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Piezo-MEMS vibration energy harvesters enable SmartMesh IP wireless sensor network

Technology News |
By eeNews Europe

The Linear mote was powered by MicroGen’s piezoelectric Micro Electro Mechanical Systems (piezo-MEMS) vibrational energy harvester or micro-power generator (MPG) technology.
    
The Linear WSN consisted of four motes, and their WSN software for efficient power managed communication was used. The self-powered motes were enabled by electronic shakers set at typical industrial vibrations levels of 120 Hz and acceleration G-level 0.2 g (g = 9.8 m/s²). MicroGen placed vibration powered motes at the Linear booth and at the X-FAB MEMS Foundry booth. These motes were on the order of 20-30 meters away from MicroGen’s booth. This was the first fully MEMS energy harvesting powered WSN completed by a commercial company.

Inside MicroGen’s BOLT Power Cell is a small semiconductor MEMS chip fabricated using similar techniques as the computer chip industry. This chip is a ~1.0 cm² piezo-MEMS MPG containing one end-mass loaded micro-cantilever containing a piezoelectric thin film. As the MPG’s cantilever bends up and down due to the external vibrational force it produces alternating current (AC) electricity. At resonance the AC power output is maximized, where it is ~100 microWatts at 120 Hz and ≥ 0.1 g, and ~900 microWatts at 600 Hz and ≥ 0.5 g.

The AC electricity is efficiently converted to direct current (DC) using Linear Technology’s LTC3588-1 piezoelectric energy harvesting AC to DC converter. After the energy is scavenged it is temporarily stored on a 300 microFarad capacitor. The output of the Power Cell ranges from 25-500 microWatts at 3.3 Volts DC, depending upon configuration and frequency. The BOLT Power Cell is intended to enable a wireless sensor mote from many different manufacturers.

The BOLT Power Cell is simply a battery replacement unit that uses vibrational energy instead of chemical energy produced by environmentally unfriendly materials. The intent is to eliminate or extend the lifetime of primary cells or rechargeable batteries in WSN industrial and building applications, where the labor to frequently change batteries is cost prohibitive for a WSN to be installed. Power cells will be offered at 50/60 Hz harmonics between 100-1500 Hz. MicroGen’s MPGs and Power Cells are very sensitive to low levels of G. At G-levels < 0.1-0.5 g (depends upon frequency) at a specific industrial signature frequency, then the Power Cell will enable the WS mote attached. In volume the MPG and Power Cell production cost are estimated be on the order of $0.50 and $1.00 each, respectively.

Linear Technology’s Boston Design Center’s Director, Sam Nork added: “MicroGen’s demonstration of its piezo-harvesting chip integrated with Linear Technology’s LTC3588 piezo conversion chip is a perfect match to efficiently produce DC electricity for WSN applications.”

MicroGen’s CEO, Robert Andosca said: “We are very pleased that we were able to show a low cost energy harvester solution to enable Linear Technology’s SmartMesh wireless motes. Our goal is to provide piezo-MEMS harvesters in a form-factor that can be used by all wireless sensor products currently on the market. Our BOLT Power Cell is the first example of doing so with a commercial MEMS-based energy harvesting generator component.”

MicroGen plans to announce the availability of the company’s products late summer 2013. Initially, MicroGen will offer MPGs and BOLT Power Cells at frequencies 100, 120 and 600 Hz. For extra energy storage, plug-in BOLT Energy Cells will be available with a 22 milliFarad Panasonic ultra-capacitor, a 50 microAmp-hr Cymbet Corporation solid-state battery, and a 7.0 milliAmp-hr Panasonic rechargeable coin cell.

Visit MicroGen at www.microgensystems.com

Visit Linear Technology at www.linear.com


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