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Many cities seek utilities monitoring with centrally managed Internet of Things (IoT) systems. This requires the development of many reliable low-cost wireless sensors, such as water temperature and flow meters, that can transmit information from subterranean pipes to surface-mounted receivers. Traditional radio communication systems are either unable to penetrate through multiple feet of earthen and manmade material, or have impractically large energy requirements which necessitate either frequent replacement of batteries, or a complex (and expensive) built-in energy harvesting system. Magnetic signaling systems do not suffer from this drawback: low-frequency electromagnetic waves are shown to penetrate well through several feet of earth and water. In the past, these signals were too weak for practical use; however, this has changed with the recent proliferation of high-sensitivity magnetometers and compact antennas using mechanically actuated rare-earth magnets. A permanent magnet can be either rotated or vibrated to create an oscillating magnetic field. Utilizing this phenomenon, two flow meter designs are proposed: one which uses a propeller to directly rotate a diametrically magnetized neodymium magnet; and, another which uses an oscillating tail to move a permanent magnet back-and-forth across a novel soft-magnet Y-stator, which projects a switching magnetic field. These oscillating magnetic fields are used to send water flow rate information to an above ground LoRa-capable Arduino receiver equipped with a magnetometer. Simulation software is used to model the oscillating electromagnetic fields. Complete system performance with remote datalogging is tested, with the aim of integrating many sensors and surface receivers into a single LoRa wireless IoT network.
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