Introduction

This project is an inexpensive earthquake detector (or will be, hopefully). It is based on this project by Jochen Lueg.

The basic idea is that a heavy weight has significant inertia. If you somehow suspend the weight, then it will only be minimally affected by other motion in the area, and so can be used as a 'reference' of sorts - you can measure the difference in position between it and another point fixed to the ground.

The movements are *tiny* in normal situations, though, so a very sensitive detector is needed. As Jochen describes in his project, a hard disc is a great source of a sensitive detector - its 'voice coil' (the bit that moves the head) is mounted on a very smooth bearing, and is of *very* low impedance (to ensure fast seek times).

My project is to attempt a refinement of Jochens design, and fit everything into a standard 3.5” harddisc casing. This will necessitate use of a smaller weight, so I am anticipating some reduction in sensitivity, although I dont know how much yet. I am also doing away with the A-D converter in his design, and will simply feed the output of my device into the input of my PCs coundcard (which has a 16 bit DAC, potentially allowing better sensitivity, making up for the smaller weight.

The picture to the right is of my project so far (the gutted remains of a Quantum 3.5” HDD)

Watch this space…