The TWIN-NODE Indoor Node is a battery-powered receiver module designed to provide local indication and alerts for a wireless water level monitoring system. It communicates with an outdoor sensor node using ESP-NOW, enabling reliable, low-latency data transfer without internet connectivity or Wi-Fi infrastructure. The design prioritizes simplicity, robustness, and real-world indoor deployment.

From a hardware perspective, the PCB is centered around the ESP-12F (ESP8266) module and integrates LED indicators and a buzzer for immediate user feedback. All components are selected for low standby current and stable operation on battery power. The schematic and PCB layout are developed in KiCad, following standard design rules to ensure manufacturability and electrical reliability.

Power efficiency is a core design objective. The indoor node leverages deep sleep operation and event-driven wake-up on wireless data reception to minimize average current consumption. This approach enables long battery life while maintaining instant response to water level updates, making the PCB suitable for continuous indoor operation without frequent maintenance or external power sources.