Chapter 1INTRODUCTION

1.1 Introduction of Intercom:Intercom is one of the most useful devices in urban area. Which is used for between the house and the shop, between the tree house and the fort, between your kids rooms, etc.? It also Keep in touch with your family members from one room to another and also from outside areas such as the garage.An intercom is personal telecommunications device which facilitates the exchange of messages between two or more locations where standard vocal communication would be difficult or impossible due to distance or obstructions. Basic intercom systems have been in existence since about a decade into the twentieth century if you only consider designs reliant on that rather handy invention of Alexander Bells; the telephone.Also the intercom is used for purpose of security at many location, like Door bell, offices, etc. The Security intercom systems are used to provide voice communications between two or more locations for security purposes. Security intercom systems are frequently used between a locked building entrance door and a constantly attended location in the building, such as a manned security control room.A simple intercom system consists of one Master Station and one Sub-Station. The Master Station is typically located at the point inside the building where communications is to be received. The Sub-Station is typically located at the point where the communication is to be originated. For example, in an office building, it may be desirable to keep the front entrance door locked, and to provide a security intercom system to allow communications between the outside of the entrance door and the receptionists desk in the lobby. In this situation, the intercom Master Station would be installed at the receptionists desk, and the Sub-Station would be installed on the wall outside of the entrance door.1.2 Background History:Intercom history has come a long way since these were first introduced as commu-nication system at the beginning of the 20th century. Descendant of the antique ring system used on trains, intercom have involved a great deal. In the beginning there was use of telephone technologies until eventually intercoms transformed into multi-way, multi-post communications systems and wireless appliances.Interoffice communication technology existed decades before the intercom. After Kellogg patented the first Intercommunicating Telephone System in 1894, the ability to communicate with an employee or broadcast official reports to an entire building took a big step forward. As the name suggests, early intercoms relied on telephone technology, but manufacturers continue to improve systems by adopting new tech.We all know the ritual of ringing at a building entry door and waiting for the buzz that will grant us access to the premises, after having dutifully identified ourselves.Theseentry intercom systemsbecame a part of our everyday life, and helped toimprove home securityto a large extent.

1.3 Project Goals:Nowadays, intercom security solutions no longer require costly maintenance and heavy hard wiring. Wireless intercoms are now available for easy installation and integration, to become at once, a part of a home intercom and entertainment system, aphone intercom, an entry intercom and even ensure that your baby is sleeping tight. Microphones and speakers can be set almost everywhere, depending on your needs.

Chapter 2DEVELOPMENT DESCRIPTION

2.1 Project Design:The implementation of the project design can be divided in two circuit parts. Both are the Transceiver, like Transmitter and as well as Receiver.And each circuit have been divided in two parts which can describe in Transmitter and Receiver. The two separate devices Unit1 and Unit2 which is shown in fig below in Block Diagram. In this fig. shows the two PCB Unit (Unit1 & Unit2). The power section can be supply to both PCB Unit either separate or with together. When signal send to the PCB Unit1 from MIC1 the PCB1 operate and transmit the signal for Loudspeaker (LSP2). Now the same operation will be process of PCB Unit2 from MIC2 to loudspeaker (LSP1), and ground will be used common for both.2.2 Block Diagram:

Fig.2.1: Block diagram of Intercom using LM386.2.3 Circuit Design:

Fig.2.2- Circuit diagram of PCB Unit1 & PCB Unit2 of Intercom.

2.4 Major Equipment:2.4.1 Multimeter:This measurement meter is very important device for developing kit. It is measure the voltage, ampere and also continuity check of circuit design wire.2.4.2 Soldering Iron: This soldering Iron is used for solder of circuit wire through the soldering lid.2.4.3 NI Instrument Application Software:This application software used for check the circuit of waveform for exact result.2.5 Component Description:This component can divide into two parts-Major Component-Basic Component-This both component have been divide for specific in work of operation. Like LM386, BC547 Transistor etc.2.5.1 Major Component:2.5.1.1 IC LM386: The LM386 is a power amplifier designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200.

Fig.2.3: LM386 IC Amplifier.TheLM386is a versatile, small power amplifier designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but with the addition of an external resistor and capacitor between pins 1-8 the gain can be set to any value from 20 to 200.The inputs are ground referenced and the output automatically biases to one-half the supply voltage. The quiescent power drain is only 24 milliwatts when operating from a 6 Volt supply, making the LM386 ideal for battery operation.

Fig.2.4 : (a) Pin diagram, (b) Circuit diagram of LM386 IC Amplifier.To make theLM 386a more versatile amplifier, 2 pins (pin 1 and 8) are provided for gain control. With pins 1 and 8 open the internal 1.35k resistor sets the gain at 20 (26 dB). If a capacitor is placed between pin 1-8, bypassing the built-in 1.35k resistor, the gain will go up to 200.If a resistor is placed in series with the capacitor, the gain can be set to any value from 20 to 200. Gain control can also be done by capacitive coupling a resistor or FET transistor from pin 1 to the ground.2.5.1.2 BC547 Transistor:BC 547 is a general purpose NPN Transistor which us very popularamong hobbyist and engineers alike. The naming or more specifically numbering of most transistor can follow any of three system :1. Pro-Electron (European)2. Joint Electron Device Council (JEDC)3. Japanese industrial Standard (JIS)BC 547 is a name registered under the Pro-Electron numbering System.ABC547transistoris a negative-positive-negative (NPN)transistorthat is used for many purposes. Together with other electronic components, such as resistors, coils, and capacitors, it can be used as the active component for switches and amplifiers. Like all other NPN transistors, this type has anemitterterminal, a base or control terminal, and a collector terminal. In a typical configuration, the current flowing from the base to the emitter controls thecollector current. A short vertical line, which is the base, can indicate thetransistor schematic for anNPN transistor, and the emitter, which is a diagonal line connecting to the base, is an arrowhead pointing away from the base.

Fig. 2.5: BC 547 Transistor.

There are various types of transistors, and theBC547is a bipolar junctiontransistor(BJT). There are also transistors that have one junction, such as the junction field-effecttransistor, or no junctions at all, such as the metal oxide field-effecttransistor(MOSFET). During the design and manufacture of transistors, the characteristics can be predefined and achieved. The negative (N)-type material inside an NPNtransistorhas an excess of electrons, while the positive (P)-type material has a lack of electrons, both due to a contamination process called doping.TheBC547transistorcomes in one package. When several are placed in a single package, it is usually referred to as atransistor array. Arrays are commonly used in digital switching. Eight transistors may be placed in one package to make layout much easier.

2.5.2 Basic Component:2.5.2.1 Condenser Microphone:

Fig.2.6 : Condenser MicrophonePrinciple: Sound pressure changes the spacing between athin metallic membrane andthe stationary back plate. The plates are charged to a total charge.Q = CV = Where is the capacitance.V is the voltage of the biasing battery.A is the Area of each plate.d is separation of the plate.A change in plate spacing will cause a change in charge Q and force a current through resistance R. This current images the sound pressure, making this a pressure microphone.

2.5.2.2 Speaker 8/ 0.5W :

Fig.2.7 :Speaker 8 ohm / 0.5 W (Small/Mini Speaker)Good performance, generally used for all types of audio projects. The speaker with resistance of 8 ohm and power rating equals to 0.5W. Usage/ApplicationsGeneral warning alarm for some projectsSimple amplifier projectsWill also fit in robots projects2.5.2.3 Radial Capacitor :1000uf (micro Farad) 25volt aluminum radial electrolytic capacitor with low leaka-age current and dissipation factor. Temperature range: 185 to -40 degrees Fahrenheit (+85 to -40 degrees Celsius) and 20% tolerance. Dimensions: 5/16" by 9/16" (8 mm x 14 mm).An electrolytic capacitor is a capacitor that uses an electrolyte (an ionic conducting liquid) as one of its plates to achieve a larger capacitance per unit volume than other types, but with performance disadvantages. All capacitors conduct alternating current (AC) and block direct current (DC) and can be used, amongst other applications, to couple circuit blocks allowing AC signals to be transferred while blocking DC power, to store energy, and to filter signals according to their frequency. Most electrolytic capacitors are polarized; hence, they can only be operated with a lower voltage on the terminal marked "-" without damaging the capacitor. This generally limits electrolytic capacitors to supply-decoupling and bias-decoupling, since signal coupling usually involves both positive and negative voltages across the capacitor. The large capacitance of electrolytic capacitors makes them particularly suitable for passing or bypassing low-frequency signals and storing large amounts of energy. They are widely used in power suppliesand for decoupling unwanted AC components from DC power connections.

Fig.2.8 : Redial Electrolite Capacitor

2.5.2.4 Ceramic capacitor :

A ceramic capacitor is a fixed value capacitor in which ceramic material acts as the dielectric. It is constructed of two or more alternating layers of ceramic and a metal layer acting as the electrodes. The composition of the ceramic material defines the electrical behavior and therefore applications. Ceramic capacitors are divided into two application classes:Class 1 ceramic capacitors offer high stability and low losses for resonant circuit applications.Class 2 ceramic capacitors offer high volumetric efficiency for buffer, by-pass and coupling applications.

Fig.2.9 : Ceramic capacitor

2.5.2.5 Resistor :

Fig.2.10: ResisterA resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. This relationship is represented by Ohm's law:I = {V \over R}Where I am the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms.The ratio of the voltage applied across a resistor's terminals to the intensity of current in the circuit is called its resistance, and this can be assumed to be a constant (independent of the voltage) for ordinary resistors working within their ratings.

2.5.2.6 Potentiometer :Potentiometers (or pots, as well call them) are incredibly versatile devices. They can act as voltage dividers, or as variable resistors. There are tons of resources on the web about pots, so what Im going to cover here are the basic types, operation, and uses specifically for guitar audio.Pots come in all sorts of shapes and sizes. The most common type we use in pedals and amps are usually of the 24mm or 16mm round metal can type. There are also multi-gang pots (which stack multiple independent pots on one shaft), slider pots, trimmer pots, etc.In the case of a standard pot, as shown above, we have a round case with three connectors and a shaft that turns. Heres what it looks like in a schematic:

Fig.2.11 :Potentiometer or Variable Resister(Pot Type).The pot has three lugs and by convention they are numbered 1, 2, and 3. Pin 2 is called the wiper. These numbers map to the schematic symbol like this:

Fig.2.12 : Potentiometer Pin Mapping.Potentiometer: as a trimmer resistor. Heres what the schematic looks like:

Fig.2.13 Schematic of PotentiometerHere we have a potentiometer where lug three is the input, and lugs 1 and 2 are connected together to form the output. As you turn the shaft, the resistance decreases. You are forming a simple resistor whose value is variable.

Fig.2 14 Schematic in Increasing modeWell that certainly works the same way. But what happens if the potentiometer fails for some reason (age, poor quality, dirty, etc.). If the wiper (which is the rotating part of the component and probably most prone to failure) shorts out, it will let the full amount of signal through.

Fig.2.15 : Potentiometer or Variable Resister(Trimmer Type).

By attaching lug 1 to lug 2, we are building in a fail-safe. This ensures that the circuit is never completely openthere will always be some resistive path in case the wiper goes south.A Volume ControlNow lets look at a more interesting example: a volume control. Assume we have a simple stomp box that does distortion or overdrive or something else interesting. At the end of the circuit we have an output. Wouldnt it be nice to control the output level (or volume) of the pedal.

Fig.2.16 Schematics of Variable ResistorHere we have the signal going to lug 3, the output coming out of lug 2, and lug 1 connected to ground. To see how this works, assume you have the shaft turned all the way clockwise, i.e. turned all the way up. In this configuration, there is little if any resistance across lugs 2 and 3 so the maximum output signal goes to the output.As you turn the shaft counter-clockwise, the resistance across 2/3 increases and the resistance across 1/2 decreases. This causes more of the signal to be dumped to ground. This dumping essentially sends the signal into oblivion, thereby lowering the overall output level.So if you think about it, you are never really turning the volume up! The volume or level in the circuit is always running at full tilt. What you are doing the above volume control is actually attenuating (making smaller) the full volume that was there to begin with.

Chapter 3WORK PROCEDURE3.1 PROCEDURE:The Kit Design mainly divided into two parts, which arranging in separated two both hardware and circuit check on the software application (like, NI Instrument). In this two PCB(Unit1 and Unit2) which construct separately. After that arrangement of component and sufficient material for constructing the PCB and circuit design, decided the circuit design on PCB. The Circuit Design makes over the use of Express PCB Software which is very easy for designing to circuit. The printed designed circuit paste on the PCB for printing of circuit strip wire and it remove the all remaining metal of PCB except the wire strip metal by chemical of Ferric Chloride. After that Soldering process will started according to circuit diagram.There are mentioned in broadly process follows as,3.1.1 COMPONENT REQUIREMENTS :3.1.1.1 Major Components Condenser Microphone Speaker 8 ohm / 0.5 W (Small/Mini Speaker) BC547 Transistor LM386 IC Amplifier3.1.1.2 Basic Components LED Red Resistor Capacitor Variable Resistor PCB Board Two Pole Switch

3.1.2 CONSTRUCTION EQUIPMENT: Soldering Iron Soldering Lead Multimeter PCB Design Software Etching Chemical(Ferric Chloride) Terminal Drilling

3.2 PCB DESIGN:The PCB design on the Express PCB software is a very much easy to design the circuit for wiring strip. In which arrangement the component of size of padding and wiring whose will place for better design.

Fig.3.1 Normal PCB Circuit Design3.2.1 PCB Etching Process:

Fig.3.2 PCB Etching Process3.2.2 Terminal Drilling:

Fig.3.3 PCB Terminal Padding Drill

3.2.2 PCB Soldering Process:

Fig.3.4 PCB Circuit Soldering ProcessChapter 4OPERATION

4.1 CIRCUIT OPERATION :

The circuit operation can divided in three groups, first Power section, second Filter section, and third Amplifying section. These are all section describe in following.4.1.1 Power section:The power circuit consist the capacitor, resistor, and LED which operate through the 9V Battery. Which is shown in below fig.3.1?In this fig. 1k resistor R15 connected in series with the LED1 and parallel with capacitor. Capacitor C4 (1000f) and capacitor C5 (0.33f) connected in parallel and both capacitor use for more voltage charge for the next circuit. Because when LED glow then voltages decreases across the LED1.

Fig. 4.1 : Power source circuit.

So capacitor 1000f maintains the voltage for next circuit if voltage decreases across the LED.In this process voltage supply continuous in manner as per requirement.4.1.2 Low Pass filter section :In this section signal is filtered by combination of resistor R2 and capacitor C2. This circuit is known as Low Pass Filter which is shown in below fig. 3:2 .

Fig.4.2 : Low pass filter circuit.The circuit is a RC low pass filter, it is use for passes low frequency AC signal, but reduces or stop high frequency signals. The reason that these circuit react to the frequency of a signals is because the reactance Xc of a capacitor depends on the frequency (f). Xc = In simple terms, at high frequency Xc is very small and so the capacitor behaves like a short circuit. On the other hand at low frequency Xc is very large, and so the capacitor behaves like an open circuit. In this low pass filter fig.4 looks like short circuit, and therefore shorts the output signals, not letting high frequencies. We can find this frequency by simply solving this equation for the frequency.f = Given the value of R2= 390 and C1= 3.3nf as shown in fig. 2, the corner frequency is therefore.f = = 123.6635 Hz

4.1.3 First stage Amplifying Signal :

In this stage Transistor BC547 use for Amplifying the signal incoming from low pass filter. Here low-Level signal isamplified by the amplifier built around transistor T1 which is shown in below fig. 3.4.

Fig. 4.3: Amplifier circuit Collector-Emitter feedback bias.

In this circuit consist of one transistor, resistor, and capacitor. Here operation with the collector-emitter feedback bias in which further improve the level of stability, the emitter resistance is connected in the collector bias circuited to provide both collector and emitter feedback. According to fig.2 circuit there mention RC=R12= 3.3k should have a minimal value. For example, if the emitter ofT1 is connected to ground, the value of R12 could be as low 1 kilo-ohm.The resistor R11=Rib=470K it is selected such that the voltage between the collector and emitter of T1 is approximately half the power supply voltage and use of capacitor C18 is optional which is shown in fig.2. Also R1 resistor shows in fig.2.1 the used for order to make the input circuit less vulnerable (pregnable) to electromagnetic noise. Because, preamplifier may exhibit instability at very high frequencies. According to fig.2.capacitor C2 and C18 use for block the DC component but allow AC signal to pass and by variable potentiometer VR1 adjust the signal.In this circuit analysis applying KVL to the base circuit shown fig.3.5 we have,Vcc - (Ic + Ib)Rc IbRb Vbe IeRe =0Vcc Vbe = (1+)IbRc + IbRb + (1+)IbReIb = Ib = FromCollectorCircuit applying KVL to collector circuit we have,Vcc (Ic + Ib)Rc- Vce-IeRe =0Therefore, Vce = Vcc Ie(Rc + Re)

Fig.4.4 First Stage Amplifying Circuit

4.1.5 Second stage Amplifier :The first stage circuitamplify the signal and pass through capacitor C17 to the second stage LM386 IC Amplifier. This type of amplifier is an audio amplifier and which amplifier built around 200gains which are enough to work with the condenser microphones. The amplified signal fed to the speaker (LSP2) by audio amplifier.

Fig.4.5 Second Stage Amplifying Circuit

Chapter 5Result and Discussion5.1 RESULT: The implementation of Realization of INTERCOM USING LM386 is done successfully. The communication is properly done without any interference between different circuit section in the design. Design is done to meet all the specifications and requirements. Circuit is implemented by several methods like, designing pcb, soldering ect. and implemented on board. It can be concluded that the design implemented in the present work provide portability, flexibility and the data transmission is also done with low power consumption.

Fig.5.1 Final Project kit

5.2 APPLICATION :In this process an electronic device has been very useful for the communication. As we know that, Intercom is one of the most useful devices in urban area. Which is used for between the house and the shop, between the tree house and the fort, between your kids rooms, etc. It also Keep in touch with your family members from one room to another and also from outside areas such as the garage.

CONCLUSION

The project titled INTERCOM USING LM386 was successfully completed. Our project provides an efficient method for communication in between two devices . The system is easy to implement and has wide applications in the areas where large amount of usage can be.

BIBLOGRAPHY:[1]http:/wild-bohemian.com/electronics[2]http:/discovermagazine.com/2009/mar/24-leds-light-times-square-but-can-they-light-your-office[3]http:/en.wikipedia.0rg/wiki/sensor[4]http:/www.fi.edu./fellows/fellow2/apr99/soundvib.html[5]http:/www.wikipedia.org/wiki/Audio_Amplifier

1