Embedded Systems · ECCE4227 · Fall 2025

Secure Access Box with Automated Locking

AVRATmega8CRFIDProteusBare-Metal

Brief

Let the right person in — and notice when someone tampers.

The box grants access two ways — a keypad PIN or an RFID card — and on a valid credential drives a servo lock open, with clear success/failure feedback on a 16×2 LCD and status LEDs. On top of authentication it watches its surroundings: an ultrasonic sensor flags someone getting too close, and a vibration sensor raises a tamper alarm. A small box, but a complete embedded loop: sense → decide → actuate → signal.

Firmware

Bare-metal C on an 8-bit AVR.

The control logic runs directly on an ATmega8 in C — scanning the keypad, reading the RC522 RFID reader over SPI, comparing credentials against the stored code, driving the servo lock, and sequencing the LCD, LEDs, and buzzer. No operating system and no framework: just registers, ports, timers, and interrupts, which is exactly where embedded fundamentals live.

Sensing & Feedback

Proximity warnings and a tamper alarm, not just a lock.

An HC-SR04 ultrasonic sensor measures distance and warns on close approach; a vibration sensor triggers a tamper alarm through the buzzer. State is reported three ways — the LCD prompts (ENTER PIN, ACCESS GRANTED), red/green LEDs for locked/unlocked, and a serial log (System Ready, Warning: Proximity!, ALARM: Vibration!, Wrong PIN) — so the box’s behaviour is observable while it runs.

Schematic & Simulation

Designed and proven in Proteus.

The full system was schematic-captured in Proteus and simulated end to end — keypad entry, the ENTER PIN → ACCESS GRANTED flow, proximity warnings, and the vibration alarm — so the firmware and wiring were verified on virtual hardware before committing to physical parts.

Proteus schematic of the access box: an ATmega8 wired to a 4×4 keypad, 16×2 LCD showing ENTER PIN, HC-SR04 ultrasonic sensor, vibration sensor, buzzer, RFID reader, and red/green status LEDs, with a virtual terminal logging system events. — Proteus capture & simulation — ATmega8 driving the keypad, LCD, ultrasonic and vibration sensors, RFID, buzzer, and status LEDs, validated before any wiring.

Bench Build

Then built and tested for real.

The design didn’t stop at simulation. It was wired up on a breadboard and run on real hardware — keypad, LCD, ultrasonic and vibration sensors, and a servo actuating a physical enclosure — closing the loop from a Proteus schematic to a working prototype.

Breadboard prototype of the access box on the lab bench: ATmega8 with an AVR programmer, a 4×4 keypad, a 16×2 LCD, an HC-SR04 ultrasonic sensor, jumper wiring, and a servo-actuated cardboard enclosure standing in for the locked box. — The breadboard prototype on the bench — ATmega8, keypad, LCD, ultrasonic sensor, and a servo-actuated enclosure, matching the simulated design.

Value

The embedded basics that everything else builds on.

Port I/O, SPI, timing, interrupts, and actuator control on a constrained 8-bit microcontroller — taken all the way from schematic to a tested bench prototype. This is the groundwork the later ESP32 glove controller scales up from.