Design and performance tests of a LED‐based two‐dimensional wireless crack propagation sensor

Summary In this study, a wireless light-emitting diode (LED)-based crack sensor is proposed for monitoring two-dimensional crack propagation on concrete structures. This sensor is developed by incorporating a LED optical navigation sensor board (ADNS-2620) into a smart wireless platform (Arduino Pro Mini + XBee). To measure crack propagation, the Arduino Pro Mini sends a signal to the ADNS-2620 to collect a sequence of images reflected from a grid pattern attached on a concrete surface. The normalized cross-correlation method is used to compute the two-dimensional crack propagation using the image sequence. Three different computational approaches were proposed and studied: the moving reference, the absolute reference, and the hybrid reference. The computed crack movements can then be transmitted wirelessly through the XBee modulus to a base station. The design of this sensor is reported herein followed by a series of calibration and performance tests. Results of the performance test on a shake table show that the accuracy of sensor is in the order of 13 µm. A bending test on a concrete beam is further used to illustrate the applicability of the sensor. Results show that the proposed sensor has a potential for monitoring crack propagation of concrete structures. Comparing to a previously developed laser-based crack sensor, the proposed LED-based crack sensor offers a better accuracy but with one third less of power consumption. Copyright © 2015 John Wiley & Sons, Ltd.