Purpose: This study aims to design and develop a house door safety device using an RFID (Radio Frequency Identification) sensor integrated with an ATmega 328 microcontroller. The device is intended to offer an easy-to-use, affordable, and practical solution to enhance comfort and security in opening house doors without the inconvenience of carrying multiple physical keys. Methodology/approach: The development process involved integrating an RFID sensor module with an ATmega 328 microcontroller as the main control unit. When a registered RFID tag card is detected, the microcontroller processes the signal and triggers a solenoid mechanism to unlock the door. The device is powered by a primary electrical source and supported by a rechargeable battery backup to ensure continuous operation. Testing procedures were conducted to verify the device’s performance against the design specifications. Results/findings: Experimental testing showed that the device successfully detected authorized RFID tags and reliably unlocked the door using the solenoid mechanism. The backup battery system maintained functionality even during power outages, ensuring uninterrupted security. Conclutions: The proposed RFID-based house door safety device with an ATmega 328 microcontroller provides a practical, low-cost, and effective solution for residential door security. It offers improved user convenience compared to traditional key-based systems. Limitations: The system currently operates only with pre-registered RFID tags and has limited range and scalability. Further development is needed for remote access, enhanced encryption, and integration with smart home systems. Contribution: This research contributes to the field of low-cost smart home security solutions by demonstrating an effective prototype of an RFID-based door safety device, which can serve as a foundation for future advancements in intelligent access control systems.

Purpose: This study aims to develop and implement a real-time sea water level monitoring system to anticipate high wave hazards, particularly in coastal areas such as Ketapang Pier, Pesawaran Regency, Lampung Province. Research methodology: The system utilizes an IoT-based approach involving an SRF04 ultrasonic sensor for water surface measurement, an Arduino Pro Mini for data processing, a NodeMCU ESP8266 for server connectivity, a DS3231 RTC for time accuracy, and a microSD card module for offline data storage. The system is powered using a 12V adapter regulated through an LM2596 module. Results: Field testing demonstrated that the system accurately records water level distances with an average relative difference of 0.205% between Blynk App and SD Card outputs. The system classifies water levels into two status categories: normal and hazard. Conclusions: The implemented monitoring instrument functions reliably in real-time conditions and offers accurate water level readings, making it suitable for coastal hazard early warning systems. Limitations: The system is dependent on continuous power and stable internet connectivity; thus, functionality may be affected in remote or offline environments. Contribution: This research provides an affordable and accurate IoT-based water level monitoring solution that can be replicated in other coastal areas for disaster risk reduction and environmental monitoring.