The document describes a DTMF based home automation project that allows controlling electronic devices in a home remotely from a mobile phone. The system uses DTMF tones detected from a receiver mobile phone connected to a circuit board that decodes the tones and operates relays connected to devices like fans, TVs and lights. When buttons on a transmitter mobile phone are pressed, the corresponding DTMF tones trigger the appropriate relays through decoding and logic circuits on the board. The project aims to provide remote control of appliances using mobile phones for convenience and automation.
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Dtmf home automation_report
1. DTMF BASED HOME AUTOMATION
(Project report for completion of B.Sc General Practical Exam)
Under gratitude guidance of
ARIJIT SARKAR
at
RAMAKRISHNA MISSION VIDYAMANDIRA
BELUR MATH , HOWRAH
SUBMITTED BY
AKASH PAREEK
BASUDEB ROY
SUBIR SARKAR
APRIL , 2016
2. ACKNOWLEDGEMENT
At this level of understanding it is often difficult to understand the wide spectrum of
knowledge without proper guidance and advice. Hence, we take this opportunity to
express our heartfelt gratitude to our project guide Arijit Sarkar who had faith in us
and allowed us to work on this project.
We would like to thanks Prof. Arnab kumar Ghoshal (H.O.D Computer Science
and Electronics) Prof. Goutam Bhattacharya for there immense interest, valuable
guidance, constant inspiration and kind co-operation throughout the period of work
undertaken, which has been instrumented in the success of our project.
We also acknowledge our profound sense of gratitude to all the teachers who have
been instrumental for providing us the technical knowledge and moral support to
complete the project with full understanding.
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.
AKASH PAREEK
BASUDEB ROY
SUBIR SARKAR
Date:14/04/16
3. RAMAKRISHNA MISSION VIDYAMANDIRA
( A Residential Autonomous Degree College under Calcutta University)
Belur Math-711202, Howrah, West Bengal
CERTIFICATE
This is to cerify that Mr. Akash Pareek (170), Mr. Basudeb Roy (209) and
Mr. Subir Sarkar (111) has completed the project entitled “DTMF HOME
BASED AUTOMATION” for completion of B.Sc Electronics General
practical exam at Ramakrishna Mission Vidyamandira.
PROJECT GUIDE HOD BOARD OF EXAMINER
4. TABLE OF CONTENTS
TITLE
Abstract
Introduction
Block diagram
System Components
DTMF
DTMF code
How to detect DTMF code
DTMF detection method
DTMF code to binary code
Binary to decimal decoder
Crystal Oscillator
Relay
Circuit
Working
Costing
Future scope
Bibliography
5. 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 uses the Dual-Tone Multi Frequency (DTMF) technique used in
telephones, to control multi electronic devices from long distances using the mobile
phone. A practical application case for this system was implemented to control three
electronic devices. A test to detect the DTMF signal received from different mobile
phones was also carried out. The automation features of this work makes it possible
for homeowners to remotely control a large number of appliances,such as TV
,AC,Fan ,light,bulb and many more using there mobile phone.
6. INTRODUCTION
The remote control used in home automation systems, is a wonderful feature that
everyone would like to enjoy, if they were not expensive to install, maintain, and able
to be use from long distance. With such automation one can switch ON and OFF
lights , Ac etc from a remote distance. In our project we have tried to implement this
home automation techinque using DTMF.
BLOCK DIAGRAM
7. SYSTEM COMPONENTS
DTMF
DTMF stands for dual tone multiple frequency. DTMF is a term which used in
telephone industry. When any key on telephone or mobile phone is pressed one tone
is generated and it is audible which is nothing but a DTMF tone.
DTMF CODE
When any of the key like “1”, “2”, “*”, “#” etc is pressed particular code is
transmitted. This code is consist of two frequency among which one is higher
frequency and second one is lower frequency. Following table shows the combination
of frequency for respected keys.
According to above table “8” is combination of lower frequency of 852 Hz and
higher frequency of 1336 Hz and “#” is of lower frequency of 941 Hz and higher
frequency of 1447 Hz.
HOW TO DETECT DTMF CODE
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. This IC can be used to encode the DTMF
code.
8.
9. DTMF Detection Method
The scheme used to identify the two frequencies associated with the button that has
been pressed is shown in the figure below. Here, the two tones are first separated by a
low pass and a high pass filter. The passband cutoff frequency of the low pass filter is
slightly above 100 Hz, whereas that of the high pass filter is slightly below 1200 Hz.
The output of each filter is next converted into a square wave by a limiter and then
processed by a bank of bandpass filters with narrow passbands. The four bandpass
filters in the low-frequency channel have center frequencies at 697 Hz, 770 Hz, 852
Hz, and 941 Hz. The four band pass filters in the high-frequency channel have center
frequencies at 1209 Hz, 1336 Hz, 1477 Hz, and 1633 Hz. The detector following each
band pass filter develops the necessary dc switching signal if its input voltage is
above a certain threshold.
10. DTMF Code to Binary Code
The MT8870 IC produces a equivalent binary code whenever it receives a valid tone
pair .The binary code is the output of the button pressed from the mobile keypad.The
table below shows the DTMF data and the binary code associated with it.
BINARY TO DECIMAL DECODER
A decoder is a circuit that changes a code into some corresponding set of signals.A
binary to decimal decoder is a circuit which converts binary code to its equivalent
decimal form.In our circuit we have used a 4*16 binary to decimal decorder IC
whose input is the Binary code output obtained from converting the DTMF code . A
fairly popular 4*16 decoder IC with 24 pins is sn74154.IC sn74154 is given below
where the decimal outputs are 0,1,2,.....,15 and A,B,C,D are binary inputs. G1 and
G2 are always connected to high.IC 74154 gives low output.
11. The above figure is a typical relay device which have different parts.NC(normally
closed) and NO(normally open) are two modes by which the secondary circuit can be
operated.To trigger the secondary circuit the small current from the primary circuit is
feeded to one of the terminals A and B and the other terminal is connected to Vcc.
Pole is the input pin for bigger current circuit.
CRYSTAL OSCILLATORS
An electronic circuit that is used to generate an electrical signal of precise frequency
by utilizing the vibrating crystal’s mechanical resonance made of piezoelectric
material. There are different types of piezoelectric resonators, but typically, quartz
crystal is used in these types of oscillators. Hence, these oscillator electronic circuits
are named as crystal oscillators.
Crystal oscillator circuit works on the principle of the inverse piezoelectric effect, i.e.,
a mechanical deformation is produced by applying an electric field across certain
materials. Thus, it utilizes the vibrating crystal’s mechanical resonance which is made
of a piezoelectric material for generating an electric signal of a specific frequency.
12. RELAY
Many sensors are extremely sensitive type of electronic components and produce
only small output currents. But we need to drive bigger electrical machines using
these sensors. Relay makes it possible for small current to trigger bigger current
circuits. A relay is an electromagnetic switch , which is activated when a small
current is passed through it.
The above figure is a typical relay device which have different parts.NC(normally
closed) and NO(normally open) are two modes by which the secondary circuit can be
operated.To trigger the secondary circuit the small current from the primary circuit is
feeded to one of the terminals A and B and the other terminal is connected to Vcc.
Pole is the input pin for bigger current circuit.
13. CIRCUIT
The above circuit is configured to operate on three appliances which are connected to
the relay circuit. Suppose that the appliances are Fan , Tv and Bulb. Our circuit can
be operated by any mobile phone with same basic knowledge as how to ON and OFF
various appliances. We have used eight buttons in our circuit, namely
1,2,3,4,5,6,7and 8. What does this button does?
We have configured it in such a way that when a user presses 1 or 3 or 5 in the
trasmitter mobile Fan , Tv and Bulb are ON respectively. When 2 or 4 or 6 is pressed
Fan , Tv, Bulb are OFF respectively. The other two buttons 7 and 8 are used to ON all
the appliances when 7 is pressed and OFF all the appliances when 8 is pressed.
Now if someone has forget to off the Fan he just need to call the receiver mobile
which is always in automatic receive call mode and press 2, the fan will be off
14. nomatter from how far the person is calling. If we want to ON only Tv and bulb then
we can either press 3 and 5 or 7 and 2.When 3 is pressed Tv is ON and when 5 is
pressed Bulb is ON. But when 7 is pressed all Fan ,Tv ,Bulb is ON and by pressing 2
the Fan goes OFF making only Tv and Bulb in ON mode.
WORKING
There are two mobile phones used in the circuit one works as a receiver and other as
trasmitter. The receiver mobile in connected to the circuit via a headphone. One of the
two wires of the headphone is connected to pin2(IN-) and pin3(GS) of the DTMF
decoder IC MT8870 and the other is grounded. A 3.579545MHz crystal oscillator is
connected to pin7(OSC1) and pin8(OSC2) of MT8870.Pin16(ESt) and pin17(St) are
connected to Vcc via 0.1µF and 390kΩ resistance.
When the trasmitter sends a valid tone data.The receiver detects the frequency pair
and gives the appropriate binary code as the output of the DTMF decoder IC.The
binary output can be obtained by pin11 to pin14.
The data detected so far is a binary data and need to be converted to its proper
decimal form.This conversion from binary to decimal is done by a 4*16 decoder IC
sn74154.The input of the IC74154 is the binary code obtained from the DTMF
decoder.
Flip-flops are used to store the data given by the user from the trasmitter mobile.
Pin15(Std) of MT8870 works as clock for the flip-flops.
In the above circuit 1, 3, 5 of IC74154 are connected to J1 , J2 and J3 of flip-flops
by ORing with output 7 of IC74154 so that when any of 1,3,5 is pressed the flip-
flops have value 1 . 7 is ORed with 1 , 3 , 5 so that when 7 is pressed all the flip-flops
have output 1 simultaneously.
Output 2,4,6 of 74154 are connectecd to K1, K2, K3 of flip-flops by ORing with 8 so
that when any of these key 2, 4, 6 is pressed flip-flops have output 0. 8 is ORed
because when it is pressed all flip-flops have value 0 simultaneously.
The output of the flip-flops are fed to the relay circuits via trasistor to operate the
secondary circuit (appliances) such as Fan , Tv , Bulb.
16. FUTURE SCOPE
Our circuit is implemented on bread-broad and in future we want to make it on vero-
board so that it can be easily carried without any bad effect on the circuit. The circuit
also has some security flaws. Anyone can control the circuit by calling the receiver
mobile . So in future we would try to overcome this flaw by introducing a password
circuit which will activate the main circuit to control the appliances.
As the circuit is connected to the appliances via the realy circuit whose input are fed
from the flip-flops ,there can arise a situation if the power of the circuit is OFF ,then
the flip-flops may no longer carry the state before the power was OFF. To overcome
this situation we can use a ROM so that it can store the last state of the flip-flops even
when the power of circuit is OFF. But including a ROM can dramatically increase the
cost of the circuit.
