Smart home security system realized by personal mobile phone interaction

Abstract: This paper introduces the design and implementation of a home security system between GSM terminals (mobile phones) using short message service (SMS) through DTMF public telephone network nodes. This intelligent home security system integrates fire prevention, theft prevention, and gas prevention, and can realize automatic detection and automatic voice dialing alarm. The system composition, DTMF transceiver circuit, and SMS sending circuit design are introduced in detail. The experimental results show that this system is practical and the information transmission is real-time and reliable, which is suitable for home security or security systems in other places.

0 Introduction

With the continuous promotion of the concept of smart home and the rapid penetration of the electronic information industry into the field of life, the realization of home informatization, networking and intelligence has become a new trend in the development of home systems. The home intelligent anti-theft alarm system can monitor the home's security environment in real time, such as fire prevention and anti-theft. Once a safety accident occurs, it will issue a corresponding alarm message, so that the owner can deal with the accident in time. Based on the design concept of easy implementation, convenient operation and close to use, this article uses MSP430 microcontroller as the control core and control terminal, and uses external devices including infrared remote control, GSM module, voice module and corresponding sensors to simulate the realization of home intelligent anti-theft alarm.

1 System overall composition

The hardware of the smart home control system is mainly composed of four parts, namely the control unit, sensor data acquisition system, GSMTC35 module, and interface and power supply. The sensor data acquisition system, GSM TC35 module and control unit complete the processing and transmission of alarm and other signals; the power supply part provides working power for each part.

The software design part is mainly composed of five parts: data acquisition and data analysis part, smart home control system, telephone exchange network program-controlled exchange signaling recognition and analysis part, GSM TC35 module interface program part, and analysis and control part. Among them, the data acquisition and data analysis part and the telephone exchange network program-controlled exchange signaling recognition need to be processed in real time; the GSM TC35 module interface program part and the analysis and control part are divided according to the acquisition and telephone exchange network exchange signaling to improve system efficiency.

The system block diagram is shown in Figure 1. The single-chip microcomputer controls the DTMF transceiver circuit, digital voice circuit, and on-hook and off-hook control circuit. The detector can quickly and accurately detect abnormal conditions in the residence, and notify the controller in time after confirmation. The single-chip microcomputer then controls the telephone interface circuit to simulate off-hook, automatically dial the pre-set phone number for voice alarm and notify the management center. When the other party responds, the alarm state is automatically restored.

2 Hardware Design

The main control part of the system uses AT89S52 single-chip microcomputer, and no external memory expansion is required. The watchdog circuit uses a programmable serial EEPROM-X25045. X25045 stores data information such as flag field, phone number, alarm code, system settings, etc.

2.1 System power supply

Since this control system has many unit circuits and has high requirements for 5V power supply, the peak current of the TC35 module can reach 2.5A, so the external voltage regulator must be sufficient to provide the rated current of TC35 and other circuits. In this system, the switching power supply chip LM2576 is used to complete the conversion from 12V to 5V as the power supply for TC35 terminals and other 5V units. It must be noted that as shown in Figure 2, the switching power supply conversion completed by the LM2576 chip requires a high-power inductor of 100 μH and a capacitor to improve the energy storage capacity and meet the power consumption requirements of the unit circuit. LM2576 is a 5.0V3A switching power supply regulator.

2.2 TC35 short message module interface circuit

The TC35 short message module is an RS-232C standard interface. The full name of the RS-232C standard (protocol) is the EIA-RS-232C standard. It specifies the connection cable and mechanical and electrical characteristics, signal functions and transmission process. Currently, the COM1 and COM2 interfaces on the PC are RS-232C interfaces. In normal operation mode, if the chip does not detect a valid signal on the receiving and sending pins within about 30 seconds, it will automatically enter the Powerdown mode, consuming 1μA at this time. If the FORCEON and /FORCEOFF pins are both high, the Auto-Powerdown Plus function is invalid. When the Auto-Powerdown Plus function is valid, if a signal input is detected on the receiving or sending pin, the chip is automatically activated and enters the normal working state. If the input voltage of any receiving channel is higher than 2.7V or less than -2.7V, or the time between -0.3V and 0.3V is less than 30 μs, the /INVALID (pin 15) pin is high (data is valid). If the input voltage of all receiving channels is between -0.3V and 0.3V for more than 30 μs, the /INVALID (pin 15) pin is low (data is invalid). The above characteristics of the chip meet the connection requirements of TC35 as a receiving and transmitting circuit of a mobile terminal.

2.3 Buzzer alarm circuit

The transistor 8050 is used to drive the buzzer. When the processor detects the alarm signal, it will give the buzzer a signal to make it work, so that the alarm in the home can sound. See Figure 4.

3 System Software Design

The software is written in C language and developed in the Keil environment. The core is the reading, conversion and display subroutine of SHT11 temperature and humidity values. The main program flow chart is shown in Figure 5.

The software flow chart for implementing the functions is shown in Figure 5. The specific implementation process is described as follows: 1) Press the button to dial the corresponding phone number for testing; 2) Press the button to send a short message for testing; 3) The microcontroller detects the signal of the glass break detector and decides whether to alarm, send a short message and call the owner of the house: 4) The owner of the house controls the devices in the home through text messages. Here, only the on and off of the LED is used for demonstration.

4 System Implementation and Analysis

4.1 Communication module implementation

The GPRS communication module realizes the control of the TC35 module by the single chip microcomputer or the zigbee wireless communication technology, thereby realizing the remote control function. FIG6 shows the communication module in operation, and FIG7 shows the SMS module in operation.

4.2 Implementation of Smart Home Security System

GPRS can send alarm information to the owner under the detection of the detector, and the owner can remotely control the home and can communicate with the owner's mobile phone through two independent buttons of the system, as shown in Figure 8. The advantage is that it has two functions of text messages and incoming calls, which can reduce the unnecessary trouble caused by the owner missing text messages at the remote end; the disadvantage is that the detector is too sensitive and will cause false alarm information, which can show the status of the home.

5 Conclusion

This paper introduces a simple smart home monitoring system based on a single-chip microcomputer. The system hardware control uses a single-chip microcomputer as a microprocessor, collects temperature and humidity signals through a temperature sensor, and uses a liquid crystal display SO12864-14C to display the current temperature, humidity and dew point; the software uses C language for functional module compilation. Compared with traditional home monitoring systems, this system is low-cost, practical and convenient, and can provide a kind of security for home life. If the system is combined with communication and the alarm function is reflected in the mobile phone information prompt, the system design will be more perfect.