Sensor-based Automated Continuous Grader for Spherical Fruits

Abstract

Weight grading is capable of more scrupulous separation than dimensional grading and reduces labor cost, damage, time, and power demand and also improves grading efficiency and accuracy. Hence a low-cost sensor-based grader for spherical fruits was developed and evaluated. The developed grader comprises of fruit feeding tray, fruit controlling shaft with gate arrangement, Electronic Control Unit (ECU), mainframe, belt conveyor, power transmission system, and collection baskets. The ECU consists of a load cell to sense the weight of the fruit, an amplifier to amplify the sensor data, a microcontroller to process the sensor signal and activate the corresponding motor and servo motors to push the fruit towards the basket by activating lever mounted on it. The machine is capable of weighing and grading the fruits into four different grades (grade I: >150 g, grade II: 130–150 g, grade III: 110–130 g and grade IV: <110 g), however, the grades can be altered as per the need by uploading in the program via USB cable. The grader was evaluated in terms of efficiency of grading, capacity and mechanical damage to the fruits at grader speeds of 3, 4, 5, and 6 rpm, respectively. The capacity of grader varied from 47.32 to 156.13 kg/h under different grader speeds.  The developed grader is easy to operate and it doesn’t require skilled persons.  It can be used for any spherical fruits and varying grades by changing the threshold values in the controller.