Motion-Activated
Treat Dispenser

/*
Parts of code sampled from ENGINEER 1P13 Ultrasonic sensor sample workshop

Some Sensor Info:
The ultrasonic sensor measures distance by emitting a high-frequency pulse and then listening back for the echo.
The time it takes for the echo to come back can be turned into distance using the speed of sound.
Note the speed of sound changes depending on the environment, but around room temperature and 1 atm of pressure, it's about 343 m/s.
We simply need to turn on the sensor by sending it a pulse on the trig pin, then listen for the pulse back on the echo pin and the rest is just math!
We can then read the distance it gives us out using a serial monitor, which is where we print out things from the Arduino, like we would in Python. - Engineer 1P13 Sample Code
*/

// Define pin numbers
#define ECHO_PIN 11 // Echo pin of ultrasonic sensor goes to pin 11 on Arduino
#define TRIG_PIN 12 // Trig pin of ultrasonic sensor goes to pin 12 on Arduino
#define LED_PIN 10  // LED positive terminal goes to pin 10 on Arduino

float distance_cm; // Distance read in cm
long duration;     // Length of the pulse we hear back on the echo pin in us

float speed_of_sound = 0.0343; // cm/us at Standard Ambient Temperature and Pressure

const int input2 = 2;  // Defining pins for the motor controller
const int input1 = 3;
const int enablePin = 5;

// Function for sensor
void pulse_trig()
{
  digitalWrite(TRIG_PIN, LOW);  // First set the pin low to clear residual signal
  delayMicroseconds(5);
  digitalWrite(TRIG_PIN, HIGH); // Start pulse
  delayMicroseconds(10);        // Keep pulse high for at least 10 us
  digitalWrite(TRIG_PIN, LOW);  // Reset pulse and listen for echo
}

// This code runs only once at startup on the Arduino
void setup()
{
  Serial.begin(9600); // Start serial monitor

  // Setting pin modes for ultrasonic sensor and LED
  pinMode(ECHO_PIN, INPUT);
  pinMode(TRIG_PIN, OUTPUT);
  // pinMode(LED_PIN, OUTPUT);

  // Motor controller pins
  pinMode(input2, OUTPUT);
  pinMode(input1, OUTPUT);
  pinMode(enablePin, OUTPUT);
}

// This code runs repeatedly while Arduino is powered
void loop()
{
  pulse_trig(); // Pulse trig pin
  duration = pulseIn(ECHO_PIN, HIGH); // Read echo time

  // Divide by 2 since pulse travels to object and back
  distance_cm = duration / 2 * speed_of_sound;

  // Distance threshold of 15 cm for Mark's hand
  if (distance_cm > 15.0)
  {
    digitalWrite(LED_PIN, HIGH); // Testing purposes
    delay(250);
  }
  else
  {
    // digitalWrite(LED_PIN, LOW);
    Serial.print("In range");
    delay(250);

    analogWrite(enablePin, 250); // Motor speed
    digitalWrite(input1, HIGH);  // Turn motor on
    digitalWrite(input2, LOW);
    delay(250);                  // Screw rotation time

    analogWrite(enablePin, 0);   // Stop motor
    digitalWrite(input1, LOW);
    digitalWrite(input2, LOW);

    Serial.print("Motor Done");
    delay(3000);
    Serial.print("Ready again");
  }

  Serial.print(distance_cm);
  Serial.println(" cm");
}