Battery-Free Water Leak Detector Design Towards High-Scale Production

Abstract

Water leaks can be a significant destructive environmental phenomenon that can result in extensive damage if not addressed promptly. Internet of Things (IoT) sensors help connect objects to the Internet for recording and processing data. IoT water leak detectors in the market all use an external power supply (generally batteries) to stay active and detect leaks. Alongside the environmental footprint, batteries result in, they can cause severe flaws in performance because of their variability with temperature and extreme environmental conditions. To fill the gap in this field, previous students working in the team developed a battery-free water leak sensor. The conceptual base of the leak detector design uses a water-induced energy harvesting method. In this thesis, the leak detector electronics and assembly design are optimized for high-scale production. The electronics unit, which includes the Energy Harvesting board and Bluetooth Low Energy (BLE) board, requires an energy harvesting scheme to activate a BLE chipset. The first step includes understanding the power generation capacities of the water-induced energy harvesting method. Subsequently, the current consumption patterns of the BLE chipset (nRF52832) are investigated at this stage. The performance of the first released design is tested, and it is clear that due to the transient nature of the water-induced energy harvesting method, the energy harvesting technique requires modifications. This involved changing resistor components, which in turn enhanced the performance of the device. Finally, a new BLE chipset (IN100) is investigated and used in the board design for lower current consumption and lower cost. The electronics unit is notably simplified to a single board. Following the simplicity of the new electronics unit, the sensor unit (power generation unit) also needs simplification in the assembly process. Besides designing a new assembly procedure, it is necessary to understand the flaws and inaccuracies in the current sensor unit enclosure design for future design iterations. The new sensor unit assembly procedure reduces the total assembly time for each sensor by 40%, compared to the initial assembly process. Finally, the performance of the final device using the new sensor unit assembly procedure and the single board electronics design is verified when applying Acceptance Quality Limit (AQL) testing.