Design of ZigBee Environment Monitoring system

In the environment monitoring of the smart home, the environment monitoring of mine, the environment monitoring of granary, the environment monitoring of the agricultural greenhouse, if the traditional cable monitoring method is used, it will lead to cumbersome wiring, high construction cost, inconvenient maintenance and poor expansibility and mobility of the system. Wireless monitoring System Not only eliminates a lot of wiring work and maintenance costs, but also more standardized network deployment. In recent years, wireless technology has played an increasingly important role in network application with its superior flexibility and convenience.

1 System Design

1 . 1 ZigBee wireless network

ZigBee A digital network is typically composed of a coordinator (Coordinator), a router (Router) node, and a sensor (End-device) node. The coordinator is a full-featured device FFD, which is responsible for creating and maintaining the entire ZigBee Wireless module network and assigning addresses to nodes that join the network, each of which must have and have only one coordinator. Router is also a full-featured device, responsible for signal routing, according to the actual situation set number.

sensor node, also known as terminal equipment, is a semi-functional equipment RFD (reducedfunction device), responsible for signal recognition and data transmission, consisting of multiple components.

According to the combination of nodes can form three kinds of network topology, such as Star, tree and Net, which plays an important role in network management and data transmission between nodes. ZigBee Wireless Module network architecture, data communication, each device needs to be assigned a network address, the allocation of the address depends on the entire network topology, and is determined by three values: the maximum depth of the network, The maximum number of child nodes owned by each parent node and the maximum numbers of routers in the maximum children node owned by each parent node. But the network address does not need to be artificially calculated, the system automatically assigns.

1 . 2 system design

The system uses a Star wireless sensor network structure, comprising a coordinator node and a number of sensor nodes, the structure is shown in 1 . The host computer is connected with the coordinator node by USB to RS232 , and the coordinator is connected with the sensor node through ZigBee Wireless digital transmission. After the coordinator establishes the ZigBee Digital transmission Module Network, the sensor node will automatically dialogue with the coordinator after power-on, and then join ZigBee Wireless network after successful matching. Then through the ZigBee Digital Transmission module transmits the sensor node data to the Coordinator, the coordinator then transmits the data transmission to the machine, by the host computer completes the data processing and the preservation, realizes the environment parameter ZigBee data collection.

Figure 1 network structure diagram

2 Hardware design

The hardware design of this system mainly involves the design of two kinds of nodes, sensor node and coordinator node. At present, ZigBee Wireless module node generally has two modes: one is to integrate the whole system into a module, the other is to design the ZigBee RF Transceiver Module as a separate module. The former system integration is good, small size, but the compatibility is poor, the latter extensibility is better, and other radio frequency modules can be used, but also used for other uses of wireless network systems. This system adopts the second method, the sensor node and the coordinator node adopt the same ZigBee wireless module .

2 . 1 sensor nodes

The system uses CC2530 single chip, which is based on IEEE 802. A. 4 Standard and ZigBee technology applications, combined with RF transceiver, enhanced 8051 CPU, Memory and ZigBee protocol stack, etc. Wireless network communication and ZigBee data acquisition can be accomplished with a little peripheral circuit and internal programming. Based on CC2530 chip design Radio frequency module, small size, low power consumption, reliable communication, high efficiency, the structure is shown in 2 .

Figure 2 sensor node hardware structure diagram

2 . 2 Coordinator node

The coordinator node adopts figure 2 sensor node hardware structure diagram is the core of the whole system, responsible for the work of the sensor nodes, but also to the sensor node data sent to the host computer. Therefore, in the design of the coordinator node in addition to the same as the sensor node ZigBee Digital transmission module , but also with the host computer communication circuit,3 is shown.

Figure 3 Coordinator node hardware structure diagram

3 Software Design

3 . 1 Upper machine

The system control by the host computer execution, the upper and lower machine has asked to answer, no answer not to execute. The upper computer operation interface is written by VB , the image is intuitive and easy to operate. When the host computer works first serial port initialization, and then detect whether there is a network exists, if there is a collection of environmental parameters, the specific flow 4 .

Figure 4 host computer workflow

3 . 1 Coordinator node

The Coordinator power on the physical channel active scan, select the appropriate physical channel and network number, set up a network. The coordinator based on the command from the host computer to collect data, according to the network address for data transmission and reception, the specific work process 5 is shown.

Figure 5 Coordinator node main flowchart

3 . 2 sensor nodes

After the sensor node is power-up, select the appropriate physical channel and network number and join the network according to the configured physical channel passive scan.

According to the command from the coordinator, data collection and transmission, the specific work process 6 is shown.

Figure 6 sensor node main flowchart

4 Commissioning and application

The test system is composed of upper computer and subordinate machine. The lower machine mainly consists of 1 coordinator nodes and 3 sensor nodes, the Coordinator and sensor node 1 is placed indoors, the sensor node 2 is placed in the corridor, the sensor node is placed outdoors, The temperature and luminosity of the system are tested at different points in time, and the results are shown in table 1 .

table 1 temperature test comparison table

5 Concluding remarks

This paper constructs a ZigBee wireless network system based on CC2530 , and carries out the ZigBee data acquisition test for temperature and luminosity, the results show that the system is reliable and the measurement result is accurate. The system can not only measure the temperature, but also promote the measurement of other environmental parameters, such as humidity, smoke, and the system can also be extended to other areas of application, such as campus security system, the elderly apartment monitoring system.

Design of ZigBee Environment Monitoring system