Overview
This was my capstone senior design project. My roles were accountant and admin of the group. I managed the purchasing funds, website page and team drive. In addition, I served as the lead designer, making most of the design decisions, creating all of the CAD and most of the physical prototype fabrication. I was also in charge of all of the graphic design.
The Team
Group Members: Johnny Yan, Kate Heitman, Patrick Hill
Problem Statement
All aspects of our lives are connected with water: the food we eat, our modes of transportation, and the rivers and lakes we so enjoy. To help keep water safe and clean the National Atmospheric Deposition Program (NADP) monitors trends in precipitation throughout North America, and tracks the impacts of pollution and other events on our environment. Currently, the precipitation sampling stations used by NADP take one collective sample of precipitation over a period of one week. This system mixes sample concentrations from separate precipitation events and allows for unwanted debris to enter the sample, reducing the accuracy of testing. Other, more complicated systems like the Digitel DRA-12 are able to separate up to 32 individual precipitation events and collect data such as weight on-site, but their cost is infeasible for the NADP. Our goal is to develop an affordable, robust event-based precipitation sampler, with additional features such as an integrated rain gauge, pH testing, and macro-filtration. Once we’ve done that, the water we rely on can be safer for everyone to enjoy.
Design
The design for our sampler consists of a CNC-like cartesian motion system with a gantry that has a claw capable of picking up and weighing the bottles. The X and Y axis motion consists of a CoreXY, belt driven, v-slot design powered by a pair of NEMA 17 stepper motors. The Z-axis is controlled using an additional NEMA 17 stepper motor and a leadscrew mechanism. Weighing the bottles is done using a load cell with a capacity of up to 5 lbs. The claw is based on a discontinued robotic claw found on a popular hobby electronics site and is driven using a DC gearmotor.
Other components of our system include a funnel that directs the precipitation through tubing which is shut off or opened using a pinch valve. The tube is positioned on the claw such that it is inserted into the opening of the bottles when the claw picks up the bottle. The 250ml nalgene bottles used to collect the precipitation samples are arranged in a grid pattern. The frame consists of a cube assembled using 20mm 8020 aluminum extrusions.
Prototyping
An initial render of the final prototype assembly.
Final Prototype
The final prototype at the NADP Poster Session
Our final prototype was constructed and completed. The CoreXY motion system, claw, bottle lifting mechanism, load cell and pinch valve were all functional and it won the Best Prototype award at the Senior Design Final Poster Presentation on May 2nd, 2019. We also presented it at the NADP Poster Session on May 14th, 2019.
The Precipistation Team at the NADP Poster Session
Johnny Yan 