Self-powered autonomous wireless sensor node using vibration energy harvesting

This paper reports the development and implementation of an energy aware autonomous wireless condition monitoring sensor system ( ACMS) powered by ambient vibrations. An electromagnetic ( EM) generator has been designed to harvest sufficient energy to power a radio-frequency (RF) linked accelerometer-based sensor system. The ACMS is energy aware and will adjust the measurement/transmit duty cycle according to the available energy; this is typically every 3 s at 0.6 m s(rms)(-2) acceleration and can be as low as 0.2 m s(rms)(-2) with a duty cycle around 12 min. The EM generator has a volume of only 150 mm(3) producing an average power of 58 mu W at 0.6m s(rms)(-2) acceleration at a frequency of 52 Hz. In addition, a voltage multiplier circuit is shown to increase the electrical damping compared to a purely resistive load; this allows for an average power of 120 mu W to be generated at 1.7 m s(rms)(-2) rms acceleration. The ACMS has been successfully demonstrated on an industrial air compressor and an office air conditioning unit, continuously monitoring vibration levels and thereby simulating a typical condition monitoring application.