  Wireless sensor networks (WSNs) are promising solutions for large
infrastructure monitoring because of their ease of installation, computing and
communication capability, and cost-effectiveness. Long-term structural health
monitoring (SHM), however, is still a challenge because it requires continuous
data acquisition for the detection of random events such as earthquakes and
structural collapse. To achieve long-term operation, it is necessary to reduce
the power consumption of sensor nodes designed to capture random events and,
thus, enhance structural safety. In this paper, we present an event-based
sensing system design based on an ultra-low-power microcontroller with a
programmable event-detection mechanism to allow continuous monitoring; the
device is triggered by vibration, strain, or a timer and has a programmed
threshold, resulting in ultra-low-power consumption of the sensor node.
Furthermore, the proposed system can be easily reconfigured to any existing
wireless sensor platform to enable ultra-low power operation. For validation,
the proposed system was integrated with a commercial wireless platform to allow
strain, acceleration, and time-based triggering with programmed thresholds and
current consumptions of 7.43 and 0.85 mA in active and inactive modes,
respectively.
