1. INTRODUCTION

The fear of theft and burglary always annoys many people. When lock and keys become less safe, one can seek help of electronic security systems. Such a portable security system is described in this project.

2. Components used :-2.1. Transmitter :-

Sl.No. Component name Range /specification Quantity

1 IC (a) NE555 timer (b) CD4011 NAND Gate

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2 Transistor (a) BC548 NPN(b) BC547 NPN(c) SL100 NPN(d) BF494 NPN

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3 Diode IN4001 14 Resistor (a) 2.2 kilo ohm

(b) 1 mega ohm (c) 10 kilo ohm (d) 47 kilo ohm (e) 1 kilo ohm (f) 220 kilo ohm (g) 1.5 m (g) 470 ohm (h) 47 kilo ohm(variable)

122221112

5 Capacitor (a) 0.1 uF ceramic (b) 220 uF,25V electrolytic (c)2.2 nF ceramic (d)0.2 uF ceramic (e)0.01 uF ceramic (f)22 pF button trimmer (g)1 uF, 6V electrolytic

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6 Relay 9V , 100 Ohm 17 Inductor Coil 2J type 18 Telescoping Antenna 19 LDR 110 Condenser MIC 1

2.2. Receiver :-

Sl.No Component Name Range /specification Quantity

1 Transistor BFW10 32 Zener Diode 9.1V 13 IC TBA820M 1

1

4 Variable capacitor 22p 15 Gang capacitor 1/2J 26 Inductor (a)5turns, 28swg wire 8mm dia with

ferrite bead (b)18 turns, 24 swg (c)11 turns , 24 swg

1

1 1

7 Loud speaker 8Ω ,1W 1

8 Variable Resistor 10k 1

9 Capacitor (a)1nf(b)2.2nf(c)47nf(d)10uf(e)180pf(f)22pf(g)220pf(h)100pf(i)10pf(j)100uf(k)0.1uf(l)220uf

111111142222

10 Resistor (a)100k(b)3.3k(c)220Ω(d)22Ω(e)1k(f)33k(g)1Ω

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3. Components details :-3.1. Integrated Circuits :-

3.1.1. NE555timer:

Fig 3.1.1 :- IC Diagram of NE555timerThe NE555 monolithic timing circuit is a highly stable controller capable of producing accurate time delays or oscillation. In the time delay mode of operation, the time is precisely controlled by one external resistor and capacitor.

For astable operation as an oscillator, the free running frequency and the duty cycle are both accurately controlled with two external resistors and one capacitor. The circuit may be triggered and reset on falling waveforms, and the output structure can source or sink up to 200mA. The

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NE555 is available in plastic and ceramic minidip package and in a 8-leadmicropackage and in metal can package version.

3.1.1.1. Pin connection :-

Fig 3.1.1.1 Pin connection of NE555 timer

3.1.1.2. Block diagram :-

Fig 3.1.1.2 Block Diagram of 555 timer

3.1.1.3. Astable Operation :-

In the transmitter circuit the 555timer works in the astable mode.When the circuit is connected as shown in figure (pin 2and 6 connected)it triggers itself and free runs as a multivibrator. The external capacitor charges throughR1 and R2 and discharges throughR2 only. Thus the duty cycle may be precisely set by the ratio of these two resistors. In the astable mode of operation, C1 charges and discharges between 1/3 Vcc and 2/3 Vcc. As in the triggered mode, the charge and discharge times and therefore frequency are independent of the supply voltage.

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3.1.2. CD4011 NAND GATE :-

3.1.2.1. Functional Diagram of CD4011 :-

Fig 3.1.2.1 Functional Diagram of CD4011

3.1.2.2. Pin Configuration of CD4011 :-

Fig 3.1.2.2 Pin Configuration of CD4011

The CD4011 BC Quad 2-input Nand buffered B series gates are monolithic complementary MOS (CMOS) integrated circuit constructed with N- and P-channel enhancement mode transistors. They have equal source and sink current capabilities and confirm to standard B series output drive. The devices also have buffered output, which improve transfer characteristic by providing very high gain.

3.1.2.3. Features :-

Low power TTL 5V-10V-15V parametric rating Symmetrical output characteristics Maximum input rating 1ua to at 15V over full temperature range.

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3.1.3 TBA280M:-

The TBA820M is a monolithic integrated audio amplifier in a 8 lead dual in-line plastic package. It is intended for use as low frequency class B power amplifier with wide range of supply voltage: 3 to 16V, in portable radios, cassette recorders and players etc. Main features are: minimum working supply voltage of 3V, low quiescent current, low number of external components, good ripple rejection, no cross-over distortion, low power dissipation. Output power: Po = 2W at 12V/8W, 1.6W at 9V/4W and 1.2W at 9V/8W.

Fig 3.1.3. IC diagram of TBA820M

3.2. Transistor :-

The transistors used in this project are BC548, BC547, SL100, and BF494 which are NPN medium frequency transistor. . They are used in this circuit as amplifier in oscillator section and mixer in the frequency mixing section.

3.2.1. BC548 &BC547 :-

Both of these transistors have similar characteristics.

Fig 3.2.1: Symbol and pin connection

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3.2.2. SL100 :-

Fig 3.2.2. Transistor Diagram

3.2.3. BF494 :-

The transistor used in this project is BF494 which is an NPN medium frequency transistor in a TO-92; SOT54 plastic package. It is used in this circuit as amplifier in oscillator section and mixer in the frequency mixing section.

Fig 3.2.3:- Transistor IC diagram

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3.2.3.1Pin connection:-

Fig 3.2.3.1. : Simplified outline (TO-92; SOT54) and symbol.

3.2.3.2. Features:-

a) Low current (max 30 mA). b) Low voltage (max 20 V). 3.2.3.3. Applications :- a) HF applications in radio and television receivers. b) FM tuners. c) Low noise AM mixer-oscillators. d) IF amplifiers in AM/FM receivers.

3.2.4. BFW10 :- It is the transistor used in the receiver section of our circuit. It is a junction field effect transistor.

Fig 3.2.4. Diagram of a JFET

3.2.4.1 Features :-

• Single and Monolithic Dual Packages• N-Channel Amplifiers

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• Tight Matching (ΔVgs=0.1mV max)• Ultra Low Noise Versions (en=3nv/√Hz type)• High Frequency Versions• High Impedance Versions (IG=0.2pA type)• Low Leakage Versions (IGSS=1pA max)• N and P Channel Single Switches• Additional Screening Available• Second Source for Motorola, National, & Siliconix

3.3. IN4001 Diode :-

Fig 3.3. Diagram of IN4001 Diode

3.3.1. Features :-

• Diffused Junction. • High Current Capability and Low Forward Voltage Drop. • Surge Overload Rating to 30A Peak. • Low Reverse Leakage Current.

3.4.Resistor :-

Different resistors of different specifications are used in this project.

Fig 3.4.1: Diagram of different ranges of resistors

3.5.Capacitor :-

We have used various ranges of ceramic capacitors which act as filters.

Fig 3.5.1: Diagram of ceramic capacitor

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As our project deals with very high frequencies, so, we have used package capacitors which are in nF range. These are also ceramic capacitors having plastic coating.

Fig 3.5.2: Diagram of package capacitor

A trimmer is a miniature adjustable electrical component. It is a variable capacitor and it is meant to be set correctly when installed in some device, and never seen or adjusted by the device's user. Trimmers can be variable resistors (potentiometers) or variable capacitors (trimmable inductors exist but are very uncommon). They are common in precision circuitry like A/V components, and may need to be adjusted when the equipment is serviced. Unlike many other variable controls, trimmers are mounted directly on circuit boards, turned with a small screwdriver and rated for many fewer adjustments over their lifetime.

Trimmers come in a variety of sizes and levels of precision; for example, multi-turn trim potentiometer exist, in which it takes several turns of the adjustment screw to reach the end value, allowing for very high degrees of accuracy. The trimmer we have used is a variable capacitor of the range 0.22pF.It is used in the tank circuit in parallel with the inductor coil which oscillates at a certain frequency. We can adjust the frequency by varying the capacitance value.

Fig 3.5.3: Diagram of a Trimmer

3.6. Light dependent resistor : It is a sensor whose resistance decreases when light impinges on it. The light falling on the brown zigzag lines on the sensor causes the resistance of the device to increase or decrease.

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Fig 3.6. Diagram of an LDR

3.7. Condenser Microphone :-

An electret microphone is a type of condenser microphone, which eliminates the need for a polarizing power supply by using a permanently charged material.Condenser means “capacitor”, an electronic component which stores energy in the form of an electrostatic field. The term condenser is actually obsolete but has stuck as the name for this type of microphone, which uses a capacitor to convert acoustical energy into electrical energy.

Fig 3.7. Diagram of condenser Microphone

3.7.1. How Condenser Microphones Work :-

A capacitor has two plates with a voltage between them. In the condenser mic, one of these plates is made of very light material and acts as the diaphragm. The diaphragm vibrates when struck by sound waves, changing the distance between the two plates and therefore changing the capacitance. Specifically, when the plates are closer together, capacitance increases and a charge current occurs. When the plates are further apart, capacitance decreases and a discharge current occurs.

A voltage is required across the capacitor for this to work. This voltage is supplied either by a battery in the mic or by external phantom power.

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Fig 3.7.1. Cross-Section of a Typical Condenser Microphone

3.8. Relay :- A relay is an electromagnetic switch operated by a relatively small electric current

that can turn on or off a much larger electric current. Think of it as a kind of electric lever or see-saw: switch it on with a tiny current and it switches on another appliance using a much bigger current. Why is that useful? As the name suggests, many sensors are incredibly sensitive pieces of electronic equipment and produce only small electric currents. But often we need them to drive bigger pieces of apparatus that use bigger currents. Relays bridge the gap, making it possible for small currents to activate larger ones. That means relays can work either as switches (turning things on and off) or as amplifiers (converting small currents into larger ones).

Fig 3.8. Diagram of a Relay

3.8.1. How relays work?

A relay uses an electromagnet (a coil of iron wire that becomes a magnet when electricity flows through it) to link two circuits together. On one side, there's an input circuit powered by a switch or a sensor of some kind. When this circuit is activated, it feeds current to an electromagnet that pulls a metal switch closed and activates the second, output circuit alongside. The relatively small current in the input circuit thus activates the larger current in the output circuit:

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Fig 3.8.1. Figure showing working of relay

1. The input circuit (black loop) is switched off and no current flows through it until something (either a sensor or a switch closing) turns it on. The output circuit (blue loop) is also switched off.

2. When a small current flows in the input circuit, it activates an electromagnet (shown here as a red coil), which produces a magnetic field all around it.

3. The energized electromagnet pulls the metal bar in the output circuit toward it, closing the switch and allowing a much bigger current to flow through the output circuit.

4. The output circuit operates a high-current appliance such as a lamp or an electric motor.

3.9. Telescoping Antenna :-

A telescopic antenna is collapsible. It is a series of small diameter tubes of 6 to 8 inches in length nested one inside the other. The antenna can be extended to its full length or retracted to a small length for storage of portability. Radio antennas are optimally sized based upon wavelength of the frequency they are expected to "see" . Even multiples of wave length are also used for antennas to minimize their length. i.e. ( 1/2 or 1/4 wavelength). Antenna wave length (lambda) is base on the speed (c) that a radio signal travels which is about 3x10^8 m/s (300000000 m/s) divided by the frequency (f) lambda = c / fFrequencies in the hertz range would have wavelengths in the 1000's of kilometres range. So any practical length antenna (2 or 3 feet in Length) would work just as well as a larger 5 to 10 foot antenna as the wavelength is so large.

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Fig 3.9. Diagram of an Telescoping Antenna

3.10. M W Antenna Coil:-

It is an inductor coil having three terminals used for generation of signals to be transmitted by an antenna. The inductance value between one terminal and the other varies and can be adjusted as per requirement.

Fig 3.10. Diagram of a 2J type medium wave coil

3.11. Battery:-

A 9-12 volt dc supply is used in the project.

3.12. Gang Capacitor:-

A combination of two or more variable capacitors mounted on a common shaft to permit adjustment by a single control. Gang capacitors are commonly used in radio tuners/receivers. Radio tuners/receivers have formation of LC (inductance and capacitor). Here this circuit has one fixed inductance and capacitor parallel with gang capacitor. Gang capacitor is used along with an inductor coil (L) in a LC circuit to tune to a particular frequency which is to be received. Normally gang capacitor is used in super heterodyne receiver.

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Fig 3.12. Diagram of a Gang Capacitor

3.13. Audio Driver Transformer:-

Traditionally, in the valve amplifier, the function of the output transformer was to convert the low alternating current music signal (that had been imposed on top of the high-voltage direct current from the plate electrode of the final output tube) into a useable high-current/low-voltage level for conversion by the loudspeakers.

Fig 3.13. Diagram of Audio Transformer

4. Working of the system :- The system has two main parts: an intruder sensor cum transmitter and a receiver. The intruder sensor reacts to light, sound, and mechanical movements. When the sensor detects a disturbance, the transmitter gets triggered and begins to send wireless signals. The receiver placed away from the transmitter receives the signals and produces an audio alarm. At the same time, a relay switch is turned on so that other security systems can be energized through this relay.

Both transmitter and receiver work on AC mains. However, battery changeover facility is provided. Both transmitter and receiver should be connected to a 9-12 volt power supply system.

The transmitter may be tuned first by moving the antenna coil and also by adjusting the trimmer (C9). It is better to tune to a deaf spot on a radio dial. Then, adjust the antenna coil and gang condenser of the receiver to get the best possible reception of transmitted signals. Pot. VR3 is to be adjusted to get the required output level from the loudspeaker.

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5. Circuit Diagram of the transmitter :-

Fig 5. Circuit Diagram of the Transmitter

6. Working of the transmitter and the sensor:

The sensor is wired around a 555 timer IC. Any light, sound and mechanical movement can be sensed by the condenser mic, LDR and a leaf switch etc. When any of these happen, transistors T1 and T2 start conducting. This brings down pin 2 of IC1 below 1/3Vcc. The output pin 3 of the IC goes high and it drives transistor T3 and relay RL1.

The positive line to the transmitter is connected through the relay. Two NAND gates (N1, N2) of IC2 (CD4011) are wired as an audio oscillator. The frequencies derived from pin 4 of IC2 are amplified by transistor T4 and applied to the RF section for modulation. Coil L1 together with capacitors C9, C10, resistor R12, and Transistor T5 forms a tuned RF oscillator.

A low frequency oscillator is wired around the remaining two gates of IC2 (N3, N4). Its output drives transistor T6. Since the emitter of T5 is connected to the ground through t6, the transmitter works only when T6 conducts.

The transmitted signals are captured by the receiver and processed to produce sharp beeps. With one metre telescopic antenna, the range of the transmitter is 50 metres.

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7. Circuit Diagram of the receiver

Fig 7. Circuit Diagram of Receiver

8. Working of the receiver :-

Using the circuit of 40-metre band direct-conversion receiver descr- ibed here, one can listen to amateur radio QSO signals in CW as well as in SSB mode in the 40-metre band. The circuit makes use of three n-channel FETs (BFW10). The first FET (T1) performs the function of ant. /RF amplifier-cum-product detector, while the second and third FETs (T2 and T3) together form a VFO (variable frequency oscillator) whose output is injected into the gate of first FET (T1) through 10pF capacitor C16. The VFO is tuned to a frequency which differs from the incoming CW signal frequency by about 1 kHz to produce a beat frequency in the audio range at the output of transformer X1, which is an audio driver transformer of the type used in transistor radios. The audio output from transformer X1 is connected to the input of audio amplifier built around IC1 (TBA820M) via volume control VR1. An audio output from the AF amplifier is connected to an 8-ohm, 1-watt speaker. The receiver can be powered by a 12-volt power-supply, capable of sourcing around 250mA current. Audio-output stage can be substituted with a readymade L-plate audio output circuit used in transistor amplifiers, if desired. The necessary data regarding the coils used in the circuit is given in the circuit diagram itself.

9. How a Wireless System Works?

A conventional wired microphone converts sound waves into an electrical audio signal that travels to the sound system through a cable. A wireless microphone system goes one step further, and converts the audio signal created by the microphone to a radio signal which is sent to the sound system through the air by a transmitter. The radio signal is similar to those used by television and FM radio stations. The receiver tuned to the same frequency as

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the transmitter picks up the radio signal, converts it back into an audio signal, and feeds it to the sound system through a short cable. The receiver is usually located near the rest of the sound system.

Each performer or presenter using wireless at a particular location (a theater, church, or school, for example) must use a system operating on a different frequency. Wireless systems at one location cannot "share" frequencies because they would interfere with each other, just as if two television stations in the same city tried to broadcast on the same channel. If two performers at one location try to use the same frequency at the same time, neither one will be picked up clearly. This potential for interference limits the number of wireless systems that can be used simultaneously at one venue. Reputable manufacturers and dealers of wireless systems can assist with selecting the appropriate frequencies for your needs.

9.1. Features:

Patented, proprietary technology Comprehensive, redundant coverage No voice channel interference Cost effective Compatible with virtually all equipment Automatic carrier switching Multiple alarm notification methods Web-enabled management Alarm transmission in less than one second Alarm acknowledgement

9.2. Benefits:

Suitable for home or office. Simple to operate using a handy remote control. Cordless detectors enable very simple installation.

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10.Trouble Shooting :-

Firstly we would like to state that it has been a very enriching experience doing this project. It was very good to try and apply the things that we have learnt in our courses so far practically, and which helped us in understanding the intricate details of everything even better. But it also had its share of troubles. Here is a list of the problems that we experienced while accomplishing this project:-

1. Firstly, we tried to get the output of the transmitter and then design the receiver according to the frequency obtained but we were not getting the output due to wrong circuit diagram.

2. The condenser microphone was creating lots of problem not giving any output.3. Moreover, we didn’t got the medium wave inductor coil as it was unavailable in the market

for which we had to wait many days.4. We changed the circuit diagram of the transmitter and got half of the output.5. Further by reforming the circuit diagram of the transmitter we got the output of the

transmitter.6. Then we connected the receiver circuit and got the output at one go. But again it stopped

working due to some loose connection.7. We faced a lot of problem in tuning the frequency of both the transmitter and receiver.8. Lots of noise was affecting the output signal.

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11. Conclusion :-

Our project wireless home security system is a very useful project in our day-to-day life. It has a lot of applications. The project we have made is mainly based on security of a house so it is widely used in home as fear of theft always annoys people. It mainly informs you the access of unwanted person into your house or office in your absence. It is mainly used for personal security purposes.

We have completed our project successfully. So in future we will try to modify our project by incorporating more inputs like smoke detector.

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12. Bibliography:-

www.google.com www.images.com Electronic Devices and Circuit Theory by Robert L. Boylestad and Louis Nashelsky. Opamp and Linear Integrated Circuits by Ramakant A. Gayakwad.

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