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Mabee Dining Hall at Trinity University has tasked the Mabee Organic Waste Solution team with the design and implementation of an in-vessel monitoring and alert device to monitor and report on the status of compost. This device is intended to provide running updates on important parameters - temperature, relative humidity, and oxygen concentration - in order to ensure production of successful, aerobic compost. If action must be taken by Mabee employees as a result of the values of these parameters falling out of an acceptable range, our device is capable of alerting the user and providing instruction to keep the compost viable.
The project requirements state that our device must be able to monitor up to 100 pounds of food waste while mitigating additional labor and unnecessary contact with the compost. It must be durable and reliable enough to withstand a full composting cycle, and intuitive enough that a user with minimal knowledge of compost care will be able to follow the given instructions with the help of a training manual provided by the team. Design constraints include the given $1200 budget, portability, ease of use, and the versatility to be implemented in any in-vessel composting unit supplied with ~100 lbs. of food waste daily. The design constraints are detailed in Sections 3.1-3.4. The full design requirements can be found in Sections 3.5-3.9.
Our final design consists of three main subsystems: the sensor capsule, which rests inside the compost to house and protect the sensor, the communications system which interprets sensor readings and transmits instructions via Bluetooth to the interface, and the interface which displays any necessary corrective actions that must be taken. Our team was able to complete preliminary testing to ensure that each subsystem is functional within the constraints of our project. In the future, we recommend fully testing the system by placing it within a compost vessel for a complete compost cycle. Additionally, as conditions across the compost are generally not homogenous, use of multiple sensor capsules throughout the vessel to provide a more comprehensive observation of the state of the compost may be beneficial.
The central microcontroller of the partially working prototype failed to display the data from its peripheral counterpart, but the devices were still able to communicate with each other and send the sensor data. Due to a short in the wiring, the working prototype’s sensors were damaged and the microcontroller in the peripheral likely to be replaced. We are mostly confident that our current prototype meets the power requirements to last a full composting cycle with our chosen battery. The corrective actions written by our team to be prescribed by measurements of the compost conditions have demonstrably improved the state of the compost in our test environment. At the time of the presentation we intend to have resolved the hardware issues with the interface subsystem, and have a fully functional working prototype ready for delivery to our sponsor.
Terry, Conner; Sturdivant, Evan; Rosenbaum, Emily; and Castillo López, Krishnan, "Monitoring and Alert System for the Mabee Organic Waste Solution Final Project Repory" (2022). Engineering Senior Design Reports. 52.