IO coincidence HW

Submitted by derek on Tue, 03/05/2013 - 22:55


I built a small doo-dad that converts utilizes tension to input a value via the FSR with the intention of bringing to life a toy/cardboard airplane with lights and sound when twirled. For practical reasons I had to abandon the idea but the mechanism remained so I made what looks like nothing in the photo but does a tiny something. The box, constructed of cardboard and duct tape (the most useful materials in the world), when tugged on from both ends generates a tone depending on how taught the threads are.  


  • Arduino UNO
  • FSR
  • Insulated wire
  • 10k Resistor
  • Piezo speaker
  • Cardboard
  • duct tape
  • thread



/* Blink without Delay
 Turns on and off a light emitting diode(LED) connected to a digital  
 pin, without using the delay() function.  This means that other code
 can run at the same time without being interrupted by the LED code.
 The circuit:
 * LED attached from pin 13 to ground.
 * Note: on most Arduinos, there is already an LED on the board
 that's attached to pin 13, so no hardware is needed for this example.
 created 2005
 by David A. Mellis
 modified 8 Feb 2010
 by Paul Stoffregen
 This example code is in the public domain.
// constants won't change. Used here to 
// set pin numbers:
const int ledPin =  13;      // the number of the LED pin
const int fsrPin = 1;
const int speakerPin = 7;
// Variables will change:
int ledState = LOW;             // ledState used to set the LED
long previousMillis = 0;        // will store last time LED was updated
int fsrVal = 0;
// the follow variables is a long because the time, measured in miliseconds,
// will quickly become a bigger number than can be stored in an int.
long interval = 0;           // interval at which to blink (milliseconds)
void setup() {
  // set the digital pin as output:
  pinMode(ledPin, OUTPUT); 
  digitalWrite(ledPin, LOW);  
void loop()
  // here is where you'd put code that needs to be running all the time.
  // check to see if it's time to blink the LED; that is, if the 
  // difference between the current time and last time you blinked 
  // the LED is bigger than the interval at which you want to 
  // blink the LED.
  unsigned long currentMillis = millis();
  fsrVal = analogRead(fsrPin);
  interval = fsrVal/2;
  if(currentMillis - previousMillis > interval) {
    // save the last time you blinked the LED 
    previousMillis = currentMillis;   
    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW)
      ledState = HIGH;
      ledState = LOW;
    // set the LED with the ledState of the variable:
    digitalWrite(ledPin, ledState);
    tone(speakerPin, fsrVal, 500);
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