Design of a Control System for Greenhouse Solar Dryer

Drying is one of the crucial post-harvest procedures to prevent losses of agricultural products in the Philippines. For the longest time, farmers have employed open sun drying as the primary means for drying agricultural products according to their safe moisture level. However, inefficiencies of conventional drying paved the way for innovative drying methods such as greenhouse drying, albeit it still lacks flexibility in its system implementation in the country. In this paper, a comprehensive solution is presented by the proponents through designing a control system that would reduce the health risk posed to workers by exposure to high temperatures while increasing the flexibility of the Greenhouse Solar Dryer. Aside from incorporating temperature control to minimize safety hazards, the proponents have integrated the relationship of moisture to the load sensor by ejecting the trays of commodities using a linear actuator and linear guide once they reach the required weight dependent on its moisture content with the utilization of a Proportional Integral Derivative (PID) controller. In that way, the usage of the dryer and the time remaining for the day if there is any will be maximized for drying commodities and will make the system more efficient. As a result, by controlling the PWM driver to activate or deactivate the fan, the PID controller achieves the desired temperature. The difference between the setpoint temperature and the actual temperature, known as a temperature offset, can, however, affect the system. A faster response can be attained by increasing the proportional gain, but this comes with the risk of exceeding the setpoint temperature and achieving a higher temperature than desired.