Design, construction and evaluation of a non-contact tool for estimating crop density by laser beam

Crop density measurement is one of the most important factors in precision farming and effect on the performance of harvesting machines such as combine and mower. So، the purposes of this study are to design، build and calibrate of an inexpensive and non-contact instrument that can estimate crop density for crops such as wheat، barley and alfalfa stems. The sensing unit is consisted of laser transmitters، LDR receivers and AVR microcontroller used as register and data processing unit. Experiments were done on Polystyrene plates for alfalfa and barley stems. The LDR receivers receive the reminder of the laser light which passes through the crop stems and with using analog to digital converter in the microcontroller data was stored on internal memory of micro and displayed on the display. Total LDRs voltage was used as an indicator of density estimating. This voltage is proportional to the density of the crop stems and the results of the voltage measurements show a correlation of 0. 93 to 0. 98 percent between the voltage and the value of alfalfa density and R2 = 0. 9 for barley. Ambient light was a factor that affecting the amount of voltage and to eliminate this effect، receivers were placed in a protective aluminum box. This method has the potential of estimating on the go measurement of various crop densities.