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Lab 2: Exploring Hidden Potentiometers or “Cinderfella”

After setting up the lab with no problems, I got started on my luv-o-meter. Constrained by the market (demand way outstripping supply at the bookstore), I bought a big square force sensing resistor. I’ve gone through a number of permutations regarding how to use it detailed below in no particular order.



A cylinder with a narrow opening at one end (possibly a bottle or the like) filled with foam and lined with silk with the sensor mounted somewhere within a finger’s reach of the opening. A number of LEDs indicate how “hot” or “cold” the user is depending on how close his/her finger comes to the sensor and how hard he’s pressing. Abandoned because of raised eyebrows.


Love Hertz

A brick-sized piece of foam with the sensor mounted in its center. When someone breaks up with the user, s/he hits the Love Hertz as hard as possible, which is not only extremely satisfying but also gauges the extent of the heartbreak as a function of the force of the hit and displays this information on an ascending scale of LEDs.
Possible variations: a leather-and-spike-clad version for the S&M crowd or a plush cushion with arms that measures hug strength.


THE WINNER: Cinderfella

Thinking about our reading over the last two weeks (and my increasingly apparent mechanical incompetence regardless of Norman’s insistences to the contrary), I decided that the interface itself is much more important than the device. I wanted to make something that was completely instinctive to use—with clear affordances and mappings, in the reading’s words—so I’m recreating Cinderella’s shoe. In a fairytale world, I would create a glass slipper out of acrylic and mount a microprocessor in the heel and LEDs along one of the straps to light up when there was a match and everyone lived happily ever after. Since I live in New York, I’m going to mount the sensor into a Converse All-Star and run wires to the processor and the LEDs which will be housed externally and we’ll all muddle along the best we can.

The idea is to mount the sensor right along the arch under a removable insole. If the person trying on the shoe’s foot is too big, then s/he’ll arch his/her foot to squeeze it into the shoe and not put enough pressure on the sensor. Red light. If the person’s foot is too small, his/her heel will put too much pressure on the sensor. Red light. Only someone whose foot actually fits in the shoe will provide the right amount of pressure to light the green light (and send a Google map of his/her exact location to the prince’s cell phone).

I’ve managed mostly through trial and error to figure out the right resistor value (4.7kΩ) to get my sensor to light up an LED using the code from the lab. I’ll probably have to tweak it some when I stick it in my shoe. I’ve mounted the sensor onto a little female adaptor and taped it up, but I fear that once it’s in the shoe it will come disconnected, so I’m going to redo the connection with glue and ensure it’s snug. Or I’m just going to wedge another chunk of wire into the socket so it fits snugly. Which seems to do the trick!

I placed the sensor in the shoe and tested it to find the right spot;

I added two LEDs to the lab setup and switched them to digital output and rewrote the code accordingly:

int shoePin = 0; // the sensor input
int sensorValue = 0; // the sensor value
int led1 = 4; // the 3 LEDs
int led2 = 6;
int led3 = 8;

void setup() {
  Serial.begin(9600); // serial connection for debugging
  pinMode(led1, OUTPUT); // set 3 LEDs to digital output
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);

void loop() {
  sensorValue = analogRead(shoePin); // read the sensor value
  if(sensorValue<250 && sensorValue>120) {
    digitalWrite(led1, HIGH); // if sensor detects my weight
    digitalWrite(led2, HIGH); // turn on the LEDs
    digitalWrite(led3, HIGH);
  else {  // Otherwise keep them off
    digitalWrite(led1, LOW);
    digitalWrite(led2, LOW);
    digitalWrite(led3, LOW);
  Serial.println(sensorValue); // monitor the sensor

I built an enclosure for the Arduino and the LED’s,

and then wired the shoe to it

Finally, I tested to make sure that when the lights lit up, the hidden message in the box was displayed


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