Dan | Stephen //Actuator

After experimenting with different input methods for our project, we had an amazing breakthrough! We started looking at "sexy" solutions, like an Optical Finger Navigation module: (http://www.parallax.com/Store/Microcontrollers/BASICStampModules/tabid/134/ProductID/715/List/1/Default.aspx), various computer mice, and an infrared emitter and detector. For different reasons, they just didn't work. We dealt with out of date code, unreliable readings, and human error (we lost the OFN module :( ). We went back to researching different ways to read RPMs for a disk. Inspired by the game show Wheel of Fortune, we ended up getting a lever switch: (http://www.radioshack.com/product/index.jsp?productId=2049719). We adapted our spinning wheel to click down the switch and had the Arduino record then convert the number of clicks to sheets of paper. The part itself doesn't come with much documentation, so it took a lot of trial and error to figure out the ground, power, and data prongs on the bottom, (that's NC, NO, and C respectively).

To test it, there's a handy preloaded example, which is documented below:

/*

  State change detection (edge detection)

 

 Often, you don't need to know the state of a digital input all the time,

 but you just need to know when the input changes from one state to another.

 For example, you want to know when a button goes from OFF to ON.  This is called

 state change detection, or edge detection.

 

 This example shows how to detect when a button or button changes from off to on

 and on to off.

 

 The circuit:

 * pushbutton attached to pin 2 from +5V

 * 10K resistor attached to pin 2 from ground

 * LED attached from pin 13 to ground (or use the built-in LED on

   most Arduino boards)

 

 created  27 Sep 2005

 modified 30 Aug 2011

 by Tom Igoe

This example code is in the public domain.

 

 http://arduino.cc/en/Tutorial/ButtonStateChange

 

 */

// this constant won't change:

const int  buttonPin = 2;    // the pin that the pushbutton is attached to

const int ledPin = 13;       // the pin that the LED is attached to

// Variables will change:

int buttonPushCounter = 0;   // counter for the number of button presses

int buttonState = 0;         // current state of the button

int lastButtonState = 0;     // previous state of the button

void setup() {

  // initialize the button pin as a input:

  pinMode(buttonPin, INPUT);

  // initialize the LED as an output:

  pinMode(ledPin, OUTPUT);

  // initialize serial communication:

  Serial.begin(9600);

}

void loop() {

  // read the pushbutton input pin:

  buttonState = digitalRead(buttonPin);

  // compare the buttonState to its previous state

  if (buttonState != lastButtonState) {

    // if the state has changed, increment the counter

    if (buttonState == HIGH) {

      // if the current state is HIGH then the button

      // wend from off to on:

      buttonPushCounter++;

      Serial.println("on");

      Serial.print("number of button pushes:  ");

      Serial.println(buttonPushCounter);

    } 

    else {

      // if the current state is LOW then the button

      // wend from on to off:

      Serial.println("off"); 

    }

  }

  // save the current state as the last state, 

  //for next time through the loop

  lastButtonState = buttonState;

  

  // turns on the LED every four button pushes by 

  // checking the modulo of the button push counter.

  // the modulo function gives you the remainder of 

  // the division of two numbers:

  if (buttonPushCounter % 4 == 0) {

    digitalWrite(ledPin, HIGH);

  } else {

   digitalWrite(ledPin, LOW);

  }

  

}

We took a couple of different approaches as I have referenced in previous posts about the kind of actuator we may use to measure the length of a sheet of toilet paper to trigger a specific noise. An optical lens from a mouse, a optical touch pad, inferred sensors among ones we tried and failed to get working.

The one we were able to get to work was a relay lever. The relay lever understand data each time it is clicked similar to how the "Wheel of Fortune" wheel spins and clicks, we have a wheel with three attached tabs that spin when toilet paper is pulled and click agains the lever. We were able to do the math to estimate that every three clicks of a .75inch diameter wheel is approximately one sheet of toilet paper pulled which then lets the Arduino know to play a sound.

The Arduino keeps track of each pull of the paper by using a 5 second delay (account for wipe time) and then reducing the amount of toilet paper allowed before negative noise the next time. This continues until two sheets and stays indefinitely until there is a break of one minute (time for next person to use the bathroom and begin wiping.