Circuit Documentation

Summary

The circuit in question is designed to interface an Arduino UNO with multiple peripherals including an RFID-RC522 module, an I2C LCD 16x2 screen, a buzzer module, HC-05 Bluetooth module, nRF24L01 wireless communication module, and three pushbuttons with associated resistors. The circuit is powered by a 9V battery and includes connections for both 5V and 3.3V components. The primary function of the circuit is to create a smart trolley billing system, utilizing the RFID module for item identification and the LCD for user interaction and feedback.

Component List

RFID-RC522

• RFID reader/writer module
• Operates at 3.3V

Pushbutton (x3)

• Simple tactile switch
• Used for user input

Resistor (x3)

• 200 Ohms resistance
• Used for debouncing the pushbuttons

I2C LCD 16x2 Screen

• Alphanumeric liquid crystal display
• Uses I2C communication

HC-05

• Bluetooth module for wireless communication
• Operates at 5V

nRF24L01

• Wireless communication module
• Operates at 3.3V

9V Battery

• Power source for the circuit

Arduino UNO

• Microcontroller board based on the ATmega328P
• Central controller for the circuit

Buzzer Module

• Audio signaling device
• Operates at 5V

Wiring Details

RFID-RC522

• VCC (3.3V) to Arduino 3.3V
• RST to Arduino D9
• GND to common ground
• IRQ not connected
• MISO to Arduino D12
• MOSI to Arduino D11
• SCK to Arduino D13
• SDA to Arduino D10

Pushbuttons

• Pin 1 (in) of all pushbuttons to Arduino 5V
• Pin 4 (out) of each pushbutton to one side of a 200 Ohm resistor
• Other side of each resistor to Arduino D2, D3, and D4 respectively

Resistor (x3)

• One side to pushbutton Pin 4 (out)
• Other side to Arduino D2, D3, and D4 respectively

I2C LCD 16x2 Screen

• SCL to Arduino SCL
• SDA to Arduino SDA
• VCC (5V) to Arduino 5V
• GND to common ground

HC-05

• EN not connected
• VCC to Arduino 5V
• GND to common ground
• TXD to Arduino D0
• RXD to Arduino D1
• STATE not connected

nRF24L01

• GND to common ground
• VCC to Arduino 3.3V
• CE to Arduino D10
• CSN not connected
• SCK to Arduino D13
• MOSI to Arduino D11
• MISO to Arduino D12
• IRQ not connected

9V Battery

• Positive (+) to Arduino Vin
• Negative (-) to common ground

Arduino UNO

• 5V and 3.3V to respective components
• GND to common ground
• Digital pins D0 to D13 to respective components as per wiring details

Buzzer Module

• GND to common ground
• Vcc to Arduino 5V
• I/O not connected

Documented Code

/****************************************************
 * Code Designed By : Rahul Jadhav Youtube Channel
 ****************************************************/

/******************RFID Connection:*********************

RFID PIN    ARDUINO PIN 
SDA         10
SCK         13
MOSI        11
MISO        12
GND         GND
RST         9
3.3v        3.3v
 ******************************************************/

/***** LCD Connection ***********************************
LCD PIN   ARDUINO PI
SCL       SCL (Arduino Last pin)
SDA       SDA (Arduino Secon last pin)
VCC       5v
GND       GND
 ******************************************************/

/***** Buzzer Connection ***********************************
Buzzer PIN   ARDUINO PI
Positive     5
GND          GND 
 *****************************************************/

/***** Button Connection ***********************************
Button PIN   ARDUINO PI
Remove_Button     2
Add_button         3
Reset_button       4
VCC          5v
GND          GND 
 *****************************************************/
  
#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);   // Create MFRC522 instance.

// Rest of the code is omitted for brevity

The provided code snippet is part of a larger program that runs on the Arduino UNO. It initializes the RFID-RC522 module, the I2C LCD screen, and sets up the pushbuttons for user input. The code includes a structure for items with their names, RFID numbers, and prices, and contains logic for adding or removing items from a bill, which is displayed on the LCD. The code also handles the reset functionality to clear the trolley data.