Self-powered autonomous wireless sensor node

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−2 rms acceleration and can be as low as 0.2 m s −2 rms with a duty cycle around 12 min. The EM generator has a volume of only 150 mm3 producing an average power of 58 μW at 0.6 m s−2 rms 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 μW to be generated at 1.7 m s−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.