Development and evaluation of electro mechanical seed metering device for raised bed planter
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Date
2012-06-30
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Abstract
One of the main factors affecting the quality and quantity of mechanized crop production systems is planting operation. The more precise the planting operation, the better the quality and quantity of crop harvested, precession of planting operation is highly influenced by type of seed metering mechanism. To increase the precision of seed metering mechanism for a better crop productivity electro-mechanical seed metering device was developed and fixed with the existed raised bed planter. The system is consisted of: (1) electronic-controller unit (ECU), (2) wheel speed sensor, (3) DC motor for driving seed dropping mechanism, (4) opto-electronic seed counter. Instead of ground wheel DC motor was used to drive seed metering mechanism. The wheel sensor measures tractor wheel speed. Based on travel speed information, speed of motor was synchronised to drop the seeds and to maintain the proper distance between the seeds. The speed synchronization can be achieved by precisely controlling the input of the high current drive circuits through PWM (Pulse Width Modulation) channel of microcontroller. The speed calibration for a better synchronization of motor speed with forward operation speed was done. According to the laboratory speed calibration the electro mechanical raised bed planter (EMRBP) was operated at speeds between 2.60 to 5.40 km h-1 and recommended seed rate and seed distribution was obtained. In order to count the number of seeds dropped during seed sowing process, an optical through beam sensor was developed.
The performance evaluation of the unit under laboratory and field was conducted on maize (CoH-3) and groundnut (TMV-2) crops for seed spacing, seed rate at different hopper depth and forward speeds. The performance of opto-electronic seed counter was also evaluated for both crops Maize (Varity; CoH-3) and groundnut (Varity; TMV-2). It was evaluated with three different rotor speeds (10, 15, 20, 25 rpm) and at motor speed of 12, 24, 36, 48, 60 rpm at a constant optimal forward speed of 3.6 km h-1. The experimental result showed that the mean number of seeds dropped (electronic count) from the metering mechanism at different seed plate speeds for maize was from 432.78 to 446.26 whereas for groundnut 436.85 to 445.63 against 450 theoretical number of seeds to be dropped from hopper. The electronic seed counter developed for row crops of maize and groundnut counted between 98.11 and 98.45 percent of the actual (hand counted) seeds by sensing the seed flow through the seed tube by which the operator could observe functioning of the planter. The EMRBP performance was compared with ground wheel raised bed planter (GWRBP). The effect of operational speeds (2.60, 3.6, 5.4 km h-1) on seed spacing was evaluated by examining the mean seed spacing, precision in spacing (coefficient of variation), miss index, multiple index, and highest quality of feed index. It was observed that raised bed planter with electro mechanical seed metering device gave superior (optimum) performance at all forward operation speeds that ground wheel raised bed planter. The electro mechanical seed metering device operating at forward speed of 3.6 km/h produced superior results with a feed index of 98.30 % and 98.0 % and a coefficient of variation in spacing of 2.10 % and 2.31 %, recording a mean seed spacing of 151 mm and 101.25 mm (recommended spacing 150 mm and 100 mm) for maize and groundnut respectively.
Based on the optimised operational parameters, performance indices of EMRBP were determined under field conditions by measuring the distribution of cotton plant spacing. A mean plant spacing of 152.25 mm was found in the field with a 6.05 % and 6.03 % precision (CV) for maize and groundnut respectively. The 95.75 % and 96.89 % of maize and groundnut seeds were distributed within acceptable range of 75-225 mm and 50-150 mm respectively in case of EMRBP whereas it was 86.62 % and 85.77 % in case of GWRBP. As laboratory and field results showed the overall performance of the electro mechanical seed metering device of raised bed planter was much better than the ground wheel driven seed metering mechanism of raised bed planter.
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