
Picocells are small cells whose coverage diameter is a few dozen meters; they are mainly used
indoors. Femtocells are cells designed for use in residential or small business environments and
connect to the service provider‘s network via a broadband internet connection. Umbrella cells
are used to cover shadowed regions of smaller cells and fill in gaps in coverage between those
cells. Cell horizontal radius varies depending on antenna height, antenna gain and propagation
conditions from a couple of hundred meters to several tens of kilometres.
2.2 GSM Carrier Frequencies
GSM networks operate in a number of different carrier frequency ranges (separated into GSM
frequency ranges for 2G and UMTS frequency bands for 3G), with most 2G GSM networks
operating in the 900 MHz or 1800 MHz bands. Where these bands were already allocated, the
850 MHz and 1900 MHz bands were used instead .In rare cases the 400 and 450 MHz frequency
bands are assigned in some countries because they were previously used for first-generation
systems. Most 3G networks in Europe operate in the 2100 MHz frequency band. Regardless of
the frequency selected by an operator, it is divided into timeslots for individual phones to use.
This allows eight full-rate or sixteen half-rate speech channels per radio frequency. These eight
radio timeslots (or eight burst periods) are grouped into a TDMA frame. Half rate channels use
alternate frames in the same timeslot. The channel data rate for all 8 channels is 270.833 Kbit/s,
and the frame duration is 4.615 ms.

2.3 Network Structure
The network is structured into a number of discrete sections:
 The Base Station Subsystem (the base stations and their controllers).
 The Network and Switching Subsystem (the part of the network most similar to a fixed
network). This is sometimes also called the core network.
 The GPRS Core Network (the optional part which allows packet based Internet
connections).
 The Operations support system (OSS) for maintenance of the network.
Fig2.3: The structure of GSM network
Fig 2.4: Evolution of 3G from GSM

2.4 Strength of GSM
• It provides wide ranges of services
• Open Standard
• User friendly System
• Widely accepted in major parts of the World
• Technical support is available easily
• Integration with other systems is not complex
2.5 Weakness of GSM
• Accessing method is TDMA which is not very secure.
• RF Channel Bandwidth is less
• Data Speed supported is very less and present day customers demand higher speed
• It is not capable to provide multi-media
• Traffic handling capacity is limited.

CHAPTER 3
3. CIRCUIT ELEMENTS AND DESCRIPTION
3.1 HT 9170: DTMF Decoder
The HT9170B/D are dual tone multi frequency (DTMF) receivers integrated with digital decoder
and band split filter functions as well as Power-Down Mode and Inhibit Mode operations. Such
devices use digital counting techniques to detect and decode all the 16 DTMF tone pairs into a 4-
bit code output.
Highly accurate switched capacitor filters are implemented to divide tone signals into low
and high group signals. A built-in dial tone rejection circuit is provided to eliminate the need for
pre-filtering.
Fig 3.1: Pin diagram of HT9170

3.1.1 PIN Description
PIN NAME INPUT/
OUTPUT
INTERNAL
CONNECTION
PIN DESCRIPTION
VP
I
Operational
amplifier Operational amplifier non-inverting input.
VN I Operational amplifier inverting input.
GS O Operational amplifier output terminal.
VREF O VREF Reference voltage output, normally VDD/2.
X1 I
Oscillator
The system oscillator consists of an inverter, a bias
resistor and the necessary load capacitor on chip. A
standard 3.5 MHz crystal connected to X1 and X2
terminals implements the oscillation function.
X2
PWDN I CMOS IN
Pull-Low
Active high. This enables the device to go into
power down mode and inhibits the oscillator. This
pin input is internally pulled down
INH I CMOS IN
Pull-Low
Logic-high. This inhibits the detection of tones
representing the character A, B, C, D. This pin
input is internally pulled down
Vss ___ ___ Negative power supply, Ground.
OE I CMOS IN
Pull-High D0 - D3 output enable, high-active
D0 – D3 O CMOS OUT
Tristate
Receiving data output terminal
OE=‘H‘: Output enable
OE=‘L‘: High impedance
DV O CMOS OUT Data valid output
When the chip receives a valid tone(DTMF) signal,
the dv goes high, otherwise it remains low
EST O CMOS OUT Early steering output.
RT/GT I/O CMOS IN/OUT Tone acquisition time and release time can be set
through connection with external resistor and
capacitor
VDD ___ ___ Positive power supply, 2.5-5.5 v for normal
operation

3.1.2 Circuit Diagram
Fig 3.1.2: Circuit diagram of IC HT9170B/D
3.2 L293D: Motor Driver
L293D is a dual H-Bridge motor driver, so with one IC we can interface two DC motors which
can be controlled in both clockwise and counter clockwise direction and if we have motor with
fix direction of motion then we can make use of all the four I/Os to connect up to four DC
motors. L293D has output current of 600mA and peak output current of 1.2A per channel.
Moreover for protection of circuit from back EMF output diodes are included within the IC. The
output supply (VCC2) has a wide range from 4.5V to 36V, which has made L293D a best choice
for DC motor driver.

A simple schematic for interfacing a DC motor using L293D is shown below:
Fig 3.2: Circuit description of IC L293D

3.2.1 L293D PIN Configuration and Input- Output Logic
Function Table:
Fig 3.2: Pin description of IC L293D

3.3 Controlling DC Geared Motor:
First basic step to control a DC motor is to control its direction in such a way that polarity of the
motor gets changed when we change the terminal of the battery using switches as shown below:
Fig 3.3: Controlling DC geared motor
3.3.1 Circuit Description
Figure shows the circuit description for controlling a DC motor using four Switches S1, S2, S3,
and S4. One of the terminals is connected to positive terminal of the battery and the other one is
connected to the ground. When switch S2 and S3 are connected the current i follows the path as
shown by the green indicator and the motor rotates in a particular direction say clockwise.
Similarly when Switch S1 and S4 are connected the motor will rotate in the reverse direction i.e.
anticlockwise due to change in the direction of current.
3.4 IC Voltage Regulators
Voltage regulators produce fixed DC output voltage from variable DC (a small amount of AC on
it). Normally we get fixed output by connecting the voltage regulator at the output of the filtered
DC. It can also be used in circuits to get a low DC voltage from a high DC voltage (for example
we use 7805 to get 5V from 12V).
There are two types of voltage regulators:
1. Fixed voltage regulators (78xx, 79xx) and
2. Variable voltage regulators (LM317).

3.4.1 Fixed Voltage Regulators
In fixed voltage regulators there is another classification
1. Positive voltage regulators 2. Negative voltage regulators
3.4.1.1 Positive Voltage Regulators
This includes 78xx voltage regulators. The most commonly used ones are 7805 and 7812. 7805
gives fixed 5V DC voltage if input voltage is in (7.5V to 20V). Suppose if input is 6V then
output may be 5V or 4.8V, but there are some parameters for the voltage regulators like
maximum output current capability, line regulation etc.
Fig 3.4.1.1: Circuit (How to get Filter +5 volt from any battery)
First task is to identify the leads of the 7805. So first we have to keep the lead downward
and the writing to our side. It can see the heat sink above the voltage regulator (1-input, 2-gnd
and 3-output). This is the same way of lead identification for all 3 terminal IC's (for e.g. Power
transistor). The above diagram shows how to use 7805 voltage regulator. In this we can see that
coupling capacitors are used for good regulation. But there is no need for it in normal case. But if
we are using 7805 in analog circuit we should use capacitor, otherwise the noise in the output
voltage will be high. The mainly available 78xx IC's are 7805, 7809,7812,7815,7824.
Fig 3.4.1.1.1: Pin Diagram of IC 7805

3.4.1.2 Negative Voltage Regulators
Mostly available negative voltage regulators are of 79xx family. We use negative voltage if we
use IC741. For IC741 +12v and -12v will be enough, even though in most circuits we use +15v
and -15v. 7805 gives fixed -5V DC voltage if input voltage is in (-7V,-20V). The mainly
available 79xx IC's are 7905,7912. 1.5A output current, short circuit protection, ripple rejection
are the other features of 79xx and 78xx IC's.
3.4.2 Variable Voltage Regulators
Most commonly variable voltage regulator is LM317, although other variable voltage regulators
are available. The advantage of variable voltage regulator is that we can get a variable voltage
supply by just varying the resistance only. LM317 can be used to drive motor because it can
handle output current up to 1.5A.
3.5 Crystal Oscillator
A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a
vibrating crystal of piezoelectric material to create an electrical signal with a very
precise frequency. This frequency is commonly used to keep track of time (as in quartz
wristwatches), to provide a stable clock signal for digital integrated circuits, and to stabilize
frequencies for radio transmitters and receivers. The most common type of piezoelectric
resonator is used in the quartz crystal, so oscillator circuits designed around them became known
as ―crystal oscillators‖.
A quartz crystal provides both series and parallel resonance. The series resonance is a
few kilohertz lower than the parallel one. Crystal oscillator circuits are often designed around
relatively few standard frequencies, such as 3.579545 MHz, 4.433619 MHz, 10 MHz,
14.318182 MHz, 17.734475 MHz, 20 MHz, 33.33 MHz, and 40 MHz. The popularity of the
3.579545 MHz crystals is due to low cost since they are used for practical circuit design.
Fig 3.5: Crystal oscillator

3.6 Resistor
Resistors offers a resistance to the flow of current and act as voltage droppers or voltage
dividers. They are "Passive Devices", that is they contain no source of power or amplification
but only attenuates or reduce the voltage signal passing through them. When we select a resistor
its value and power rating should be the deciding parameter. Therefore for high current
operations we use resistance of higher current ratings. The size of the resistor determines its
power rating (i.e. as size/thickness increases power/current carrying capacity of resistance
increases).
Types of resistors:
Mainly they are of two types: a. Fixed resistors and
b. Variable resistors.
Fig 3.6: Fixed and variable resistors

3.7 Capacitor
A capacitor is used to store charge. Like resistors there is fixed as well as variable capacitor also.
But we mostly use fixed capacitor in robotics; variable capacitors are mainly used in analog
communication. There are capacitors with no polarity and polarity. Ceramic and Mica capacitors
available are of no-polarity, but electrolytic capacitors are of polarity. There is a variation in
their symbols also.
Fig 3.7: Capacitors and their symbols
In the above figure we see different symbols for capacitors. Mica and ceramic capacitor
don't have polarity while electrolytic have polarity, so one lead of electrolytic capacitor is bend
(negative lead). We can identify negative lead of electrolytic capacitor by checking the length of
the lead, one with less length is negative. On the body of electrolytic capacitor negative symbol
is shown.

CHAPTER 4
4. PROJECT
4.1 Project Overview
GSM CONTROLLED CAR KIT
Project Statement: To make a robot that could be controlled using mobile phone keypad.
Basic Principle: DTMF, i.e. Dual Tone Multi Frequency concept.
Theory: This robot is based on a simple logic of controlling the direction of motors using mobile
phone and involves use of only 2 IC‘s DTMF decoder IC HT9170 and a motor driver IC L293D
and does not require any micro-controller for working. In this project we have focused on a
general terminology of GSM network in the field of robotics.
Requirements:
1. DTMF IC HT9170B.
2. Motor IC L293D.
3. Two DC geared motors.
4. A Mobile phone at the receiver section.
5. A Headphone jack.
6. Crystal oscillator 3.579592 MHz.
7. Resistance: 100KΩ and 300KΩ.
8. Capacitors: 0.1μF, 20Pf.
9. Voltage Regulator: 7805 and 7812.

4.2 Block Diagram
Fig 4.2: Block Diagram for GSM controlled car kit

4.3 Circuit Design with Description
Our first objective is to design a circuit which can decode the keypad tone of the mobile into its
digital format. For this purpose, IC HT9170B is used. IC HT9170B is a DTMF decoder, such
devices use Digital Counting Techniques to detect and decode all the 16 DTMF tone pairs into a
4-Bit Code Output. It takes analog tone/DTMF tone as input and produce 4 bit digital output.
To fulfil this objective we have design a circuit which will decode the keypad tone into
its digital format. To verify the result, four LED‘s are connected at the output port of IC
HT9170B.
Fig 4.3: DTMF Decoder

4.4 Verification of Digital Output
In mobile phone each button produce different frequency tone and this IC produce different
output for different frequency.
If ‗1‘ is pressed output is 0001
If ‗*‘ is pressed output is 1011
If ‗#‘ is pressed output is 1100
4.5 Assembling The DC Motors
After verifying the digital output we assembled the two DC motors with IC L293D, which is the
motor driver IC. The figure below describes the installation of the two DC geared motor with IC
L293D.
Fig 4.5: DC motors connected with IC L293D

As shown in the above circuit diagram, the two DC geared motors are connected to the output
port of IC L293D, i.e. Motor 1 is connected to pin 3 & 6 and Motor 2 is connected to pin 11 &
14. Pin 1 & 9 being the enable port, are connected to +5 volt DC supply. Pin 4,5,12 & 13 are
grounded and the VSS, pin 16 is connected to +5 volt DC. To supply the optimum voltage to the
two DC motors, the VS, pin 8 is connected to +12 volt DC supply.
4.6 Interfacing IC L293D with IC HT9170B
After completion of the two circuit, the two IC‘s are linked together. The verified output port of
IC HT9170B is connected to the input port of IC L293D. The IC L293D will command the two
DC motors to rotate in clockwise or anti-clockwise direction according the instruction given by
the decoder IC HT9170B after interfacing.
The input ports of ICL293D are connected to the output ports of IC HT9170B according
to the connection listed below:
Fig 4.6: Interfacing table
The above mentioned connections are done in a very precise manner so that neither of the
connections is shorted.
Now when key ‗2‘ is pressed in the mobile keypad, the IC HT9170B will decode the tone
frequency into its binary equivalent of ―0010‖. Corresponding to the binary equivalent, pin 12
will be high and the remaining pins 11, 13, 14 will be active low. After interfacing, pin 12 of IC
HT9170B is connected to pin 7 of IC L293D, which will correspond to active high. This will
command the motor to start.

4.7 Circuit Diagram:
Fig 4.7: Project circuit diagram

4.8 Working:
In this project, the car is controlled by a mobile phone that makes a call to the mobile phone
attached to the car kit. 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 ‗dual-tone multiple-
frequency‘ (DTMF) tone. DTMF signalling is used for telephone signalling over the line in the
voice-frequency band to the call switching centre. The version of DTMF used for telephone tone
dialling is known as ‗Touch-Tone.‘ The car perceives this DTMF tone with the help of the phone
stacked in the robot. The mobile that makes a call to the mobile phone stacked in the car kit acts
as a remote. So this simple robotic project does not require the construction of receiver and
transmitter units.
In order to control the car, we need to make a call to the cell phone attached to the car kit
(through head phone) from any phone, which sends DTMF tones on pressing the numeric
buttons. The cell phone in the car kit is kept in ‗auto answer mode. If the mobile does not have
the auto answering facility, receive the call by pressing ‗Answer‘ key on the mobile.
Now we may press any button on your mobile to perform actions as listed in Table
shown below. The DTMF tones thus produced are received by the cell phone in the car kit.
These tones are fed to the circuit by the headset of the cell phone. The IC HT9170B decodes the
received tone and sends the equivalent binary number to the IC L293D, which command the car
to move in specified direction.

As per the description listed in the previous table, the two motor will respond to the mobile
transmitter. The figure below shows the logical diagram of IC L293D for the corresponding
response.
Fig: Logic Diagram of IC L293D
4.9 Results & Conclusion
The Cell Phone Operated Car Kit is remotely controlled by any mobile. When mobile
number of GSM module is called by other any mobile, then it will automatically receive the call
due to auto answering mode. Upon pressing a number in mobile, DTMF tones will be generated
in mobile of GSM module. This DTMF signal is again decoded by IC HT9170B and given to
motor IC L293D which is finally actuating a relay drive to control the two DC motors.

4.10 SAFETY & PRECAUTIONS
Before all, check the components, connecting wires, IC‘s etc. for continuity test or their value &
for their proper working then we proceed further.
BEFORE SOLDERING:
1. Clean all the components‘ leads. Else, leads will not hold the solder.
2. After cleaning the leads should be tinned. Else, the soldering won‘t be perfect & will not
give proper continuity.
3. Tinning should not be so thick. Else the components cannot enter into the pads on the
PCB.
4. While tinning, the components shouldn‘t be over heated. Else, the components may burn.
FOR MOUNTING THE COMPONENTS ON THE PCB:
1. Insert the components (especially the resistors and capacitors) at the proper position &
allignment (for unidirectional devices) by observing the footprints. Else, the circuit will be
wrong.
2. If required then bend the component leads at perfect right angle. Else, the components
will bend and different components may get shorted.
3. Maintain a suitable gap between the components and PCB surface. Else, the components
can‘t dissipate heat properly.

FOR SOLDERING:
1. Heat the soldering iron properly. Else, soldering can‘t be done properly.
2. Use flux for the ease of melting the solder but not in excess. Else, the soldering will be
black in appearance.
3. Keep the soldering tip clean always. Else, there will be dry soldering.
4. Avoid fans/wind during soldering. Else, there will be bridge soldering.
5. The multi-strand wires should be twisted to give a single structure. Else, any strand may
get shorted with some other components /tracks in the PCB.

G.S.M CONTROLLED CAR KIT

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (8)

Similar to G.S.M CONTROLLED CAR KIT

Similar to G.S.M CONTROLLED CAR KIT (20)

Recently uploaded

Recently uploaded (20)

G.S.M CONTROLLED CAR KIT