Ultrasonic Sensor M&M Dispenser by Leah and Jojo

This is an M&M dispenser that is controlled by and Arduino Uno. There is an ultrasonic sensor that detects the distance from a persons hand to the device. If the hand is within a certain range, then the windmill inside the dispenser will rotate and M&Ms will be released.

Materials:

- Ultrasonic sensor

- Vex DC motor

- Arduino Uno

- 11 wires

- 220 Ohms resistor

- Transistor

- Diode

- Jar

- Funnel (made of cardboard)

- Gear and axis

- 3D printed circular cage (for gear)

- Nuts and bolts

- Paper

- M&Ms!

Extra:

- Hot glue gun and glue

- Box cutter

- Wood pieces

Add 6 paddles onto a sprocket

Insert an axle through the wheel

attach to the motor

Design a cylinder to fit your windmill piece

Print two of them

Put the windmill piece through the holes

Enclose using hot glue

You may need to use bolts to hold it into place

Attach a wire going from pin 6 to the breadboard

Add a 270 Ohm resistor connected to the wire

Add a transistor with the middle prong connected to the other end of the resistor

Add a wire going from the negative column to the left end of the transistor

Put one end of a diode in the same row as the right prong on the transistor

Add a white wire going from that same column (with the right prong of the transistor) to a different row

Add a wire going from the right end of the diode to the positive column

Add a wire going from that column (with the right end of the diode) to next to the white wire

Finally, plug the motor (with the windmill) into the breadboard so that it lines up with the white wire and the most recently placed wire

Connect a blue wire from pin 2

Connect a white wire from pin ~3

Line a black and red wire up with the ones in the + and - column

The ends of all these wires should go together in the sequence of

--------red---white---blue---black-------

Your sensor has 4 prongs line each of them up in the same row as shown in the picture above

Your circuit should now look like this

For the base we constructed a metal triangle

In the middle of the triangle we added a plate to fit the motor on with the 3D printed case

Then we constructed a funnel out of paper and duct tape for the M&Ms to go through

#define echoPin 2 // attach pin D2 Arduino to pin Echo of HC-SR04

#define trigPin 3 //attach pin D3 Arduino to pin Trig of HC-SR04

long duration; // variable for the duration of sound wave travel

int distance; // variable for the distance measurement

int motorPin = 6; // variable for the motor pin

void setup() {

pinMode(trigPin, OUTPUT); // Sets the trigPin as an output

pinMode(echoPin, INPUT); // Sets the echoPin as an input

Serial.begin(9600); // Sets up the serial monitor

pinMode (motorPin,OUTPUT); // Sets the motor pin as an output

}

void loop() {

// Clears the trigPin condition

digitalWrite(trigPin, LOW);

delayMicroseconds(2);

// Sets the trigPin HIGH (ACTIVE) for 10 microseconds

digitalWrite(trigPin, HIGH);

delayMicroseconds(10);

digitalWrite(trigPin, LOW);

// Reads the echoPin, returns the sound wave travel time in microseconds

duration = pulseIn(echoPin, HIGH);

// Finds the distance between the object (hand in this case) and the sensor

distance = duration * 0.034 / 2;

// Displays the distance on the Serial Monitor

Serial.print("Distance: ");

Serial.print(distance);

Serial.println(" cm");

if (distance <= 10) // Asks if the distance is less than or equal to 10 cm

{

digitalWrite(motorPin, HIGH); // If so, apply power to the motor pin

}

else

{

digitalWrite(motorPin, LOW);

// If not, don’t apply power to the motor pin

}

}