Seed State-Detection Sensor for a Cotton Precision Dibble

Abstract

In Xinjiang, precision hole-sowing technology is used for cotton cultivation. A disc-type seed disperser has problems with missing seeds and multi-seeding; therefore, an interdigital (multiple pairs of coplanar electrodes crossed) capacitance sensor is designed to determine the seed pick-up status by gathering electrical capacity information. Firstly, a theoretical derivation is performed for calculating the capacitance of the sensor, and it is concluded that the interdigital spacing, interdigital width, and interdigital logarithm all affect the output capacitance. Then, by analyzing the working process of the dibble, the assemblage position of the sensor and the dimensional constraints were determined. In order to explore the impact of various structural parameters on the sensor’s performance (signal strength and capacitance variation), a Maxwell simulation platform was established, and orthogonal tests were created to optimize the structural parameters. In addition, the STM32 microcontroller is utilized as the core, and it is linked with the PCAP01-AD chip to form a tiny capacitance-detecting circuit. Finally, the capacitance threshold division test determined the capacitance threshold at different seed states. The test results demonstrate that the interdigital capacitive sensor can accurately determine the precision dibble’s seeding status, with detection accuracies of 96.9% for normal seeding, 99.67% for miss-seeding, and 93.77% for multiple seeds. These results can be used as a research reference for capacitive seeding status-detection technology.