Graduation design thesis of household infrared alarm system

Design of Intelligent Wireless Anti-theft System

The basic principle and composition block diagram of intelligent wireless anti-theft system are introduced systematically, and the receiving method of telephone network is described in detail. This paper discusses the pyroelectric infrared sensor, voice and other circuits, and gives some basic circuits and software flow.

Keywords: wireless burglar alarm pyroelectric infrared sensor

With the popularization of intelligent community construction in China, anti-theft system has become a necessary equipment for intelligent communities. In this paper, an intelligent wireless anti-theft system with networking function is developed by using single chip microcomputer control technology and wireless network technology, and related sensors are developed. Using wireless data transmission mode, there is no need to rewire, which is especially suitable for decoration users and places with inconvenient wiring.

1 Basic principle of intelligent wireless anti-theft system

Intelligent wireless anti-theft system consists of sensors, home intelligent alarm, alarm host of property management center and related control and management software. Figure 1 is the block diagram of home intelligent alarm, and Figure 2 is the block diagram of alarm receiving host of property management center.

1. 1 host circuit

As shown in figure 1, the host circuit receives the alarm signal from the transmitter through the RF receiving module, and the address and data type of the alarm sensor obtained after decoding by the decoder (PT2272) can only be received by the host if the addresses of the host and the sensor are the same. The decoded output number represents the sensor type, and the output signal enters the INT 1 of CPU, triggering the interrupt handler. The interrupt processor dials the telephone number preset by the user (such as mobile phone number and office number) through the DTMF transceiver circuit for remote dialing alarm; At the same time, the voice circuit is started, and the pre-recorded voice signal is transmitted to the host through the telephone line to realize the voice prompt communication function. The CPU outputs the siren trigger signal, and after amplification, it pushes the siren or horn to drive away and intimidate thieves. Users can also remotely set/deploy defense through telephone lines, input remote control signals, control wired electrical equipment through eight control outputs, and control wireless electrical equipment through coding circuits and RF transmitting modules. In the display part, RT 12232A graphic dot matrix liquid crystal module is used to realize the display function of Chinese characters. Display alarm time and alarm type. The keyboard can realize password modification, voice input and information viewing.

The receiving host of the property management center not only has the function of home alarm host, but also can realize the communication function with the property management center through RS232, and realize networking and community control.

1. 1. 1 DTMF transceiver circuit

DTMF transceiver circuit is the key part to realize telephone line remote communication. It will realize the functions of automatic dialing, busy tone recognition, ringtone recognition, remote control key digital signal recognition and so on. We choose MT8888 dual-tone multi-frequency (DTMF) transceiver, combined with single chip microcomputer and audio amplification circuit, to realize the detection of various signal tones and the generation of DTMF signals, and send the DTMF signals to the telephone line, as shown in Figure 3.

MT8888 is an integrated circuit with DTMF signal transceiver produced by CMOS process. The transmitter adopts switched capacitor D/A converter with small signal distortion and high frequency stability, which can send out 16 kinds of dual-tone multi-frequency DTMF signals. The receiving part is used to complete the composition, separation and decoding of DTMF signals and output them as 4-bit parallel binary codes.

Figure 3

When the interrupt mode is selected, when an effective audio signal is received or sent, the IRQ/CP pin outputs a low level to generate an interrupt signal for the CPU, and the data is latched at the output end at the transition edge of the delay control voltage; When the call processing (CP) mode is selected, only 250 ~ 550 Hz signal tones can be received. When it is rejected or there is no input, the IRQ/CP pin outputs a low level.

(1) Phone Ring Format

Busy tone: 450 Hz, 350 milliseconds, no 350 milliseconds, dial tone: 450 Hz, continuous. Ring back tone: 450Hz, with 1, without 4s.

(2) the way to judge the signal tone

Connect the IRQ/CP pin of MT8888 to the T0 pin of AT89S52, and all kinds of signal tones in the process of telephone conversation are filtered and limited by MT8888 to get a square wave, which is output from the IRQ of MT8888 to the T0 pin of AT89S52, and the signal count of T0 pin is 5s. The count value is in the range of 2 175 ~ 2357, which is a dial tone; When the count value is in the range of1041~1212, it is a busy tone; The count value is in the range of 425 ~ 475, which is a ring back tone. In actual programming, considering the counting error and the simplification of the program, the scope can be appropriately relaxed, but it cannot overlap.

(3) Automatic off-hook

The controller and the home phone are connected in parallel on the telephone line. In order to alarm with one wire, the off-hook circuit is set as follows: the telephone ringing signal is input to the it pin of AT89S52 through the photoelectric coupler TP52 1 and counted. When the ringing signal is received, if the user rings 10 times continuously and still does not go off-hook, it will automatically turn to the home intelligent alarm, and the CPU will set the P 1.5 pin to "1" to turn on the relay K 1 to realize the automatic off-hook function. If the user connects the phone during the ringing of 10, the controller does not respond, so that the controller and the phone do not interfere with each other. After off-hook, the dual-tone multi-frequency signal output by MT8888 is detected, and the remote information sent by users is read to realize remote communication and control functions.

Figure 4

(4) Automatic alarm

After receiving the wireless alarm signal of pyroelectric sensor, CPU immediately sends out the alarm signal and transmits it to remote users through telephone line. The alarm mode is as follows: the user calls 10 through the panel equipment and stores it in the 24C04 memory. After receiving the alarm, dial from 1 to 10 and call back three times. If any phone sends back the confirmation signal of the "#" key, it means that it has received the alarm and will not continue dialing. Every number needs to be dialed. Each number needs to dial 100ms, and the interval between numbers is 500 ms. When dialing, first check the telephone number stored in 24C04. If it is empty, it means that this phone is not set, skip dialing and continue to dial the next phone number. In this way, users can set several alarm phone numbers at will. We stipulate that the length of the number should not exceed 4 digits at most, so that it can be stored in 24C04.

1. 1.2 voice circuit

In order to facilitate communication, voice chip is used to realize voice indication and alarm functions. ISD 1420 is a monolithic integrated chip for voice recording and playback, and the recording time is 20s. It can be divided into 160 segments, and each segment is 125ms. Record when REC pin is low, and play when PLAYE or PLAYL is low. ISD 1420 can be recorded continuously or in sections.

Segmented playback: first send the stop recording and playback code P 1.2 ~ P 1.4 = 000, then send the playhead address A7 ~ A0, and start playback when P 1.3 or P 1.4 is low level (PLAYE or PLAYL); The playback is delayed, and finally the recording and playback stop code P 1.2 ~ P 1.4 = 000 is sent to complete the playback of this segment. By repeating the above process, you can play several segments of voice. Fig. 4 is the principle of the voice circuit.

1. 1.3 encoding/decoding circuit

PT2262/2272 is a universal codec circuit with low power consumption and low CMOS produced by Pucheng Company of Taiwan Province Province. PT2262/2272 can have at most 12 bits (A0 ~ A 1 1) three-state address terminal pins (floating, connected to high level and connected to low level), and any combination can provide 53 144 1 address code.

PT2262 can have 6-bit (D0 ~ D5) data terminal pins at most, and the set address code and data code are serially output from pin 17. The coded signal sent by the coding chip PT2262 consists of address code, data code and synchronization code. The address code must be the same as the address of the decoding chip PT2272 in the home control host to distinguish the home controller. Data codes can be used to distinguish sensor types. When there is an alarm signal, the pin 14 of PT2262 is at a low level, enabling PT2262, outputting an encoded signal from the pin 17 and transmitting it through the RF module.

After receiving the signal, the decoding chip PT2272 compares and verifies its address code twice, and then the high level output by the VT pin is sent to the INT 1 of 89S52, which triggers the interrupt handler to read the data codes of D0 ~ D3 and learn the alarm sensor status and alarm type. Fig. 5 is the principle of an encoding/decoding circuit.

1. 1.4 RF transmitter module and RF receiver module

The principle of RF transmitter module and RF receiver module is shown in Figure 6 and Figure 7, and the working frequency is 433MHz. The maximum transmission distance can reach1000 m.

Design of 1.2 sensor

1.2. 1 passive infrared thermoelectric sensor

The human body temperature is constant, generally at 37℃, so it will emit infrared rays with a specific wavelength of about 10μm. The working principle of passive infrared probe is to detect the infrared rays emitted by human body. The infrared rays emitted by human body are about10 μ m, which are enhanced by Fresnel filter and concentrated on the infrared sensor. Thermoelectric elements are usually used as infrared induction sources. When the temperature of infrared radiation emitted by human body changes, such components will lose charge balance and release charge to the outside world, and subsequent circuits will generate alarm signals after detection and processing.

Fig. 8 shows the internal circuit of the binary thermoelectric infrared detection element LHI968. It consists of two binary pyroelectric ceramics, which induce infrared signals and then amplify them through field effect transistors. The resistance at D terminal and the capacitance at S terminal have anti-electromagnetic interference ability.

Figure 7

The signal is led out from the S terminal, amplified in the previous stage, amplified again after passing through the 47μF capacitor, and compared with the set mosfet, the alarm output signal is obtained. 47μF capacitor can eliminate DC component, thus eliminating the influence of using environment (sunlight, light, fire source, etc.). ) on the detector, a delay trigger circuit is added to facilitate the owner's defense and withdrawal. Now there is a special integrated chip BISS000 1 to realize the above functions. In order to meet the needs of the owner to lift the door, an alarm delay circuit is designed. The delay length must meet the following requirements: when a person moves 0.2m from the front of the detector at the speed of 1m/s, no alarm will be generated; However, alarm should be given when moving for 3m, and the test speed should be able to detect the speed range of 0.3 ~ 3m/s or wider.

1.2.2 door magnetic drive surprise device

Generally speaking, the file of the wireless door magnetic sensor is above the inside of the door. It consists of two parts: the smaller part is a permanent magnet with a permanent magnet inside to generate a constant magnetic field; The larger one is the main body of the wireless door magnet, which has a normally open reed switch. When the permanent magnet is close to the reed switch (less than 5 mm), the wireless door magnetic sensor is in a waiting state; When the permanent magnet leaves the reed switch for a certain distance, the wireless door magnetic sensor immediately sends out a 433MHz high-frequency radio signal, which contains the address code and its own identification code (i.e. data code). The host computer judges whether it is the same alarm system by identifying the address code of this radio signal, and then determines which wireless door magnetic alarm is according to its own identification code (namely data code).

2 network center control host design

The design of the network center control host is basically the same as that of the home controller, except that an RS232 interface is added to realize the connection with the PC. The monitoring function of the community network is realized by the PC placed in the property management center.

label

Using the existing telephone network, combined with radio frequency wireless communication technology and single chip network control technology, the anti-theft alarm system is economical, reliable and flexible in networking. The family does not need to wire the sensor; It has broad market development prospects.

Other related:

/Detail/2006 1208 1 1247 15753 _ 1/

For reference only, please learn by yourself.

I hope it helps you.