Smart Parcel Box

Safe Drop is a secure IoT-enabled parcel delivery system engineered to eliminate missed deliveries, unauthorised access, and unattended package theft. The system autonomously authenticates delivery personnel, secures parcels through automatic locking, and provides real-time remote monitoring and tamper alerts without requiring the recipient to be physically present.

The system architecture combines embedded sensing, electromechanical locking, cloud connectivity, and event-driven firmware into a fully integrated smart parcel handling platform. The ESP32 microcontroller coordinates all sensing, authentication, locking, notification, and security operations in real time.

• →ESP32-WROOM-32D as the central embedded controller
• →Real-time Wi-Fi communication using Blynk IoT platform
• →Interrupt-driven event handling for critical security events
• →Integrated sensing, locking, and cloud notification architecture
• →Autonomous parcel monitoring and secure access workflow

The enclosure was fully designed in Autodesk Fusion 360 with emphasis on structural rigidity, modularity, printability, and integrated component mounting. The design involves modular walls and compartments with sliding-joints and mechanical interlocking for DIY printability and assembly. It also separates the parcel storage chamber from the electronics compartment to improve electrical safety, maintainability, and long-term operational reliability.

• →Complete parametric CAD design developed in Fusion 360
• →Sliding-joint assembly eliminates screws and adhesives
• →Dual-compartment architecture for parcel isolation and electronics protection
• →Integrated mounting geometry for sensors, servo, display, and keypad
• →Optimised for support-free FDM printing using PLA+ filament
• →Dedicated cable-routing channels and maintenance access paths

Enclosure model in Fusion 360

Sliding-joint modular walls

Separate electronics compartment

The hardware subsystem integrates sensing, locking, user interaction, and wireless communication into a compact embedded architecture. Components were selected based on reliability, ease of integration, and suitability for real-time IoT operation.

• →ESP32 microcontroller with integrated Wi-Fi and Bluetooth
• →IR sensors for parcel presence detection
• →Hall-effect sensor for door-state monitoring
• →Servo-actuated locking mechanism for automated securing
• →4×4 keypad for authenticated access control
• →2.8-inch SPI TFT display for OTP and system feedback
• →WS2812 RGB LED matrix for visual state indication
• →SW-520D vibration sensor for tamper detection
• →Active speaker for audible alerts and interaction feedback

ESP32 and electronics wiring

Separate wiring compartment

The embedded firmware was developed around an event-driven control architecture running on the ESP32-WROOM-32D using Embedded C and the Arduino framework. The system coordinates delivery authentication, parcel detection, lock actuation, tamper monitoring, OTP management, and cloud communication through parallel state handling and interrupt-driven execution.

• →Finite-state workflow controlling authentication, parcel deposition, secure locking, and recipient access
• →Parallel interrupt routine for vibration-based tamper detection and real-time theft alert generation
• →Dynamic OTP generation and secure access verification for recipient-side authentication
• →Hall sensor and IR sensor fusion for door-state and parcel-presence monitoring
• →Automatic timeout, failed-attempt lockout, and intrusion alert handling logic
• →Real-time Blynk cloud synchronisation for mobile notifications and remote system monitoring

Safe Drop implements a multi-stage authentication and security pipeline to ensure controlled access and secure unattended parcel delivery. The workflow autonomously validates access, monitors delivery status, and responds instantly to abnormal events.

• →Unique password generated and transmitted to recipient through Blynk
• →Delivery access granted only after correct password verification
• →Automatic door locking after parcel insertion and closure confirmation
• →Lockout timer triggered after repeated incorrect password attempts
• →Tampering events generate immediate cloud alerts and audible alarms
• →Real-time parcel placement and removal monitoring

Unique password generation and transmission

Correct password verification

Lockout timer

Parcel placement validation

Tamper detection

Parcel removal detection

Experimental testing evaluated system responsiveness, cloud communication latency, locking reliability, and structural capability under operational conditions. The platform demonstrated stable IoT communication and reliable autonomous parcel handling behaviour.

• →Average complete delivery process time: ~26 seconds
• →Sub-second notification latency under normal network conditions
• →Average Wi-Fi connection delay between 6–8 seconds
• →Automatic lock engagement validated after parcel confirmation
• →Load-bearing capability optimised through controlled infill selection
• →50% infill configuration supported approximately 32 kg load capacity

Parcel placement detection

Parcel placement and autolocking validation

The primary engineering challenge involved integrating mechanical locking, embedded sensing, and cloud-based communication into a compact, serviceable enclosure while maintaining reliable autonomous operation under real-world delivery conditions.

• →Synchronising physical events with real-time cloud communication
• →Designing a reliable servo-based locking mechanism
• →Managing wiring density within constrained enclosure volume
• →Reducing false triggers in vibration-based tamper detection
• →Ensuring modular assembly for maintenance and upgrades
• →Balancing structural strength with print time and material usage

The Safe Drop system successfully demonstrated autonomous parcel authentication, secure locking, real-time monitoring, and tamper detection within a fully self-contained IoT-enabled platform. The project was awarded 2nd place at the departmental project expo and subsequently filed for intellectual property protection.

• →Awarded 2nd place at Department Project Expo
• →Patent published in India — Application No. 202511076582
• →Patent granted in Germany — Patent No. 202025104999
• →Successfully validated end-to-end autonomous delivery workflow