This circuit is designed to function as a door lock system, utilizing a 4x4 membrane matrix keypad for input, an LCD I2C display for user feedback, a relay module to control a 12V solenoid lock, and an Arduino UNO as the central microcontroller. The system prompts the user to enter a password on the keypad, displays the input on the LCD, and if the correct password is entered, activates the relay to unlock the solenoid lock for a brief period.
5V
and GND
are used to power the LCD I2C display and the relay module.A4 (SDA)
and A5 (SCL)
are connected to the corresponding SDA and SCL pins on the LCD I2C display for I2C communication.D2
to D9
are connected to the keypad pins C4
to R1
respectively.D10
is connected to the signal pin S
of the relay module.VCC
connected to 5V from the Arduino UNO.GND
connected to GND on the Arduino UNO.SDA
connected to A4 on the Arduino UNO.SCL
connected to A5 on the Arduino UNO.5V
connected to 5V from the Arduino UNO.GND
connected to GND on the Arduino UNO.S
(signal) connected to digital pin D10
on the Arduino UNO.COM
connected to the positive terminal of the 9V battery.NO
(Normally Open) connected to the VCC
of the 12V solenoid lock.R1
to R4
connected to digital pins D9
to D6
on the Arduino UNO.C1
to C4
connected to digital pins D5
to D2
on the Arduino UNO.VCC
connected to NO
on the relay module.GND
connected to the negative terminal of the 9V battery.+
connected to COM
on the relay module.-
connected to GND
on the 12V solenoid lock./*
* Door Lock System using 4x4 Keypad, LCD, and Relay
* This code reads input from a 4x4 keypad, displays it on an LCD using I2C,
* and checks if the entered code matches a predefined password to
* unlock the door by activating a relay. Feedback is provided on incorrect
* entry, and blocking delays are prevented.
* Password: 1234
*/
#include <Keypad.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
const byte ROWS = 4; // Four rows
const byte COLS = 4; // Four columns
char keys[ROWS][COLS] = {
{'1','2','3','A'},
{'4','5','6','B'},
{'7','8','9','C'},
{'*','0','#','D'}
};
byte rowPins[ROWS] = {9, 8, 7, 6}; // Connect to the row pinouts of the keypad
byte colPins[COLS] = {5, 4, 3, 2}; // Connect to the column pinouts of the keypad
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);
LiquidCrystal_I2C lcd(0x27, 16, 2); // Set the LCD address to 0x27 for a 16 chars and 2 line display
const int relayPin = 10; // Pin connected to the relay
String password = "1234";
String input = "";
unsigned long lastInteraction = 0;
const unsigned long timeout = 3000; // 3 seconds timeout for feedback
void setup() {
pinMode(relayPin, OUTPUT);
digitalWrite(relayPin, LOW); // Ensure relay is off initially
lcd.begin(16,2);
lcd.backlight();
lcd.print("Enter Password:");
}
void loop() {
char key = keypad.getKey();
if (key) {
lastInteraction = millis();
if (key == '#') {
if (input == password) {
lcd.clear();
lcd.print("Access Granted");
digitalWrite(relayPin, HIGH); // Activate relay
delay(5000); // Keep relay on for 5 seconds
digitalWrite(relayPin, LOW); // Deactivate relay
} else {
lcd.clear();
lcd.print("Access Denied");
}
input = "";
} else if (key == '*') {
input = "";
lcd.clear();
lcd.print("Enter Password:");
} else {
input += key;
lcd.setCursor(0, 1);
lcd.print(input);
}
}
if (millis() - lastInteraction > timeout && input != "") {
lcd.clear();
lcd.print("Enter Password:");
input = "";
}
}
This code is responsible for the operation of the door lock system. It initializes the keypad and LCD, waits for user input, compares the input to a predefined password, and controls the relay to lock or unlock the door accordingly. The LCD provides feedback to the user, prompting for the password and indicating whether access is granted or denied.