Grain Situation Measuring And Controlling System Based On Low Pressure Power-line Carrier

Along with our country national economy's unceasing development, the country enlarges unceasingly in the agricultural aspect's investment, the implementation in the national subordinate stockpiles the grain storage items, more and more high request has been put forward to grain situation measuring and controlling system. The grain situation measuring and controlling system has become the modernized grain storage necessary security Grain preserve management infrastructure. In four item of grain preserve new technology ( The grain cools, Mechanical ventilation, Circulation fume, Grain situation measure and control), the Grain situation measure and control is a foundation, is the grain preserve success's or failure's key, it is each item of grain preserve technology running status viewer and the movement result real reflection. At present our country's grain situation measuring and controlling system has some problems, urgent needs to design one kind newly to adapt our country national grain situation measuring and controlling system. Complied with the situation need, this article has designed one kind grain situation measuring and controlling system based on the low pressure power line carrier..This system is composed of the superior machine (the PC computer), the measuring and controlling main apparatus , the measuring and controlling extension apparatus, the temperature and humidity instrument, the collection station ,the air blower controller, the temperature measurement cable and so on. It is one includes the grain situation measure, the intelligent analysis and the air blower controll bigger scale computer system. The superior machine and the main apparatus places the computer room of the grain situation measuring and controlling system, Their distance is very near, between connects with RS232. the extension apparatus to place each extension apparatus box, they use the grain storage ready-made low pressure power line are connected through the low pressure electric power carrier and the main apparatus. the temperature and humidity instrument, the collection station ,the air blower controller meet the extension apparatus through special-purpose four core cable. The temperature measurement cable and the collection station is connected.The main apparatus and the extension apparatus are the typical microprocessor system, select contains Flash memory's AT89C51 (or AT89C52) the microprocessor system, like this does not need to carry on program memory's expansion, both reduced the volume, the weight and to enhance the reliability. the main apparatus is mainly completes the superior machine and the extension apparatus correspondence protocol conversion, it connects the superior machine by 232 levels, and connects extension apparatus by special-purpose electric power modulation demodulation chip SC1128 through the power circuit. This may use the ready-made low pressure power line network substitution to need to lay down the special line 485 or the CAN main line network, reduced the system cost greatly and the installation and trial run the difficulty. the extension apparatus major function is: (1) gathers the air temperature and humidity and the grain temperature information to save, display; (2) adopts the low pressure electric power carrier and the superior machine communication; (3) acts according to the superior machine command to control air blower controller movement; (4) provides the power source to the collection station and the temperature and humidity instrument and so on. the extension apparatus also to be able to be separated from the network work, after namely is separated from the superior machine network, can complete the observed value to inspect independently, the data demonstration printing, the value hypothesis, the draft control and so on, when the superior machine or the communication network present the breakdown guarantees the grain situation measure and control.In this system, The grain temperature is a key parameter which its must monitor, this parameter is measured by Collection station through the temperature measurement electric cable's temperature sensor in the grain piles. The collection station design quality direct relation grain temperature examination accuracy. In order to control the cost, this system's temperature sensor still selected the thermistor, but selects the collection station which is composed of Microchip Corporation's PIC16C57(Because it has the work supply voltage scope width, the power loss lowly, internal to include the watch-dog, the price low) to replace the existing system's jack box. Using the PIC16C57 software and hardware's coordination, does not need the independent A/D transformation chip to complete the temperature digitized gathering. Like this both simplified Collection station structure, and causes its and the extension apparatus by the digital quantity transmission, reduced disturbance in the transmission, enhanced the temperature measurement accuracy.The granary inside and outside air's humiture is another key parameter which must monitor this system, it is examined by the temperature and humidity instrument which is hanging in the granary inside and outside The temperature and humidity instrument's design holds the pivotal status in the overall system. In this temperature and humidity instrument, the temperature examination are completely same to the collection station. The humidity sensor still selected the low in price the electric capacity type, its examination electric circuit obtains one along with the electric capacity change frequency value Using 555 oscillating circuit's frequency along with capacitance value change principle of work. The frequency value after humiture meter's PIC16C57 gathering transmits for the extension apparatus. , the table look-up may obtain the corresponding humidity value in the extension apparatus. Like this both has achieved the humiture meter and extension apparatus's digital quantity transmission, and has saved A/D switching circuit, has guaranteed the humidity examination precision. The air blower controller's function is equal to the multi-relay switch electric circuit, it acts according to extension apparatus's signal to decide that relay's opening and closing, achieves controls the goal which the air blower gets up stops.The superior machine selects the ordinary computer, computer's software selects object-oriented development language Delphi to complete. Its major function is processes the data which the extension apparatus transmits and sends control command to the extension apparatus according to the processing result, Saves possesses by the measuring point historical data and according to needs to demonstrate that to print certain by functions and so on measuring point observed value and parameter variation curve.In this system, because uses power line this widespread application the resources to take the communications channel, it cannot lay down the communications cable, the construction quantity is small, the investment province, the service is convenient; Because the existing system temperature and humidity examination electric circuit has been made the improvement, it caused them also to use in the original moderately-priced sensor's situation to enhance the stability and the accuracy; The main apparatus and the extension apparatus have been carried on the redesign by using 89 series microprocessor, these made their structure to be simpler, their stability to be higher, their volume to be smaller; The computer software is designed by using delphi which is ideal tool of design operation contact surface, these cause its operation contact surface to be friendlier, to be more direct-viewing. This system has obtained user's widespread approval In the experiment movement.