29306350 home automation using phone dtmf touch tone modified version

7/27/2019 29306350 Home Automation Using Phone Dtmf Touch Tone Modified Version

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Miniproject Report On

DTMF Teleswitch


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CONTENTS

Sl No. Contents Page No

1. Cover Page 2

2. C e r t i f i c a t e 3

3. Acknowledgement 4

4. C o n t e n t s 5

5. A b s t r a c t 6

6. I n t r o d u c t i o n 7

7. B l o c k D i a g r a m 8

8. C i r c u i t D i a g r a m

9. C i r c u i t D e s c r i p t i o n

10. P C B D e s i g n & F a b r i c a t i o n

11. P C B L a y o u t

12. R e s u l t s & C o n c l u s i o n

13. R e f e r e n c e

14. D a t a s h e e t s


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ABSTRACT

Todays busy world is an assemblage of many communication

networks; some are yet to have their entries. The amazing thing is

that these all are being used for various communication purposes

only, though it is possible to extend their impacts in a variety of

manner by the manifestation of interesting systems where we can

directly have an aid from these. We are coming up with one of such

interesting systems by which we can access even our bedroom

electronic devices even from the most far off places in the world,

provided the network under use has good range everywhere.

Here we are demonstrating a system namely RAN as an

abbreviation for Remote Automation using Networks. In this most

basic demonstration, the transmitter is chosen as a mobile phone and

the decoding receiver as the land phone for convenience. One can

have either two mobile phones or two land phones for the same

purposes. To demonstrate such a system we will control, simply

turning ON and OFF of four LEDs representing the actual devices,

using any mobile phone from anywhere. Here we are designing such

an electronic assemblage which can decode the signals from the

mobile phone and can drive the four LEDs with the help of the BSNL

network and the receiving land phone, representing the receiver

section.

Such a system is really an asset for this busy modern

world, where everything is being sought for automation ..................


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INTRODUCTION

Here we are restricting our discussion about RAN in

the receiver section alone as the transmitting section is alike the

common communication system with the only change that instead of

a verbal message, a number (or numerical code) representing the

code for a device to be controlled is transmitted. This code is

decoded and used to drive the LED represented by the number using

the receiver section.

The underlying principle mainly relies up on the abilityof DTMF (Double Tune Multi Frequency) ICs to generate DTMF

corresponding to a number or code in the number pad and to detect

the same number or code from its corresponding DTMF. In detail, a

DTMF generator generates two frequencies corresponding to a

number or code in the number pad which will be transmitted through

the communication networks, constituting the transmitter section

which is simply equivalent to a mobile set. In the receiver part, the

DTMF detector IC, for example IC MT 8870 detects the number or

code represented by DTMF back, through the inspection of the two

transmitted frequencies. The DTMF frequencies representing the

number/ codes are shown below.


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5

BLOCK DIAGRAM

As mentioned earlier, as the relevance of our

design confines in the receiver section to drive the devices

represented by the LEDs from the DTMF transmitted by the

mobile phones to the land line, we are restricting our whole

discussion therein.

RING DETECTION

DECODING SECTION

OUT PUT SECTION

Input to thelandline

INTERFACE

RELAY


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CIRCUIT DESCRIPTION

Now lets have a detailed look into the whole circuit section wisely.

Before getting in to the description, for the sake of easiness, lets confirm

our aim or lets predict our expectation regarding its working.

We are supposed to send a code word from the mobile phone, which

is the transmitter and is sending the corresponding DTMF frequencies

along. At the receiver end, i.e. at the land line end we need to detect the

code back using our circuitry and it is to be used for driving the devices,

represented by the LEDs.

RING DETECTION_SECTION

Refer the circuit diagram of this section....Regarding the need of

this section, we want to use this circuitry in the device mode i.e. to control

the devices turn off and turn on while maintaining the normal functionality

and usage of the land line to make and accept calls. So we must allow

sometime for the land line to get into the off hook mode, also it is

necessary to get the landline from on hook mode to off hook mode to

enable the DTMF reception. If the land line is already in the off hook mode,

then it wont be able to receive any signal as in the normal speech

communication through networks. So using this section we are aiming to

automatically activate our circuitry after a number of rings are heard from

the landline, while the coupling for automation is done using a relay. Here

we have designed such that the DTMF signals will automatically be coupled

to the


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Decoding section just after the 6th

ring.

Now getting into the detailed analysis, the initial high ring

voltage is coupled to a zener diode circuitry to reduce the voltage level for

protection, at the same time maintaining the enough magnitude for

detection using the opto-coupler. See the details in the circuit diagram.

Whenever a ring occurs a sufficient amount of ring voltage is established

across the inputs of the opto-coupler which causes the internal transistor to

conduct and effectively the output 5

th

and 4

th

pin to get short. This resultsin an effective coupling of input ring voltage to pass through. Now we will

exploit this signal to use it as a clock signal for the decade counter IC 4017,

which will produce a high logic level at its Q5 pin upon reception of the 6th

ring, which was changed into a quality clock signal. The diode-resistor-

capacitor network along with the NAND gates of the IC 4093 is used to

shape up the irregular voltage signal obtained at the output of the opto-

coupler into a quality clock pulse for the IC 4017. Because of this, as

mentioned earlier, just after the 6th ring the counter 4017 will produce a

high level at the Q5 pin till the next clock occurs. This logic 1 level of Q5

pin is then used to drive the monostable multivibrator using 555 timer IC

through BC 547 transistor coupling. The monostable multivibrator is

designed for a period of about 60 seconds which is the allotted time for the

operator to control the device using the palm device he has. Thus the

monostable multivibrator will produce logic 1 level for a period of about 60

seconds at its output which is used to drive a relay as shown through

transistor coupling, which will couple a low resistance in between the RING

and the TIP terminals of the landline, resulting in the manifestation of a DC

loop driving the landline from ON HOOK to OFF HOOK preparing the

decoding section for the reliable reception of the signal transmitted from

the mobile phone.


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Now, we have to contend with a problem arising from the

past counting of the IC 4017. Suppose a fellow called to our landline and cut

the phone at the 4th or 5th ring. After this if somebody calls again then right

at the first ring the landline will get into the OFF HOOK mode contrary to

our expectation at the 6th

ring. How can we avoid this error? To solve this,

what we have with us is only the RESET pin of IC 4017. So the solution is

that we must reset the IC 4017 every time just after once the 6th

ring has

occurred or the decoding section is coupled for decoding. So for this we use

the retrigerrable monostable multivibrator using IC 74LS123 commonly

called as the MISS-PULSE-DETECTOR. For this we supply the same clock

pulse of 4017 to the IC74123, which has been designed for a period of more

than twice as long as the duration of a single ring signal, which is about 5

seconds. The out put from the 4th

pin of IC 74123, which is the TOGGLED Q

output, is then supplied to the active high RESET pin of IC 4017. Thus this

arrangement will avoid the past counting nature of IC 4017 by resetting it

just after the completion of the 6th

ring and the consequent coupling of the

decoding section.

Now that we have effectively coupled the signals from the palm device

to the decoding section, lets see how the decoding section performs the

decoding function.

DECODING_ SECTION

Refer the circuit diagram of this section....when the 1k resistor is

brought across the RING and TIP terminals the landline also brought to OFF

HOOK mode so that the decoding section is now connected to the

transmitted signal and can receive it.


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The input capacitor-zener-resistor network is meant for both theprotection of the DTMF decoder IC 8870 from comparatively higher ring

voltage and the coupling of the signal to the same IC. Based on the

reference DTMF frequencies the DTMF decoder IC 8870 decodes the binary

equivalent of the keys or numbers in the number pad of the transmitting

mobile phones. The decoding scenario of the IC 8870 can be consolidated as

given below.

Q3

Off

Off

Off

On

On

On

On

Off

Off

Off

* On Off On On

# On On Off On

KEYS

1

2

Q4

Off

Off

3 Off

4 Off

5 Off

6 Off On

7 Off

8 On

9 On

0 On


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A On On Off On

B On On On Off

C On On On On

D Off Off Off Off

The output of the DTMF decoder IC 8870 is binary code, which is then fed

to the binary to decimal decoder IC 74HC154 retrieving the original

transmitted key or number. But the IC 74HC154 has active low output pins.

So these active low outputs are converted to active high ones by passing

them through NOT gates. Note that here we are using only five outputs of

IC 74HC154 to control four devices represented by LEDs as an instance.

Specifically the pins we are using are the 13th

pin which produces an active

low corresponding to the code *, the 2nd

pin which produces an active low

corresponding to the code 1, the 3rd

one for the code 2, the 4th

one for thecode 3 and finally the 5

thone for the code 4. Thus in the decoding section

we retrieve back the same number or code transmitted from the mobile

phone.

OUT PUT_ SECTION

Refer the circuit diagram of this section....using the converted

active high outputs of the decoding section we are now supposed to

control the TURN OFF and TURN ON of four LEDs. The output


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corresponding to the code * from the decoding section is used to trigger a

monostable circuitry in the output section, which is designed to produce a

high pulse at its output for a period of about 5 seconds. This high pulse

with the duration of 5 seconds is used to activate the four tristate buffers

i.e. the ICs 74LS126 enabling the coupling of the respective inputs of the

buffers to their respective outputs. Now with in this 5 second duration we

can have our control signals to pass through the buffers and can be used to

control the D flip flops i.e. the ICs 74LS74, which has been set in the

latching mode to get its output toggled upon receiving consequent clock

pulses, thus triggering the turn ON and turn OFF of the devices once thesame code is transmitted for a second time. In a nutshell, the latching mode

operation of D flip flops causes a device to get turn on from off state or vice

versa on reception of the code word. The IC 74LS74 is a positive edge

triggered IC. One of the practical limitation we face here is to create a

positive edge at the clock input of the D flip flop IC, using the isolated pulse

coming through the buffer to its output. If we directly apply the pulse to

the D flip flop to work in the latching mode it wont work due to the lack of

establishment of the positive edge to its clock input, resulting from the

occurrence of logic 1 level at the clock input of D flip flop right at the time

of biasing or when connected to the power supply. For this purpose to

create a positive edge going from logic 0 level to logic 1 level we pass the

pulse coming out of the buffer through another NOT gate as shown.

Finally, we need to find out a code which we have to

transmit from the mobile phone so that we can establish a well shaped

pulse as clock pulse at the clock input pin of the D flip flop for it to work in

latching mode i.e. to get the LEDs turned on if they were in the off state

and vice versa.


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First of all we must activate the buffer in the output section

for the predetermined time by triggering the monostable circuitry there in.

So the first symbol in the code word should be *. Now, we need to

transmit a high level through the activated buffer using another symbol

specific to each of the device represented. From the circuit diagram we

can see it can be 1 for the 1st

device, 2 for the second one and so on. Thus

by sending *(ordinal number of the device) we can create a low to high

transition at the out of the buffer. But its not yet been a well defined pulse

with both trailing and falling edge. So to get a falling edge we should now

send a symbol other than ordinal number of the device. Let it also be * to

have a convenient code. Now, as we know we use * for triggering the

monostable circuitry in the output section we must not end our code

word with *. Other wise, it will cause the triggering input of the

monostable multivibrator to continue in the logic 1 level even after the

specified 5 seconds which in turn forces it not to get triggered for a second

time on pressing * as there lacks the transition from low to high level at

its triggering input. Hence we must end our code word with a symbol

other than both * and ordinal number of the device. Let it be 0. Thus, wegot the code word that is to be send for our expected control as * ordinal

number

of the device*0. For example, to change the state of first device we have to

send a code-*1*0, for the 2nd

one *2*0 etc...

By following the similar logic, it is possible to find some other

formats of code words. For example, the code word * ordinal number ofthe device 0 is also seeming to be worthy of.

Thus the whole control procedure can be consolidated as first of

all we need to make a call to the land line, just after the 6th

ring it will

automatically get on to the OFF HOOK mode for about 1minutes, during

this time we can control the required devices with code words of specified

format with in the installments of 5 seconds.


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RING

C1

0.47uF (250V)

R7

1K

TIP

2

1

T1BC547

4N25

OPTO

+5V

R5

100K

6

R3 D44

5

0.1uF

+5V GND

1K 1N4148

C5

100uF

GND

6

7

2

+5V

IC4

NE555

TRE

TRI

DIS

GND

C2

1uF

VCC+

/RES

CONGND

OUT

8

3

5

1

2

1

GND

4093N

IC5A 5

0.1uF

C8

+5V GND

3

R12

1K

6

T2BC547

4093N

IC5B4

K1_D PDT

15

14

13

+5V GND

4017N

+5V GNDIC3

6 5

7 8

CLK

ENA

RES

K1_D PDT

K1_D PDT

CO

Q0Q1

Q2Q3

Q4Q5

Q6Q7

Q8Q9

24

3

7

5

69

10

1

11

12

+12V


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JP2

R7

1K

OPTO

R5

100uF

100K

C3

R3

1K

C7

0.1uF

1 N4148

74LS123N

D4

NE555

4093N

R12

1K

JP3

U$1

M01PTH

IC3


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+5V

IC3 +5V

Q11N4148

VDDD117 GND

1STIGT

2 16

18

7ESTOSC1

8 15STDOSC2

3.57MHz1 10

TOEIN+

2 11IN- Q1

12

3Q2

GS13

Q3

12

3

44

Q4

VREF

14

10K5

INH JP7

150K9

6VSS

VSS GNDR8 GND

CM8870CP M01PTH

R2R6

56K JP856K

M01PTH

JP9

56K 56K

R5R7

R1

1K

+5V

IC1P

GND

+5V

IC2P

GND


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JP1

C2

0.1uF(250V)

JP4

M01PTH

JP6

C3

0.1uF(250V)R11K

M01PTH

R6

56K

56K

R7

. z

Q1

R2

56K

56K

R5

R8

150K

JP10

M01PTH

IC3

74HC154N

0.1uF

C1

JP3

74HCT04N

D1

1 N4148

JP2

JP8

JP9

M01PTH

M01PTH


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+5V GND

1310

+5V

VCC

6

4

T5

GND

1

+5V

IC5

TRE VCC+8

4

/RES

R77BC547 3DIS OUT

51K

2

i1uF

C1

NE555

TRI

CON

GND1

C3

47uF(35V)

GND


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C2

0.1uF

JP3

IC5

JP1 JP2

R7

1K

BC547 BC547

74LS74N

T 1T 2

LED1 LED2

74LS126N

74HC04N

74LS74N

T32

3 12

3 1

LED3 LED4

T4BC547


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35 11

2

1TR1

230-12VAC

4

3

GND

470uF

C2

1VO

GND

78L05Z

VI

IC2

3

GND

0.1uF

C1


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JP2 JP6 JP5 JP3 JP1 JP4

M01PTH

1C2

TR1

P1

VP3 1

S1

M01PTH


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RESULTS AND CONCLUSIONS

The Remote Automation using Networks

[RAN] on test performed exceptionally well to its

capability and accuracy. All the inherent parts of the

circuit performed consistently. It helped us to come out

with good judgment. With the features what it inherits, it

seems to be advantageous to the present era.


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Final Implementation

29306350 home automation using phone dtmf touch tone modified version

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