01-10-2016, 11:52 AM
1457204915-114421229ProjectReportonDtmf.pdf (Size: 1.97 MB / Downloads: 3)
INTRODUCTION
Cell-phone is an ubiquitous device and so when it got combined with the digital door lock technology; it is
able to give us more secure, easy and comfortable door lock system. Now with digital door lock systems, it
is easier to control the door movement of the vehicle. This new automated technology does not require a
key to lock or unlock the door of the vehicle. This digital door entry system is in fact controlled by cell-phone
which is actually performing the role of remote controller over here.
Door lock device inside the vehicle is consisting another cell-phone with an electronic circuit. The user’s cellphone
transmits DTMF (dual tone multiple frequency)
[5] signals via air to another device of the system
installed inside the vehicle. And so the door lock system can be operated from any part of the word. The
working of this digital door locking system [1] is very simple. You just have to use the cell phone you carry
with yourself and you can control the lock from anywhere without any problem. It is a password based
system. The owner has to enter the password on the cell phone for controlling the locking system.DTMF
tones are input to decoder which sends the BCD code to 8051 microcontroller [3][4]
.Buzzer system installed
with it will be able to give owner the information whether the door has been locked safely, like in case
password has been pressed wrong by mistake by owner. Nowadays theft cases are increasing everywhere
and the key based locking system is no longer a safe option. It is quite easy to open the traditional key based
doors either with duplicate keys or some other way. Therefore for safety of vehicles, this system can be
installed.it is simple to install and cheap too. With this system, you will never be in tension of leaving your
house and vehicle out of your supervision. Not only this ,it also help us to move out of some really odd
situations like you locked the door and left and in your absence your friends came back and then they will
have to wait outside if they were not having key with themselves.
Thus DTMF based locking system provides a greater sense of security to users. It is an user-friendly device
and very easy to install. Undoubtedly there is scope for improvement and can be made for enhanced safety purposes.
1.1 MOTIVATION
Keyless entry has been a luxury whose availability is confined primarily to vehicles. The cell phone security
system takes this idea of keyless entry and transforms it into a convenient, versatile security system that
utilizes cell phone technology and the landline telephone network. By taking advantage of caller
identification and dual-tone multi-frequency signaling, the security system has the ability to introduce twolevels
of security. The first level will be decoding the calling party’s identification information while the
second level would consist of the user attempting a password entry over the phone. By combining the
mobility of this telecommunication medium with microcontrollers, the system achieves a secure,
convenient, and automated form of security for a place of residence [2]
.
1.2 DEFINITION
The cell phone security system is the result of a fusion of a creative idea with an attempt to motivate
change. Even though modern technology has allowed for the automation of many aspects of domestic
lifestyles, from automatic motion sensing lights to automatic garage door openers, vehicle security has not
seen much benefit from this revolution. Vehicle locking system has been a very manual routine with little
effort to automate the process, at least in India. Entry into a vehicle is still primarily limited to a manual
process which involves inserting a key into a bolt and physically moving the locking-mechanism. So to
automatize the entire process we have introduced a DTMF controlled locking system in cars which will allow
the users to operate the lock from a remote location.
1.3 OBJECTIVE
The fundamental requirements for the cell phone security system remained fixed throughout the design
process. The goal was to design a system which would allow the user automated and convenient access to
their car security system through a cell phone network.
The fundamental objectives of the system include:
1. Correctly decode the DTMF signals from the user.
2. Allow the user to automatically lock the entryway.
3. Allow the user to automatically unlock the entryway.
4. Allow the user to reset password
1.4 LIMITATIONS OF THE PROJECT
No doubt DTMF based locking system ensures a greater extent of safety but this project bears some
limitations like caller identification and mobile authentication. In case user is in no network coverage area he
will have to move near his vehicle to lock his vehicle. Also due to limitation of memory user can not set
password of large length (here it is limited to four digit only).All these limitations are can be easily removed
at the expense of increased budget.
1.5 ORGANISATION OF DOCUMENTATION
In this project documentation we have initially put the definition and objective of the project as well as the
design of the project which is followed by the implementation and testing phases. Finally the project has
been concluded successfully and also the future enhancements of the project were given in this
Documentation.
INTRODUCTION TO DTMF
DTMF is the global standard for audible tones that represent the digits on a phone keypad with touch-tone
land-line phones, pressing a key on the dial pad generates the corresponding DTMF tone for that key. The
land-line phone system can then "listen" and decode that tone to determine which key was pressed enabling
dialing.
Mobile phone networks use digital signals instead of DTMF for direct dialing, but DTMF is still used over
mobile phones to navigate automated systems such as phone menus, and for secondary dialing, such as
using a calling card. Each DTMF "tone" is actually two tones - a low-frequency tone and a high-frequency
tone -combined. (Hence the name "dual tone multi-frequency".) Looking at the standard phone keypad as a
grid, the low tone corresponds to the row, while the high tone corresponds to the column.
Dual-tone multi-frequency signaling (DTMF) is used for telecommunication signaling over analog telephone
lines in the voice-frequency band between telephone handsets and other communications devices and the
switching center. The version of DTMF that is used in push-button telephones for tone dialing is known as
Touch-Tone. It was developed by Western Electric and first used by the Bell System in commerce, using that
name as a registered trademark.
ANALYSIS OF PROJECT
3.1 INTRODUCTION
After analyzing the requirements of the task to be performed, the next step is to analyze the problem and
understand its context. The first activity in the phase is studying the existing system and other is to
understand the requirements and domain of the new system. Both the methods are equally important but
the first system forms a basis of giving the functional specifications and then successful design of the
proposed system. Understanding the properties and requirements of a new system is more difficult and
requires creative thinking as well as understanding of existing system is also difficult. Improper
understanding of present system can lead to diversion from exact solution.
3.2 HARDWARE REQUIREMENTS
3.2.1 MT8870DE DTMF DECODER CIRCUIT
The MT8870D/MT8870D-1 is a complete DTMF receiver integrating both the band split filter and digital
decoder functions. The filter section uses switched capacitor techniques for high and low group filters; the
decoder uses digital counting techniques to detect and decode all 16 DTMF tone-pairs into a 4-bit code.
Internal functional block diagram of DTMF decoder is shown below in figure 3.