Many commercial greenhouses and indoor grow operations currently use the artificial light sources such as high-intensity discharge (HID) or high-pressure sodium (HPS) lamps to optimize plant growth in a controllable environment. Recently, the light-emitting diodes (LEDs) has been introduced as the alternative light sources, thanks to its benefits (compared to the traditional HID/HPS bulbs) of light intensity, energy-use, control, longevity, heat control, color spectrums, power management, and long-term costs. The Photosynthetic Photon Flux Density (PPFD), which is a measure of the number of photosynthetically active photons per area per second, is found to be a key parameter facilitating photosynthesis, hence promoting plant growth. Therefore, the aim of this work is to artificially supply the necessary PPFD values through the height adjustment of the LED lights to maintain the threshold PPFD values required for the optimal growth rate of the specific plant species of concern. A pulley-based, semi-automatic system has been proposed earlier, which consists of a movable LED light fixture positioned by a DC motor through a speed-reducing gearbox. A set of ultrasonic distance sensors were implemented for measurement of the distance between the plants and the light fixture, and the Arduino microcontroller along with an H-bridge is implemented to change the direction of rotation of the motor to raise or lower the light fixture. The apparatus spans an existing table size of 36 in. by 96 in., and the suspended light fixture size is 24 in. by 84 in. In this work, a series of efforts have been made to improve the performance of the apparatus to allow for a more reliable operation. First of all, small structural improvements have been made at the component level, which include the replacement of the 3D-printed gears with real ones, waterproofing the control panel, and reducing the noise due to the friction between the cord and the pulleys. A better sensory system has also been implemented in the upgraded system. Ultrasonic sensors were found to be too delicate to work in a humid and dusty environment inside the greenhouse. Moreover, the system were easily fooled by the sound waves that were bouncing off from the ground when the platform was too close to the ground. As a solution to this problem, a Pixy2 model camera has been implemented to replace the ultrasonic sensors, as the camera provides a better reading once calibrated using a reference object of known dimensions. Finally, a diffuser is added to provide a smoother distribution of the light intensity across the entire platform. With the changes implemented, the upgraded apparatus will improve the functionality and the overall lifespan of the proposed system, thus improving plant growth and aiding better quality research into botany.


Design and Implementation of a Pulley-Based Movable LED System for Optimal Plant Growth

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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