Application based on practical granary temperature and humidity measuring system
source: 21IC Author: Wang Mingming, Wang Zhilin, Yuan Hao, pan Hui time: 2012-03-08
In order to temperature and humidity of the large granary monitor, using CC2500 RF chip SHT11 and digital temperature and humidity sensor, designed a kind of practical granary temperature and humidity measuring system based on MSP430 and the software and hardware structure based on the correlation. The system construction of the distributed wireless sensor network using ZigBee wireless communication technology, acquisition and transmission of the temperature and humidity data by the sensor nodes, network construction is simple, easy maintenance, low operation cost, can realize the reliable wireless data transmission.
Keywords: temperature and humidity; CC2500; MSP430; ZigBee; SHT11
Grain storage systems modernization put forward higher requirements on safety of food. In the warehouse management process, humidity and temperature are two important control index, directly affect the grain storage quality. In order to ensure the daily work, the primary issue is to strengthen the monitoring of the temperature and humidity in the warehouse. Traditional manual testing method is time-consuming and laborious, low efficiency, and the test temperature and humidity errors, random; if the use of wired communication network cable sensor nodes granary temperature and humidity detection network, the need for power, large scale on the granary inside cable installation work, not for subsequent inspection, repair and reconstruction. Therefore, measurement and control of temperature and humidity on the wireless, intelligent and information-based management has already become the development trend of storage technology including the granary system.
This paper adopts the design of wireless sensor network technology to detect and control the environment. Wireless sensor network does not require high bandwidth, but requires a lower transmission delay, at the same time, the power consumption is very sensitive, so choose wireless transmission chip and ultra low power embedded processor, wireless sensor monitoring network construct distributed, in order to realize network of granary temperature and humidity of the real-time detection and alarm, ventilation and humidity control.
1 MPS430 chip
The 1.1 chip function
MPS430 is a series of ultra low power microprocessor produced by TI company. Its remarkable characteristic is low power consumption, with 5 low power modes to choose from, and wake up time is very short, only 6 ¦Ì s, also has powerful processing ability, rich on-chip peripheral module, clock system flexible, stable work, convenient and efficient development way. These characteristics make it the preferred microprocessor battery-powered portable devices
1.2 chip structure
this system with MSP430F449
As the sensor and wireless RF chip MCU, the minimum system schematic diagram is shown in figure 1.
2 wireless communication network
2.1 ZigBee Technology
ZigBee is a wireless technology in short distance, low complexity, low power consumption, low data rate, low cost. Mainly suitable for automatic control and remote control field.
from the network node logic function, ZigBee equipment can be divided into terminal equipment, routing nodes, the network coordinator; a ZigBee network has only one coordinator, responsible for the equipment to start the network configuration, members of the network address, network maintenance etc.. Router mainly realize the expansion of network and routing message function, terminal equipment connected with the monitoring object is responsible for the real, is to achieve specific functional unit. The topology model of ZigBee technology can employ the star, cluster tree and mesh network structure.
The network structure of
this system uses the cluster tree network structure, the utility model has the advantages of routing is relatively simple, easy to expand, can simplify the connection. Cluster tree network structure formed by connecting a coordinator and a plurality of star structure, including a plurality of data acquisition node of each star structure (terminal) and one or more nodes, the network topology is shown in figure 2.