Pir Based Security System for Border Areas

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PIR BASED SECURITY SYSTEM

INTRODUCTION A PIR (passive infrared) detector coupled with an electric light is now widely used for intruder protection. PIR are also available as stand-alone units which usually have a switched output for controlling external loads. To enable the PIR detector to work in daylight also, you have to cover the internal light/darkness sensor (usually an LDR).

The PIR detector used in this circuit reacts to fast temperature variations caused by the movement of people or animals in an enclosed space. All mammals radiate a certain amount of heat, and it is this that causes local variations in temperature. The radiant heat energy occupies the electromagnetic spectrum between light and radio waves, i.e. 0.74….300µm, which is usually called the infra-red region. The radiant energy is picked up by a Fresnel lens, at the focus of which is a double differential pyroelectric sensor. The detector is largely unaffected by other electrical radiation. Also, it does not react to movement outside the guarded space.

METHODOLOGY The space to be monitored is divided by the lens into a number of zones. The number of zones depends on the number of segments of which the lens is composed. When somebody moves from one zone into another, there is a change in temperature which is collected by the lens as a variation in radiant energy. At the focus of the lens is a pyroelectric sensor which reacts to such a change by generating a small electric signal. That signal is processed and used to actuate the alarm installation.

The signal generated by the sensor is filtered to filter out unwanted frequencies. Filtered signal is amplified and fed to the schmitt trigger to shape the pulses. The output of the schmitt trigger is used to trigger the monostable multivibrator. The high out of the monostable drives a relay via a relay driver. The relay in turn activates the alarm.

Source: Magnum Technologies.

RF RX LCD 16 X 2

PIR SENSOR

MONOSTABLE MULTIVIBRATOR

BUFFER

DRIVE

MICROCONTROLLER 89C51

RF ID TX

VIDEO RECEIVER

INTRODUCTION
A PIR (passive infrared) detector coupled with an electric light is now widely used for intruder protection. PIR are also available as stand-alone units which usually have a switched output for controlling external loads. To enable the PIR detector to work in daylight also, you have to cover the internal light/darkness sensor (usually an LDR).

The PIR detector used in this circuit reacts to fast temperature variations caused by the movement of people or animals in an enclosed space. All mammals radiate a certain amount of heat, and it is this that causes local variations in temperature. The radiant heat energy occupies the electromagnetic spectrum between light and radio waves, i.e. 0.74….300µm, which is usually called the infrared region. The radiant energy is picked up by a Fresnel lens, at the focus of which is
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Source: Magnum Technologies.

a double differential pyroelectric sensor. The detector is largely unaffected by other electrical radiation. Also, it does not react to movement outside the guarded space.

METHODOLOGY
The space to be monitored is divided by the lens into a number of zones. The number of zones depends on the number of segments of which the lens is composed. When somebody moves from one zone into another, there is a change in temperature which is collected by the lens as a variation in radiant energy. At the focus of the lens is a pyroelectric sensor which reacts to such a change by generating a small electric signal. That signal is processed and used to actuate the alarm installation.

The signal generated by the sensor is filtered to filter out unwanted frequencies. Filtered signal is amplified and fed to the schmitt trigger to shape the pulses. The output of the schmitt trigger is used to trigger the monostable multivibrator. The high out of the monostable drives a relay via a relay driver. The relay in turn activates the alarm.

1. INTRODUCTION
Until well into the twentieth century, most of devices developed for measuring

distance/movements worked on the same principle; comparison of the measured distance with the standard unit of length. Other advanced means are available now. One of these is the measurement of time taken by an electromagnetic / sound wave to cover a certain distance. This sound normally lies beyond human hearing and known as Ultra-sonic waves.

The novel Ultrasonic Movement Detector presented here is suitable for detecting any moving objects within the range between 25 cm and about 6 meters. The detected action in intimated by alarm sound.

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Source: Magnum Technologies.

You will find many uses for this movement detector. It is built around a matched pair of ceramic transducers, which convert movement energy to electrical energy and vice versa. The operating frequency of the pair is 40kHz. Any movement in the area scanned by the pair of transducers will be detected and a 6V pulse produced. In this Ultrasonic Movement Detector system the pulse turns on a LED. Pads are provided to take this pulse to add on circuits where it may be used to switch between an automatic reset after the detector has been triggered or to stay triggered. The unit will work reliably upto three meters after calibration. Methodology: The basic principle used in this device is the property of ultrasonic and waves of getting reflected when medium density charges. The ultrasonic and sound waves having a frequency range from 40 kHz are generated by an Astable Multivibrator, having 50% duty cycle. The waves generated are amplified and transmitted through a transmitting Transducer with the help of a driver stage. The waves travel ahead and are reflected back when they strike a moving object. The receiving transducer selects the reflected waves and further they are processed in receiver section. The receiver section consists of pre amplifier, buffer, driver and a buzzer, which gives the final output. The buffer is included to provide unit gain amplification to the received waves and passes them to Driver. The output is thus amplified to drive the output stage. The output stage is a buzzer. LED is also included in the output stage for the convenience. ADVANTAGES: 1 2 Easy to use. Manual error in security is nullified

APPLICATIONS: 1 2 For homes. For industrial security etc.

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Source: Magnum Technologies.

2. BLOCK DIAGRAM DESCRIPTION

BUFFER: This buffer isolates Ultra-sonic Receiver section from the rest of the circuit. This is necessary as Buzzer is used to give audible indication, and thus leads to loading effect on entire circuit while buzzing. The reference signal passes through this block and is fed to Driver block.

DRIVER: This block drives the Buzzer, which needs extra current while buzzing the alarm. As all the blocks deal with low voltage leveled reference signal, this Buzzer acts as strong current driving load to the system. So to avoid that loading effect, Driver block is created. This block drives the Buzzer, as soon it receives the reference signal from the Ultrasonic Receiver Block.

BUZZER: This buzzer is an output device, which starts sounding / alarming as soon it receives the reference signal from the Ultrasonic Receiver Block.

POWER SUPPLY UNIT: The specially designed power supply provides +12 V for Op-amp & Driver Stage and +5V for rest of the circuit.

APPLICATIONS 1) This system is used in shops to keep an eye on shop-lifters. It can be used at homes to prevent intruders from invading your privacy

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Source: Magnum Technologies.

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