#define wheelDiameter 69.5
#define wheelCircumference wheelDiameter*3.14

boolean debounce = false;

long pulses = 0;

#include <TM1638.h> // required because the way arduino deals with libraries
#include <TM1640.h>

// define a module on data pin 3, clock pin 2
TM1640 module(4, 5);

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

  attachInterrupt(0, sensorTrigger, CHANGE); //Pin 2
}

void loop()
{
  long distance = wheelCircumference * (pulses / 2);

  char text[17];
  sprintf(text, "%u", distance / 1000);
  module.setDisplayToString(text);
}

unsigned long lastSensorTrigger = 0;
void sensorTrigger()
{
  if (millis() - lastSensorTrigger < 20) return;
  lastSensorTrigger = millis();

  pulses++;
}