Piggy Bank

Note

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Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

Name	Includes Arduino board	PURCHASE LINK
Ultimate Sensor Kit	Arduino Uno R4 Minima	BUY
Elite Explorer Kit	Arduino Uno R4 WiFi	BUY
3 in 1 Ultimate Starter Kit	Arduino Uno R4 Minima	BUY
Universal Maker Sensor Kit	×	BUY

Course Introduction

In this lesson, you’ll use an IR Sensor Module, a servo motor, an I2C LCD, and Arduino to create a smart piggy bank system.

When a bill is detected by the IR sensor, the servo automatically opens the bank entrance to let the money drop inside. The LCD then updates the bill count, and the servo returns to the closed position, creating a simple automatic counting effect.

Note

If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Arduino UNO R4 Minima/Arduino UNO R4 WIFI	1	BUY
2	USB Type-C cable	1
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	IR Obstacle Avoidance Sensor Module	1	BUY
6	I2C LCD 1602	1	BUY
7	Digital Servo Motor	1	BUY

Wiring

Common Connections:

Digital Servo Motor
- Connect to breadboard’s positive power bus.
- Connect to breadboard’s negative power bus.
- Connect to 9 on the Arduino.
I2C LCD 1602
- SDA: Connect to SDA on the Arduino.
- SCL: Connect to SCL on the Arduino.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.
IR Obstacle Avoidance Sensor Module
- OUT: Connect to 2 on the Arduino.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.

Writing the Code

Note

You can copy this code into Arduino IDE.
To install the library, use the Arduino Library Manager and search for LiquidCrystal I2C and install it.
Don’t forget to select the board(Arduino UNO R4 Minima/WIFI) and the correct port before clicking the Upload button.

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Servo.h>

// -------------------- Pins --------------------
const int IR_PIN = 2;
const int SERVO_PIN = 9;

// -------------------- LCD ---------------------
LiquidCrystal_I2C lcd(0x27, 16, 2);

// -------------------- Servo -------------------
Servo bankServo;

// Adjust these angles based on your structure
const int SERVO_CLOSED_ANGLE = 0;
const int SERVO_OPEN_ANGLE = 90;

// -------------------- Counter -----------------
int billCount = 0;

// -------------------- Timing ------------------
const unsigned long openTime = 1000;      // door open time
const unsigned long settleTime = 300;     // small delay before counting
const unsigned long cooldownTime = 1200;  // anti-repeat timing

// -------------------- Sensor Logic ------------
// Most IR obstacle modules output LOW when an object is detected.
// If your sensor behaves the opposite way, change LOW to HIGH.
const int IR_DETECTED_STATE = LOW;

// -------------------- State -------------------
bool lastDetected = false;
unsigned long lastActionTime = 0;

void updateLCD() {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Piggy Bank");
  lcd.setCursor(0, 1);
  lcd.print("Bills: ");
  lcd.print(billCount);
}

void openBank() {
  bankServo.write(SERVO_OPEN_ANGLE);
}

void closeBank() {
  bankServo.write(SERVO_CLOSED_ANGLE);
}

void setup() {
  pinMode(IR_PIN, INPUT);

  bankServo.attach(SERVO_PIN);
  closeBank();

  lcd.init();
  lcd.backlight();
  updateLCD();
}

void loop() {
  bool currentDetected = (digitalRead(IR_PIN) == IR_DETECTED_STATE);
  unsigned long now = millis();

  // Trigger only when the bill is newly detected
  if (currentDetected && !lastDetected && (now - lastActionTime > cooldownTime)) {
    // Step 1: IR detects the bill
    // Step 2: Open the piggy bank
    openBank();

    // Wait for the bill to enter
    delay(openTime);

    // Step 3: Increase bill count
    billCount++;

    // Step 4: Update LCD
    updateLCD();

    // Step 5: Return servo to initial position
    delay(settleTime);
    closeBank();

    lastActionTime = millis();
  }

  lastDetected = currentDetected;
}