PROJECT REPORT ON

DTMF BASED APPLIANCES CONTROL

KAMAL KUMAR 116026227GOPAL BARDHAN 116021193MD AQUIB KHAN 116029284ARIJIT DATTA MONDAL 116009099MD SADDAM ANSARI 116030298GUIDED BY:- Prof. AMIT KUMAR RAY

INTRODUCTION

What had been thought impossible at one time was achieved by man.

As technology advanced man was able to control everything from one place.

Controlling electrical appliances with mobile is one of the examples.

This makes the use of DTMF(Dual Tone Multi Frequency) technique.

The DTMF Decoder circuit is made using M8870 Decoder IC.

Just connect your cell phone headset (headphone) jack to the mobile phone and then mobile control electrical appliances and electrical equipment via DTMF key pad of your cell phone.

REQUIREMENTS

1. Transformer 9-0-9, 750MA 2. Voltage Regulator 7805,7812

3. Resistors (1k Ω; 10kΩ; 100kΩ; 330kΩ)

4. Paper Capacitors (0.1µFx 2)

5. Electrolytic Capacitor i)10uf,63v ii)1000uf ,35v

6. Crystal Oscillator (3.579545MHz, 12MHz )

7. BC548 Transistor

8. Diode1N4007

9. 12 V DC Relay

10. 89S52 MicroController

11. DTMF Decoder IC (M-8870)

12. Headphone Jack

13. Continuous Vero Board

14. Leds

WORKINGThe project uses M-8870 DTMF decoder IC which decodes tone generated by the

keypad of cell phone.When we press keys in our cell Phone when call is in progress, the other person will

hear some tones with respect to keys pressed. These tones are based on the DTMF technology.

Data is transmitted in terms of pair of tones. The receiver detects the valid frequency pair and gives the appropriate BCD code as the output of the DTMF decoder IC.

DTMF signal can be tapped directly from the microphone pin of cell phone device.Cut the microphone wire and we will see 4 wires. Among these wires we need only 2

wires Ground and Right.Take the right wire and connect it as input to the decoder circuit. Ground of jack should be

connected to common ground of our circuit.The signals from the microphone wire are processed by the DTMF decoder IC which

generates the equivalent binary sequence as a parallel output as Q1, Q2, Q3, and Q4.

CIRCUIT DIAGRAM

A varying current in the transformer's primary winding creates a varying magnetic flux in the core and a varying magnetic field impinging on the secondary winding. This varying magnetic field at the secondary induces a varying electromotive force (EMF) or voltage in the secondary winding. The primary and secondary windings are wrapped around a core of infinitely high magnetic permeability[d] so that all of the magnetic flux passes through both the primary and secondary windings. With a voltage sourceconnected to the primary winding and load impedance connected to the secondary winding, the transformer currents flow in the indicated directions

A transformer is a static machine used for transforming power from one circuit to another without changing frequency. This is a very basic definition of transformer

TRANSFORMER

A voltage regulator is designed to automatically maintain a constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages.Electronic voltage regulators are found in devices such as computer power supplies where they stabilize the DC voltages used by the processor and other elements. In automobile alternators and central power station generator plants, voltage regulators control the output of the plant. In an electric power distribution system, voltage regulators may be installed at a substation or along distribution lines so that all customers receive steady voltage independent of how much power is drawn from the line.

VOLTAGE REGULATOR

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 function

8051 Microcontrollers AT89S52

8051 is the name of a big family of microcontrollers. The device which we used in our project was the 'AT89S52' which is a typical 8051 microcontroller manufactured by Atmel™. The block diagram provided by Atmel™ in their datasheet that showed the architecture of 89S52 device seemed a bit complicated.

Pin Diagram

This circuit detects the dial tone from a telephone line and decodes the keypad pressed on the remote telephone. The dial tone we heard when we pick up the phone set is call Dual Tone Multi-Frequency, DTMF in short. The name was given because the tone that we heard over the phone is actually make up of two distinct frequency tone, hence the name dual tone. The DTMF tone is a form of one way communication between the dialer and the telephone exchange. A complete communication consist of the tone generator and the tone decoder. In this article, we are use the IC MT8870DE, the main component to decode the input dial tone to 5 digital output. These digital bits can be interface to a computer or microcontroller for further application eg. remote control, phone line transfer operation, LEDs, etc...

DTMF Decoder IC (M-8870)

1209 Hz1209

1336 Hz

1477 Hz

1633 Hz

697 Hz 1 2 3 A

770 Hz 4 5 6 B

852 Hz 7 8 9 C

941 Hz * 0 # D

DTMF keypad frequencies (with sound clips)

WORKING OF DTMF DECODER

The output Q4 from the DTMF decoder IC is fed to the clock input of IC 7474 d flip flop which acts as a buffer to the output from M8870 DTMF decoder IC.

IC7474 is configured as Toggling mode that is if it gets a clock pulse the output of this IC (Pin 5) sets to high and further clock pulse reset back the IC. (The outputs toggle whenever a key is pressed).

When we press and release any of the keys among 1, 3, 5, 7, 9 and * keys, the DTMF decoder IC generates a high pulse which acts as a clock to our flip flop and sets the output flip lop to high.

The output of flip flop is connected to the relay driver circuit via 100Ω resistor; this output energizes the relay coil through BC547 transistor and turns ON the bulb that connected at the normally open terminal of relay circuit

A relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solid-state relays. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits as amplifiers: they repeated the signal coming in from one circuit and re-transmitted it on another circuit. Relays were used extensively in telephone exchanges and early computers to perform logical operations.

RELAY

TOP VIEW FRONT VIEW

DEVICE DURING RUN-TIME

APPLICATIONS

This system can be used in industrial applications.

This system can be employed in houses ,where people often forget to switch off electrical appliances

This system can be used to control AC’s to set the room temperaturewhen we are outside

We can extend this circuit to control many electrical devices with some modifications using 4 x16 decoder IC.

ADVANTAGES Quick response is achieved. Construction is easy. Easy to maintain and repair. Comparatively the operation cost is less. Design is efficient and low cost. Power consumption is low. Controlling electrical devices wirelessly Saves electricity (when we forget to switch off and go out). We can control appliances from any place round the globe.

DISADVANTAGES

This system is not capable of displaying the feed back status of the devices being operated. This system needs a cell phone to be placed in circuit. Any one who knows the phone number and code can control our

electrical appliances Number of electrical appliances that can be controlled by this circit

is limited

FUTURE SCOPEThis project can be further enhanced to the High voltage A.C Applications by changing the ratings of the Relay.

In this project in future we can add a multimedia camera to see what is going inside the home by sitting in office or somewhere

We can also add some security features in the circuit. One of the way is password protection.

We can control and monitor the high speed induction motors as well as synchronous motors. This can be done in an economical way

Through this only selected people can access this control over the home appliances.

The project has been developed by integrating features of all the hardware components used. Presence of every module has been reasoned out and placed carefully thus contributing to the best working of the unit.

CONCLUSION

Using highly advanced IC’s and with the help of growing technology the project has been successfully implemented.

Finally we conclude that “DTMF BASED APPLIANCES CONTROL” is an emerging field and there is a huge scope for research and development.

-:Bibliography:- www.circuitgallery.com

www.wikipedia.orgwww.elprocus.com

WWW.google.com

THANK YOU