Disaster-Preparedness

Motion Sensor

Under construction until the end of Fall 2014 semester unless indicated otherwise.

Purpose

• Detect and measure motion.
• Use multiple cheap, inexpensive sensors to increase accuracy/reliability/functionality.
• Be cheap and portable.
• Provide data that can be aggregated over a network.

Sensors

• We used tilt switches, a piezo element, a laser / photoresistor combo, and an accelerometer.
• We specified thresholds for each

Tilt

Use

• A tilt switch uses a material to complete a circuit (E.G. press a button) when it reaches either end of the container.
• We used mercury switches on the X and Z axes.
• The Y axis wasn't very sensitive. It only seemed useful for seeing if the device had flipped over.
• Tilt switches work best when the motion is parallel to them. This loss of resolution can be minimized by adding more sensors at half-steps. For example, we could add two tilt in-between XZ to measure diagonal motion more effectively. (add a picture)
• We looked exclusively for change. This means we didn't care about what state the tilt switch was in, just if it had changed since the last read.
• We averaged readings so that lots of activity in a small time frame would be easier to recognize.
• Noise isn't an issue.

Wiring

• Power, ground, and signal.
• 10k resistor on power.
• Signal is digital.

Code Sample

const int tiltPin = 2;
int tiltState = 0;

void setup() {
  pinMode(tiltPin, INPUT);     
}

void loop(){
  tiltState = digitalRead(tiltPin);
}

Resources

• [wikipedia]
• [useful code]

Piezo Element

Use

• A very cheap, diverse piece of kit.
• Can be used as a button, a knock sensor, to detect vibration, to detect sound, or to produce sound similar to a buzzer.
• We used it as a vibration sensor.
• Vibration sensitivity is increased dramatically when the piezo element is attached to a solid object by a weight, glue, or tape.

Wiring

• Signal and ground. Signal serves as power.
• 1k resistor on the signal; 10k worked similarly, so 1k+ is probably fine
• analog
• minimal noise

Code Sample

const int piezoPin = 2;
int piezoState = 0;

void setup() {
  pinMode(piezoPin, INPUT);     
}

void loop(){
  piezoState = analogRead(piezoPin);
}

Resources

• [product page]
• [arduino tutorial]
• [technical datasheet]
• [wikipedia]

Accelerometer

Use

• It didn't fit on the normally sized breadboard so we ran power/ground underneath and used the one available row for the xyz/sleep pins. This was a non-issue on the prototype board.
• There are existing code libraries but we didn't use them. They can be found [here] with examples. We could still use this library to setup the accelerometer, but I've written my own library for reading values and would prefer to use that.
• Noise was an issue, but the noise was reduced considerably when using a prototype board instead of a breadboard.

Wiring

• Power, ground, xyz, and sleep. Pins are labeled on the device.
• The device uses Arduino's pullup resistors, so no external resistors are required.
• xyz is analog and sleep is digital.

Code Sample

Using existing libraries,

#include "Accelerometer.h"

Accelerometer acc = Accelerometer();

void setup()
{
  Serial.begin(9600);

  //        SL GS 0G X   Y   Z
  acc.begin(3, 4, 5, A0, A1, A2);

//calibrate for a start position
Serial.println("Please place the Accelerometer on a flat\nLevel surface");
delay(2000);//Give user 2 seconds to comply
acc.calibrate();
}

void loop()
{
  delay(2000);
  acc.read();
  Serial.print(acc._Xgs);
  Serial.print("x, ");
  Serial.print(acc._Ygs);
  Serial.print("y, ");
  Serial.print(acc._Zgs);
  Serial.println("z");
}

Resources

• [manufacturer documentation]
• [libraries]
• [product]
• [wikipedia]

Research

These are notes and observations from research.

Earthquake

Waves produced by an earthquake.

How to measure earthquakes accurately.

• occur due to movement in tectonic plates
• only seconds of notice, 5-10 seconds
• [p waves] are much faster than [s waves] and the actual waves that cause the earthquake.
  • earthquakes travel at about the same speed as data networks
• can be measured by motion (on surface or underground) and pressure (underground)
  • downside of underground monitoring is 1) power and 2) transmission
    • can use repeaters or solar power to solve these issues
  • advantage of being underground is distance from noise (such as animals and humans) and being closer to the source of the earthquake
  • being attached to rock is good

Resources

[introduction]

[wave types]

Tsunami

Possible methods to predict and measure tsunamis.

• in the deep sea pressure sensors are used to measure the relatively small sea-level change (in centimeters)
• nearer to shore, where waves start to form, altitude could be measured by buoy
• travel at hundreds of miles per hour
• tsunami headquarters in Hawaii
• notification could be minutes to hours in advance depending on distance from source of tsunami
• height/speed of wave reduces with distance