Cell Phone Controlled Home Automation System using DTMF Technology

Thesis submitted in partial fulfilment of the

requirements for the Degree of Bachelor of Technology

in Electronics & Communication Engineering

2012-2016

Submitted by

Name Roll No

Taufique Sekh 28000312018

Under the guidance of

Prof. Shabana Huda, Asst. Prof.

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

Camellia Institute of Engineering

Affiliated to

Maulana Abul Kalam Azad University of Technology (Formerly known as West Bengal University of Technology)

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Contents

Topic Name Page No

ABSTRACT 1-2

THEORY 3-5

CIRCUIT PRINCIPLE 6-7

CIRCUIT COMPONENTS 8-19

BUDGETARY ESTIMATION 20-21

CIRCUIT DESIGN AND CIRCUIT OPERATION 22-26

RESULTS 27-29

ADVANTAGES AND LIMITATIONS 30-31

CONCLUSION 32-33

FUTURE SCOPE 34-35

REFERENCES 36-37

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Chapter 1

ABSTRACT

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Abstract:

Generally, appliances used in our home are controlled with the help of switches. These days, we can see automation of these appliances using many technologies. This project presents the controlling of home appliances using DTMF technology.

This home appliances control or home automation project   uses DTMF decoder circuit to control home and office electrical appliances. Just connect your cell phone headset (headphone) jack to the mobile phone and then mobile will control electrical appliances and electrical equipment through the DTMF key pad of your cell phone. Here for demonstrating, we are controlling an electrical bulb using this circuit project but you can extend this circuit to control many electrical devices with some modifications using4×16 decoder IC.

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Chapter 2

THEORY

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Theory:

DTMF is acronym for Dual Tone Multi Frequency. So, just think when we make call for customer care, they will ask you to press 1, 2 or any other number. When we press a number from our mobile, one particular action is happening. All this is because of DTMF. When a button is pressed in our mobile keypad, it will generate a tone of two frequencies. These tones are called row and column frequencies.

Generally, row frequencies are low frequencies and column frequencies are high frequencies. These frequencies for DTMF are chosen in such a way that they don’t have harmonic relation with the others, so that they will not produce same tones. The column frequencies are slightly louder than the row frequencies to compensate for the high-frequency roll off of voice audio systems.

We have learned that each button pressed in keypad will produce a tone which differs from others. Now we should use these tones for our appliances. So this DTMF encoder is present in mobile. Output from keypad can be converted into digital form using DTMF decoder IC HT9107B.

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Table showing DTMF Low and High frequency tones and decoded output:

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Chapter 3

CIRCIUT PRINCIPLE

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DTMF Controlled Home Appliances Circuit Principle:

The main principle of this circuit is to control appliances like light and fan using DTMF technology. DTMF encoder is present in our mobile and decoder is HT9107B IC. Mobile jack is connected at 1nf capacitor. Mobile jack consists of two wires (Red and black). Red wire is connected to the decoder IC and Black is grounded. When a button is pressed from mobile it generates a tone which is decoded by the decoder IC and it is sent to the HT12E encoder chip and this signal is fed to TX 433MHz transmitter module which is transmit the DTMF signal and this signal is received by RX433 MHz Receiver module. Receiver module is connected to the Decoder chip HT12D which is decoding the signal to convert binary format. When we press any key in the remote, the transmitter section generates the corresponding RF signal and this signal is received by the receiver section, hence it switches the corresponding appliance.

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Chapter 4

CIRCUIT COMPONENTS

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Circuit Components:

This circuit mainly consists of the following components.

HT9170B IC DTMF DecoderHT12E EncoderHT12D DecoderCD4013 D Flip-FlopRelay Driver StageResistors – R1, R2 and R3Capacitors – C1, C2, C3 and C4Crystal Oscillator X1, 3.57MHzRX and TX Module 433 MHzBC547B Transistor

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HT9170B IC DTMF Decoder :

HT9170 is the series of Dual Tone Multi Frequency (DTMF) receivers. They employ digital counting techniques to detect and decode the 16 DTMF tones into 4 bit output code.

Fig: HT9170B IC DTMF Decoder HT9170 series receivers do not require any external filters as they use highly accurate switched capacitor filters for filtering low and high frequency signals from the DTMF tones. They also support power down (PWDN) and inhibit (INH) modes. PWDN mode is used to power off the crystal, while INH mode to inhibit the A, B, C & D DTMF tones. The clock is provided by a 3.58 MHz crystal.

In simple terms, HT9170 IC detects and decodes the 16 DTMF tones into 4 bit output. In case the tones are not detected, the four output bits remain low. The DV pin goes high on detection of a valid tone.

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Pin Diagram :

Fig: Pin Diagram of HT9170

Pin Description:

Pin Name I/OInternal

Connection Description

VP IOPERATIONA

L AMPLIFIER

Operational amplifier non-inverting input

VN I Operational amplifier inverting input

GS O Operational amplifier output terminalVREF O VREF Reference voltage output, normally VDD/2

X1 I

OSCILLATOR

The system oscillator consists of an inverter, a bias resistor and the necessary load capacitor on chip.A standard 3.579545MHz crystal connected to X1 and X2 ter- minals implements the oscillator function.

X2 O

PWDN I CMOS INPull-low

Active high. This enables the device to go into power down mode and inhibits the oscillator. This pin input is internally pulled down.

INH I CMOS INPull-low

Logic high. This inhibits the detection of tones representing characters A, B, C and D. This pin input is internally pulled down.

VSS -- ---- Negative power supply

OE ICMOS INPull-high D0~D3 output enable, high active

D0~D3 O CMOS OUTTristate

Receiving data output terminals OE=”H”: Output enableOE=”L”: High impedance

DV O CMOS OUTData valid outputWhen the chip receives a valid tone (DTMF) signal, the DV goes high; otherwise it remains low.

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Pin Name I/OInternal

Connection Description

EST O CMOS OUT Early steering output (see Functional Description)

RT/GT I/O CMOS IN/OUT

Tone acquisition time and release time can be set through connection with external resistor and capacitor.

VDD --- ----- Positive power supply, 2.5V~5.5V for normal operation

DVB O CMOS OUTOne-shot type data valid output, normal high, when the chip receives a valid time (DTMF) signal, the DVB goes low for 10ms.

HT12E Encoder :

HT12E is an encoder integrated circuit of 212 series of encoders. They are paired with 212 series of decoders for use in remote control system applications. It is mainly used in interfacing RF and infrared circuits. The chosen pair of encoder/decoder should have same number of addresses and data format.

Fig: HT12E Encoder   Simply put, HT12E converts the parallel inputs into serial output. It encodes the 12 bit parallel data into serial for transmission through an RF transmitter. These 12 bits are divided into 8 address bits and 4 data bits.

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   HT12E has a transmission enable pin which is active low. When a trigger signal is received on TE pin, the programmed addresses/data are transmitted together with the header bits via an RF or an infrared transmission medium. HT12E begins a 4-word transmission cycle upon receipt of a transmission enable. This cycle is repeated as long as TE is kept low. As soon as TE returns to high, the encoder output completes its final cycle and then stops.

Pin Diagram: 

Fig: Pin Diagram of HT12E

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Pin Description: 

 Pin No  Function  Name

1

8 bit Address pins for input

A0

2 A1

3 A2

4 A3

5 A4

6 A5

7 A6

8 A7

9 Ground (0V) Ground

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4 bit Data/Address pins for input

AD0

11 AD1

12 AD2

13 AD3

14 Transmission enable; active low TE

15 Oscillator input Osc2

16 Oscillator output Osc1

17 Serial data output Output

18 Supply voltage; 5V (2.4V-12V) Vcc

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HT12D Decoder:

HT12D is a decoder integrated circuit that belongs to 212 series of decoders. This series of decoders are mainly used for remote control system applications, like burglar alarm, car door controller, security system etc. It is mainly provided to interface RF and infrared circuits.  They are paired with 212 series of encoders. The chosen pair of encoder/decoder should have same number of addresses and data format.

Fig: HT12D Encoder

In simple terms, HT12D converts the serial input into parallel outputs. It decodes the serial addresses and data received by, say, an RF receiver, into parallel data and sends them to output data pins. The serial input data is compared with the local addresses three times continuously. The input data code is decoded when no error or unmatched codes are found. A valid transmission in indicated by a high signal at VT pin. HT12D is capable of decoding 12 bits, of which 8 are address bits and 4 are data bits. The data on 4 bit latch type output pins remain unchanged until new is received.

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Pin Diagram:

Fig: Pin Diagram of HT12D

Pin Description:  Pin No  Function  Name

1

8 bit Address pins for input

A0

2 A1

3 A2

4 A3

5 A4

6 A5

7 A6

8 A7

9 Ground (0V) Ground

10

4 bit Data/Address pins for output

D0

11 D1

12 D2

13 D3

14 Serial data input Input

15 Oscillator output Osc2

16 Oscillator input Osc1

17 Valid transmission; active high VT

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18 Supply voltage; 5V (2.4V-12V) Vcc

ASK RF RX and TX Module :

The RF module, as the name suggests, operates at Radio Frequency. The corresponding frequency range varies between 30 kHz & 300 GHz. In this RF system, the digital data is represented as variations in the amplitude of carrier wave. This kind of modulation is known as Amplitude Shift Keying (ASK).

Fig: ASK RF RX and TX Module Transmission through RF is better than IR (infrared) because of many reasons. Firstly, signals through RF can travel through larger distances making it suitable for long range applications. Also, while IR mostly operates in line-of-sight mode, RF signals can travel even when there is an obstruction between transmitter & receiver. Next, RF transmission is more strong and reliable than IR transmission. RF communication uses a specific frequency unlike IR signals which are affected by other IR emitting sources. 

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This RF module comprises of an RF Transmitter and an RF Receiver. The transmitter/receiver (Tx/Rx) pair operates at a frequency of 434 MHz. An RF transmitter receives serial data and transmits it wirelessly through RF through its antenna connected at pin4. The transmission occurs at the rate of 1Kbps - 10Kbps.The transmitted data is received by an RF receiver operating at the same frequency as that of the transmitter. The RF module is often used along with a pair of encoder/decoder. The encoder is used for encoding parallel data for transmission feed while reception is decoded by a decoder. HT12E-HT12D, HT640-HT648, etc. are some commonly used encoder/decoder pair ICs.

Pin Diagram:

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Pin Description: RF Transmitter

 

Pin No Function Name

1 Ground (0V) Ground

2 Serial data input pin Data

3 Supply voltage; 5V Vcc

4 Antenna output pin ANT

 

 

RF Receiver

 

Pin No Function Name

1 Ground (0V) Ground

2 Serial data output pin Data

3 Linear output pin; not connected NC

4 Supply voltage; 5V Vcc

5 Supply voltage; 5V Vcc

6 Ground (0V) Ground

7 Ground (0V) Ground

8 Antenna input pin ANT

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Chapter 5

BUDGETARY ESTIMATION

BUDGETARY ESTIMATION:Sl.No Component Rate(Rs.) Quantity Amount(Rs.)

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1 HT9107B IC DTMF Decoder

25 1 25

2 HT12E Encoder 30 1 30

3 HT12D Decoder 30 1 30

4 Relay Driver Stage 50 2 100

5 Resistors – R1, R2 and R3

.50 6 3

6 Capacitors – C1, C2, C3,C4 and C5

.50 5 2.5

7 Crystal Oscillator X1, 3.57MHz

5 1 5

8 RX and TX Module 433 MH

250 1 250

9 Bulb + Holder+Plug 75 1 75

10 Cabinet 100 1 100

11 12V SMPS 2A 400 1 400

12 EP Jack 10 1 10

13 Battery 10 2 20

14 EP Socket 5 1 5

15 IC Vero Board 20 3 60

16 CD4013 13 2 26

17 BC547B 3 2 6

18 Connecting wires 30 --- 30

Total Amount 1,177.50

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Chapter 6

Circuit Design &

Circuit Operation

Circuit Design of DTMF Controlled Home Appliances:24

IC HT9107B DTMF Decoder:

The decoder IC consists of an inbuilt operational Amplifier. The output of op-amp is given to the pre-filters to separate low and high frequencies. Then it is passed through frequency and code detector circuits, thus 4-bit binary code is latched.

Tone from mobile is sent to op-amp through series of resistor (100 kilo-Ohm) and capacitor (1nf). Pin1 of DTMF IC i.e. non inverting pin is connected to pin4 i.e. Vref. Pin3 is the output of operational amplifier which is feedback to pin2 using 100 kilo-Ohm resistor. 7 and 8 pins are connected to crystal oscillator of frequency 3.579545 MHz. 15th pin is data valid pin it becomes high when DTMF tone is detected else remains low. The process of frequency detection to digitalization of the signal is done by steering circuit consisting of EST, RT/GT, and resistor (10k), capacitor. Pins 11 to 14 produce the decoded output.

DTMF Transmitter and Receiver using RF Module:

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HT12E Encoder IC will convert the 4 bit parallel data given to pins D0 – D3 to serial data and will be available at DOUT.

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This output serial data is given to ASK RF Transmitter. Address inputs A0 – A7 can be used to provide data security and can be connected to GND (Logic ZERO) or left open (Logic ONE). Status of these Address pins should match with status of address pins in the receiver for the transmission of the data. Data will be transmitted only when the Transmit Enable pin (TE) is LOW. 33k resistor will provide the necessary external resistance for the operation of the internal oscillator of HT12E.

RF Receiver receives the data transmitted using RF Transmitter. HT12D decoder will convert the received serial data to 4 bit parallel data D0 – D3. The status of these address pins A0-A7 should match with status of address pin in the HT12E at the transmitter for the transmission of data. The LED connected to the above circuit glows when valid data transmission occurs from transmitter to receiver. 750KΩ resistor will provide the necessary resistance required for the internal oscillator of the HT12D.

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Relay Driver Circuit:

As per the specifications of the IC, its outputs correspondingly switch ON and OFF in accordance with the DTMF tones generated and transmitted by the transmitter stage. The above switching of the outputs of HT12D IC is integrated to 4 discretely configured IC 4013 based flip flop stages which respond by toggling the attached relay driver stages. The relays can be wired to the relevant loads for achieving the intended switching via the DTMF transmitter handset. The output of flip flop is connected to the relay driver circuit via 1KΩ resistor; this output energizes the relay coil through BC547 transistor and turns ON the bulb that is connected at the normally open terminal of relay circuit.

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Chapter 7

Results

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Before Pressing Cell Phone keypad:

 

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After Pressing Cell Phone keypad:

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Chapter 8

ADVANTAGES

& LIMITATIONS

Advantages of DTMF Controlled Home Automation System Circuit:

1. One can control home appliances from anywhere.32

2. It reduces wastage of electricity when we forgot to switch off the lights & fans and gone outside.3. It is very low cost compared to other technologies like GSM.

Limitations of DTMF Controlled Home Appliances:

1. Number of appliances is limited as our mobile can generate only 16 tones.

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Chapter 9

CONCLUSION

Conclusion:34

Mobile phones have become an indispensable part of our life. Our system uses a controller and a cellular phone for its operations. The systems can be used as a test bed for any application that requires on-off switching based applications. Wireless controlled home appliances in the comforts of any environment will revolutionize our way of living.

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Chapter 10

FUTURE SCOPE

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FUTURE SCOPE: 1) Possibility of confirming the devices initial condition (status) using short messaging system(SMS) 2) Though mobile in the control panel required to be charged, therefore charging system should be automated which meant a timer can be implemented so that mobile can be charged after a certain period and disconnected from the charger when not required. 3) The system can be expanded to provide such control over the GPRS. In this way, the capabilities of the internet can be combined with the capabilities of our physical line free communication system. Furthermore, by adding a closed loop control facility, the system capabilities can be improved.

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Chapter 11

REFERENCES

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REFERENCES:

[1] GSM SYSTEM SURVEY ,Student text, EN/LZT 1233321, R5B revised upgrade edition. p. 192. [2] Dual-tone multi-frequency, Available: http://en.wikipedia.org/wiki/Dual-tone_multi-frequency [3] Schenker, L., “Pushbutton Calling with a Two-Group Voice-Frequency Code” - The Bell system technical journal (ISSN 0005-8580) vol:39 iss:1 pp:235-255, 1960 [4] DTMF decoding, Available: http://www.dattalo.com/technical/theory/dtmf.html [5] “Microcontroller Technology:16F84A”, prentice hall , 7th edition, page32, 2002 [6] I. Coskun and H. Ardam, “A Remote Controller for Home and Office Appliances by Telephone”, IEEE Trans. Consumer Electron. , vol. 44, no. 4, pp. 1291- 1297, November 1998 [7] PIC16F84A microcontroller data sheet, Available: http://ww1.microchip.com/downloads/en/devicedoc/35007b.pdf [8] Daldal Nihat, “GSM Based Security and Control System” (In Turkish), M.Sc. Term Project, Gazi University, Ankara, 2003. [9] E. Wong, “A Phone-Based Remote Controller For Home And Office Automation”, IEEE Trans.Consumer Electron. , vol. 40, no. 1, pp. 28-33, February 1995. [10] Relay Information, Available:

http://en.wikipedia.org/wiki/Relay

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THE END

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