Smart home control system based on mobile phone remote control and Internet of Things technology

1.1 Introduction

 The 21st century is the century of informatization. Various new telecommunications and Internet technologies have promoted the great progress of human civilization. Do you want to be in a comfortable environment with light, temperature and humidity as soon as you step into your home? Do you worry about the safety of your home when you are outside? Do you want to control the home appliances through a simple phone call from outside? The digital home control system introduced in this article allows people to remotely control any home appliance (air conditioner, water heater, rice cooker, lighting, audio, DVD recorder) at any time and any place through mobile phones or telephones; you can also turn on the air conditioner at home in advance on the way home from get off work, let the water heater boil hot water in advance, and cook the rice cooker to cook fragrant rice...; and all this is achieved by just making a simple phone call. In addition to the mobile phone remote control function, the system can also perceive the specific conditions of the external environment through its own sensor module, and make appropriate adjustments according to the actual situation. In gloomy weather, it will automatically turn on the lights and adjust the brightness of the lights. In sunny weather, it will automatically turn off the lights or dim the lights, and cooperate with the blinds to control the illumination of the home. Since this project uses LED lights with adjustable brightness, it is of great significance for energy saving and environmental protection. In addition, the system can also enable the family to have multiple functions such as multi-channel alarm and remote monitoring. If some kind of dangerous situation unfortunately occurs, you and 110 can be notified at the first time to take further action. Comfortable and fashionable home life is a sign of social progress. The smart home control system can conveniently control the home appliances, lights, power supply, and home environment without changing any home appliances, so that people can enjoy the simple and fashionable modern life brought by high technology.

The realization of intelligence is inseparable from the operation and control unit. This system uses AT32UC3A0512 as the main control device. The single-chip microcomputer application system consists of hardware and software. The hardware consists of the single-chip microcomputer's extended memory, input/output devices, and various interface circuits that realize the control requirements of the single-chip microcomputer system and related peripheral circuit chips or components; the software consists of various working programs and management programs that the single-chip microcomputer application system realizes its specific control functions. In the process of developing a single-chip microcomputer application system, the software and hardware should be constantly adjusted, and the software and hardware design should be coordinated to improve work efficiency. When the system hardware and software are closely coordinated and consistent, a high-performance single-chip microcomputer application system can be formed. This project has completed the overall design, hardware design, software design and system debugging of the single-chip microcomputer application system in its development process. According to the actual needs of development, they are coordinated, cross-linked and carried out organically. The interfaces and standards of the MCU and various chips and modules of this design strictly follow the relevant national standards, providing a good foundation for future productization.

The mobile phone remote control of this system is based on the international dual-audio communication standard DTMF communication method of the telephone exchange network. The program-controlled exchange signaling is used as the system control command and is implemented using the MT8870 dual-audio codec circuit. The single-chip microcomputer recognizes the control signal from the mobile phone network through the MT8870. The user only needs to dial the control mobile phone at home and can select keys according to the system's voice prompts to realize user identity recognition, remote control and security operations; the detection of various sensors uses the data acquisition system to convert multi-channel measured values ​​into digital quantities, and then the data is processed by the single-chip microcomputer to realize real-time measurement and control; the short message sending part uses the mobile terminal hardware circuit composed of devices such as SIEMENS TC35 GSM module TC35 modem and TI's level conversion chip MAX3238 to complete functions such as short message sending and receiving.

When designing this system, facing various detection objects and a large number of control units, it is necessary to use various interface standards and MCU for connection, and then process the data through MCU to realize real-time measurement and control. At this time, the use of single-chip microcomputer to realize the intelligent home control system not only has the advantages of convenient, simple and flexible acquisition control, but also can greatly improve the coordination of various modules and chips, thereby greatly improving the availability of the system. This system design system organically combines MT8870, TC35 modem and AT32UC3A0512 single-chip microcomputer to successfully complete the requirements of this design. And realize the learning remote infrared remote control function, which provides a good foundation for controlling infrared home appliances and equipment. This system can also be used in industry and agriculture to realize remote monitoring of unmanned posts.

1.2 Project Background/Motivation for Topic Selection

The 21st century is the information age, and various new telecommunication technologies have promoted the progress of human civilization. Since Alexander Graham Bell invented the telephone in 1876, telephone networks in countries around the world have developed very rapidly. In the past decade, China's fixed-line telephone business has shown a remarkable rapid growth. In August 1997, the total capacity of local telephone exchanges exceeded 100 million lines, and the network scale jumped to the second place in the world. At the beginning of 2006, the total number of fixed-line telephone users reached 355.392 million, and the number of mobile phone users reached 404.072 million. Modern telephone networks are exchanged and transmitted by program-controlled exchanges, and mobile communications have also moved from the analog era to the highly digital era. Their performance has made great progress, and their reliability is very high.

It is precisely because of the rapid development and improvement of communication technology, computer technology, network technology, and control technology that families have realized the modernization of life and the comfort and safety of living environment. These high technologies have affected all aspects of people's lives, changed people's living habits, and improved people's quality of life. It is under this situation that home intelligence has emerged. The main functions of smart home control systems include communication, automatic equipment control, and security prevention.

With the development of new technologies and automation, the number of sensors used is increasing, and their functions are becoming more and more powerful. Various sensors have been standardized and modularized, which greatly facilitates the design of smart home control systems.

As a relatively new topic, mobile phone remote control shows certain advantages compared with conventional remote control methods, and does not require special wiring. At the same time, since mobile phones are connected to the Internet in various places, they can make full use of the existing mobile phone network, so the remote control distance can cross provinces and cities, and even cross countries. In addition, mobile phones are duplex communication means. Therefore, this can greatly reflect the greater advantages of using mobile phones for remote control. The operator can instantly understand the relevant information of the controlled object through various prompt sounds, so as to perform further operations. Some topics of mobile phone remote control have been involved, but they are still limited to the laboratory stage, so there is still a certain gap from practical application, especially for daily life, and it cannot fully reflect the duplex communication characteristics of mobile phone remote control. This design has made great improvements in this regard, adopting single-chip intelligent control, using different prompt sounds to achieve prompts for different operations and information feedback on the status of the controlled party, so that the operator can timely understand the information of the controlled party, making the product interactive and intelligent.

Short Message Service (SMS) is an application service provided by the GSM (Global System for Mobile Communications) system for sending and receiving text messages between GSM terminals (mobile phones) through a service center, where the service center completes the storage and forwarding functions of the information. As a basic service of the GSM network, the short message service has been paid more and more attention by system operators and system developers, and various applications based on this service have also flourished. Since the GSM network has achieved networking and roaming across the country and has the characteristics of strong network capabilities, users do not need to form a separate network, which greatly improves the network coverage and saves customers expensive network construction and maintenance costs. At the same time, it has no restrictions on the number of users, overcoming the defects of traditional private network communication systems with high investment costs, high maintenance costs, and limited coverage and number of users of network monitoring. It has an incomparable advantage over traditional cluster systems in wireless network coverage, and the data transmission function of GSM SMS itself has made these applications rapidly popularized. Wireless communication using the GSM short message system also has a two-way data transmission function and stable performance, providing a powerful support platform for remote data transmission and communication of monitoring equipment. Here, GSM network is used as the wireless data transmission network. It can be applied to bank and savings point computer room monitoring, telecommunication computer room power environment monitoring, remote unattended station computer room monitoring and remote maintenance in the communication industry (such as mobile communication base stations, microwave stations, optical fiber relay stations, etc.) and other unattended points (such as warehouses, office buildings, etc.) monitoring and urban public utilities real-time monitoring and maintenance systems such as gas pressure regulating stations, tap water, sewage pipe networks and thermal systems, power systems, urban power grids, etc. This system uses Siemens' new generation wireless communication GSM module TC35, which is compact in design and has low power consumption, which greatly facilitates the design of smart home control systems.

In addition, this system applies the most popular Internet of Things technology, uses wireless technology in the terminal control devices and corresponding nodes of smart homes, and is ready to use Zigbee or RF modules to achieve an ideal wireless home environment. In addition, smart buildings are also a relatively emerging market today. The State Council mentioned the Internet of Things in the 12th Five-Year Plan, and also mentioned the development direction and key public relations of smart homes. It is believed that smart homes and related technologies such as the Internet of Things will be greatly developed in the next ten years.

Moreover, in China, although the development of smart home is not long, it can be seen from the fact that domestic home appliance giants and network giants have tried their hand at the smart home market and many international large companies have acquired domestic smart home manufacturers that China's smart home market has huge potential business opportunities. With the vigorous development of the national real estate industry, the intelligentization of residential areas has become a basic requirement. Coupled with smart homes, the concept of "full intelligence" will inevitably bring new selling points and vitality to the real estate industry. Therefore, "full intelligence" is the theme that real estate developers are pushing in the 21st century, which also means that my country's smart home industry has ushered in a development opportunity.

China's wealthy class is forming. The average annual income of this group of families is more than 56,000 yuan, with a population of about 44.6 million and more than 14 million households, accounting for 10% of the urban population, 3.5% of the total population, and about 17% of the total social consumption purchasing power of 6 trillion yuan. Therefore, the total market volume of smart home systems mainly targeting this group of people is 14 million sets. It is under this circumstance that in the past two years, the sales volume and total sales of smart home systems have shown a continuous upward trend. The smart home market has radiated from the southern coastal areas and large and medium-sized cities in the inland to the western region. In 2009, the scale of my country's smart home market reached 42 billion yuan. Due to the stimulation of a series of positive factors, the market scale will grow by more than 20% in the next few years, and it is expected to reach 124 billion yuan in 2015. This project is based on this market factor, and the smart home terminal control system is set up one by one, so it has a large market prospect.

2. Demand Analysis

2.1 Functional requirements

1. According to the current ambient temperature, humidity and light intensity and the pre-set temperature, humidity and light intensity, the indoor environment is automatically adjusted by adjusting the blinds, PWM-controlled LED fluorescent lamps, air conditioners and humidifiers to make the overall environment reach the most suitable state.

2. You can remotely control the home appliances through your mobile phone. When controlling with a mobile phone, the voice chip will record the sound in advance, and the voice prompt will enter the password. After entering the correct password, the pre-set voice command will be played. For example, please press 1 for the air conditioner, press 2 for the TV, etc., and then press Enter. There will be relevant shutdown and opening prompts. Press the corresponding button to control the home appliances.

3. It can realize simple anti-theft and alarm functions, and can take simple measures. For example, when there is a gas leak at home, it can automatically detect it, turn on the gas pump, and report it to the owner in time through text messages. It can prevent intrusion by outsiders and realize pyroelectric and other intruder detection.

4. The brightness of the LED lights in the home can be manually controlled, and the overall lights can be controlled through PWM to achieve energy saving and emission reduction, which is also in line with the environmental protection advocated in today's era.

5. Simple control and detection functions can be realized on the computer side, and the device can be operated through the remote network node.

Figure 1 System architecture

2.2 Performance requirements

1. The system can reserve interfaces for electrical appliances that may be needed in the future

2. The mobile phone remote controller is easy to use and prevents misoperation. It can identify passwords and ringing signals. Only when the password is correct can the appliance and system be controlled. The password can be modified, but the modification must be done through special means, such as setting a self-locking switch on the console end. If you want to modify the password, you must close the switch. After the modification, the switch must be opened to work normally. [page]

3. The system can meet the safety of household electricity use, requiring the LED lights to be able to manually adjust the brightness. In addition, the system is required to be able to shut down the equipment when not in use to prevent power consumption.

4. Using pyroelectric and other systems, it is possible to replace doorbells and other anti-theft functions. It is required to have two modes, home mode and home mode, and the same is true for door magnetic switches.

3. Solution Design

3.1 System Function Implementation Principle

This article uses AT32UC3A0512, MT8870, TC35 modem and various home sensors to realize the corresponding functions.

The hardware part of the smart home control system is mainly composed of five parts, namely the mobile phone remote control part, the control unit, the sensor data acquisition system, the GSM module TC35 modem and the interface and the power supply part. The mobile phone remote control part is mainly composed of MT8870 and voltage detection components, which are the key components of the control part of the system. It and the control unit form the control part function; the sensor data acquisition system, the GSM module TC35 modem and the control unit complete the processing and sending of alarm and other signals; the power supply part provides working power for each part.

3.1.1 System Hardware Block Diagram

System hardware structure diagram

3.1.2 Remote control design and analysis

The system controller receives the DTMF signal sent from the remote end by MT8870 and decodes it. The decoded signal is collected and processed by the central processing unit. In order to facilitate user use, the system is designed with a voice prompt interface. Mobile phone remote control systems generally work in an unattended environment, so they should have automatic offline, online, and reset functions. In order to meet the requirements of intelligence, the system uses AT32UC3A0512 as the central processor. At the same time, the normal operation of the telephone remote control system also requires auxiliary circuits such as power supply circuits and drive circuits. The system composition block diagram is shown in Figure 2.2-1. As can be seen from the figure, the system is mainly composed of ring detection circuit, analog off-hook circuit, DTMF audio decoding circuit, voice prompt circuit, central processing unit (AT32UC3A0512), control circuit, power supply circuit, etc.

Figure 2.2-1 Remote control system

Figure 3.2-3 Dual audio decoding MT8870 circuit

Figure 3.2-4 Language recording and playback circuit

The controller realizes relevant control through the headphone port of the mobile phone.

3.1.3 Sensor signal acquisition design and analysis

1. Fire prevention smoke sensor

Fire smoke sensor is a kind of alarm equipment commonly used in fire management and security prevention system. It is reliable and compact. Fire smoke sensor converts smoke signal into electrical signal. When designing the circuit, a special bayonet can be designed on the back to fix it on the wall or ceiling. When in use, the temperature detector in the kitchen and the smoke detector in the living room and bedroom can be used to monitor whether there is a fire in each room. If a fire occurs, the controller will send out sound, light and SMS alarm signals to notify family members and the property management department of the community. The home controller can also adjust the sensitivity of the temperature detector and smoke detector according to whether someone is at home or not. This system uses NIS-09C smoke sensor.

2Combustible gas leak sensor

The combustible gas detector installed in the kitchen monitors whether there is gas leakage in the gas pipeline and stove. If there is gas leakage, the home controller will send out an audible and visual alarm signal, and close the solenoid valve on the gas pipeline, open the window to exhaust, and send a text message to the family and the community property management department. The TP-2 high-temperature carbon monoxide sensor alarm is used here, and the system should start the alarm when the carbon monoxide concentration reaches the set value.

3 Anti-theft sensors

The protection area of ​​the anti-theft alarm is divided into two parts, namely, residential perimeter protection and residential area protection. Residential perimeter protection refers to installing door magnetic switches on the doors of the residence, and residential area protection refers to installing thermal release sensors in the main passages and important rooms. When someone is at home, the anti-theft alarm device (door magnetic switch) for residential perimeter protection is armed, and the anti-theft alarm device (thermal release sensor) for residential area protection is disarmed. When the family members go out, the anti-theft alarm device (door magnetic switch) for residential perimeter protection and the anti-theft alarm device (thermal release sensor) for residential area protection are both armed. When there is an illegal intrusion, the home controller sends out an audible and visual alarm signal, and notifies the family and the community property management department by SMS. In addition, the level of the alarm device and the sensitivity of the alarm can be set through the program.

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4 Temperature and humidity sensors

Here we use DHT-11 humidity sensor to detect indoor temperature and humidity.

5. Indoor temperature automatic adjustment sensor

By setting up a temperature sensor in the house, it is possible to monitor whether the temperature exceeds the set value. If it exceeds the set value, the ceiling fan will be automatically turned on or the air conditioner in the house will be turned on through a learning remote control device to adjust the room temperature. The temperature sensor integrated in the board is used here.

6Indoor brightness automatic adjustment sensor

By setting up a light intensity sensor in the house, the light intensity in the house can be monitored. Once the light intensity in the house is outside a certain range, the light intensity in the house can be adjusted by controlling the blinds and the lighting devices in the house to make the light in the house at the most appropriate brightness. Here, the light intensity is detected by on-board integration.

3.1.4 GSM module interface and design

1 TC35 module composition

Siemens' TC35 module is mainly composed of six parts: GSM baseband processor, GSM radio module, power supply module (ASIC), flash memory, ZIF connector, and antenna interface. As the core of TC35, the baseband processor mainly processes voice and data signals in the GSM terminal and covers all analog and digital functions in cellular radio equipment. It can support FR, HR and EFR voice channel coding without the need for additional hardware circuits.

2 TC35 module communication circuit

The data communication circuit mainly completes the functions of short message reception and transmission, communication with microcomputer, software flow control, etc. The data interface of TC35 adopts serial asynchronous reception and transmission, which complies with the ITU-T RS-232 interface circuit standard and works at CMOS level (2.65V). The data interface is configured with 8 data bits, 1 stop bit, and no parity bit. It can run at a baud rate of 300bps to 115kbps, and the supported automatic baud rate is 4.8kbps to 115kbps (except 14.4kbps and 28.8kbps). The TC35 module also supports hardware handshake of RTS0/CTS0 and software flow control of XON/XOFF.

3. Connection between TC35 module and MCU

The microcontroller and TC35 generally use a serial asynchronous communication interface, with two connection methods: infrared and communication cable. The level conversion and serial communication functions are based on TI's MAX3238 chip, and the communication speed can be set, usually 19200bps. The advantage of using an infrared interface is that the microcontroller system and the mobile phone are electrically isolated, do not interfere with each other, the interfaces are independent, and easy to use; the disadvantage is that the communication distance is short, and the directionality of infrared propagation has requirements on the relative position of the interface. When using a cable connection, the reliability of data transmission is better; its main disadvantage is that the electrical parameters of the interface are incompatible, and improper design will affect the communication quality of the mobile phone. This microcontroller system is actually a GSM mobile phone module with GPRS function plus a microcontroller control system. The GSM mobile phone module is mainly used to establish a wireless channel, receive and send short messages. The microcontroller system is used to control the mobile phone module, and interpret and execute the received short message information. At present, there are 8 short message formats in the country, including short messages sent from the Internet platform. This system uses a communication cable connection method.

3.1.4 Infrared learning remote control design

1. Concept of infrared learning remote control

For infrared controlled home appliances such as air conditioners and televisions that require infrared remote controls to control, it is impossible to put them into working state by simply connecting to the AC power supply. Therefore, I propose to use infrared remote control to control air conditioners and other infrared electrical appliances, so that the infrared learning function of the system can effectively control such home appliances. For example, infrared sockets and infrared switches, although infrared remote controls are widely used in home appliances, the remote controls of various products are not compatible with each other. The universal remote controls commonly seen on the market can only control certain products and are not truly "universal". This system can learn and memorize the remote control commands of various infrared controlled home appliances, use the single-chip microcomputer to measure the waveform of the remote control's transmission signal, and then play back the measured data. Since it only cares about the width of the high and low levels in the transmission signal waveform, regardless of how it is encoded, it is truly "universal". It also provides a good foundation for the realization of the entire controller. When the user can control such home appliances through any operation method, the infrared socket or switch will send the corresponding infrared remote control command to the controlled appliance, thereby controlling the operating state of the appliance.

2. Implementation of infrared learning remote control

After sufficient demonstration and discussion, this system is implemented by centralized control of each device. The method of centralized control of each device is to first identify and store the infrared remote control signal of each device, and then restore it when necessary to control the corresponding device action. The centralized controller is composed of a single chip, which is the core part of self-learning and restoration. The infrared receiving part is composed of a CX20106 demodulation circuit or an integrated infrared receiving head, and the transmitting part is composed of an infrared light-emitting tube and its driving part.

Usually, the infrared remote control modulates the remote control signal on a 38KHz carrier wave, and after buffering and amplification, sends it to the infrared light-emitting diode, converts it into an infrared signal and transmits it. There are many forms of binary pulse codes, among which the most commonly used are PWM code (pulse width modulation code) and PPM code (pulse position modulation code). PWM code uses a wide pulse to represent 1 and a narrow pulse to represent 0. PPM code has the same pulse width, but the width of the code bit is different. The wide code bit represents 1 and the narrow code bit represents 0.

The remote control coded pulse signal (taking PPM code as an example) is usually composed of the guide code, system code, system inverse code, function code, function inverse code and other signals. The guide code is also called the start code, which is composed of a high level with a width of 9ms and a low level with a width of 4.5ms (different remote control systems have certain differences in high and low levels), and is used to mark the beginning of the remote control coded pulse. The system code is also called the identification code, which is used to indicate the type of remote control system to distinguish other remote control systems and prevent misoperation of various remote control systems. The function code is also called the instruction code, which represents the corresponding control function. The microcontroller in the receiver can complete various functional operations according to the value of the function code. The system inverse code and the function inverse code are the inverse codes of the system code and the function code. The addition of the inverse code is to be able to check whether errors occur during the transmission process at the receiving end. In order to improve the anti-interference performance and reduce power consumption, the above remote control coded pulse is subjected to pulse amplitude modulation (PAM) on the carrier signal with a frequency of 38KHz (a period of 26.3ms), and then sent to the infrared light-emitting tube after buffer amplification to transmit the remote control signal.

Since the binary coded pulse of the remote control has a certain width, and its high and low levels are constantly changing alternately, it is easy for us to think of an easy and convenient method, pulse width measurement. Although the widths of the high and low levels of its binary pulses are different, they are mostly in the millisecond level. Therefore, it is completely possible to use the timer of the microcontroller to measure its pulse width, and then store and restore it. In practice, it has been proved that this idea is feasible, and the circuit is simple and easy to implement.

The corresponding relationship is stored in the external storage 24C256 waiting for the call to be sent.

Figure 3.5-1 Design of infrared learning remote control receiving circuit

Figure 3.5-2 Infrared learning remote control sending circuit design

3.1.5 Power supply circuit design

1. 5V switching power supply regulator circuit

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 meet the conditions that are 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 3.3-1, the switching power supply conversion completed by the LM2576 chip requires high-power inductors (100uH) and capacitors 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.

Figure 3.3-1 5V switching power supply regulator circuit

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2 Other power regulator circuits

The design of this system also involves sensor signal acquisition and signal amplification, in which the amplifier and other parts need to use ±12V power supply. Therefore, according to the design requirements, the ±12V power supply provided by the 7812/7912 three-terminal voltage regulator IC is added. As shown in Figure 3.3-2, the 220V AC power is stepped down by the AC transformer T to become 12V AC power. The low-voltage AC power is then rectified by the full-bridge to become a pulsating DC of about 17V to provide power for the three-terminal voltage regulator. The pulsating DC power is filtered by a 4700u electrolytic capacitor and a 0.1u ceramic capacitor, and sent to the input end of the voltage regulator block for voltage stabilization. Then the three-terminal voltage regulator outputs a ±12V DC voltage, and the ±12V DC power is filtered by 2200u and 0.1u capacitors to output a relatively stable ±12V DC voltage to supply power to the module.

Figure 3.3-2 ±12V power supply regulator circuit

3.2 Hardware platform selection and resource allocation

The hardware platform uses the EVK1105 provided by the 2011 ATMEL AVR Campus Design Competition. It has a light sensor and is a development board and experimental platform based on AT32UC3A0512. It has a high main frequency, a color LCD screen, and a wifi interface and USB network interface, which meets the relevant requirements of this design.

3.3 System Software Architecture

The software architecture mainly uses the operating system. The preliminary operating system plan is uC-OS II or Free RTOS, and then the corresponding program is written on it. Through the operating system, the overall hardware resources are integrated together to achieve unified scheduling. In addition, the GUI graphical interface is selected in this system to make the display more user-friendly, and functions such as touch screen can be added according to actual conditions.

System software architecture diagram

3.4 System Software Process

Program operation flow chart

3.4 Expected Results of the System

A smart home system that can remotely control home appliances through a mobile phone, automatically adjust the indoor environment according to the temperature, humidity and light intensity of the environment, and also has manual intelligent adjustment of the intensity of indoor LED lighting. It has simple anti-theft and gas leakage alarm functions, can monitor and control home appliances on the computer, and has network functions.