A refractance window dryer of a throughput capacity of 14.5kg/hr was developed to effectively dry food product of 3mm thickness on the conveyor belt. The dryer comprises of a moving conveyor belt onto which food product is placed and drying is achieved by circulating hot water in a tray below the moving conveyor belt. The dryer needed to be automated for effective performance, therefore the research aimed at automating the water circulation system and conveyor belt movement as well as calibrating the dryer for different food products. All systems are designed for quick response in command processing and timely output execution. The automation system comprises of an ARDUINO centered control system, an arrangement of sensors and the output components. The microcontroller receives signals from sensors and sends commands to the respective devices to operate accordingly. A computer program was written in Arduino environment and uploaded on to the control board to process all commands and respond to the appropriate output device accordingly. The program compilation was successful. All systems were first simulated in Proteus simulation environment and the simulation was a success. Components were then tested on onto a bread board before attaching the actual components onto a circuit board. In the design of the food conveyance system to achieve a smooth drive of the belt, a 2.5hp Altivar 31 variable frequency drive was selected which was able to convert single phase to 3phase power to drive the conveyor motor. The VFD mounting volume was designed to be 0.018m3 with a clearance of 50mm on either side of the drive to allow sufficient air circulation around the drive for effective cooling. For effective calibration of the dryer, a 0-5V potentiometer was used for selecting a desired drying temperature. A calibration equation was formulated with the potentiometer maximum angular sweep found to be 295° and was able to attain a 65°C minimum and 94.9996°C maximum system temperature for any selected product. In this research, the system was calibrated for mango, tomato and pineapple but the system can be calibrated for other food products since the optimum drying temperature for most food products falls within the considered range. The calibration system was found to be 97.6% accurate at attaining the desired temperature. All systems were tested for performance and the results showed that the systems run efficiently as simulated. The tests revealed a timely command execution where the system turned on the conveyor belt and water pump only when the desired water temperature set by the knob was reached in the boiler. A product performance tests was done on mango slices at 85°C that revealed a total drying time of 90 minutes to change moisture content from 77.9% to 22.4%. The highest recorded temperature at the tray entrance was 89.9°C after 50 minutes of drying, and the lowest temperature was 31.1°C at the exit of the tray. However, dried slices were found stacked on the conveyor belt after cooling making it difficult to remove. Eliminating the cooling section of the dryer is recommendation to possibly ease dried product removal from the belt based on the previous trials. The food system, water system and conveyor system were found well synchronised in a timely manner. Therefore the setup can be up scaled to a bigger dryer.

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