At89c2051 Projects -

This project demonstrates a security system. The user must enter a 4-digit code; if correct, a relay is energized to open a lock. Rows to P3.0-P3.3 (outputs), Columns to P1.0-P1.3 (inputs with pull-ups). Scan the keypad using the classic row-scan method. Code logic: unsigned char code[4] = 1,2,3,4; // correct code unsigned char entered[4]; unsigned char pos = 0; void main() while(1) unsigned char key = get_key(); if(key != 0xFF) entered[pos++] = key; beep(); if(pos == 4) if(memcmp(entered, code, 4) == 0) relay_on(); delay_ms(3000); relay_off(); else // wrong code: beep error

I/O pin control, timing loops. Project 2: 7-Segment Display Counter (0-9) Difficulty: Beginner Components: Common cathode 7-segment display, 8x 220Ω resistors Circuit: Connect segments a-g and DP of the display to P1.0 – P1.7 via 220Ω resistors. Common cathode to GND. Code snippet (lookup table): unsigned char segment[] = 0xC0, 0xF9, 0xA4, 0xB0, 0x99, 0x92, 0x82, 0xF8, 0x80, 0x90; // Common anode // For common cathode, invert the bits: ~segment[i] & 0x7F void main() unsigned char count = 0; while(1) P1 = ~segment[count]; // active low for common cathode? // Adjust based on your display type. delay_ms(1000); count++; if(count > 9) count = 0; at89c2051 projects

Timer/counter modes, frequency measurement techniques. Project 5: Simple Servo Motor Controller Difficulty: Intermediate Components: SG90 or MG995 servo, 5V supply, potentiometer (10k) This project demonstrates a security system

void init_uart() = 0x20; TH1 = 0xFD; // 9600 @11.0592 MHz TR1 = 1; Scan the keypad using the classic row-scan method

Servos require a 50Hz PWM signal with pulse widths from 1ms to 2ms.

void main() // Configure Timer0 in mode 1 TMOD