Introduction
Access control systems are widely used for security purposes in homes, offices, and other buildings. These systems allow only authorized individuals to enter restricted areas. In this project, we will design a door access control system using the 8051 microcontroller and a keypad for input.
Components Required
8051 Microcontroller (e.g., AT89S52)
4x4 Keypad
16x2 LCD Display
Relay Module (to control the door lock)
Buzzer (for incorrect access alert)
Resistors (10kΩ, 1kΩ, 330Ω)
Capacitors (33pF, 100μF)
Crystal Oscillator (11.0592 MHz)
Breadboard and Connecting Wires
Power Supply (5V for the 8051 and components)
Circuit Diagram
The keypad is used to enter a password, which is checked against a predefined code stored in the microcontroller. If the entered password is correct, the relay is activated to unlock the door. The LCD displays status messages, and a buzzer sounds if an incorrect password is entered.
+5V ----- +5V | | Keypad +---+ | | | | | +---------- P1.0 - P1.3 (8051 rows) | +---------- P1.4 - P1.7 (8051 columns) | | GNDLCD Display VSS to Ground VCC to +5V VEE to Potentiometer (for contrast control) RS to P2.0 (8051) RW to Ground E to P2.1 (8051) D4 to P2.2 (8051) D5 to P2.3 (8051) D6 to P2.4 (8051) D7 to P2.5 (8051)Relay Module VCC to +5V GND to Ground IN to P3.0 (8051) NO to one terminal of the door lock COM to power supply for the lockBuzzer Anode to P3.1 (8051) through 330Ω resistor Cathode to GroundPin Connections
Keypad:
Rows connected to P1.0 to P1.3 of the 8051
Columns connected to P1.4 to P1.7 of the 8051
LCD Display:
VSS to Ground
VCC to +5V
VEE to the potentiometer for contrast control
RS to P2.0 of the 8051
RW to Ground
E to P2.1 of the 8051
D4 to P2.2 of the 8051
D5 to P2.3 of the 8051
D6 to P2.4 of the 8051
D7 to P2.5 of the 8051
Relay Module:
VCC to +5V
GND to Ground
IN connected to P3.0 of the 8051
Buzzer:
Anode connected to P3.1 of the 8051 through a 330Ω resistor
Cathode connected to Ground
Software Implementation
The code is written in C using Keil uVision IDE. It involves reading the keypad input, comparing it with a predefined password, and controlling the relay and buzzer based on the input.
#include <reg51.h>#include <lcd.h> // Include a custom LCD library#define PASSWORD "1234" // Predefined passwordsbit RELAY = P3^0; // Relay control pinsbit BUZZER = P3^1; // Buzzer control pinunsigned char keypad[4][4] = {{'1','2','3','A'}, {'4','5','6','B'}, {'7','8','9','C'}, {'*','0','#','D'}};unsigned char row, col;void delay(unsigned int time) { unsigned int i, j; for(i = 0; i < time; i++) for(j = 0; j < 1275; j++);}void keypad_init() { P1 = 0xF0; // Set P1.0-P1.3 as inputs (rows) and P1.4-P1.7 as outputs (columns)}char keypad_getkey() { while(1) { for(col = 0; col < 4; col++) { P1 = ~(0x10 << col); // Ground one column at a time row = P1 & 0x0F; // Read the rows if (row != 0x0F) { while(P1 & (0x10 << col)); // Wait for key release row = P1 & 0x0F; if(row == 0x0E) return keypad[0][col]; if(row == 0x0D) return keypad[1][col]; if(row == 0x0B) return keypad[2][col]; if(row == 0x07) return keypad[3][col]; } } }}void main() { char entered_password[5]; unsigned char i; char key; lcd_init(); // Initialize the LCD keypad_init(); // Initialize the keypad RELAY = 0; // Initially turn off the relay BUZZER = 0; // Initially turn off the buzzer while(1) { lcd_clear(); lcd_print("Enter Password:"); i = 0; while(i < 4) { key = keypad_getkey(); lcd_cmd(0xC0 + i); // Move cursor to the second line lcd_data('*'); // Display '*' for each entered digit entered_password[i] = key; i++; } entered_password[4] = '\0'; // Null-terminate the string if(strcmp(entered_password, PASSWORD) == 0) { lcd_clear(); lcd_print("Access Granted"); RELAY = 1; // Unlock the door delay(5000); // Keep the door unlocked for 5 seconds RELAY = 0; // Lock the door } else { lcd_clear(); lcd_print("Access Denied"); BUZZER = 1; // Sound the buzzer delay(2000); // Keep the buzzer on for 2 seconds BUZZER = 0; // Turn off the buzzer } delay(1000); // Small delay before the next password entry }}Explanation
Initialization:
LCD Initialization: The lcd_init() function configures the LCD for display.
Keypad Initialization: The keypad_init() function sets up the keypad rows as inputs and columns as outputs.
Relay and Buzzer: The relay and buzzer pins are initially set low.
Keypad Reading:
The keypad_getkey() function scans the keypad to detect key presses. It grounds each column one at a time and reads the rows to identify the pressed key.
Main Loop:
Password Entry: The main loop prompts the user to enter a 4-digit password. Each digit is displayed as an asterisk on the LCD.
Password Verification: The entered password is compared with the predefined password. If it matches, the relay is activated to unlock the door, and a success message is displayed. If it doesn't match, the buzzer sounds, and an error message is displayed.
Delay Function:
The delay function introduces a small delay between operations to ensure stability and provide adequate response times.
Conclusion
This project demonstrates the use of the 8051 microcontroller to create a door access control system. By integrating a keypad for password input, an LCD for user feedback, a relay for door control, and a buzzer for alerts, the system provides a secure and user-friendly access control solution. This project is a great way to learn about keypad interfacing, LCD display control, and using microcontrollers for security applications.
Want us to guide you through your project or make the project for you ?
Create Various Projects
Check out our Free Arduino Projects Playlist - Arduino Projects
Check out our Free Raspberry Pi Projects Playlist - Raspberry Pi Projects
Check out our Free TinkerCAD Projects Playlist - TinkerCAD Projects
Check out our Free IoT Projects Playlist - IoT Projects
Check out our Free Home Automation Projects Playlist - Home Automation Projects
Check out our Free NodeMCu Projects Playlist - NodeMCu Projects
Comments