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HOME AUTOMATION USING DTMF
A MINOR PROJECT REPORT
Submitted by
Amardeep – 02296302811
Pratik Kumar – 01896302811
Aditya Kumar Singh - 01696302811
in partial fulfilment for the award of the degree
of
BACHELOR OF TECHNOLOGY
IN
ELECTRONICS & COMMUNICATION ENGINEERING
At
DEPARTMENT OF ELECTRONICS & COMMUNICATION
ENGINEERING
MAHARAJA SURAJMAL INSTITUTE OF TECHNOLOGY,
JANAKPURI, NEW DELHI.
December 2014.
2
CANDIDATE’S DECLARATION
I hereby certify that the work which is being presented in the Minor Project entitled
“HOME AUTOMATION USING DTMF” in partial fulfilment for the award of the Degree of
Bachelor of Technology in Electronics & Communication Engineering affiliated to Guru
Gobind Singh Indraprastha University, New Delhi and submitted to the Department of
Electronics & Communication Engineering of Maharaja Surajmal institute of Technology,
Janakpuri, is an authentic record of my own work carried out during a period from June 2014 to
December 2014. The matter represented in this report has not been submitted by me for award
of any other degree of this or any other institute/university.
Date: - 01/12/2014
Amardeep – 02296302811
Pratik Kumar – 01896302811
Aditya Kumar Singh - 01696302811
This is to certify that the above statement made by the candidate is correct to the best of our
knowledge.
Date: I/c Minor Project Head - ECE
Examiner
(External)
3
ABSTRACT
Traditionally electrical appliances in a home are controlled via switches that regulate the
electricity to these devices. As the world gets more and more technologically advanced, we find
new technology coming in deeper and deeper into our personal lives even at home. Home
automation is becoming more and more popular around the world and is becoming a common
practice. The process of home automation works by making everything in the house
automatically controlled using technology to control and do the jobs that we would normally do
manually. Home automation takes care of a lot of different activities in the house. This project
we propose a unique System for Home automation utilizing Dual Tone Multi Frequency
(DTMF) that is paired with a wireless module to provide seamless wireless control over many
devices in a house. This user console has many keys, each corresponding to the device that needs
to be activated. The encoder encodes the user choice and sends via a GSM transmitter. The GSM
receiver receives the modulated signal and demodulates it and the user choice is determined by
the DTMF decoder. Based upon this the required appliance is triggered.
ACKNOWLEDGEMENT
4
It Is Indeed a Great Pleasure and a moment of immense satisfaction for us to express our
gratitude towards our mentor Ms. PARUL CHAUDHARY for their priceless help and moral
support during the completion of project.
We would like to extend our thanks to all the faculty members for their valuable help
during the project. We remember so many students who participated actively in the teaching learning
process which, in effect, gave us tips and suggestions on how this project should be. We thank
them all and place on record my appreciation of their curiosity and determination to delve into
the project beyond mere superficiality.
Equally we are thankful to our colleagues and students who compelled us to make this
project. Finally, we would like to thank all the people who directly or indirectly have contributed
to the completion of this project.
Amardeep – 02296302811 Pratik Kumar – 01896302811
Aditya Kumar Singh - 01696302811
5
TABLE OF CONTENTS
CHAPTER NO. TITLE PAGE NO.
CANDIDATE DECLARATION i
ABSTRACT ii
ACKNOWLEDGEMENT iii
TABLE OF CONTENTS iv
LIST OF FIGURES vii
1. INTRODUCTION
1.1 Dual-tone multi-frequency 1
1.2 Keypad 4
2. RELATED WORK
2.1 Implementation of µVision 5
2.1.1 µVision 5
2.1.2 General Remarks and Concepts 5
2.1.3 Positioning Windows 7
2.2 8051 Burner Software 9
2.2.1 Features of PRO51 9
2.2.2 System Requirements 10
2.2.3 Getting Started 10
2.2.4 PROG51 User Interface 10
2.2.5 Procedure To Program a Chip 11
6
2.3 Construction and Testing 12
2.4 Precaution 12
2.4.1 Soldering Precaution 12
2.4.2 Components Precaution 13
3 PROBLEM DESCRIPTION AND SPECIFICATION 14
3.1 Problem Statement 14
3.2 Components Required 14
3.2.1 Step Down Transformer 14
3.2.2 Diode 15
3.2.3 Voltage Regulator 7805 15
3.2.4 Crystal Oscillator 16
3.2.5 CM8870 17
3.2.5.1 Features 17
3.2.5.2 Applications 17
3.2.5.3 Descriptions 17
3.2.5.4 Functional Descriptions 18
3.2.5.5 Pin Descriptions 19
3.2.6 Relays 20
3.2.6.1 Types of Relays 20
3.2.6.2 Electromagnetic Relay 20
3.2.7 Capacitor 21
3.2.8 Resistor 21
3.2.9 Microcontroller 22
7
3.2.9.1 Features 22
3.2.9.2 Description 22
3.2.9.3 Pin Descriptions 23
3.2.9.4 Block Diagram 26
3.2.9.5 Instruction Set 27
4 SYSTEM DESIGN 32
4.1 Design Characteristics 32
4.2 About DTMF IC8870 32
4.3 Interfacing 33
4.4 System Design 34
4.4.1 Design Values for CM8870 34
4.4.2 Design Values for Microcontrollor(AT89S52) 35
4.5 Component List 35
4.6 Implementation Of System 36
4.6.1 System Algorithm 36
4.6.2 Program Algorithm 36
4.7 Performance and Evaluation Of System 37
5 VERIFICATION AND VALIDATION 38
5.1 Flowchart 38
6 CRITICAL EVALUATION 40
6.1 Application 40
6.2 Limitaion 41
CONCLUSION 43
8
REFERENCE 44
APPENDIX 45
9
LIST OF FIGURES
No. Title Page No.
1.1 A DTMF Telephone Keypad 3
2.1 µVision 6
2.2 µVision 7
2.3 Keil Software 8
2.4 8051 Burner Software 9
2.5 PROG51 User Interface 11
3.1 Step Down Transformer 15
3.2 Diode 15
3.3 Voltage Regulator 7805 16
3.4 Crystal Oscillator 16
3.5 18 Pin CERDIP 18
3.6 20 Pin SSOP 18
3.7 Relay 21
3.8 Capacitor 21
3.9 Resistor 22
3.10 Pin Description of AT89S52 23
3.11 Block Diagram 26
4.1 DTMF IC 8870 32
4.2 Interfacing 33
5.1 Flow Chart 39
10
CHAPTER-1
INTRODUCTION
DTMF Home Automation lets you operate your home appliances like lights and water
pump from your office or any other remote place. So if you forgot to switch off the lights or
other appliances while going out, it helps you to turn off the appliance with your cell phone.
Your cell phone works as remote control to your home appliances. You can control the desired
appliance by presetting the corresponding key.
The Project “Home Automation using mobile communication” has different sections such as:
1.Microcontroller
2.DTMF decoder
3. Relays
1.1 Dual-tone multi-frequency
Dual-tone multi-frequency (DTMF) signaling is used for telephone signaling over the
line in the voice-frequency band to the call switching center. The version of DTMF used for
telephone tone dialing is known by the trademarked term Touch-Tone and is standardized by
ITU-T Recommendation Other multi-frequency systems are used for signaling internal to the
telephone network.
As a method of in-band signaling, DTMF tones were also used by cable television
broadcasters to indicate the start and stop times of local commercial insertion points during
station breaks for the benefit of cable companies. Until better out-of-band signaling equipment
was developed in the 1990s, fast, unacknowledged, and loud DTMF tone sequences could be
heard during the commercial breaks of cable channels in the United States and elsewhere.
Today, most telephone equipment use a DTMF receiver IC. One common DTMF
receiver IC is the Motorola MT8870 that is widely used in electronic communications
circuits. The MT8870 is an 18-pin IC. It is used in telephones and a variety of other
applications. When a proper output is not obtained in projects using this IC, engineers or
11
technicians need to test this IC separately. A quick testing of this IC could save a lot of
time in re-search labs and manufacturing industries of communication instruments.
DTMF IC. It can be assembled on a multipurpose PCB with an 18-pin IC base. One can
also test the IC on a simple breadboard.
For optimum working of telephone equipment, the DTMF receiver must be designed
to recognize a valid tone pair greater than 40 ms in duration and to accept successive digit
tone-pairs that are greater than 40 ms apart. However, for other applications like remote
controls and radio communications, the tone duration may differ due to noise
considerations. Therefore, by adding an extra resistor and steering diode the tone duration .
can be set to different values. The circuit is configured in balanced-line mode. To reject
common-mode noise signals, a balanced differential amplifier input is used. The circuit
also provides an excellent bridging interface across a properly terminated telephone line.
Transient protection may be achieved by splitting the input resistors and inserting ZENER
diodes (ZD1 and ZD2) to achieve voltage clamping. This allows the transient energy to be
dissipated in the resistors and diodes, and limits the maximum voltage that may appear at
the inputs.
Whenever you press any key on your local telephone keypad, the delayed steering (Std)
output of the IC goes high on receiving the tone-pair, causing LED5 (connected to pin 15
of IC via resistor R15) to glow. It will be high for a duration de-pending on the values of
capacitor and resistors at pins 16 and 17. The optional circuit shown within dot-ted line is
used for guard time adjustment. Whenever you press any key on your local telephone
keypad, the delayed steering (Std) output of the IC goes high on receiving the tone-pair,
causing LED5 (connected to pin 15 of IC via resistor R15) to glow. It will be high for a
duration de-pending on the values of capacitor and resistors at pins 16 and 17. The optional
circuit shown within dot-ted line is used for guard time adjustmed. The LEDs connected
via resistors R11 to R14 at pins 11 through 14, respectively, indicate the output of the IC.
The tone-pair DTMF (dual-tone multi-frequency) generated by pressing the telephone
button is converted into bi-nary values internally in the IC. The binary values are indicated
by glowing of LEDs at the output pins of the IC. LED1 represents the lowest signifi-cant
bit (LSB) and LED4 represents the most significant bit (MSB). So, when you dial a
number, say, 5, LED1 and LED3 will glow, which is equal to 0101. Similarly, for every
other number dialed on your telephone, the corresponding LEDs will glow. Thus, a non-
defective IC should indicate proper bi-nary values corresponding to the decimal number
pressed on your telephone key-pad. To test the DTMF IC 8870/KT3170, proceed as
12
follows:
Connect local telephone and the circuit in parallel to the same telephone line.
Switch on S1. (Switch on auxiliary switch S2 only if keys A, B, C, and D are to be
used.)
Now push key ‘*’ to generate DTMF tone.
Push any decimal key from the telephone keypad.
Observe the equivalent binary as shown in the table.
If the binary number implied by glowing of LED1 to LED4 is equivalent to the pressed key
number, the DTMF IC 8870 is correct Keys A, B, C, and D on the telephone keypad are used for
special signaling and are not available on standard pushbutton telephone keypads. Pin 5 of the IC
is pulled down to ground through resistor R8. Switch on auxiliary switch S2
Fig 1.1
A DTMF telephone keypad
13
1.2 Keypad
The DTMF keypad is laid out in a 4×4 matrix, with each row representing a low
frequency, and each column representing a high frequency. Pressing a single key (such as '1' )
will send a sinusoidal tone of the two frequencies (697 and 1209 hertz (Hz)). The original
keypads had levers inside, so each button activated two contacts. The multiple tones are the
reason for calling the system multi frequency. These tones are then decoded by the switching
center to determine which key was pressed.
1209 Hz 1336Hz 1633 Hz
697 Hz 1 2 3
770 Hz 4 5 6
852 Hz 7 8 9
941 Hz * 0 #
DTMF keypad frequencies
Table 1.1
14
CHAPTER-2
RAELATED WORK
2.1 IMPLEMENATION OF µVISION
2.1.1 µvision
The μ Vision IDE is, for most developers, the easiest way to create embedded system
programs. This chapter describes commonly used μ Vision features and explains how to use
them
2.1.2 General Remarks and Concepts
Before we start to describe how to use μVision, some general remarks, common to many
screens1 and to the behavior of the development tool, are presented. In our continuous effort
to deliver best-in-class development tools, supporting you in your daily work, μVision has
been built to resemble the look-and-feel of widespread applications. This approach decreases
your learning curve, such that you may start to work with μ Vision right away.
Based on the concept of windows:
μ Vision windows can be re-arranged, tiled, and attached to other screen areas or windows
respectively It is possible to drag and drop windows, objects, and variables.
15
Fig 2.1
A Context Menu, invoked through the right mouse button, is provided for most objects. You
can use keyboard shortcuts and define your own shortcuts. You can use the abundant features
of a modern editor. Menu items and Toolbar buttons are greyed out when not available in the
Current context.
Graphical symbols are used to resemble options, to mark unsaved changes, or reveal objects
not included into the project. Status Bars display context-driven information. You can
associate μVision to third-party tools
16
Fig 2.2
The Project Windows area is that part of the screen in which, by default, the Project
Window, Functions Window, Books Window, and Registers Window are displayed.
Within the Editor Windows area, you are able to change the source code, view
performance and analysis information, and check the disassembly code.
The Output Windows area provides information related to debugging, memory,
symbols, call stack, local variables, commands, browse information, and find in files results.
If, for any reason, you do not see a particular window and have tried displaying/hiding it
several times, please invoke the default layout of μVision through the Window – Reset
Current Layout Menu.
2.1.3 Positioning Windows
The μVision windows may be placed onto any area of the screen, even outside of the μVision
frame, or to another physical screen.
Click and hold the Title Bar1 of a window with the left mouse button
17
Drag the window to the preferred area, or onto the preferred control, and release the
mouse button.
Please note, source code files cannot be moved outside of the Editor Windows2.
μVision displays docking helper controls3, emphasizing the area where the window will be
attached. The new docking area is represented by the section highlighted in blue. Snap the
window to the Multiple Document Interface (MDI) or to a Windows area by moving the
mouse over the preferred control.
Keil software converts the C-codes into the Intel Hex code.
Fig 2.3
18
2.2 8051 Burner Software
Fig 2.4
PRO51 BURNER provides you with software burning tools for 8051 based
Microcontrollers in there Flash memory. The 51 BURNER tools, you can burn AT89SXXXX
series of ATMEL microcontrollers.
2.2.1 Features of PRO51
Flash Programmer for 89C1051, 89C2051, 89C4051, 89S51, 89S52, 89C51 and 89C52
micros.
Operates on single 5V supply which can be taken from USB Port of PC.
User friendly windows based Graphics User Interface.
Interfaces with PC through COM1 or COM2 serial ports.
19
2.2.2 System Requirements
PC with at least one serial and one USB ports and at least 600x800 VGA resolution.
If USB port is not available you need a regulated +5V supply.
Windows operating system
2.2.3 Package Contents
PRO51 unit
Interface Cable between PC and PRO51
CD containing PROG51 software
2.2.3Getting Started
1.Install PROG51 programs using setup from the CD. This would normally create these
programs in a program group INFONICS. You may like to create a separate folder like
INFONICS on your disk where these programs will be installed.
2.Connect PRO51 to COM port and USB on your PC using the Y cable provided with
PRO51. Follow instruction given in the following sections.
2.2.4 PROG51 User Interface
Prog51 is used for programming the 89C1051, 89C2051 and 89C4051 Microcontrollers. User
interface includes:
Load Hex/Binary file in Buffer
Save Buffer as Binary File
Display / Specify Target Device to be Programmed.
20
Com Port Selection.
Identify Target Device with the device specified by you in the designated area.
Read Microcontroller Program in Buffer
Erase Microcontroller Program Memory
Check if Target Device is Erased
Program Buffer Contents in Target device
Verify the Device contents with data in the buffer
3.Lock Target Device. Once the device is locked it can not be read or verified.
Fig 2.5
2.2.5 Procedure to Program a Chip
1. Connect the PRO51 to COM port and USB port on your PC. USB is used for +5V power
supply only. You can use regulated 5V supply and connect it on pin 4 of the 9 Pin connector.
2. Start PROG51 from your program menu.
21
3. Select appropriate com port on your PC.
4. Insert desired device in the ZIF socket on PRO51. 20 Pin devices like 89C2051 should be
aligned with the bolltom side, i.e., pin 10 on the 89C2051 should be inserted in Pin 20 of the
socket.
5. Specify the device in the target device text box.
6. Click Identify button to check if the device inserted matches with the one you specified in
the Target Device text box.
7. Load Hex or Binary file generated using compiler or assembler in the buffer.
8. Click on Erase button to erase the contents of the flash memory of the microcontroller.
Erase process will automatically be followed by a blank check.
9. Click on Program button to write the buffer contents in to the program memory of the
microcontroller. Program action will automatically be followed by a verify cycle.
10. If you wish click on Lock button to secure the device.
11. Remove the device from ZIF socket.
2.3 CONSTRUCTION AND TESTING
In the process of realizing this project, the construction was initially carried out on a
breadboard to allow for checking and to ascertain that it is functioning effectively.All
irregularities were checked then tested and found to have a satisfactory output. The
component were then removed and transferred to a Vero board strip and soldered into place
and all discontinuous point were cut out to avoid short-circuiting.
2.4 PRECAUTIONS
2.4.1 SOLDERING PRECAUTIONS
The construction was carried out with care. The precautions taken during the soldering
were:
22
The tip of soldering iron was kept clean with the help of a file from time to time.
The solder wire was of smaller thickness.
Extra solder was not used in order to avoid a cause of short circuit in the conductive path.
The overheating of components was avoided to prevent component damage as a result of
excessive heat on the components due to the heat from the soldering iron.
The leads of the components were kept clean before soldering, with the use of sand paper.
2.4.2 COMPONENTS PRECAUTION:
IR sensor used should be sensitive. Before using in the circuit it should be tested with
a multi-meter.
I.C should not be heated much while soldering; too much heat can destroy the I.C. For
safety and ease of replacement, the use of I.C socket is suggested.
While placing the I.C pin no 1 should be made sure at right hole.
Opposite polarity of battery can destroy I.C so please check the polarity before switching
ON the circuit. One should use diode in series with switch for safety since diode allows
flowing current in one direction only.
Each component was soldered neatly and clean.
We should use insulated wire.
23
CHAPTER-3
PROBLEM DESCRIPTION AND
SPECIFICATION
3.1 Problem Statement
The objective of this project is to develop a device that allows for a user to remotely control
and monitor multiple home appliances using a cellular phone. This system will be a powerful
and flexible tool that will offer this service at any time, and from anywhere with the
constraints of the technologies being applied. Possible target appliances include (but are not
limited to) climate control systems, security systems, and lights; anything with an electrical
interface.
The proposed approach for designing this system is to implement a microcontroller-
based control module that receives its instructions and commands from a cellular phone over
the GSM network. The microcontroller then will carry out the issued commands and then
communicate the status of a given appliance or device back to the cellular phone. For security
purposes, a means of identification and user authentication will be implemented, and will
combine caller identification with a password authorization.
3.2 Components Required
3.2.1 STEP DOWN TRANSFORMER
Step down transformer from 220 volt Ac to 9-0-9 ac. We use step down transformer to
step down the voltage from 220 to 9 volt ac. This AC is further connected to the rectifier
circuit for AC to DC conversion. Transformer current rating is 750 ma.
24
Fig 3.1
3.2.2 DIODE
In this project we use IN 4007 diode as a rectifier. IN 4007 is special diode to convert
the AC into DC.
In this project we use two diode as a rectifier. Here we use full wave rectifier. Output of
rectifier is pulsating DC. To convert the pulsating dc into smooth dc we use Electrolytic
capacitor as a main filter. Capacitor converts the pulsating dc into smooth dc and this DC is
connected to the Regulator circuit for Regulated 5 volt DC.
Fig 3.23.2.3 VOLTAGE REGULATOR 7805
The Digilab board can use any power supply that creates a DC voltage between 6 and 12
volts. A 5V voltage regulator (7805) is used to ensure that no more than 5V is delivered to
the Digilab board regardless of the voltage present at the J12 connector (provided that voltage
25
is less than 12VDC). The regulator functions by using a diode to clamp the output voltage at
5VDC regardless of the input voltage - excess voltage is converted to heat and dissipated
through the body of the regulator. If a DC supply of greater than 12V is used, excessive heat
will be generated, and the board may be damaged. If a DC supply of less than 5V is used,
insufficient voltage will be present at the regulators output.
Fig 3.3
3.2.4 CRYSTAL OSCILLATOR
A miniature 4 MHz quartz crystal enclosed in a hermetically sealed HC-49/US package, used
as the resonator in a crystal oscillator.
A crystal oscillator is an electronic 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/receivers.
Fig 3.4
26
3.2.5 CM8870
3.2.5.1 Features
• Complete DTMF Receiver
• Low power consumption
• Internal gain setting amplifier
• Adjustable guard time
• Central office quality
• Power-down mode
• Inhibit mode
• Backward compatible with MT8870C/MT8870C-1
3.2.5.2 Applications
• Receiver system for British Telecom (BT) or CEPT Spec (MT8870D-1)
• Paging systems
• Repeater systems/mobile radio
• Credit card systems
• Remote control
• Personal computers
• Telephone answering machine
3.2.5.3 Description
The MT8870D/MT8870D-1 is a complete DTMF integrating both the band
split filter and Digital decoder functions. The filter section uses witched
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. External component count is minimized by on chip provision of a
differential input amplifier, clock oscillator and latched three-state bus
interface.
3.2.5.4 Functional Description
27
The MT8870D/MT8870D-1 monolithic DTMF receiver offers small size, low power
consumption and high performance. Its architecture consists of a bandsplit filter section,
which separates the high and low group tones, followed by a digital counting section which
verifies the frequency and duration of the received tones before passing the corresponding
code to the output bus.
18 PIN CERDIP/PLASTIC DIP/SOIC
Fig 3.5
20 PIN SSOP/TSSOP
Fig 3.6
28
3.2.5.5 PIN DESCRIPTIONS
Table 3.1
The CM8870/70C decoder uses a digital countingtechnique to determine the frequencies
of the limited tones and to verify that these tones correspond to standard DTMF frequencies.
A complex averaging algorithm is used to protect against tone simulation by extraneous
signals (such as voice) while providing tolerance to small frequency variations. The
averaging algorithm has been developed to ensure an optimum combination of immunity to
“talk-off” and tolerance to the presence of interfering signals (third tones) and noise. When
the detector recognizes the simultaneous presence of two valid tones (known as “signal
29
condition”), it raises the “Early Steering” flag (ESt). Any subsequent loss of signal condition
will cause ESt to fall.
3.2.6 RELAYS
In order to enable a circuit to be isolated from the system only under faulty conditions,
protective relays are used. In normal cases, it is open circuit relay. The relay is usually
provided with 4 terminals, two of which are connected to relay winding and other two are
connected to the circuit to be controlled. It has following characteristics :
Sensitivity
Speed
Selectivity
3.2.6.1 TYPES OF RELAYS :
Electromagnetic Attraction Type : These relays are actuated by DC or AC
quantities.
Electromagnetic Induction Type : It’s operation depends upon EMI phenomena.
Thermal Relays : It’s operation depends upon the heating effect of electric Current.
Distance Relays : It’s operation depends upon the ratio of voltage to current.
3.2.6.2 ELECTROMAGNETIC RELAY :
These relays are electromagnetically operated. The parts of these relays are an iron
core & its surrounding coil of wire. An iron yoke provides a low reluctance path for magnetic
flux, the yoke being shaped so that the magnetic circuit can be closed by a movable piece of
iron called the armature, and a set of contacts. The armature is hinged to the yoke and is held
by a string in such a way that there is an air gap in the magnetic circuit. Figure shows the
principle of operation of this relay. When an electric current flows in the coil, the armature is
attracted to the iron core. Electrical switching contacts are mounted on the armature. When
the armature coil is energized, these movable contacts break their connections with one set of
fixed contacts and close a connection to a previously open contact. When electric power is
removed from the relay coil, spring returns the armature to its original position.
Standard voltages for D.C. relay are 6,12,24,48 & 110 volts and for A.C. relays are
6,12,24,48,120 & 240 volts.
30
Basic Diagram Showing the Operating Principle of a Relay
Fig 3.7
3.2.7 CAPACITOR
A capacitor is an electrical/electronic device that can store energy in the electric field
between a pair of conductors (called "plates"). The process of storing energy in the capacitor
is known as "charging", and involves electric charges of equal magnitude, but opposite
polarity, building up on each plate.
Capacitors are often used in electric and electronic circuits as energy storage devices. They
can also be used to differentiate between high frequency and low-frequency signals This
property makes them useful in electronic filters.
Fig 3.8
3.2.8 RESISTOR
A resistor is a two-terminal electrical or electronic component that opposes an electric
current by producing a voltage drop between its terminals in accordance with Ohm's law: The
electrical resistance is equal to the voltage drop across the resistor divided by the current
31
through the resistor while the temperature remains the same. Resistors are used as part of
electrical networks and electronic circuits.
Fig 3.9
3.2.9 MICROCONTROLLER AT89S52
3.2.9.1 Features
8K Bytes of In-System Programmable (ISP) Flash Memory
4.0V to 5.5V Operating voltage.
Fully Static Operation: 0 Hz to 33 MHz
256 * 8-bit Internal RAM
32 Programmable I/O Lines
Three 16-bit Timer/Counters
Eight Interrupt Sources
Full Duplex UART Serial Channel
Interrupt Recovery from Power-down Mode
Power-off Flag
Fast Programming Time
Flexible ISP Programming
3.2.9.2 Description
The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K
bytes of in-system programmable Flash memory. The device is manufactured using Atmel’s
32
high-density nonvolatile memory technology and is compatible with the indus-try-standard
80C51 instruction set and pinout. The on-chip Flash allows the program memory to be
reprogrammed in-system or by a conventional nonvolatile memory programmer. By
combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip,
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. The Idle Mode stops the CPU while allowing the
RAM, timer/counters, serial port, and interrupt system to continue functioning. The Power-
down mode saves the RAM con-tents but freezes the oscillator, disabling all other chip
functions until the next interrupt or hardware reset.
3.2.9.3 Pin Description
33
Fig 3.10
VCC Supply voltage.
GND Ground.
Port 0 Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin can
sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high-
impedance inputs. Port 0 can also be configured to be the multiplexed low-order
address/data bus during accesses to external program and data memory. In this mode, P0
has internal pull-ups. Port 0 also receives the code bytes during Flash programming and
outputs the code bytes during program verification. External pull-ups are required
during program verification
Port 1 Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 output
buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are
pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that
are externally being pulled low will source current (IIL) because of the internal pull-ups.
In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external count input
(P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively, as shown in the
following table. Port 1 also receives the low-order address bytes during Flash
programming and verification.
Port 2 Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 2 output
buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are
pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that
are externally being pulled low will source current (IIL) because of the internal pull-ups.
Port 2 emits the high-order address byte during fetches from external program memory
and during accesses to external data memory that use 16-bit addresses (MOVX @ DPTR).
In this application, Port 2 uses strong internal pull-ups when emitting 1s. During accesses
to external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents
of the P2 Special Function Register. Port 2 also receives the high-order address bits and
some control signals during Flash programming and verification.
Port 3 Port 3 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 3 output
buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are
pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that
are externally being pulled low will source current (IIL) because of the pull-ups. Port 3
34
receives some control signals for Flash programming and verification. Port 3 also serves
the functions of various special features of the AT89S52.
RST Reset input. A high on this pin for two machine cycles while the oscillator is
running resets the device. This pin drives high for 98 oscillator periods after the Watchdog
times out. The DISRTO bit in SFR AUXR (address 8EH) can be used to disable this
feature. In the default state of bit DISRTO, the RESET HIGH out feature is enabled.
ALE/PROG Address Latch Enable (ALE) is an output pulse for latching the low byte of
the address during accesses to external memory. This pin is also the program pulse input
(PROG) during Flash programming. In normal operation, ALE is emitted at a constant rate
of 1/6 the oscillator frequency and may be used for external timing or clocking purposes.
Note, however, that one ALE pulse is skipped dur-ing each access to external data
memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH.
With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the
pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller
is in external execution mode.
PSEN Program Store Enable (PSEN) is the read strobe to external program memory.
When the AT89S52 is executing code from external program memory, PSEN is activated
twice each machine cycle, except that two PSEN activations are skipped during each
access to external data memory.
EA/VPP External Access Enable. EA must be strapped to GND in order to enable the
device to fetch code from external program memory locations starting at 0000H up to
FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on
reset. EA should be strapped to VCC for internal program executions. This pin also
receives the 12-volt programming enable voltage (VPP) during Flash programming.
XTAL1 Input to the inverting oscillator amplifier and input to the internal clock operating
circuit.
XTAL2 Output from the inverting oscillator amplifier.
35
3.2.9.4 Block Diagram
Fig 3.11
The 89S52 has 4 different ports, each one having 8 Input/output lines providing a total of
32 I/O lines. Those ports can be used to output DATA and orders do other devices, or to read
the state of a sensor, or a switch. Most of the ports of the 89S52 have 'dual function' meaning
that they can be used for two different functions.
The first one is to perform input/output operations and the second one is used to
implement special features of the microcontroller like counting external pulses, interrupting
the execution of the program according to external events, performing serial data transfer or
connecting the chip to a computer to update the software. Each port has 8 pins, and will be
treated from the software point of view as an 8-bit variable called 'register', each bit being
connected to a different Input/Output pin.
36
There are two different memory types: RAM and EEPROM. Shortly, RAM is used to
store variable during program execution, while the EEPROM memory is used to store the
program itself, that's why it is often referred to as the 'program memory'. It is clear that the
CPU (Central Processing Unit) is the heart of the micro controllers. It is the CPU that will
Read the program from the FLASH memory and Execute it by interacting with the different
peripherals.
3.2.9.5 8051 Instruction Set
i. Arithmetic Operations
Mnemonic Description Size Cycles ADD A,Rn Add register to Accumulator (ACC). 1 1
ADD A,direct Add direct byte to ACC. 2 1
ADD A,@Ri Add indirect RAM to ACC . 1 1
ADD A,#data Add immediate data to ACC . 2 1 ADDC A,Rn Add register to ACC with carry . 1 1
ADDC A,direct Add direct byte to ACC with carry. 2 1
ADDC A,@Ri Add indirect RAM to ACC with carry. 1 1
ADDC A,#data Add immediate data to ACC with carry. 2 1
SUBB A,Rn Subtract register from ACC with borrow. 1 1 SUBB A,direct Subtract direct byte from ACC with borrow 2 1
SUBB A,@Ri Subtract indirect RAM from ACC with borrow. 1 1
SUBB A,#data Subtract immediate data from ACC with borrow. 2 1
INC A Increment ACC. 1 1
INC Rn Increment register. 1 1 INC direct Increment direct byte. 2 1
INC @Ri Increment indirect RAM. 1 1
DEC A Decrement ACC. 1 1
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DEC Rn Decrement register. 1 1
DEC direct Decrement direct byte. 2 1
DEC @Ri Decrement indirect RAM. 1 1 INC DPTR Increment data pointer. 1 2
MUL AB Multiply A and B Result: A <- low byte, B <- high byte. 1 4
DIV AB Divide A by B Result: A <- whole part, B <- remainder. 1 4
DA A Decimal adjust ACC. 1 1
ii. Logical Operations
Mnemonic Description Size Cycles
ANL A,Rn AND Register to ACC. 1 1
ANL A,direct AND direct byte to ACC. 2 1
ANL A,@Ri AND indirect RAM to ACC. 1 1 ANL A,#data AND immediate data to ACC. 2 1
ANL direct,A AND ACC to direct byte. 2 1
ANL direct,#data AND immediate data to direct byte. 3 2
ORL A,Rn OR Register to ACC. 1 1
ORL A,direct OR direct byte to ACC. 2 1 ORL A,@Ri OR indirect RAM to ACC. 1 1
ORL A,#data OR immediate data to ACC. 2 1
ORL direct,A OR ACC to direct byte. 2 1
ORL direct,#data OR immediate data to direct byte. 3 2
XRL A,Rn Exclusive OR Register to ACC. 1 1 XRL A,direct Exclusive OR direct byte to ACC. 2 1
XRL A,@Ri Exclusive OR indirect RAM to ACC. 1 1
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XRL A,#data Exclusive OR immediate data to ACC. 2 1
XRL direct,A Exclusive OR ACC to direct byte. 2 1
XRL direct,#data XOR immediate data to direct byte. 3 2 CLR A Clear ACC (set all bits to zero). 1 1
CPL A Compliment ACC. 1 1
RL A Rotate ACC left. 1 1
RLC A Rotate ACC left through carry. 1 1
RR A Rotate ACC right. 1 1 RRC A Rotate ACC right through carry. 1 1
SWAP A Swap nibbles within ACC. 1 1
iii. Data Transfer
Mnemonic Description Size Cycles MOV A,Rn Move register to ACC. 1 1
MOV A,direct Move direct byte to ACC. 2 1
MOV A,@Ri Move indirect RAM to ACC. 1 1
MOV A,#data Move immediate data to ACC. 2 1
MOV Rn,A Move ACC to register. 1 1 MOV Rn,direct Move direct byte to register. 2 2
MOV Rn,#data Move immediate data to register. 2 1
MOV direct,A Move ACC to direct byte. 2 1
MOV direct,Rn Move register to direct byte. 2 2
MOV direct,direct Move direct byte to direct byte. 3 2 MOV direct,@Ri Move indirect RAM to direct byte. 2 2
MOV direct,#data Move immediate data to direct byte. 3 2
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MOV @Ri,A Move ACC to indirect RAM. 1 1
MOV @Ri,direct Move direct byte to indirect RAM. 2 2
MOV @Ri,#data Move immediate data to indirect RAM. 2 1 MOV DPTR,#data16 Move immediate 16 bit data to data pointer register. 3 2
MOVC A,@A+DPTR Move code byte relative to DPTR to ACC (16 bit address). 1 2
MOVC A,@A+PC Move code byte relative to PC to ACC (16 bit address).1 2
MOVX A,@Ri Move external RAM to ACC (8 bit address) . 1 2
MOVX A,@DPTR Move external RAM to ACC (16 bit address). 1 2 MOVX @Ri,A Move ACC to external RAM (8 bit address). 1 2
PUSH direct Push direct byte onto stack. 2 2
POP direct Pop direct byte from stack. 2 2
XCH A,Rn Exchange register with ACC. 1 1
XCH A,direct Exchange direct byte with ACC. 2 1 XCH A,@Ri Exchange indirect RAM with ACC. 1 1
XCHD A,@Ri Exchange low order nibble of indirect
RAM with low order nibble of ACC 1 1
iv. Boolean Variable Manipulation
Mnemonic Description Size Cycles
CLR C Clear carry flag. 1 1
CLR bit Clear direct bit. 2 1
SETB C Set carry flag. 1 1 SETB bitSet direct bit 2 1
CPL C Compliment carry flag. 1 1
CPL bit Compliment direct bit. 2 1
ANL C,bit AND direct bit to carry flag. 2 2
ANL C,/bit AND compliment of direct bit to carry. 2 2
40
ORL C,bit OR direct bit to carry flag. 2 2
ORL C,/bit OR compliment of direct bit to carry. 2 2
MOV C,bit Move direct bit to carry flag. 2 1
MOV bit,C Move carry to direct bit. 2 2
JC rel Jump if carry is set. 2 2 JNC rel Jump if carry is not set. 2 2
JB bit,rel Jump if direct bit is set. 3 2
JNB bit,rel Jump if direct bit is not set. 3 2
JBC bit,rel Jump if direct bit is set & clear bit. 3 2
v. Program Branching
Mnemonic Description Size Cycles
RET Return from subroutine. 1 2 RETI Return from interrupt. 1 2
SJMP rel Short jump (relative address). 2 2
JMP @A+DPTR Jump indirect relative to the DPTR. 1 2
JZ rel Jump relative if ACC is zero. 2 2
JNZ rel Jump relative if ACC is not zero. 2 2 CJNE A,direct,rel Compare direct byte to ACC and jump if not equal. 3 2
CJNE A,#data,rel Compare immediate byte to ACC and jump if not equal.3 2
CJNE Rn,#data,rel Compare immediate byte to register and jump if not equal.3 2
CJNE @Ri,#data,rel Compare immediate byte to indirect and jump if not equal.3 2
DJNZ Rn,rel Decrement register and jump if not zero. 2 2 DJNZ direct,rel Decrement direct byte and jump if not zero. 3 2
41
CHAPTER-4
SYSTEM DESIGN
This system is designed for controlling the devices, it includes a cell phone which is
connect to the system via head set. To active the cellular phone part of the system a call is to
be made and as the call is answered, in response the user would enter a three/four(as he/she
want) digit password to access the system to control devices. As the caller press the specific
password, it results in turning ON or OFF specific device. The device switching is achieved
by Relays.
4.1 Design characteristics
First of all a short list of embedded control system design characteristics and their
application to the current subject of home/building automation systems. These are the
characteristics a design engineer has to keep in mind when designing such an automation
system:
4.2 About DTMF IC 8870 - Dual Tone Multi Frequenc
Fig 4.1
The M-8870 is a full DTMF Receiver that integrates both band split filter and decoder
functions into a single 18-pin DIP or SOIC package. Manufactured using CMOS process
technology, the M-8870 offers low power consumption (35 mW max) and precise data
handling. Its filter section uses switched capacitor technology for both the high and low
42
group filters and for dial tone rejection. Its decoder uses digital counting techniques to detect
and decode all 16 DTMF tone pairs into a 4-bit code. External component count is minimized
by provision of an on-chip differential input amplifier, clock generator, and latched tri-state
interface bus. Minimal external components required include a low-cost 3.579545 MHz color
burst crystal, a timing resistor, and a timing capacitor. An MT8870 series DTMF decoder is
used here. All types of the MT8870 series use digital counting techniques to detect and
decode all the 16 DTMF tone pairs into a 4-bit code output. The built-in dial tone rejection
circuit eliminates the need for pre-filtering. When the input signal given at pin 2 (IN-) in
single-ended input configuration is recognized to be effective, the correct 4-bit decode signal
of the DTMF tone is transferred to Q1 (pin 11) through Q4 (pin 14) outputs.
4.3 Interfacing DTMF 8870 IC 8051 Microcontroller
Fig 4.2
43
In Interfacing DTMF 8870 is very simple but is should be done with proper care about
the circuit designing. Here we will discuss simple project of caller id with 8051
Microcontroller. This Project can be used in home, shops, offices. This keep an eye on every
incoming number on the selected telephone line. Basically it is the built in caller id system.
When telephone rings it displays the telephone number on the LCD screen attached with the
circuit. 8051 Microcontroller is responsible for every operation in the given project from
controlling DTMF IC and LCD. DTMF is also called as Multi Frequency Signaling because
for each key you press two tones of specific frequencies are generated. This is done so that a
voice cannot imitate the tones. One tone is generated from a high frequency group and the
other from a low frequency group.
DTMF decoder ic 8870 here we are using in our project for designing Caller ID system.
It's very simple circuit using DTMF decoder MT8870 (or CM8870). As shown here. When
incoming call comes it interrupts the microcontroller and microcontroller decodes the number
and display it on the microcontroller. In our circuit output of DTMF is connected to INT of
the microcontroller which is the interrupt service routine. DTMF is functions in such a way
that when incoming call comes the pins of 8870 from 11-14 are activated and tells the
incoming numbers. Microcontroller is direct connected with these pins. So Microcontroller
gets the incoming number and process for displaying on the LCD screen or LED.
4.4 SYSTEM DESIGN
4.4.1 Design values for CM8870
1.The DTMF tones from the mobile phone on the receiver side are given to a differential
amplifier whose gain can be varied by connecting a feedback resistor from pin no. 3(which is the output of
op-amp) of CM8870.In our application the required gain is unity so we select,
R1=100Kohms
R2=100Kohms
=>Gain=R2/R1=1.
44
2.The internal clock circuit of CM8870 is completed with addition of a ceramic
resonator having resonant frequency of 3.58MHz.The internal clock circuit of CM8870 is
completed with addition of a ceramic resonator having resonant frequency of 3.58MHz.
3.Before the registration of a decoded tone pair, the receiver (CM8870) checks for a valid
signal duration (duration for which a key is pressed by the remote user).This check is performed by an
external RC time constant driven by E.The minimum time duration for which a key should be pressed
to validate itself is decided by R 3& C3.There values aredecided by the formula:
Trec=Tdp+Tgtp
Where,
Tgtp=0.67*R 3*C3
Tdpis the time to detect the presence of a valid signal. So it is a parameter of the device.trecis the minimum
time duration for which a key must be pressed by the remote user for validation.
For,
trec= 40ms
R 3=300Kohms
C3=0.1uf
4.TOE(pin no. 10 of CM8870)->This is the Tone Output Enable. A low level shifts Q1-Q4
toits high impedance state. A high level makes the binary output available on the output pins(Q1-Q4).
4.5 Design values for Microcontroller (AT89S52):
1.Port 1 of the microcontroller is made an input port by writing all one’s to it, and port 0 is the
output port which is connected to the relay driver IC (U3).
2.The reset pin of U2 (pin no. 9) is connected to the reset circuit ie,
R 4=10Kohms
C5=10uf
4.6 Components List:
To build and access this project the requisites are:
1.Transformerwith turns ratio 230:15.
2.A voltage regulator IC(7805)
3.2 diodes(1N4007)
4. 1 electrolytic capacitorsof 470uf.
5. 4 ceramiccapacitors, 2 of value 33pf and 2 of 0.1uf.
45
6. 4 Resistances: 100 Kohms (2 q)
300 Kohms(1q)
10 Kohms(1q)
7. 2 crystals: 3.58MHz12MHz
8. 4 two pinrelimates(male and female).
9. Two phones-We need one cell phone with auto answer facility on the receiver side and one phone(which
can either be a cell phone or land line) with the remote user.
10. A Chord with a male connector-We need a chord with a male connector connected onone side and one end left
open. The dimensions of the connector should be same as thedimensions of the jack present in the phone with
the control unit. (In our case we used a 3.5mm jack)
11.DTMF tone decoding IC-IC for converting DTMF toness to their respective binaryvalues. We used CM8870.
12. Microcontroller-AT89s52 microcontroller.
13.Relay deriver IC- ULN 2803
14.Two relays of 5v driving voltage each.
15.Two bulbs of power rating 25Watts.
4.7 IMPLEMENTATION OF SYSTEM
4.7.1 System Algorithm:
1. Person who wants to switch on/off a device calls on the phone at the receiver side.
2. The call gets answered automatically if it is not picked up manually till 5seconds.
3. Once the call gets answered we have to enter a password for authentication (in our case it
is1 2).
4. Then after entering the password we have to make a choice for switching on/off any device
(Press ‘*’ for switch on and ‘#’ for switch off).
5. Then we have to enter the corresponding number for a device that we wish to switch
on/off (‘6’ for first device and ‘7’ for the second).
6. After switching on/off device once, if we again want to switch on/off a device than
weagain have to enter the password and repeat the whole procedure. Note:On the transmitter
side the user controlling the appliance’s has to press each digit for aminimum duration of
time, which is40ms
46
.
4.7.2 Program algorithm:
1. On start of the system all the devices are off.
2. If a key press is detected, program goes to 3, else it stays here.
3. If the pressed key is 1 then program goes to 4, else it goes to 2.
4. If 2 is pressed (correct password) program goes to 5,else it goes to 2.
5. Now the microcontroller checks whether you want to switch on/off the device.
4.8 Performance and evaluation of the system
1. The receiver must reside in a location where a signal with sufficient strength can be
received from a cellular phone network.
2. The only person who can communicate with the control module is the person who will be
successfully authenticated.
3. Only devices with electrical controlling input ports will be possible targets for control.
4. The receiver must have a power source (230V) attached at all times.
47
CHAPTER 5
VERIFICATION AND VALIDATION
5.1 FLOWCHART
The implementation of the project follows a flowchart that has been described in details
which follows the sequence:
1. Ports of microcontroller are set
i. Port A is set as input for DTMF signal.
ii. Port B is set as output for switching relays.
2. Call is established between the remote station phone and phone attached to DTMF system.
3. The phone is in auto pickup mode.
4. DTMF Decoder decodes the DTMF signal into binary form and sends to microprocessor
for further action.
5. Process is as follows
i. If 9 is pressed all the appliances will be turned off.
ii. If 1 is pressed once relay 1 will be turned on.
iii. If 1 is pressed twice relay 1 will be turned off.
iv. If 2 is pressed once relay 2 will be turned on.
v. If 2 is pressed twice relay 2 will be turned off and so on.
6. After that microprocessor will check if the is on hook or not, if not it will wait for next
instruction.
48
CHAPTER 6
CRITICAL EVALUATION
6.1 APPLICATIONS OF HOMEAUTOMATION USING DTMF
There are numerous application areas of home automation using DTMFThe purpose of
this Application Note is to provide information on the operation and application of DTMF a
few of which are outlined below:
6.1.1 Effective control of home appliances
Effective control of home appliances like Air Conditioners, Water Heaters, Thermal
Baths, Furnaces Incubators. Home appliances control, Hotel lights/ fans Control, Shops and
Showrooms appliances control, Industrial appliances etc.
6.1.2 Turn Your Webcam into a Security Camera
Instead of installing a surveillance camera you can always use the webcam for keeping
track on your children as it can successfully perform the activity of taking note of all
activities. Also it is cheap and very minute and the activities can be checked with the help of
the internet.
6.1.3 Install a Wireless Intercom
You are busy eating your food and suddenly you see the vegetables are over. You call
out to your spouse to give you some who is busy in some work. You have to scream at the
top of your voice which is very embarrassing. Instead of shouting you could simply attach a
wireless intercom and call out to her and ask her for the vegetable. In this way you can save
your energy and time too.Its visible around us that crime is on the increase, families are
beginning to aim at purchasing security alarm systems for their homes. Home Automation adds a
extra sense of security to your home, using the automation system you can monitor your homes
security cameras using a remote device.
49
6.1.4 Capture Party Moments without using your Digital Camera or DSLR
The best way to capture party moments without your DSL would be with the help of a
webcam. Set the time and let it go on capturing videos and images. There are software’s
available for windows. The software helps in saving the captured pictures as JPEG files. In
that case you no more need to worry to take your camera along if you have a webcam with
you.
6.1.5 Use Automatic Sprinklers to Water your Garden
You can make your own DIY automatic sprinkler that will reduce your effort of dragging
the sprinklers out in the garden. Again you can set a time so that the sprinkler automatically
sprinkles water in the yard at the set time.
6.2 LIMITATIONS OF HOMEAUTOMATION USING DTMF
6.2.1 Number of appliances is limited
DTMF is limited to 16 pairs of tones because it was developed for telephone keypads and
the largest foreseeable matrix size I guess was 4 x 4 - this means 16 and there is no chance of
extending this because the chipsets used are not going to be revamped.
6.2.2 No security
Anyone can control the appliances by calling the mobile connected to module. This is
just a limitation in the foresight of the guy writing the article you linked - he envisaged 16
appliances that could be controlled remotely corresponding to the 16 keys. Why not use two
key-presses to activate an appliance - this technique is only limited by the ability of the user
to remember the codes AND why not have it password protected so, when you "connect" thru
to the telephone decoder the microcontroller won't allow any activation or deactivation
without a 4 digit code being entered.
6.2.3 Human Error
50
If the equipment is not handled & installed safely, this can lead to the equipment being
damaged, and the risk of the system crashing is high.
6.2.4 Reliability
This occurs on a very rare occasions, depending on the age of the equipment it can have a
effect on the system, but otherwise the technology in the home automation systems are all up
to date.
6.2.5 Other limitations of home automation
The receiver must reside in a location where a signal with sufficient strength can be
received from a cellular phone network.
The only person who can communicate with the control module is the person who
will be successfully authenticated.
Only devices with electrical controlling input ports will be possible targets for control.
The controlled devices will have I/O ports that will make communication with the
receiver possible.
The receiver must have a power source (120V) attached at all times.
Operation of the controlling unit is only possible through a cell phone with SMS
messaging capabilities.
The controlling unit must be able to receive and decode SMS messages.
51
CONCLUSION
This Project presented a method to control home appliances using mobile phone and DTMF
decoder. DTMF tone is generated by pressing the keypad buttons of the mobile phone.The
extensive capabilities of this system are what make it so interesting. From the convenience of
a simple cell phone, a user is able to control and monitor virtually any electrical device in a
household. This makes it possible for users to rest assured that their belongings are secure,
that the garage door is shut, and that the television was not left running when they left the
house to just list a few of the many uses of this system. The end product will have a simplistic
design making it easy for users to interact with. This will be essential because of the wide
range of technical knowledge that homeowners have.
The popularity and availability of the mobile and mobile network makes this kind of control
very useful and powerful. The main advantages of the proposed system are its reliability, low
cost, and wide area coverage. Future works for this system can be following
- Adding SMS message to carry controlling commands as alternate way for DTMF tone.
- Upgrading the system to control more than one machine at same time.
52
REFRENCES
9.1 BOOKS REFFERED
1. Introduction to Telecommunications Network Engineering By Tarmo Anttalainen
Artech House, 01-Jan-2003 - Technology & Engineering.
2. Voice over IP Fundamentals By Davidson Jonathan, Publication- Pearson Education
India, 01-Sep-2008.
3. Introduction to Telecommunications By Anu A. Gokhale , Publication- Cengage
Learning, 2004.
4. Digital Signal Processing-Sie By Mitra, Publication- Tata McGraw-Hill Education
5. Digital Signal Processing By J.S.Chitode, Publication- Technical Publications, 01-Jan-
2008.
6. Exploring C for Microcontrollers: A Hands on Approach , Publication-Springer Science
& Business Media, 31-May-2007.
7. Microcontrollers: Principles and Applications By Ajit Pal, Publication- PHI Learning
Pvt. Ltd., 2012.
9.2 RESEARCH PAPERS
1. Remote Control System through Mobile and DTMF By Abdiweli Abdillahi Soufi1,
Information Technology College. Sudan University of Science and Technology,2000
2. Gaurav Thakur ,DTMF Remote Appliance Control System Using Mobile Phone, New
York, Oct 2013.
9.3 WEBSITES
1. http://www.atmel.com/devices/at89s52.aspx
2. http://www.wvshare.com/datasheet_html/AT89S52-PDF.html
3. http://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling
4. http://www.smerobot.org/08_scientific_papers/papers/Calcagno_et-al_ISR-Robotik06.pdf
5. http://www.datasheetdir.com/NATIONAL-DM74LS373+Latches
6. http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Dual-tone_multi-frequency.html
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APPENDIX
RESEARCH PAPERS
54
55
