PYROELECTRIC INFRARED SENSOR FOR INTRUDER DETECTION M. Moghavvemi, Lu Chin Seng Department of Electrical Engineering, University of Malaya, 50603 Lembah Pantai, Kuala Lumpur, Malaysia.
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TENCON 2004. 2004 IEEE Region 10 Conference (Volume:4 ), pp. 656 – 659. DOI: 10.1109/TENCON.2004.1415018
ABSTRACT Nowadays, the installation of affordable automation and security system for residential and office usage has been a necessity in line with the increasing number of break-in cases in urban city. The demand for the mentioned installation is going to increase rapidly in near future. The crux of providing such systems is the occupancy map of interested areas. The occupancy map will overlook the status of the protected areas. Hence, most of the security systems nowadays have the tendency of providing occupancy map of the designated areas. In most of the security systems, presence detectors are used to achieve a secured home or office. Passive infrared detector is widely used in the presence detector as a mean of human detection. This paper discusses the application of pyroelectric infrared sensor (PIR) and the application of processing algorithm in handling sensor information so as to provide real time occupancy map on computer in control unit. PIR sensor is used to detect the presence of human in a protected room. Wireless communications network by using frequency modulation technique is developed to handle data transmission through the air. The personal computer plays a significant role in providing the intelligent centralized controls of the entire system. A software package has been developed for visual display, control mechanism configuration, and embedded server-client application. INTRODUCTION The system is termed as “People Tracker”, which is a sensor system that is capable of tracking occupants in a building for security purposes. In this project, PIR is used as the motion detector to detect the presence of human in a designated area. PIR sensor is made of a crystalline material that generates a surface electric charge when exposed to heat in the form of infrared radiation. Infrared radiation exists in the electromagnetic spectrum at a wavelength that is longer than the visible light. Infrared radiation cannot be seen but it can be detected. When the amount of radiation striking the crystal changes, the amount of charges also changes and this can then be measured with a sensitive FET device built into the sensor. The sensor elements are sensitive to radiation over a wide 0-78038560-8/04/$20.00©2004 IEEE range. So, a filter window is added to limit the incoming radiation to the 8 -14 µm range which is most sensitive to human body radiation. [1] PIR sensor is widely used nowadays. Hans J. Keller [2] has presented in his paper that he used four PIR sensors instead of one PIR sensor in the presence detector to increase the number of detection zones to 300˚ for full room coverage. The presence detector can provide a complete occupancy picture of the building and can take over all people-relevant controls. Another usage of PIR sensor is in People Sensor. [3] People Sensor is an Electronic Travel Aid designed to address two issues of importance to visually impaired people: inadvertent cane contact with other pedestrians and objects and speaking to a person who is
no longer within the hearing range. The device uses PIR and ultrasound sensors to locate and differentiate between animate (human) and inanimate (non-human) obstructions in the detection path. The passive vehicle detector which is presented by M. A. G. Clark, A. Hodge and P. Kinson [4] is primarily intended for mounting on signal heads at intersections and pelican crossings to detect oncoming vehicles. The detector responds to heat emanating from the object that is to be detected. The main purpose of this project is to develop and implement a sensor system that is able to track occupants in a designated area, switch on alarm when intrusion occurs, notify client of the intrusion and provide real time monitoring function by using personal computer through the internet. Besides, this project is also aimed to develop a wireless communications network that involves implementation of a transmitter and a receiver by using Frequency Modulation (FM) as the signal transmission technique. SYSTEM DESCRIPTION The block diagram of the system is illustrated in Figure 1. The basic elements of the system consist of a PIR motion detector which is mounted on the wall in each protected room. PIR sensor responds to the infrared radiation of the human body whose radiation is strongest at wavelength of 9.4µm. Three PIR sensor circuitries are implemented and placed at three separated rooms for testing. When an intruder 656entered the protected area, the body heat as well as the infrared radiation generated by the heat of the intruder will be detected by the sensor. Then the sensor will generate an output signal at its source pin. Since the output signal from the sensor is very small, in the range of mVpp, signal conditioning circuit must be implemented. Hence, a two-stage amplifier having signal conditioning circuits like window comparator is connected to the pin 2 of PIR sensor. Amplifier is used to amplify the signal generated from the PIR sensor whereas window comparator is used to generate a pulse when intrusion occurs with positive voltage level indicates the occurrence of intrusion while zero voltage level indicates peace (no intrusion occurs). To focus the infrared radiation emitted by the intruder, Fresnel lens is put in front of the sensor. It divides the area of coverage into multiple zones of detection. By using Fresnel lens, the maximum detectable distance of the sensor module is increased. The output from PIR sensor modules are wired to a microcontroller. The microcontroller acts as the heart of the system and processes these sensor signals. The control signals to LED indicators and encoded data to transmitter are produced then. The operation of the microcontroller is controlled by two push buttons. The microcontroller operates in two different modes, namely normal mode and intrusion protection mode. The waveform sent to FSK modulator is in asynchronous serial waveform where the communication protocol utilized is 300 baud rate, 8 data bits and 1 stop bit. The FrequencyShift Keying (FSK) modulator converts the digital data into analog form. FSK represents the two binary values by two different frequencies near the carrier frequency. Then, the modulated signal is fed to the Frequency Modulation (FM) transmitter where the signal is transmitted through the wireless media. At the receiving end, the received signal will be amplified because the signal is very weak. After that, the signal is converted back to its digital form by using FSK demodulator before it is sent to the personal computer. A RS232 transceiver chip is used to interface the receiver with the computer through serial port by performing voltage conversion from TTL standard to RS232 standard. The software-based control panel consists of a graphical user interface that displays the security status of the protected areas by showing the occupancy map. This is accomplished by decoding the data captured from receiver. Upon occurrence of intrusion, the software will initiate preset-actions immediately, such as notifying client by phone calls and triggering alert tone. The security state of the protected areas could be remotely viewed on the screen of another computer in other places via the communication network that supports the Transmission Control Protocol/Internet Protocol (TCP/IP). HARDWARE IMPLEMENTATION
In this project, PIR sensor used is IRA-E700ST0 manufactured by Murata Company. The transmitter module consists of peripheral interface controller (PIC), hardware based control panel, FSK modulator and FM transmitter circuit. PIC16F873A is the microcontroller used and it is programmed by using PICSTART PLUS. Hardware control panel consists of alarm system, LED indicators and push buttons. The alarm is switched on when intrusion occurs and the operation mode is intrusion protection mode. LED indicators show the occupancy status of the protected room. The FSK modulator circuit with XR2206 IC chip as the heart is implemented. In this project, the mark and space frequency are chosen as 1200Hz and 2200Hz respectively. For the FM transmitter, the transmission frequency is set as 91.3MHz. 657FM receiver circuit is implemented by using TDA7000 IC chip. The frequency of reception must match with the transmission in order to obtain the transmitted signal back. Since the received signal is weak, amplifier circuit is implemented to boost up the signal. LM386N is used in the amplifier circuit. To obtain the digital signal back, FSK demodulator with XR-2211A IC chip is developed. The amplified signal is then converted back to binary 0 and binary 1 based on the frequency of the signal. For interfacing with the personal computer, serial interface circuit is implemented by using HIN232. RESULTS AND DISCUSSIONS The results are obtained at the FSK demodulator output when every operating unit of the hardware part is combined together. The signal transmitted consists of ten bits with first bit and tenth bit as start bit (always 0) and stop bit (always 1) respectively. The second bit, third bit and fourth bit shows the status of area A, B and C respectively. Binary 0 denotes that the area is peace while binary 1 shows that intrusion occurs in that particular area. The fifth bit indicates the operation mode of the system. Binary 0 represents the normal mode and binary 1 represents the alert mode. The sixth data bit until ninth data bit is set to binary 0 where these data bits are unassigned to any particular function. Table 1 displays sample of possible data format of the demodulated signal. Start Bit Area A Area B Area C Operation Mode Data Bit Data Bit Data Bit Data Bit Stop Bit 0 1 (on) 1 (on) 1 (on) 0 (normal) 0 0 0 0 1 0 1 (on) 1 (on) 0 (off) 0 (normal) 0 0 0 0 1 0 1 (on) 0 (off) 1 (on) 0 (normal) 0 0 0 0 1 0 1 (on) 1 (on) 1 (on) 1 (alert) 0 0 0 0 1 Table 1: Possible data format of the demodulated signal. FM Transmission Peripheral Interface Controller (PIC) wires Hardware Control Transmitter Receiver Serial Interface Circuit FSK Modulator FSK Demodulation Modem Amplifier PIR sensor circuit (Area C) PIR sensor circuit (Area B) PIR sensor circuit (Area A) Internet Client
CONCLUSION The implemented PIR sensor module is able to detect the presence of human in a protected area with maximum distance of around 7 meters. The angle of detection of the sensor module is around 120q where the coverage is quite wide. This motion detector is quite sensitive to the human motion. A slight movement of the human body will be detected. However, the stationary human body will not be detected. Besides, the infrared beams of the PIR sensor are invisible to human eyes and thus it will not be defeated by intruders easily. The FM transmitter and receiver module are functioning well. The transmitted signal still can be received at the distance of around 20 meters without being disturbed by other non-significant noise. The signal demodulated is acceptable and can be interpreted by the personal computer correctly. The status of the areas shown in the occupancy map of the Graphical User Interface is also coincided with the actual status of the areas protected.
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