C8.2 - An Electro-Dynamic Energy Harvester Supplying a Wireless Sensor Node

Nowadays, most wireless sensor nodes are supplied by electrical energy with built-in batteries or wireconnected to an external electrical energy source. Additionally, in some industrial applications wireless sensor nodes are hermetically sealed into housings even without any electrical conductive connections through the shape. Compared to batteries an installed energy harvesting module requires no costly maintenance, but its power output depends on the used energy source, during data transmission the instantaneous power input of wireless sensor nodes surmounts the energy harvester’s average power, and has higher production cost. This paper presents a wireless sensor node supplied by an energy harvesting module. A frequency adjusted and by an electro-dynamic converter only lightly damped spring/mass oscillator converts mechanical energy of bulk vibrations into electrical power. Both the converter properties and the data transmission are modeled in the paper. The discussed energy harvester module was model based designed and built in our lab, has a resonance frequency of about 50 Hz, provides an electrical average power of more than 50 mW by a vibration amplitude of 0.1 mm, and goes up to 200 mW at increased excitation. In the current design state the wireless sensor node transmits acquired data from both, a 3D acceleration and a temperature sensor. The data transmission is scheduled by a proprietary ALOHA protocol and works reliable for distances up to 10 meter (indoor) with a transmission rate of about 150 Bytes per second.