In recent years, the continuous development of computer technology and the continuous improvement of the degree of informatization have provided a solid technical platform for the research and development of smart home systems . The smart home is usually defined as a whole, that is, using advanced computer technology, network technology, and integrated wiring technology, through the family information management platform, the various parts related to home life are organically combined into a special integrated system. With the continuous refinement of smart home functions, the concept has gradually been extended, taking into account the full range of residents' requirements for residential environmental performance. Therefore, the current smart home system has transformed from an intelligently focused product to an integrated system with the following conditions: First, establish a communication network in the home to provide the necessary access to family information in the family. Under the control of the network operating system, control and monitoring of all home appliances and devices are realized through corresponding hardware and executing agencies. Secondly, all home appliances and devices must form a communication channel with the outside world through a certain media platform to achieve Information exchange in the external world to meet the needs of remote control, monitoring and exchange of information; finally, to meet the needs of people for home safety, comfort, convenience, efficiency and environmental protection.
The control commands and information transmission of the smart home system can be realized in two ways: wireless transmission mode and wired transmission mode. With the growing economic power, the high-speed, reliable public telephone network (PSTN) has covered most areas and homes, and the dual-tone multi-frequency (DTMF) signal on the wired telephone line is used to establish a call connection. It can also be widely used in data communication, and has strong anti-interference ability, so it is technically feasible to use the public telephone network to realize the control of the home facility. Compared with the use of wireless communication, the use of public telephone network does not require special wiring, nor does it occupy radio frequency resources, basically no electromagnetic pollution, and does not require a large amount of additional investment; and communication with a wired IP network (Internet) Compared with the mode, the communication method using the public telephone network has higher security and real-time performance. Therefore, the smart home solution based on public telephone network has certain advantages in terms of technical feasibility and cost economics. It is of great practical significance to research and develop a smart home system based on public telephone network.
1 Systematic overall research
1. 1 system functional requirements
The functional requirements of the home system mainly include comfortable and comfortable family living space, home security protection (hereinafter referred to as security), remote monitoring of household appliances, etc. Therefore, the smart home system based on the public telephone network can set the following functions:
1) Intelligent control of curtains, including remote control, timed opening and closing control, light control, rain control and other humanized automatic control .
2) Home safety monitoring and alarm, mainly including gas (gas, natural gas, liquefier) ​​leakage monitoring, window and window detector monitoring, door magnetic coupling monitoring.
3) Remote control of household appliances. After dialing in the home phone number at the far end, the system automatically turns on after a delay of several seconds. The user can enter the password first, and then input the operation command to remotely control the home appliance. The necessary voice prompts will be given during the operation.
1. 2 overall plan of the system
According to the function setting of the system, combined with the characteristics and requirements of computer technology, automatic control technology and communication technology, the whole system can be divided into three parts: environment and security detection, control, and device driver. The environment and security detection section is composed of light detectors, rainwater, gas detectors, window detectors, and door detectors. The control part is mainly composed of a main control module (also called a main control board) and a security alarm and home appliance control module (also called an alarm and control board), wherein the main control board is responsible for the control of the intelligent curtain and the collection of the security alarm signal. The alarm and control panel complete the automatic telephone dialing, alarm, prompt voice recording and playback, as well as the storage, query and modification of the telephone number and home appliance control operation code (password and instruction code). The system structure is shown in Figure 1.
Figure 1 The overall structure of the system
2 system hardware design
This system strives to use the cost-effective circuit chip to achieve various functions. After technical analysis, the main control board and the alarm and control board are all based on MCU (microcontroller), using Atmel's AT89S52 microcontroller. This kind of single-chip microcomputer is a low-power, high-performance 8-bit microcontroller with embedded 8K programmable flash memory. It belongs to the MCS microcontroller product series and has been selected for many embedded systems. The MCU of the curtain remote control uses the chip MCS89C2051 microcontroller in this series to meet the requirements of volume and power consumption.
2. 1 main control module
The main control module mainly includes MCU and peripheral circuit, curtain motor control circuit, window screen detection (infrared sensing) processing and gas detection processing unit circuit, and interface between MCU and sensors, alarm and control board for illumination, rainwater, door magnetism, etc. as shown in picture 2.
Figure 2 Circuit structure of the main control module
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