Based on infrared alarm technology security systems

1 The introduction

1.1 The research significance of this topic research situation at home and abroad

With the development of society and science and technology unceasing development, peoples living standards been improved greatly, and to the private property protection means in the unceasing enhancement, the intelligent facilities for anti-theft puts forward new requirements. This design is to meet the need of modern residential anti-theft designed family electronic alarm system. It in previous devices based on improved greatly, because use the single-chip processor signal, not only can used for single residential area, also can be used in a large-scale residential security systems. Its the job of the performance is good, do not appear to report and misstatement phenomenon, safe and reliable.

In our country, the present market condition alarm basically has triggered alarm system pressure switch electron and alarm system and pressure shading triggered alarm system, etc. Various kinds of alarm, but this several common alarm there are some shortcomings. This system USES a human pyroelectric infrared sensor in the human body detector in the flied, passive pyroelectric infrared detectors because of its low cost, easy fabrication, low cost, installation is more convenient, anti-theft performance is stable and high sensitivity, safe and reliable, has attracted broad family characteristics such as popular with the customers. And alarms installation concealment, not easily by rogue found.

1.2 Infrared alarm technology introduction

1.2.1 Nature objects of the infrared radiation

The nature of any object, as long as the temperature above absolute zero (273 ℃), constantly outward issued infrared radiation, and travel at the speed of light energy. Object radiate outward infrared radiation of energy and the object of temperature and infrared radiant wavelength. Assuming objects launching infrared radiation of peak wavelength for a few, its temperature for T, the radiation energy equals infrared radiation of peak wavelength gerben and object product temperature T. This product is a constant, namely:

The higher the temperature of the objects, emit infrared radiation of the smaller peak wavelength, send out infrared radiation energy is bigger also.

1.2.2 Pyroelectric effect

Passive infrared detector also called pyroelectric infrared detector, its main working principle is pyroelectric effect. Pyroelectric effect means if make some strong dielectric material (such as qin batio3, qin wrong acid lead P (zT), etc.) of the surface temperature changes, then with the temperature rise or fall, material surface occurs polarization, namely on the surface of the charge will be produced change, and material surface charge lost balance and eventually charge will change withvoltage or current form output.

1.2.3 Pyroelectric infrared sensor basic structure

Pyroelectric infrared sensors from sensor detection yuan, interference filters and mosfet verifier three parts. According to the number of detecting yuan to points, pyroelectric infrared sensors have unit, double yuanhe four yuan to wait for a few kinds, for human detection of infrared sensor adopts double yuan or four yuan type structure. According to pyroelectric infrared sensor utility cent, have the following kinds: used for measuring temperature sensor, its the job of the wavelength of (1-20) nano, Used for flame detection sensor, its the job of the wavelength for

0.435 / - 0.15 nano, For human detection sensor, its the job of the wavelength of 7 to 15 feet. Figure 1-1 is a double detection yuan pyroelectric infrared sensor structure schematic drawing. The sensor will two opposite polarity, special

Figure1-1 Structure of passive infrared sensor

1.2.4 Pyroelectric infrared detector basic principle

Pyroelectric infrared sensor by receiving mobile human radiation that certain wavelengths of infrared radiation, can be transformed into and human body movement speed and distance, the direction of low-frequency signals about. When pyroelectric infrared sensor by ir radiation sources of radiation, its internal sensitive materials temperatures will rise, polarization intensity is abate, surface charge reduce, usually will release this part of the charge called pyroelectric charge. Because of pyroelectric charge how many can reflect material changes of temperature, so by pyroelectric charge by circuit transformed into the output voltage can also reflect material changes in temperature, thus detect ir radiation energy changes.

1.3 AT89S52 MCU of function characteristic description

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes of in-system programmable Flash memory. The device is manufactured using Atmelrsquo;s high-density nonvolatile memory technology and is compatible with the indus-try-standard 80C51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory pro-grammer. By combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications.The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89S52 is designed with static logic for operation down to zero frequency and supports two software selectable pow

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