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AUTOMATIC PET FEEDER

February 27, 2025 by
AUTOMATIC PET FEEDER
My Company (Chicago), Hub360
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Imagine coming home to find that your pet has already been fed, without you having to lift a finger. This automatic pet feeder project is designed to bring that convenience into your daily life by integrating simple yet effective sensor technology with precise mechanical control. 

The system employs an ultrasonic sensor to continuously monitor the area around the feeder, detecting when your pet is nearby. Once the pet is detected within a specific range, the sensor sends a signal to an Arduino microcontroller, which in turn activates a servo motor to dispense an accurately measured portion of food. This thoughtful combination of sensors and actuators ensures that food is delivered only when needed, helping to maintain proper portion sizes and prevent overfeeding. By automating the feeding process, the feeder not only simplifies pet care but also provides a reliable solution for pet owners who want to ensure that their pets are cared for even when they are away. This project highlights how modern automation can bring practical benefits to everyday routines, making pet care more efficient and worry-free.

Components Required

  • Arduino Uno
  • HC-SR04 Ultrasonic Sensor
  • Servo Motor
  • Food Dispenser Mechanism (e.g., chute or container)
  • 9V Battery or USB Power Supply
  • Jumper Wires
  • Breadboard
  • Enclosure/Feeder Chassis

Circuit Diagram

Component Connections

1. Connecting the Ultrasonic Sensor to Arduino
The HC-SR04 sensor detects objects by sending out an ultrasonic pulse and measuring the time until the echo returns. It communicates with the Arduino using simple digital signals.

Wiring the Ultrasonic Sensor to the Arduino

  • VCC (Power Input): Connect to the Arduino’s 5V pin to power the sensor.
  • GND (Ground): Connect to the Arduino’s GND for a common reference.
  • TRIG (Trigger Pin): Connect to a digital output pin (e.g., D9) on the Arduino.
  • ECHO (Echo Pin): Connect to a digital input pin (e.g., D10) on the Arduino.

These connections allow the Arduino to trigger the sensor and receive timing data for distance calculations.

2. Connecting the Servo Motor to Arduino
A servo motor is used to rotate the dispensing mechanism, releasing a measured amount of food when a pet is detected.

Wiring the Servo Motor to the Arduino

  • Signal Wire: Connect to a PWM-enabled pin (e.g., D6) on the Arduino to control the servo position.
  • VCC (Power): Connect to the 5V output on the Arduino.
  • GND (Ground): Connect to the Arduino’s GND.

This setup lets the Arduino precisely control the servo’s rotation, ensuring accurate food dispensing.

3. Powering the System
To provide consistent power to the Arduino and peripheral components, follow these steps:

Powering the Feeder

  • Food Dispensing Mechanism: Use a 9V battery connected to the motor driver or power circuit that controls the servo if not using USB power.
  • Arduino Power: Connect the Arduino to a USB power source or the battery’s VIN pin (through a proper voltage regulator) to avoid damaging the board.

4. Installing the Components on the Feeder

  • Mounting the Ultrasonic Sensor: Secure the sensor on the feeder’s exterior so it can detect an approaching pet reliably.
  • Positioning the Servo Motor: Attach the servo so that its arm is aligned with the food dispensing chute, ensuring smooth operation when activated.
  • Enclosure Setup: Assemble all components onto the feeder chassis, taking care to route wires neatly and securely.

5. Uploading the Code to the Arduino

  • Open the Arduino IDE on your computer.
  • Paste the provided Arduino code into a new sketch.
  • Connect the Arduino using a USB cable and select the correct board and port.
  • Click the Upload button to transfer the code, allowing the feeder to begin monitoring and dispensing food when triggered.

CODE

#include <Servo.h>
#define TRIG_PIN 9
#define ECHO_PIN 10

Servo dispenser;
int thresholdDistance = 30; // Distance in centimeters

void setup() {
  Serial.begin(9600);
  dispenser.attach(6);  // Attach servo to pin D6
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
}

long getDistance() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  long duration = pulseIn(ECHO_PIN, HIGH);
  long distance = duration * 0.034 / 2;
  return distance;
}

void loop() {
  long distance = getDistance();
  Serial.print("Distance: ");
  Serial.println(distance);
  
  if (distance > 0 && distance < thresholdDistance) {
    activateDispenser();
  }
  
  delay(2000); // Wait before the next reading
}

void activateDispenser() {
  // Rotate the servo to dispense food
  dispenser.write(90);
  delay(1000);
  // Return servo to initial position
  dispenser.write(0);
  delay(1000);
}

CODE EXPLANATION

1. Including Necessary Libraries

#include <Servo.h>
  • What It Means: This line tells the Arduino to include the Servo library, which is a set of pre-written code that helps you control servo motors.
  • Why It's Important: ​Without this library, the Arduino wouldn’t know how to move the servo motor to a specific angle.

2.Defining Pin Connections and Setting a Threshold

#define TRIG_PIN 9
#define ECHO_PIN 10
int thresholdDistance = 30;
  • Pin Definitions:
    • TRIG_PIN 9: This means we are connecting the Trigger pin of the ultrasonic sensor to digital pin 9 on the Arduino. The Trigger sends out a sound pulse.
    • ECHO_PIN 10: This connects the Echo pin of the sensor to digital pin 10. The Echo pin listens for the sound pulse to bounce back.
  • Threshold Distance:
    • int thresholdDistance = 30; This sets a value (in centimeters) that tells the Arduino when to dispense food. If an object (like your pet) comes closer than 30 cm, the feeder will activate.

3.Setup Function (Initialization)

void setup() {
  Serial.begin(9600);
  dispenser.attach(6);  // Attach servo to pin D6
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
}
  • servoPin = 9; → The servo motor is connected to pin 9 on the Arduino.
  • buttonPin = 7; → A push button for registering new fingerprints is connected to pin 7.

4. Setting Up the System in setup() Function

void setup() {
  Serial.begin(9600);
  finger.begin(57600);
  pinMode(buttonPin, INPUT_PULLUP);
  lockServo.attach(servoPin);
  • Serial Communication:
    • Serial.begin(9600);
      This starts communication between the Arduino and your computer so you can see what the Arduino is "thinking" by printing messages on the Serial Monitor.
  • Servo Attachment:
    • dispenser.attach(6);
      This tells the Arduino to control the servo motor through pin 6. It’s like assigning a remote control channel to your servo.
  • Setting Pin Modes:
    • pinMode(TRIG_PIN, OUTPUT);
      This configures the Trigger pin as an output, meaning the Arduino will send a signal out from this pin.
    • pinMode(ECHO_PIN, INPUT);

​      ​This sets the Echo pin as an input, meaning the Arduino will listen for a signal coming in.

5. Measuring Distance

long getDistance() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  long duration = pulseIn(ECHO_PIN, HIGH);
  long distance = duration * 0.034 / 2;
  return distance;
}
  • How It Works:
    • Send a Signal:
      • The code first sets the Trigger pin LOW, waits a couple of microseconds, then sets it HIGH for 10 microseconds before setting it LOW again. This sends a short burst of ultrasonic sound.
    • Receive the Echo:
      • The pulseIn(ECHO_PIN, HIGH); function listens on the Echo pin and measures how long it takes for the sound pulse to bounce back.
    • Calculate Distance:
      • The duration of the echo is converted into a distance in centimeters. The multiplication factor (0.034) is based on the speed of sound, and dividing by 2 accounts for the trip to the object and back.
  • Why It’s Useful:

​This function lets the Arduino “see” how far away an object is. In our case, it helps decide if a pet is near enough to trigger the food dispensing.

6. Main Loop (Monitoring and Activation)

void loop() {
  long distance = getDistance();
  Serial.print("Distance: ");
  Serial.println(distance);
  if (distance > 0 && distance < thresholdDistance) {
    activateDispenser();
  }
  delay(2000); // Wait before the next reading
}
  • Continuous Monitoring:
    • The loop() function runs over and over. Every cycle, it measures the distance using getDistance().
  • Displaying the Distance:
    • The Serial.print and Serial.println commands help you see the distance value in the Serial Monitor. This is very useful for debugging and understanding how the sensor is working.
  • Activation Condition:
    • The if statement checks whether the detected distance is less than the set threshold (and more than zero to avoid errors). If it is, it calls the activateDispenser() function to dispense food.
  • Delay Between Readings:
    • delay(2000); pauses the loop for 2 seconds to prevent constant triggering, giving the sensor a moment before checking the distance again.

7. Dispensing Food

void activateDispenser() {
  // Rotate the servo to dispense food
  dispenser.write(90);
  delay(1000);
  // Return servo to initial position
  dispenser.write(0);
  delay(1000);
}
  • How It Works:
    • Rotate the Servo:
      • dispenser.write(90); rotates the servo motor to 90 degrees. This movement can be designed to open a gate or move a dispenser mechanism so that food is released.
    • Wait:
      • delay(1000); waits for 1 second to allow the food to be dispensed.
    • Reset the Servo:
      • dispenser.write(0); returns the servo to its starting position.
    • Final Delay:
      • Another 1-second delay ensures that the servo has enough time to return to its initial position before the next cycle begins.

How It Works Together

The ultrasonic sensor continuously measures the distance to any object in front of the feeder. Once a pet comes within the set range, the Arduino triggers the servo motor, which rotates to release a portion of food. After dispensing, the servo resets, readying the feeder for the next pet visit.

OBSERVING FUNCTIONALITY

  • Idle Mode: The feeder remains inactive until a pet is detected.
  • Pet Approaching: When the distance is less than the threshold, the servo activates, dispensing food.
  • Reset: The servo returns to its default position, ensuring no extra food is released.

COMMON PROBLEMS AND SOLUTIONS

1. No Food Dispensing:

  • Cause: Incorrect servo wiring or calibration issues.
  • Solution: Verify servo connections and adjust the angle values in the code if necessary.

2. Inconsistent Detection:

  • Cause: Ultrasonic sensor misalignment or interference.
  • Solution: Ensure the sensor is securely mounted and free from obstructions.

3. Power Issues:

  • Cause: Inadequate power supply to either the Arduino or servo.
  • Solution: Confirm that power is supplied correctly, and consider using an external power source if needed.​

Conclusion

This automatic pet feeder project demonstrates how sensor integration and servo control can combine to create a smart, responsive pet care device. By leveraging the HC-SR04’s distance measurements and the precision of servo operations, the system dispenses food at just the right moment, ensuring that your pet is fed in a timely and efficient manner while reducing the need for constant human oversight.

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