Robotics

MARSH

At the beginning of my senior year, I became interested in autonomous growing methods. Having been brought up on an organic farm and studied soil amendment properties for tropical oxisols, I had some of the necessary fundamentals for understanding plant growth. During the summer I took an advanced elective at UCLA that covered sustainable cities and architecture and was inspired by the urban farming practices that utilized large scale equipment and advanced technology to optimize plant growth in cities. When I came back to school and began working in the lab once again, I was motivated to create this autonomous hydroponics machine that was a similar size to a desktop FDM 3D printer, no larger than the footprint of the Makerbot 2x model (1 ft x 2 ft x 2 ft). I imagined that this machine could be used by students and urban dwellers who wanted to grow an array of plants, but did not necessarily have the know-how or the time to do this. Since I was a full time student and I had wanted to grow my own plants in my small apartment, this became the perfect opportunity to do so.

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MARSH User Interface

Over the course of my senior year, I designed and built the MARSH to be an automated hydroponics system that tracks and provides a closed loop nutrient/environmental system, which optimizes plant growth and maintains the user’s garden with little to no user input. MARSH was designed mechanically to be modular so that the user could disassemble and reassemble MARSH relatively easily during cleaning scenarios. Its small footprint made it versatile to place around the apartment or house and it’s closed encasement prevented bugs and other pests from entering the system. While the first prototype was designed to provide system feedback to the user’s computer as well be the user’s interface to the module using a line connection, the later MARSH prototypes would incorporate an app that the user could access from their phone.

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MARSH Prototype I activated.

Technically speaking, this prototype featured a range of sensors within a 3-gallon reservoir container. Three pumps individually controlled the inflow of fertilizer, water and aeration in the reservoir. The tank aeration was set at a constant value whereas the water and fertilizer (slightly acidic fertilizer) were controlled based on the feedback from a pH sensor. If too acidic, some water would flow into the tank, if too basic, some fertilizer would flow into the tank depending on the necessary pH needed for the specific plant, thus a variety of plants could be grown within. The system limited the amount of fluid that could be pumped into the reservoir at a time with a water level sensor, so that the reservoir would not overflow. The upper roots of each plant were provided with a light spray of water whereas the bottom roots were soaked in the reservoir.

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MARSH Prototype I deactivated.

A heating and cooling system provided the necessary temperature to the reservoir and the plant’s chamber. When the temperature sensor (also a humidity sensor) required the reservoir or the plant chamber to be a certain temperature, the resistance heaters would turn on for a period of time and if the plant chamber needed to cool down, then a steady air stream would enter via an inlet filtered fan and then be released through an exhaust vent. Heating the reservoir also meant that a certain amount of vapor could be produced to increase the humidity in the chamber via the passive vents between the reservoir and the chamber. The lights in the current prototype were specifically chosen for both the growing and flowering stages.  MARSH was designed to offer the means and lightning for germination (within the dry reservoir tank), growth and flowering.

In regards to materials, the reservoir was made of black, cast acrylic and food-grade silicone sealant since polymers are inert and an opaque material so that light was blocked from reaching the reservoir so as to not encourage algae growth. The supports were made from 80-20 due to its easy prototyping nature and the water/fertilizer tanks were made from average off-the-shelf tupperware. The panels surrounding the growth chamber were made from clear, cast acrylic due to its ease of laser cutting/machining. Clear acrylic allows for the user to see what’s happening in the growing unit, but unfortunately does not block the exposed light.  A majority of the electronics were purchased from Robotshop, Adafruit and Digikey whereas the rest of the raw materials and vent/fan components were sourced from McMaster and the lights were sourced from SuperLeds.

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With Tonie Leatherberry and other BU ENG alumns discussing the importance of utilizing hydroponics to grow healthy foods.

Lettuce was grown in the chamber (was not germinated in MARSH). The machine was then entered into Boston University’s College of Engineering’s 2017 Imagineering Competition (an annual competition sponsored by the Imagineering Lab for sustainability and innovation). The MARSH won first place. Overall the MARSH gave me my first real challenge in systems engineering. My academic background is in mechanical engineering and thus learning circuitry, software and then interfacing all of these different components into a single device was fairly difficult. Not only did I learn various hands on skills, but I also learned how to bring an idea from design to reality. I also learned how it’s so important to begin interfacing electronics and other disciplines together during the design phase in order to avoid assembly problems in the latter stage of the product’s development cycle. While there are many things I want to improve in the current configuration of the Marsh, I am overall pleased with the outcome of the product. Future iterations of the Marsh will entail a means to grow the machine with the plants, reduce the amount of supporting material/components utilizing DFMA, reduce the price per unit, limit the amount of light exposure that may affect the user’s eyes and create a simple, yet effective user interface. I hope to one day create something that can be used by NASA.

Find more information in these articles pertaining to the competition.

Author

smundon@bu.edu

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