Intelligent monitoring anti-theft alarm system

0 Introduction
The role of intelligent anti-theft alarm system in maintaining the property security of the country, the collective and individuals is becoming more and more important. Therefore, the research on intelligent anti-theft alarm system with complete functions, stable performance and convenient operation has become the focus of people's attention.
The design of this paper is mainly based on the remote control system, infrared sensor monitoring alarm system and single-chip microcomputer application system.

1 System Features
The system functions include two parts: remote control system function and monitoring alarm system function.
The remote control system consists of four parts: remote control standby/unlock key, digital keys, operation keys and function keys. When the remote control has no operation for more than a certain period of time, the remote control keyboard will be locked, the digital tube display will be turned off, and the remote control system will enter the automatic standby power saving mode. At this time, only by pressing the two unlock keys at the same time can the remote control keyboard be unlocked and work normally again. The digital keys include numbers 0 to 9, which are used to enter the alarm phone number and password.
The operation keys include up key, down key, clear key, return key, select key and home key. The selection keys of the operation keys can select menus and functions at all levels; the up and down keys can browse menu directories and alarm phone books at all levels in a loop; the return key can return to the subdirectory selected at the previous level until the home page; the home key can directly return to the home page in any menu state.
Function keys include menu keys, monitoring arming/disarming keys, and system power on/off keys. Function keys can realize the editing, adding and deleting of alarm phone numbers of the monitoring alarm system, setting and modifying passwords, monitoring arming and disarming, system power on and off, and selecting short messages or telephone dialing remote alarm methods.
The key data transmitted by the remote control is encapsulated in the frame protocol at the software layer, and the infrared transmission and reception signal modulation and demodulation are performed at the hardware layer, so that the remote control can perform wireless data transmission with high reliability and can perform multi-channel remote control. As long as the same receiving system supports it, multi-channel remote control can be performed, so many devices that need to be remotely controlled can be easily managed with the same remote control.
The monitoring alarm system can monitor and alarm multiple alarm situations in real time in parallel. The alarm situation timing acquisition frequency is 1.67kHZ. Each alarm situation can be monitored and alarmed separately. Therefore, it has good concurrent processing and real-time processing performance. Infrared signal modulation and demodulation realizes resistance to environmental interference such as light and temperature, and day and night alarm monitoring. The on-site alarm circuit can emit high-decibel screams under the control of the relay to take effective deterrent measures against thieves. After the system three-bus technology expansion, the monitoring alarm system has 32K data storage, a large number of external expansion I/O ports, LCD display and other rich peripheral resources. The expanded 32K external data storage can realize large-capacity information communication with the intelligent anti-theft alarm equipment communication system, thus providing hardware system support for the expansion of alarm image acquisition and storage, and GPRS MMS transmission of alarm scene images. This system has outstanding features such as fast remote control operation, convenient system settings, reliable alarm monitoring, real-time multi-channel alarm, rich peripheral resources, and flexible expansion and modification.

2 System hardware design
The hardware design of this system includes the hardware design of the remote control system and the monitoring alarm system. The remote control system hardware design consists of power supply circuit, matrix keyboard scanning circuit, standby and unlocking circuit, infrared wireless transmission circuit, and digital tube display circuit; the monitoring and alarm system hardware mainly designs the alarm monitoring modules, system expansion, LCD display, on-site alarm, infrared remote control receiving modules, and the overall hardware circuit of the system.
2.1 System hardware overall architecture
The intelligent anti-theft alarm equipment consists of five parts: remote control system, monitoring and alarm system, single-chip expansion system, LCD display, and alarm communication system. The overall structure of the system hardware is shown in Figure 1.

2.2 Infrared remote control module
The infrared remote control is controlled by AT89C52RC single-chip microcomputer. The hardware consists of remote control keyboard scanning circuit, single-chip microcomputer standby unlocking circuit, power supply circuit, digital tube key value display circuit, single-chip microcomputer minimum system circuit and infrared data transmission circuit. [page]

The working principle of the remote control mainly includes: the remote control key value is captured and read by the matrix keyboard scanning circuit; the key jitter is eliminated by software and the long key reuse is identified; after obtaining the key value, the frame is encapsulated according to the custom wireless transmission protocol; the frame signal is modulated at 38kHz; the transmission program is started to transmit the infrared modulation signal; the remote control data is sent and the response is completed; the transmission data is displayed on the digital tube, and repeated transmission data is identified and specially displayed; the remote control is started for idle monitoring, and the count timeout automatically enters the standby power saving mode; wait for the unlock interrupt to resume normal work. As shown in Figure 2, the remote control keyboard scanning circuit, remote control standby/unlocking circuit, power supply circuit, digital tube key value display circuit, single-chip minimum system circuit and infrared transmission circuit constitute a complete remote control circuit.

2.3 System expansion module
The monitoring alarm system uses AT89C52RC single-chip microcomputer, which has 8K ROM on the chip. This design uses full decoding addressing and expands the 32K data storage RAM. The expansion circuit is shown in Figure 3.

In addition, a large number of I/O ports are expanded through the 74LS573 latch. In order to save logic gate devices, partial decoding is used in the upper 32K byte address, and partial decoding is performed by P2.6, P2.5, and P2.4 through the decoder 74LS138.
2.4 Infrared transceiver module
The infrared transmitting power supply circuit is shown in Figure 4. Its transmission is controlled by the signal terminal IR S. When IR S is high, the infrared transmitting tube IR is turned off, and when it is low, IR is turned on to transmit infrared waves. Loading a 38kHz square wave signal at the IR S terminal can modulate the spectrum of the infrared transmitting wave. The 38kHz modulated square wave is generated by a hardware design scheme. It is obtained by the multivibrator circuit designed by the 555 timer. The EN terminal controls the generation and stop of the square wave signal. EN=1, the circuit works normally, and the 38K S terminal generates a 38kHz square wave signal. EN=0, the 38K S terminal only outputs a high level.

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The infrared receiving sensor can sense the infrared light emitted by the infrared transmitting sensor and generate a corresponding electrical signal. The infrared receiving module consists of an infrared receiving tube, a preamplifier, a limiting amplifier, a bandpass filter, a peak detector, a shaping circuit, and an output amplifier circuit. Since the signal received by the infrared receiving diode is relatively weak, a high-gain amplifier circuit must be added. The circuit of the infrared receiving sensor is shown in Figure 5. When the infrared receiving sensor senses the infrared light wave modulated by 38kHz, it outputs a low level, otherwise it outputs a high level.

2.5 Sensor signal processing
Sensor signal processing includes monitoring area adjustment and multi-channel parallel real-time monitoring. Each infrared transmitting sensor transmits infrared signals at an angle of 60 degrees. When the infrared receiving sensor is in its transmitting area, it can perform effective detection. The sensor transmitting and receiving positions need to be reasonably allocated in the field environment. This design uses the 7420 AND gate chip to perform hardware parallel processing on multiple signals. According to the actual situation, infrared transmitting and receiving sensors can be added for parallel monitoring. Increase the monitoring area and eliminate monitoring blind areas.
The alarm signal is read in by the extended external I/O. The design of the external I/O port adopts a data bus acquisition scheme. The port address is uniformly addressed with the external data memory, and the same instructions as the external data memory are used to facilitate reading and writing. Each read and write is two instruction cycles, which can quickly and real-time read multiple alarm signals from the extended external I/O. The parallel collected alarm data scans the multiple alarm signals through the bit cycle shift test method. The alarm analysis uses statistical judgment waves to eliminate burrs, which improves the monitoring reliability. After a certain alarm occurs and triggers the alarm execution, the other monitoring signals continue to scan and monitor in real time, and the concurrent performance is good.

3 System software design
The overall structure of the system software consists of a remote control subsystem and a monitoring and alarm subsystem. The remote control system software design includes a matrix keyboard key capture scanning program, a keyboard debounce and multiplexing program, an infrared transmission signal modulation program, a sleep wake-up trigger and processing program, a key display program, etc. The monitoring and alarm system software design includes an interrupt management program, an infrared remote control receiving program, a clock and delay management program, a bit and byte read and write program of an external I/O port, an NVRAM read and write program of an ME card, an alarm monitoring program, an on-site alarm control program, a remote communication alarm trigger program, a LCD display driver, a remote control operation scheduling program, etc.
The interrupt events involved in this system include the standby and unlock interrupts of the remote control system, the timing interrupts of the remote control infrared transmission pulse, the timing interrupts of the infrared signal square wave modulation, and the alarm sampling interrupts of the monitoring and alarm system, the infrared remote control receiving interrupts, the UART communication receiving interrupts, the UART communication sending interrupts, the power-on and power-off interrupts, etc.
3.1 Infrared data transceiver program
This system design adopts infrared transmission technology, designs an infrared 38kHz modulation carrier through a single-chip microcomputer timer, and then designs the transmission and receiving protocols for the remote control and the main control system respectively. The flow chart of the sending and receiving protocol definition is shown in Figure 6.

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3.2 Monitoring and alarm function program
Figure 7 shows the software flow chart of the monitoring and alarm system. The alarm monitoring uses the highest priority of the system interrupt to perform regular alarm sampling. After the alarm is initially detected, interference elimination measures are taken for further analysis. When the alarm is confirmed to have occurred, the road alarm is registered in the alarm management variable. At the same time, the on-site alarm and remote alarm are triggered.

4 System Simulation
The complete system simulation circuit is designed by PROTEUS software. The simulation circuit can test and debug the hardware design scheme and software design scheme except the remote control transmission modulation and demodulation circuit and the sensor monitoring circuit. The overall system simulation circuit is shown in Figure 8.

5 Conclusion
This paper describes the design of an infrared remote control and a multi-channel anti-theft monitoring alarm system. This system can realize the editing, adding, deleting and deleting of the alarm phone of the anti-theft monitoring alarm system by the remote control, the selection of remote wireless alarm mode by short message or phone call, anti-theft monitoring arming and disarming, system startup and shutdown, and password management of user operation permissions.
The main advantages of this system are alarm, rich peripheral resources, intelligent system diagnosis, and flexible expansion and modification. This system has achieved satisfactory results in the tests of reliability, stability, real-time, concurrent processing, energy saving and other indicators, and has the value of being used in actual anti-theft alarm occasions and the advantage of final product development.