In this research we developed wireless sensor system for security application. We have used geophone to detect seismic signals which are generated by footsteps. Geophones are resonant devices. Therefore, vibration on the land can generate seismic waveforms which could be very similar to the signature by footstep. The signals from human footstep have weak signals to noise ratio and the signal strength is subject to the distance between the sensor and human. In order to detect weak signals from footstep, we designed and fabricated 2-stage amplification circuit which consists of active and RC filters and amplifiers. The bandwidth of filter is 0.7Hz-150Hz and the gain of amplifier is set to 1000. The wireless sensor system also developed to monitor the sensing signals at the remote place. The wireless sensor system consists of 3 units; a wireless sensor unit, a wireless receiver unit, and a monitoring unit. The wireless sensor unit transmits amplified signals from geophone with Zigbee, and the wireless receiver unit which has both Zigbee and Wi-Fi module receives signals from the sensor unit and transmits signals to the monitoring system with Zigbee and Wi-Fi, respectively. By using both Zigbee and Wi-Fi, the wireless sensor system can achieve the low power consumption and wide range coverage.

Date Published: 30 March 2010
PDF: 8 pages
Proc. SPIE 7646, Nanosensors, Biosensors, and Info-Tech Sensors and Systems 2010, 76460W (30 March 2010); doi: 10.1117/12.849289

Published in SPIE Proceedings Vol. 7646:
Nanosensors, Biosensors, and Info-Tech Sensors and Systems 2010
Vijay K. Varadan, Editor(s)