Abstract A design methodology is proposed for electronic systems powered by energy harvesting. The methodology first considers the operating environment. It then evaluates the supply-side (the attributes of the harvester), the demand-side (the engineering application or load which receives and uses the converted power), and the power conditioning needed between supply and demand. A test case is presented in which the vibrations of an electromagnetic device are harvested, converted, and used to power a wireless sensor node. Such a node is being used for the condition based monitoring of manufacturing equipment.

This paper presents new results in the testing and characterization of a MEMS sensor for AC electric current. The sensor is comprised of a piezoelectric MEMS cantilever with a microscale permanent magnet mounted to its free end. When placed near a wire carrying AC current the magnet couples to the oscillating magnetic field around the wire, deflecting the cantilever and generating a sinusoidal voltage proportional to the current. Unlike inductive sensors, this sensor does not need to encircle the conductor and it can measure current in a two-wire "zip-cord". It is also self-powered, and is thus more suitable for wireless sensor node applications than a powered sensor device. The theoretical basis of this new sensor's operation is presented, as well as the fabrication of a MEMS sensor device, and the first test results of this new sensor measuring current in single-wire and two-wire conductors. Sensor response is linear (R-2 > 0.99) with sensitivity in the range of 0.1-1.1 mV/A. An integrated self-powered sensor device is also presented, which employs a piezoelectric energy harvester to power the sensor's signal conditioning circuitry at a 2.6% duty cycle.

A new type of MEMS sensor has been developed for measuring AC electric current. The sensor is comprised of a piezoelectric aluminum nitride MEMS cantilever with a microscale composite permanent magnet mounted to its free end. When placed in proximity to a wire carrying AC current, the alternating magnetic field surrounding the wire induces a sinusoidal force on the sensor magnet, deflecting the piezoelectric cantilever and thus producing a voltage signal proportional to the current in the wire. This sensor does not need to encircle the conductor and its use of piezoelectric materials eliminates the need for a power source. This paper details an improved micromagnet fabrication process using dispenser-printed epoxy and a neodymium alloy magnetic powder. Also presented are the first test results of working MEMS current sensor devices, as well as the development of a fully self-powered sensor package that uses a piezoelectric energy harvester to power circuitry that amplifies the MEMS sensor's signal.