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eSafe
Name: Dascalu Stefan-Nicolae
Group: 331CA
Introduction
eSafe is a digital lockbox implemented on an Arduino Uno. It uses a 4×4 matrix keypad for PIN entry, an SG90 servo for a mechanical latch, a DS1307 real-time clock (I²C) to enforce access windows, and a 16×2 I²C LCD to display status and time. Three wrong PIN attempts trigger an alarm tone and flashing red LED; valid entries drive the servo to unlock, light a green LED, and display “UNLOCKED.”
This project integrates functionalities from three labs:
- Lab 2 (Interrupts & GPIO): keypad row-change detection
- Lab 3 (Timers): debounce via Timer 2 CTC and alarm timing
- Lab 6 (I²C): shared bus for LCD and RTC
Hardware Design
Below are both the abstract block diagram and the detailed wiring schematic with an Arduino Uno:
Note on Simulation vs. Real RTC
In Tinkercad I used a generic 7-segment I²C display; the real build uses the DS1307 module on the same SDA/SCL, so no rewiring or code changes are needed.
Hardware Functionality
- Keypad: row-interrupt + Timer 2 CTC debounce
- Buzzer: tone/noTone alarm, driven directly from Arduino pin
- LEDs: status indicators with resistors
- Servo: 50 Hz PWM; relocked non-blocking after 5 s
- LCD/RTC: HD44780 via PCF8574; DS1307 battery-backed timekeeper
- Power: on-board 5 V regulator (~500 mA); peak draw ~270 mA
Pin-out Detail
| Component | Interface | Arduino pin | Direction | Rationale |
|---|---|---|---|---|
| Keypad row/col | GPIO | D2–D9 | input | Pin-change ISR on D2–D5; columns polled on D6–D9 |
| Passive buzzer | GPIO | D11 | output | direct drive with tone()/noTone() |
| Red LED | GPIO | D13 | output | Built-in LED pin |
| Green LED | GPIO | D12 | output | Digital status LED (no PWM on D12) |
| Servo SG90 | PWM | D10 | output | attach() supports D10 |
| LCD I²C | I²C (TWI) | A4/A5 | bidir | Hardware Wire bus |
| RTC DS1307 | I²C (TWI) | A4/A5 | bidir | Shares same TWI bus |
Bill Of Materials
| Component | Purchase link |
|---|---|
| Arduino Uno R3 (ATmega328P) | https://www.optimusdigital.ro/ro/placi-avr/4561-placa-de-dezvoltare-compatibila-cu-arduino-uno-r3-atmega328p-atmega16u2-cablu-50-cm.html |
| 4×4 Matrix Keypad | https://www.optimusdigital.ro/ro/senzori-senzori-de-atingere/470-tastatura-matriceala-4x4-cu-conector-pin-de-tip-mama.html |
| DS1307 RTC Module (I²C) | https://www.optimusdigital.ro/ro/altele/4746-modul-ceas-in-timp-real-ds1307.html?search_query=Modul+Ceas+in+timp+real+DS1307&results=3 |
| LCD 1602 I²C Blue Backlight | https://www.optimusdigital.ro/ro/optoelectronice-lcd-uri/2894-lcd-cu-interfata-i2c-si-backlight-albastru.html |
| SG90 Micro-Servo | https://www.optimusdigital.ro/ro/motoare-servomotoare/26-micro-servomotor-sg90.html?search_query=Micro+Servomotor+SG90+90° |
| Breadboard + jumper wires + LEDs + resistors | https://www.optimusdigital.ro/ro/kituri/12026-kit-plusivo-pentru-introducere-in-electronica-0721248990075.html |
Photos of the eSafe project
Software Design
Implementation Status
- Full feature set in ~200 lines of C++ on Arduino Uno
- PIN entry, servo latch, LEDs, buzzer, I²C LCD & RTC, time window, unlock log
- Stable on hardware; manual end-to-end tests completed
Library Choices
| Library | Purpose | Justification |
|---|---|---|
| Wire / RTClib | I²C + DS1307 | Adafruit’s proven RTC driver |
| LiquidCrystal_I2C | I²C LCD | Minimal wiring, easy print interface |
| Keypad | 4×4 scan + debounce | handles interrupts + debouncing |
| Servo | SG90 control | official Arduino, simple API |
Novelty Element
- Time-lock feature enforcing business hours
- Unlock log on LCD
- Integration of multiple lab modules into one device
Development
- Arduino IDE / PlatformIO
Core modules
- `updateDisplay()`: live clock, PIN prompt/asterisks, last-unlock
- `handleKey()`: ‘C’ clear, digit entry, ‘D’ submit with window check
- `unlockDoor()`: unlock sequence + schedule non-blocking relock
Libraries
- Wire/RTClib
- LiquidCrystal_I2C
- Keypad
- Servo
Safety & Build Quality
- neat wiring on breadboard
- LEDs have 330 Ω current-limiting resistors
Conclusions
eSafe demonstrates integration of GPIO, interrupts, timers, PWM, and I²C into a user-friendly digital safe. Non-blocking design ensures smooth UI and reliable timekeeping.
Bibliography & Resources
- ATmega328P Datasheet
- DS1307 RTC Datasheet
- LiquidCrystal_I2C Library Guide
- Keypad Library Reference
- PlatformIO Documentation
