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Smart home technology based on ZigBee wireless sensor network design

In Electronic Infomation Category: S | on April 21,2011

With the development of the times, people will focus more attention on the living environment of safety, comfort and AD734BN datasheet and convenience, and AD734BN price and thus give rise to the concept of smart home. Intelligent home control system makes it possible for any home appliance for the digital control, the use of computer technology, network communication technology and AD734BN suppliers and home life, the organic combination of a variety of devices, centralized management, so home life more comfortable, safe and effective. In this paper, ZigBee technology for intelligent home network within the wireless network, through the ZigBee wireless sensor network node design, implementation of various sensor node information collection, transmission and control functions.

1 Zigbee technology

ZigBee technology is a great emphasis on low power, very low-cost short-range wireless network technology, follow the IEEE802.15.4 standard. It focuses on low-rate transmission control, network capacity, time is short, to provide data integrity checking, encryption algorithm AES-128, network scalability strong, effective coverage range of 10 ~ 75 m, the specific basis of the size of the actual transmission power and a variety of different applications the mode, basically to cover normal family environment, communication frequency is 2.4 GHz unlicensed band.

ZigBee is a wireless standard based on IEEE802.15.4 developed, the networking, security and application software, technical standards. IEEE802.15.4 MAC layer and only defines the physical layer protocol, while the ZigBee Alliance is its network layer and application layer were standardized. ZigBee Alliance has also developed security layer to ensure that no accidental release of the portable device identification, and that such use will not be long-distance transmission network access to other nodes.

2 System Design

Wireless sensor network system consists of sensors, CC2430 wireless modules, the structure shown in Figure 1.


Figure 1 System structure diagram

Wireless sensor network using tree structure, the network has a coordinator, responsible for the entire network, data processing, forwarding and network management. Terminal nodes (sensor nodes) on reset, it will search for the coordinator node, while able to search coordinator, direct application to join the network. When the terminal node search not the coordinator, the time will be found through the router node to join the network coordinator.

After joining the network to maintain the standby mode, when data needs to be sent, in accordance with the path when the network to send and receive data. Coordinator and the PC, connected via the serial port using HyperTerminal to send commands to achieve or display data.

3 Hardware Design

The designed wireless sensor network system hardware structure is dominated by coordinated modules, router modules, sensor modules, serial converter modules, power modules and PC, and so on. A coordinator, router, sensor 3 modules as the primary wireless communication module, the master chip CC2430 as the data processing and wireless transceiver. Schematic diagram of the system hardware circuit shown in Figure 2.


Figure 2 Schematic diagram of the system hardware

3.1 control chip

Used as a wireless transceiver CC2430 chip, and data processing and controller. CC2430 single chip RF front-end integration of ZigBee, memory and microcontroller. It uses enhanced 8051MCU, 32/64/128 kB flash memory, 8 kBSRAM and other high-performance modules, also includes analog-digital converter, several timers, AES-128 co-processor, the watchdog timer. 32 kHz crystal oscillator timer sleep mode, power on reset circuit, brownout detection circuit and 21 programmable I / O pins.

3.2 wireless module design

1) coordination module

Coordinator node by the voltage conversion module, the key modules, LCD modules, LED indicator, clock, processor CC2430, antennas and other components. CC2430 operating voltage of 3 ~ 3.3 V, so use the voltage converter module reduces the voltage from 5 V to 3.3 V or so; LED indicator to display the coordinator node network state information (such as whether the network successfully); LCD module is user interface and sensor networks, to display the power up to the menu, the user through the button to select the function menu. The circuit shown in Figure 3.


Figure 3 node circuit

2) sensor module and the router module

Sensor module which is a terminal node module, consists of sensors, processors, CC2430, Antenna, LED indicator, clock and other components. LED lights from the P1.0, P1.1 port control. Sensor module is based on the coordination module to remove the LCD, and joined the sensors. Sensor selected DHT11 temperature and humidity sensors, and P0.0 port connected, to be responsible for data collection. Router module and the sensor module, the same hardware, just different programming functions.

4 Wireless Network Software Design

In the ZigBee network, only those who can be a ZigBee coordinator device to create a new network. First, the Executive Coordinator channel scan, if you find a suitable channel for the new network coordinator will select a PAN ID, and then the coordinator into the * state of readiness to respond to other nodes in the network request.

ZigBee network, there are two types of devices: full function node (FFD) and semi-functional node (RFD). RFD for the terminal nodes, FFD can serve as a coordinator or routing. Software design process including the network coordinator and routers, terminal node. They are including initialization procedures, protocol stack configuration, networking configuration program, the processing layer setup and launch programs and receive program. Initialization program mainly for CC2430, Stack, UART serial port initialization, etc.; launch the program the data collected and passed through the modulation CC2430 RF output directly to the DMA; receiving data reception process is completed, remote and return information processing. Main program flow shown in Figure 4.


main program flow chart in Figure 4

Main program is divided into two parts, the network program coordinator and routers, terminal node.

Network coordinator for the main program, first initialize the CC2430, and then initialize the protocol stack. After the procedure to create a new network, determine the network ID number and channel number. After the program began to enter the monitoring state. If a new device request to join the network, the network address assigned to approve its accession to the network. Similarly, the coordinator sends to the wireless terminal device receives information and sends to the host computer through the serial port, or receive commands from the host computer, sent a terminal device.

For routers, terminal node program, first initialize the CC2430, and then initialize the protocol stack. After the program starts the search network, when the neighborhood of the network, then apply to join the network. After the program enters standby hibernation. If the terminal sensor information to be sent, or received by the coordinator of the command, then wake up the device, the wireless transmit or receive. When the event processed, to re-enter standby hibernation.

5 system to achieve

Function of the system include the following aspects: the establishment of tree topology; query each node in the network of information and sensor data, such as battery power, junction temperature information; control node of the switch functions.

The system uses four wireless network nodes, this can form a basic wireless network. And under the circumstances to do a variety of network test:

1) 1 a coordinated node, three terminal nodes;

2) 1 a coordinated node, a router node, two terminal nodes;

3) 1 a coordinated node, two router nodes, a terminal node.

2) and 3) cases, according to the coordinator node and the distance between the nodes, the distance between the different nodes, will produce a variety of networking. For example, 2) case, the terminal nodes from the coordinator the past, then connect directly with the coordinator; and when not search coordinator, it will connect through the router. Figure 5 to 3) in case of a network structure.


Figure 5, node management interface

Figure 5 shows C51RF-WSN network monitoring software capture, through this software, you can view network status in real time and can send commands to the various nodes of information, for example, view network status, view the signal quality, battery power, data acquisition information.

Smart home system can include many elements of the terminal nodes in order to achieve a number of subsystems. For example: lighting, climate control, alarm system, home appliance control system. In our wireless network system designed to achieve the remote control light switch lighting; use DHT11 temperature and humidity sensors to achieve the temperature and humidity monitoring terminal node, the information can be very good in PC, display.

Figure 6 shows the measured two sensor nodes and a terminal router nodes temperature and humidity information.


Figure 6, temperature and humidity information

6 Conclusion

For the rapid development of intelligent home background, this paper based on ZigBee technology for intelligent home networking hardware and software design. ZigBee wireless sensor network system to CC2430 RF chip as the core, saving costs, and terminal node size, placement flexibility, low power consumption, improved monitoring capabilities, coupled with a tree network structure makes communication more reliable, easier to control very convenient and practical, and low cost. Therefore, ZigBee technology will have broad application prospects.

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