Smart Shopping Trolley Using Arduino UNO & RFID

Project Overview & Features

The Smart Shopping Trolley uses RFID technology to scan products automatically when placed near the trolley's RC522 reader. Each product has an RFID tag. When scanned, Arduino looks up the product name and price from a local database, updates the running total, and displays everything on the 16×2 LCD. A buzzer beeps to confirm each scan.

📡

Auto RFID ScanningHands-free product detection using the RC522 reader

💰

Real-time BillingBill updates instantly on every scan

🖥️

16×2 LCD DisplayShows item name, price, and running total via I²C

🔔

Buzzer AlertAudio confirmation on each successful scan

🔘

Push ButtonsAdd, Remove, and Reset controls built-in

⚡

Queue-Free CheckoutNo cashier needed — pay directly at exit

Components Required

#	Component	Specification	Qty
1	Arduino UNO	ATmega328P, 5V	×1
2	RFID Reader Module	RC522, SPI, 3.3V	×1
3	RFID Tags / Cards	Mifare 1K (13.56 MHz)	×4+
4	LCD Display	16×2 with I²C backpack (0x27)	×1
5	Buzzer	Active Buzzer, 5V	×1
6	Push Buttons	6×6mm tactile switch	×3
7	Breadboard	830-point or mini	×1
8	Jumper Wires	Male-Male, various lengths	×20
9	Power Supply	USB 5V or 9V DC barrel	×1

ℹ️ The RC522 RFID module operates at 3.3V — never connect its VCC to the Arduino's 5V pin, as this will damage the module.

Circuit Diagram

Full System Schematic

Pin Wiring Guide

RC522 RFID → Arduino UNO (SPI)

RC522 Pin	Arduino Pin	Notes
SDA	D10	Slave Select (SS)
SCK	D13	SPI Clock
MOSI	D11	Master Out Slave In
MISO	D12	Master In Slave Out
RST	D9	Reset pin
3.3V	3.3V	⚠️ Use 3.3V only!
GND	GND	—

16×2 LCD (I²C backpack, addr 0x27) → Arduino UNO

LCD Pin	Arduino Pin	Notes
SDA	A4	I²C Data
SCL	A5	I²C Clock
VCC	5V	Power
GND	GND	—

Buzzer & Buttons → Arduino UNO

Component	Pin	Arduino Pin
Buzzer (+)	Positive	D5
Buzzer (−)	GND	GND
Remove Button	One leg	D2
Add Button	One leg	D3
Reset Button	One leg	D4
All Buttons	Other leg	GND

⚠️ If your buttons read noisy values, add 10kΩ pull-down resistors from each button data pin to GND, or enable internal pull-ups and invert the logic in code.

Step-by-Step Assembly

Install Required Libraries

Open Arduino IDE → Sketch → Include Library → Manage Libraries. Search and install: MFRC522 by GithubCommunity, LiquidCrystal_I2C by Frank de Brabander.

Find Your LCD I²C Address

Upload an I²C scanner sketch to find your LCD's address. It's usually 0x27 or 0x3F. Update the address in the code: LiquidCrystal_I2C lcd(0x27, 16, 2);

Wire the RC522 RFID Module

Connect SDA→D10, SCK→D13, MOSI→D11, MISO→D12, RST→D9. Connect VCC to the 3.3V pin (not 5V) and GND to GND.

Wire the LCD (I²C)

Connect SDA→A4, SCL→A5, VCC→5V, GND→GND on the Arduino.

Connect Buzzer & Buttons

Buzzer (+) → D5, (−) → GND. Each button: one leg to D2/D3/D4, other leg to GND.

Scan Your RFID Tag UIDs

Upload the MFRC522 DumpInfo example sketch and scan each RFID tag. Note the UID printed on the Serial Monitor (e.g., B3 23 E4 11). You'll need these for the product database.

Update the Item Database in Code

Replace the UIDs and product details in the item_list[] array with your scanned UIDs, product names, and prices.

Upload & Test

Upload the code, open Serial Monitor at 9600 baud. Scan a tag — the LCD should show the product name and price, and the buzzer should beep once. Test all three buttons.

💡 Pro Tip: Attach RFID tags to product boxes using double-sided tape. Position the RC522 reader at the trolley's entrance opening so tags are scanned automatically when items are dropped in.

Arduino Code

Arduino / C++

// Smart Shopping Trolley — makemindz.com
// RFID RC522 + 16x2 I2C LCD + Buzzer + 3 Push Buttons

#include <SPI.h>
#include <MFRC522.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

const int remove_button = 2;
const int add_button    = 3;
const int reset_button  = 4;
const int buzzer_Pin   = 5;
#define SS_PIN  10
#define RST_PIN  9
MFRC522 mfrc522(SS_PIN, RST_PIN);

struct item {
  String item_name;
  String item_number;
  int    item_price;
};

const int number_of_item = 4;
const item item_list[number_of_item] = {
  // Name          RFID UID         Price (Rs)
  {"Tata salt",  "B3 23 E4 11",  100},
  {"Milk Powder","A3 51 A0 0D",   50},
  {"Bournvita",  "13 1F A3 0D",   20},
  {"Ball_Pen",   "E3 68 DC 12",   10},
};

int bill_amount      = 0;
int add_item_flag    = 1;
int remove_item_flag = 0;

void setup() {
  pinMode(remove_button, INPUT);
  pinMode(reset_button,  INPUT);
  pinMode(add_button,    INPUT);
  pinMode(buzzer_Pin,    OUTPUT);
  Serial.begin(9600);
  SPI.begin();
  mfrc522.PCD_Init();
  digitalWrite(buzzer_Pin, LOW);

  lcd.init();
  lcd.backlight();
  lcd.clear();
  lcd.setCursor(0, 0); lcd.print("Smart Trolley");
  lcd.setCursor(0, 1); lcd.print("Billing System");
  delay(2000);
  lcd.clear();
  lcd.setCursor(0, 0); lcd.print("Start purchasing");
  lcd.setCursor(0, 1); lcd.print("your item");
}

void loop() {
  int remove_buttonState = digitalRead(remove_button);
  int add_buttonState    = digitalRead(add_button);
  int reset_buttonState  = digitalRead(reset_button);

  if (remove_buttonState) {
    add_item_flag = 0; remove_item_flag = 1;
    lcd.clear();
    lcd.setCursor(0, 0); lcd.print("You Can now");
    lcd.setCursor(0, 1); lcd.print("Remove your item");
    delay(2000);
  } else if (add_buttonState) {
    add_item_flag = 1; remove_item_flag = 0;
    lcd.clear();
    lcd.setCursor(0, 0); lcd.print("You Can now");
    lcd.setCursor(0, 1); lcd.print("add your item");
    delay(2000);
  } else if (reset_buttonState) {
    lcd.clear();
    lcd.setCursor(0, 0); lcd.print("Resetting");
    lcd.setCursor(0, 1); lcd.print("Trolley data");
    delay(2000);
    lcd.clear();
    lcd.setCursor(0, 0); lcd.print("Start Purchasing");
    lcd.setCursor(0, 1); lcd.print("Your item");
    bill_amount = 0;
  }

  if (!mfrc522.PICC_IsNewCardPresent()) return;
  if (!mfrc522.PICC_ReadCardSerial())   return;

  String content = "";
  for (byte i = 0; i < mfrc522.uid.size; i++) {
    content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
    content.concat(String(mfrc522.uid.uidByte[i], HEX));
  }
  content.toUpperCase();

  for (int i = 0; i < number_of_item; i++) {
    if (content.substring(1) == item_list[i].item_number) {
      if (add_item_flag == 1) {
        bill_amount += item_list[i].item_price;
        digitalWrite(buzzer_Pin, HIGH); delay(500); digitalWrite(buzzer_Pin, LOW);
        lcd.clear();
        lcd.setCursor(0, 0); lcd.print(item_list[i].item_name);
        lcd.setCursor(0, 1); lcd.print(String(item_list[i].item_price) + " Rs");
        delay(2000);
      } else if (remove_item_flag == 1) {
        if (bill_amount > 0) {
          bill_amount -= item_list[i].item_price;
          digitalWrite(buzzer_Pin, HIGH); delay(500); digitalWrite(buzzer_Pin, LOW);
          lcd.clear();
          lcd.setCursor(0, 0); lcd.print(item_list[i].item_name);
          lcd.setCursor(0, 1); lcd.print("removed");
          delay(2000);
        } else {
          lcd.clear();
          lcd.setCursor(0, 0); lcd.print("Your trolley is");
          lcd.setCursor(0, 1); lcd.print("empty now");
          delay(2000);
        }
      }
    }
  }

  lcd.clear();
  lcd.setCursor(0, 0); lcd.print("Total Billing");
  lcd.setCursor(0, 1); lcd.print(String(bill_amount) + " Rs");
  delay(2000);
}

Run the Simulation

🖥️

Try it on Wokwi — No Hardware Needed

Simulate the entire Smart Trolley project in your browser. Click RFID cards to scan products and watch the LCD update in real time.

▶ Open Wokwi Simulator 🔧 Try on Tinkercad

💡 Wokwi Instructions: (1) Create new Arduino UNO project → (2) Paste diagram.json → (3) Paste sketch code → (4) Press Play → (5) Click RFID cards on-screen to simulate scanning!

How It Works

The system follows a simple but powerful flow. Each product has an RFID tag with a unique UID. When the tag enters the RC522 reader's electromagnetic field, the reader communicates via the SPI protocol to pass the UID to the Arduino. The Arduino then compares the UID against its local item_list[] database. If matched, it updates the bill, triggers the buzzer, and refreshes the LCD.

①

RFID Tag Detected

RC522 reader detects a tag in its ~5cm range and reads the UID via SPI bus.

②

UID Lookup

Arduino searches the item_list[] array for a UID match to retrieve product name and price.

③

Bill Updated

Depending on the mode (add/remove), the price is added or subtracted from the running bill_amount.

④

LCD + Buzzer Feedback

The 16×2 LCD shows the product name and price, followed by the updated total. Buzzer beeps once to confirm.

ROBOTICS

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