Seismic sensor using opam and piezo sensor

The project on Seismic sensor circuit described here senses pressure variation or mechanical strain and responds by sounding a speaker. It can be used at prohibited places to alert any unwanted entry. Such sensors can be placed on the floors of these places and whenever an intrusion would occur, the speaker would go off.

The term “Seismic” is used majorly for all the operations and processes related to the earth, its crust and lower layers. The similar areas are there where this sensor finds its applications:

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1. {C}{C}{C}{C}{C}{C}{C}{C}{C}{C}Decoding natural vibrations under the earth’s crust through seismograph

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2. {C}{C}{C}{C}{C}{C}{C}{C}{C}{C}Aid in large industrial processes of oil extraction drilling process, mining, tunnel construction etc.

This circuit in this project takes input from a piezo diaphragm which is provided to non-inverting pin of op-amp in LM324 (pin3). The inverting input of the op-amp is grounded through R1 (1k). The op-amp is thus configured to be used in non-inverting mode. This means that the output is in phase with the input of op-amp. If someone tries to walk over a restricted area, the pressure variations of the feet are sensed by the piezo sensor which gives the analog output. This output is amplified by the op-amp and its gain depends on the input resistors R1 (1k) and R2 (3.3k) in accordance with the relation:G = (1 + R2/R1).

The output of op-amp is sufficient enough to drive a speaker, connected to its output, after getting filtered by a capacitor C1 (10uF).