Our team of five was tasked with designing an apparatus to keep a money tree alive without human contact for ten weeks. With our limited budget, I proposed to build a micro-controller, solar panel, battery and pump system to water the plant. The challenge with this project was that the money tree survives best with light watering once a week. The solution I proposed was ultimately what we pursued, and it worked great. The simple program that I wrote keeps track of the last time it watered the plant in non-volatile memory, so that the system can survive if the battery goes dead. When the solar panel charges the battery enough, the micro-controller checks the current time from a real time clock on board, checks if it is time to water, and if it is, signals a relay to use the battery to power a small pump in a reservoir underneath the plant. The plant is then watered and the micro-controller calculates the next time to water. The main limitation of this solution was that the reservoir will eventually dry up. By my calculation, this would happen after about sixty cycles, or over a year of operation without needing to be filled up again.

Design for Failure, Manufacture and the Environment

Fall 2016


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