This project is for use with a model I made with the Lego WeDo robot kit. If the model is shaken (either by an earthquake, or by someone wobbling it), the amount of wobble will be plotted on the screen. If the wobble is hard enough, a warning gong will sound. You can see another photo of the model inside the project as a backdrop, and a video of it in action here: https://vimeo.com/133287269 This seismometer uses the WeDo distance sensor to measure the distance to the green panel. When there is an earthquake, this panel moves, as it can swing freely on the end of the red arm. This isn’t a very good seismometer, partly because it can only measure movement along the line in which the arm can swing. It also keeps swinging from its own inertia after the earthquake has stopped.
The earthquake detector was invented by Zhang Heng in 132 AD.