Intruder Alarm

ELECTRONICS 2

INTRUDER ALARM

PREPARED BY:

MUHAMMAD ZAID MASOOD SCHOOL OF ENGINEERING FACULTY OF ENGINEERING JANUARY 2016

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INTRODUCTION.

• This is the circuit of a simple burglar alarm  that

produces a loud beep when somebody crosses a protected area or door. The circuit is highly sensitive and can detect the shadow of the moving person from a distance of up to 1 meter. • Here IC2 uA 741 is wired as a sensitive comparator. • IC555 is wired as a monostable multivibrator. • When there is an intruder near the LDR the shadow causes its resistance to increase. Based on this effect the circuit gets activated.

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Components.  555

timer IC.  u741 IC  LDR(Light Dependent Resistor).  Resistor.  Capacitor.  Led(Diode).  Transistor (NPN and PNP).  Protoboard or Breadboard.  Buzzer.  Battery 9v.

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The

term operational amplier TOPIC or "op-amp" refers to a class of high-gain DC coupled ampliers with two inputs and a single output.  The op-amp is a linear amplier with Vout / Vinp. The DC openloop voltage gain of a typical opamp is 103 to 106.  The gain is so large that most often feedback is used to obtain a specific transfer function and control the stability. The input voltage range for a 741 IC is ±13V.

IC USED: • 555 is a very commonly used IC for

generating accurate timing pulses. • It is an 8pin timer IC and has mainly two modes of operation: • Monostable • Astable. • In monostable mode, time delay of the pulses can be precisely controlled by an external resistor and a capacitor whereas in astable mode the frequency & duty cycle are controlled by two external resistors and a capacitor. • 555 is very commonly used for generating time delays and pulses. • It has 8 pins. Supply voltage is 4.5 to 15 V

OP AMP (741)

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Classes of Amplifier.

• •

NE 555:

•

Saving electrical power is now becoming a concern. Equipment utilizing Class D systems save significant operating power.

•

Class D systems attain 75% efficiency without significant effort.

555 timers is a class D amplifier. In its most simplistic form it can be built with a single 555 and the 200mA current capability is enough to drive a small speaker, making it a good replacement for a low power amplifier.

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• •

uA741:

•

It is a part of A class because of its multipurpose applications, low power consumption and the complete amplification of an input signal.

A μA741 integrated circuit, one of the most successful operational amplifiers. It belongs to class A of the amplifier due to its high gain. It can be used as a comparator, integrator and differentiator as well.

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Circuit Diagram.

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Working of the Circuit. 1.

The shadow of an intruder passing through a distance of up to one meter nearby the circuit is enough to trigger the alarm.

2.

Here IC2 uA 741 is wired as a sensitive comparator ,whose set point is set by R6 &R7. The voltage divide by LDR and R9 is given at non inverting pin of IC2. At standby mode these two voltages are set equal by adjusting R9.

3.

Now the output (pin6) of comparator will be high. Transistor Q1 will be off. The voltage at trigger pin of IC1 will be positive and there will be no alarm.

4.

When there is an intruder near the LDR the shadow causes its resistance to increase.

5.

Now the voltages at the inputs of comparator will be different and the out put of IC2 will be low.

6.

This makes Q1 on. This makes a negative going pulse to trigger the IC1 which is wired as a monostable multivibrator.

7.

The out put of IC1 will be amplified by Q2 (SL 100) to produce alarm.

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Applications • To protect the entry of unauthorized person in restricted • • • • •

area. It is easy to understand that a security alarm system provides peace of mind when you’re away from your place of business, and is there to meet insurance requirements while minimizing burglary loss. It can be used as fence alarm to protect your garden from animals. It can be used at night by shopkeepers to protect the valuables in their showrooms. You can also use it at your doors to indicate that some stranger is present on door. This circuit can also be used for home securities too.

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Advantages.

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• Cheaper and easier to build either on breadboard or Pcb board. • This circuit is easy to implement and all the components used • • •

in this circuit are available in the market. Requires a very small power 9v to make the circuit run. Can detect the shadow up to range of one meter. The timing of the alarm can be adjusted on the basis of the power of resistors by using IC 555.

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Disadvantages.

• False alarms that bring unnecessary police responses which eventually can result in fines. • Alarms being heard too often, along with car alarms, and eventually being ignored by residents in densely urbanized settings. • If the alarm is set and the burglar happens to trip it, he will immediately flee from the area and move on to a different home or place. • Most professional burglars are very familiar with home intruder alarms and know exactly how to deal with them. • Requires a very clean and stable power supply. • Nowadays laser technologies that has a better of safety over LDR.

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CONCLUSION. This electronic device is designed to alert the user to an intrusion. It detects the interruption whenever an object or person comes near the LDR. This interruption results in a signal generation i.e, LED glows and buzzer sound. These devices are installed at various locations in houses or offices, especially near doors, windows. The circuit has to found to have greater application in security reliable and less expensive and is guaranteed to perform the best of the duration of their life time.

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References. 1)Class D Power Amplifier. (2015). Retrieved from

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Circuits Today. website: http://www.circuitstoday.com/class-d-power-amplifiers. 2)Super Sensitive Intruder Alarm. (2015, October 11). Retrieved from Electronics Hub. website: http://www.electronicshub.org/super-sensitiveintruder-alarm/ 3) Sethiya, A. (n.d.). Intruder Alarm. Retrieved from Engineers Garage. website:http://www.engineersgarage.com/electroniccircuits/intruderalarm#slider

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Thank You