Ambient air temperature aeration controller

Abstract

Aeration is an important component in the successful bulk storage of grain. Without it, grain can degrade in quality, destroying profits. To achieve the best results from aeration, an automatic aeration controller should be used. This device monitors the condition of ambient air and automatically activates aeration fans, during the coolest period of the day, to cool the stored grain. The system has been designed by researching existing control methods, in quest of improvements and alternatives, and developed into a working prototype. A PICAXE microcontroller is used to process data and determine the optimal period to operate the aerators. A combined Relative Humidity and Temperature sensor is utilised to measure the state of the ambient air. The Relative Humidity is combined with a lookup table to determine an approximate wet-bulb temperature. By utilising wet-bulb temperature, a greater cooling effect is achieved through an evaporative cooling effect. A LCD display provides a user interface exhibiting useful data in relation to the device. The CSIRO Time Proportioning Control Method was implemented, providing Normal and Rapid outputs. An alternative method of calculating set-points, involving cumulative probability, was applied. The final prototype constructed was tested successfully, logging data and determining set-points for operation. Improvements and further work aimed at improving the design are discussed.