UDP broadcast, operating within Module 4 between AR2 and AR3, provides high-frequency sensor data delivery at 10 hertz. Arduino AR2 operates as a WiFi access point with SSID "Arduino2_AP", creating a dedicated wireless network for this critical sensor link. AR3 connects as a client and receives broadcast packets containing pipe-delimited key-value pairs of all sensor readings. A typical UDP packet might contain: EXT_TEMP:35.20|INT_TEMP:30.15|WATER_LEVEL:2.85|FLOW_OUT:165.30|BAT:13.20|OIL_OK:1|WATER_PV:0.15. The choice of UDP rather than TCP reflects the real-time nature of sensor data—if a packet is lost, the next reading will arrive in 100 milliseconds, making retransmission unnecessary and avoiding the latency that TCP's guaranteed delivery would introduce. The broadcast nature of UDP also means that multiple devices could listen to the sensor stream if future expansion requires it.
SMS communication to Module 5 provides the ultimate backup control path, operating entirely independently of the local network infrastructure. If both the NBN and local network fail, operators can still command the pump via the mobile network, ensuring that manual control remains possible under the most adverse conditions. This path is intentionally kept simple—a text message with a specific format sent to the pump controller's phone number can force pump activation or deactivation, bypassing all other control logic.
Autonomous control As described later, if all external communication is lost the system continues to operate using inputs from AR2 and control decisions from AR3 in Module 3 transmitted by cable to the Relay Module (AR2).
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