Earthquakes don't happen very often in East Tennessee, so while waiting to get a device installed near Yellowstone I have a little extra time on my hands at this stage in the project. Just to add a little somethin' to my "indoor" seismometer, I bought a inexpensive little solid state ultraviolet laser module and an inexpensive laser control module on eBay, Total cost about $20.

Fluorite contains yttrium, europium and samarium in a calcium fluoride matrix. The first three elements absorb ultraviolet light, hold on to the energy for a while and emit it later as visible light. This type of photoluminescence is a combination of fluorescence and phosphorescence. The entire ball glows nicely when illuminated from below by the laser through a small hole in the seismometer base - the laser light itself is invisible.

It's aliiiive!

The Arduino code to make it dim and brighten is bone simple:

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int laserPin = 5;

void setup() {

pinMode (laserPin, OUTPUT); //actual pin is 5

pinMode(6, OUTPUT); //we will use pin 6 as a ground for the electrodes in digital pin 5

digitalWrite(6, LOW); //pin 6 is used as ground for the electrodes, so the program never changes this.

}

void loop() {

int x = 1;

for (int i = 0; i > -1; i = i + x) {

digitalWrite(laserPin, HIGH);

delayMicroseconds(i * 20); // vary the brightness of the fluorite ball

// with this number; 20 is "subtle" in the daytime

digitalWrite(laserPin, LOW);

if (i == 255) x = -1; // switch direction at peak

delay(10);

}

}

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The code can be added on to the main seismic noise program as well, so that the ball also changes intensity in response to vibrations in the home, but that delay(10) statement makes it a time hog. It is best to have a separate Arduino Uno controller for the laser and the Yun for the seismic noise device.