Experiments are directed towards creating two parts of a device - the first an oscillator/network of oscillators that will pick up ground vibrations, and the second being some method of converting these sensed oscillations into human readable information.
Subir's setup: A 1 m long thin rod (2.5 mm) is fixed at one end (top) and it cantilevers over to the mouse end (bottom). A small rubber piece dangles in front of the mouse detecting surface. Mouse is connected to a Raspberry Pi where a Python program records the X and Y displacements over time.
Below is a spectrogram of over 1/2 hour of mouse data with the above experimental setup. Because of the fan in the room (yes it was hot so i had to compromise the experiment) we see a 1.25 Hz vibration of the rod which I guess is the natural frequency. The rest is noise. [Subir Bhaduri]
Nish Kothari's frugal oscillator + deconstructed mouse
Nish Kothari's frugal oscillator + deconstructed mouse
Pisani, M., Astrua, M. (2006). Angle amplification for nanoradian measurements. Applied Optics. 45(8)
According to Pisani and Astrua (2006), if there are 2 parallel mirrors and a laser beam is incident on one edge (mirror A) at an angle, then the mirrors together form a kind of 'disturbance amplifier'. Meaning if mirror B is moved by say a small angle gamma, then the out-coming laser beam has an angular displacement of ${n\gamma}$, where $n$ is the number of reflections. In the figure above, the number of reflections are 6, hence the angular displacement is $6\gamma$.
Subir's experimental setup - 2 mirrors, a simple laser pointer and an orange. The laser is on the top right corner. Some of its reflections are visible. The laser beam exits the setup somewhere in between the glass plates and falls on the top ceiling.
View of the setup from various angles
We tried this as above. With some hackery, it did work and we had a spot of laser on the wall in front which vibrated, if ever so slightly, when the experimenter walked around the setup. This works but it depends on the number of reflections to make it relevant. Subir could hardly achieve 5-6 of these, because of non-alignment as well as for lack of being a non-front coated glass. The latter causes significant decrease in Laser intensities due to multiple reflections. Another experiment with using reflective strips cut from a old CD was tried. Again, getting correct alignment and maximizing number of reflections is the key.
On the right are 2 cut pieces of a CD, stuck in an angle with hot glue. To reduce the angle, a piece of rubber is added on the top part. Note how the Laser changes its direction from the pointers towards the hand.
Here's a rough sketch of how this should work.
