Design of intelligent apartment security measurement and control system based on ARM

Looking at the current status of campus security, it is not optimistic for both colleges and universities and primary and secondary schools. The theft of students' belongings in school dormitories and fires caused by students' improper use of electrical appliances are "big problems" in college management. With the adjustment and development of sensor technology, network technology, control technology and communication technology, it is possible to modernize and dynamically manage student apartments, improve the living safety of student apartments, control safety accidents to a minimum, and relieve the worries of students and schools. This paper follows the principles of reliability, independence, safety, linkage, scalability, practicality and economy to design an ARM-based intelligent security measurement and control system for student apartments. The system consists of two parts: the acquisition terminal and the remote centralized control terminal. The two communicate serially through the RS232 bus, which can realize remote control and multi-terminal network synchronous control. It not only has the functions of human body detection, smoke detection, sound and light alarm, keyboard password alarm, and recording of valuables in and out of the dormitory, but also has the characteristics of simple circuit design, high reliability, strong pertinence, friendly human-computer interaction and low cost.

1. System composition and basic principles

This system consists of multiple dormitory monitoring stations and a building management station, as shown in Figure 1. The dormitory monitoring station is installed in the part of the dormitory that needs to be protected, and completes the reliable detection of various parameters (such as human pyroelectric infrared signals, fire smoke concentration) before various disasters occur in the undetected area of ​​the dormitory, and transmits them to the building management station through the RS232 bus. The building management station is located in the duty area. In order to facilitate query and storage functions, it is implemented using a PC. The information displayed on the PC monitors each dormitory so that the alarm can be issued in time and the administrator can be notified to take corresponding measures.

Figure 1 System diagram

The dormitory monitoring station consists of various detectors, microprocessors, sound and light alarms, displays and interface circuits, and its block diagram is shown in Figure 2. Human body detectors are used to monitor illegal human intrusion and personnel entry and exit information; infrared detectors and smoke sensors are used to collect fire scene information; magnetic sensors are used to monitor the movement of valuables. Its workflow is as follows: the microprocessor processes and saves the information provided by the data acquisition module according to the pre-set program, and at the same time, the theft and fire situations are realized with sound and light alarms, and sent to the remote PC management terminal through the RS232 interface.

The building management station consists of a main control computer, communication interface chip, monitoring management software, laying bus and power supply. Its operation process is as follows: the building management station monitors the situation of the dormitory monitoring station through the information displayed by the main control computer, saves and processes the alarm information when the dormitory monitoring station sends it, and notifies the administrator to take necessary measures.

Figure 2 Overall block diagram of dormitory monitoring station

2 Hardware Circuit Design

Since the functions of the building management station are mainly realized by the monitoring management software, the circuit design of the system is mainly the circuit design of the dormitory monitoring station.

Main control module: This system uses the ARM-based Easyarm LM3S1138 as the main control module chip to process and save the information sent by the data acquisition module. Easyarm LM3S1138[5] has 32-bit code instructions, 32-bit address bus, 34 interrupt sources, a total of 64 KB single-cycle Flash, 16 KB single-cycle SRAM, 32-bit address width, two synchronous serial ports (SSI), 3 fully programmable serial ports, ADC and multiple GPIO. It has rich internal resources. Its high-performance 32-bit computing power can easily control the entire system. At the same time, its low power consumption and low cost are in line with the application environment. In particular, its rich interrupt sources provide great convenience for receiving data from the collector.

Infrared detection module: It uses E18-D80NK infrared obstacle avoidance sensor. The module consists of two sensor devices, the infrared barrier outside the south gate and the infrared barrier inside the gate, arranged side by side.

When someone enters, the device outside the door is first covered and detects the signal, and transmits a low-level signal to the main control chip. The switch inside the door is then covered and detects the signal, and transmits a low-level signal to the main control chip. When the level signals of the sensors on both sides of the door disappear, it means that the terminal has detected that someone has entered. If someone leaves the room, the principle is the opposite. [page]

Human body detection module: mainly uses DYP-ME003 human body sensing module, and the module circuit is turned on when the number of people recorded is zero. If someone enters the sensing range, it will output a high level, and the sound and light module will alarm: if the person enters the correct password through the keyboard to unlock the door before entering, the sound and light module will stop alarming, realizing the anti-theft function. If the counter is zero and the door switch circuit is disconnected, the module will output a high level, the sound and light module will alarm, and the door lock prompt function will be realized.

Smoke detection module: mainly uses GH-312 smoke sensor module, which can detect the generation of harmful gases and smoke. When the indoor smoke exceeds the threshold, it outputs a high level, and the ARM processing makes the sound and light module alarm to achieve fire prevention function.

Valuables detection module: This module uses SEN-65 magnetic sensors to detect objects with specific magnetic strips. When someone leaves the room with valuables with magnetic tags, the magnetic induction device detects it and sends a high level to the main control module. The controller activates the alarm system to detect the entry and exit of valuables.

Communication module: The system communication module uses a programmable resistor communication protocol, and the level conversion between ARM and PC is completed through MAX232. Set the basic communication parameters for the installed system, as shown in Table 1.

Table 1 Basic parameter values

The circuit schematic is shown in Figure 3.

Figure 3 Circuit diagram

3 Software Design

The software design of this system is implemented using C language and IAR Systems Embedded Workbench tool. Workbench tool [6] is a flexible integrated environment for developing and applying various Japanese standard processors. It provides a convenient window interface for rapid development and debugging. Embedded Workbench supports a variety of different target processors. Users can define Japanese standard projects one by one on a project basis when developing projects with different Japanese standard processors.

3.1 Dormitory Monitoring Station Software Design

The dormitory monitoring station mainly collects information (information on illegal human intrusion and entry and exit of personnel obtained by human body detectors, on-site fire information captured by infrared detectors and smoke sensors, and valuables movement information captured by magnetic sensors). The software flow of data collection is shown in Figure 4.

Figure 4 Data acquisition software flow chart

3.2 Software Design of Building Management Station

The building management station uses the information uploaded by each dormitory monitoring station displayed on the human-machine interface to monitor the situation of each dormitory station, uses the serial port to realize data transmission between the dormitory monitoring station, receives the alarm information sent by the dormitory monitoring station, saves and processes it, and notifies the administrator to take necessary measures. The flow chart of the building management station data processing is shown in Figure 5. [page]

Figure 5 Data processing software flow chart

The building management station uses serial communication and the human-machine interface of the PC host computer to realize real-time query and display of the security status of each alarm system in the network, and record the security status for query. The human-machine interface was developed under the VC development environment [7], as shown in Figure 6.

Figure 6 Human-machine interface

4 System Implementation and Testing

The system mainly consists of 6 parts: indoor pyroelectric sensor and smoke sensor, infrared obstacle avoidance device, ARM controller and PC. The controller is placed on the right frame outside the door at about 155 cm above the ground, which is convenient for personnel to enter the password to unlock. The two infrared obstacle avoidance sensors are placed side by side on both sides of the right door frame at about 145 cm above the ground. The magnetic induction module is placed on the right side of the door frame at 120 cm above the ground. The indoor smoke sensor is placed on the beam, and the indoor pyroelectric sensor is placed on the left door frame at 160 cm above the ground. The main controller is connected to the PC through the RS232 bus to realize remote monitoring. The system installation diagram is shown in Figure 7. Then the function and performance of the system are tested, and the specific results are shown in Tables 2 and 3.

Figure 7 System installation diagram

Table 2 Test results of the influence of wind and light on the detection angle

Table 3 Test results of the influence of wind and light on detection distance

The test results show that the maximum average detection angles under windy and windless natural light conditions are 70.2° and 100.8° respectively, and the average maximum detection distances are 5.5 m and 7 m respectively; while in windless conditions, strong light has a greater impact on the maximum detection angle and maximum detection distance.

5 Conclusion

Through the test of system functions and performance, the results show that this system not only realizes the functions of human body detection, sound and light alarm, password input alarm, in and out personnel counting, door lock reminder when the last person goes out, valuables out detection, network information transmission, etc., but also has the characteristics of simple circuit design, high reliability, friendly human-computer interaction and low cost, which meets the needs of intelligent management of student apartments, helps to improve the safety of student apartments, and solves the worries of schools and students. However, this system still has some shortcomings. For example, this system uses wired transmission. When the wired network is interrupted, the collected data cannot be transmitted to the monitoring terminal in time, and the alarm cannot be issued in time. Therefore, the system needs to be further improved.

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