Nobody Puts a Finger on My Butterfinger

So one of my friends is obsessed with butterfingers. Like absolutely obsessed. Her vice, and the old slogan used by Butterfinger (remember the commercials with bart simpson…) tempted me to think up this idea for the Form and Motion assignment.

The idea is very simple: a security box that protects a butterfinger by attacking anyone trying to steal it. If an unsuspecting thief puts their hand in the box a spiked paddle swings down on to them. The owner knows that a secret switch on the side needs to be pressed to safely retrieve the Butterfinger bar.

The mechanism is fairly simple: IR sensor mounted on top that when tripped caused a servo-powered paddle to swing down. When a button on the side, powered by a 9V external power source, is held down a Green “Go” LED is lit and the Servo is disabled.

The box is made out of foamcore. The paddle is a dowel attached to foamcore with thumbtacks as spiked in the foamcore paddle. This paddle worked well because it was light however I would have liked the paddle to be even faster and believe that this might be in part because of the weight of the paddle. The light diffuser on the green LED is a ping pong ball and everything else is just stuck together with red electrical tape.

Some stuff to mention: In the video the paddle will go down when nothing appears to be in the way. This is mainly because the IR sensor was tilted a tiny bit which caused objects to interrupt it even though they weren’t directly in the box. Also you might notice that the butterfinger is an empty wrapper…the project took me longer than expected and I got a bit hungry 😛

Arduino Sketch in comment

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2 Responses to “Nobody Puts a Finger on My Butterfinger”

  1. // This program is called “Dont lay a finger on my butterfinger!” by Rohit Kabra, 10/16/09, Making Things Interact
    // The project is a trap box where intruders who try stealing the prize trip a sensor and get hit with a
    // spiked paddle. The only way to retrieve the prize is to hold down a switch and simultaneously take the
    // prize.
    // Any change in distance of the IR sensor causes the servo motor to go directly from 0-180 at full speed.
    // By holding down a switch, a Button LED is lit and the servo is turned off.

    #include

    Servo myservo; // the name of my servo motor

    int irTrap = 6; // the pin of the IR sensor
    int ledButton = 3; // the LED that is powered externally but signals if user pressed the secret button
    int buttonState; // variable of whether button is pushed or not
    int changeDistance; // variable for the IR sensor distance
    void setup() {
    myservo.attach(9); // assigns pin 9 to the servo
    myservo.write(15); // starts of the servo at 15 degrees. I used 15 instead of 0 because the paddle needs to be in front of the foamcore backing
    pinMode(irTrap, INPUT); // ensures that the IR sensor is an input
    pinMode(ledButton, INPUT); // ensures that if switch is pressed and LED is on we know
    Serial.begin(9600);
    }

    void loop()
    {
    buttonState = digitalRead(ledButton); // saves the current state of the button
    if(buttonState) // is the button pressed?
    myservo.write(15); // then shut of the servo
    else
    {
    changeDistance = digitalRead(irTrap); // writes the distance from the irsensor to the changeDistance variable
    if (changeDistance) //if something gets in the way of the IR sensor by going for the prize
    {myservo.write(120); //turn the servo (and paddle) 120 degrees as fast as possible to catch the intruder
    delay(1000);} //delay 1 second with paddle down
    else
    myservo.write(15); //makes sure that paddle goes back up if obstruction is gone
    }
    myservo.write(15); //double check to ensure always at right position
    }

  2. Cute idea and nice documentation !

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