Cold-Chain Logistics Tracker with Automated Blockchain Logging

Vaccines, dairy, seafood, and pharmaceuticals spoil when the cold chain breaks — a truck's refrigeration unit fails, a warehouse door stays open, and nobody notices until the goods are ruined. Existing loggers record temperature locally, but their records can be edited or lost, so there is no trustworthy proof of what happened in transit. This project builds a GPS-enabled IoT tracker that logs temperature and humidity through the journey and anchors the readings to a blockchain ledger, creating a tamper-evident record that the sender, transporter, and receiver can all verify.

The ESP32 collects temperature and humidity readings from the DHT22 sensor and geographic coordinates from the NEO-6M GPS module. Current temperature and operating status are shown locally on the OLED display.

The ESP32 sends collected information through Wi-Fi to a backend service. The backend processes the shipment record and can submit selected data or a cryptographic representation of the record to a blockchain smart contract. This creates a traceable history of cold-chain conditions that can later be checked for abnormal temperature events or missing records.

Design clarification: blockchain logging is implemented in this build, not optional. Every batch of sensor readings is hashed and the hash is written to the ledger via smart contract; the full readings live in the database for fast queries. Verification means re-hashing a database record and comparing it with the on-chain hash — a mismatch proves the record was altered.

1. Real-time temperature and humidity monitoring
2. GPS-based shipment location tracking
3. Automatic timestamped logistics data logging
4. Blockchain-based tamper-resistant record storage through backend integration
5. OLED display for live temperature and device status
6. ESP32-based IoT connectivity and data processing
7. Temperature threshold monitoring for cold-chain conditions
8. Historical shipment and sensor-data tracking

Source code, circuit diagram, component information, project report, abstract, presentation, firmware configuration, backend/blockchain architecture guidance and basic setup support.

1. This is an academic prototype and not a certified pharmaceutical or industrial cold-chain monitoring device.
2. DHT22 accuracy and response time are suitable for demonstration but may not meet regulated industrial cold-chain requirements.
3. GPS reception may be weak or unavailable indoors, inside metal containers or in obstructed environments.
4. Internet connectivity is required for real-time remote monitoring and blockchain logging.
5. Blockchain records depend on successful backend and network communication.
6. Battery operating time depends on GPS usage, Wi-Fi activity, transmission frequency and battery capacity.
7. Hardware components may vary depending on availability.
8. Blockchain network, cloud hosting, API, domain or third-party service charges are not included unless specifically agreed.
9. Additional dashboards, mobile applications, GSM/4G communication or advanced analytics require separate customisation.
10. Delivery time may change when additional hardware or software features are requested.