Research For The Intelligent Temperature And Humidity Detecting System Of Grain Depot

This paper designs an intelligent temperature and humidity detecting system of grain depot that based on MCU and sensor, which performs real time measurement of temperature and humidity of the air in the grain depot. The administrator can monitor the temperature and humidity of the air conditions in the grain depot by using it.The system adopts multilevel distributed structure and multi-MCU technique composed of the upper set, the mid-controller and the lower set. The lower set mainly fulfils the environment data collecting and processing. Then the data will be transmitted to the mid-controller through RS485 BUS. There is one mid-controller in each grain depot that displays the data transmitted by the lower set in turn and gives off an alarm signal when the data is beyond the threshold value that was set by users. The upper set performs the mid-controller address setting, the mid-controller working condition inquiring and the threshold value of environment element setting and then achieves uniform management of several grain depots.Adopting multilevel distributed structure not only avoids the loss of analog signal caused by long-distance transmission, but also simplifies the wiring and facilitates adding the amount and sorts of sensors. The system is easy to be extended and upgraded.In the paper DS18B20 and HS1101 are used as temperature and humidity sensor respectively. The output of DS18B20 is digital value. HS1101 and 555 Timer composed an oscillating circuit, so the output frequency of the oscillating circuit is linear to the humidity. The signals of temperature and humidity are directly delivered to MCU without via amplifier and A/D, so the measurements of temperature and humidity are more precise than before.This paper brings forward a method to expand the UART of P89C662 by using an AT89C2051, which performs the unattached communication between the mid-controller to the upper set and the mid-controller to the lower set.The paper mainly completes both the software and hardware design of lower set and mid-controller and presents a kind of intelligent temperature and humidity detecting system that can be applied to the grain depot.