When operating in remote mode under Home Assistant control rather than autonomous mode, the system provides operators with control options that balance automation convenience with manual oversight. The manual intermittent sprinkler system for P1 exemplifies this balance.
Master lock control: A LOCK control system set in the ARMAC Home Assistant dashboard provides a master safety mechanism to avoid inadvertently triggering valves, and particularly the pump, for example through a 'pocket dial'. When LOCK is active, outputs P0 (pump), P1 (sprinkler), P3 (high flow), and P4 (gel) are forced off, regardless of any other command source or autonomous algorithm decision. Only P2 (shed cooling) remains operational during LOCK, recognizing that equipment protection via the gravity-fed cooling system should continue even when fire defence is administratively disabled.
The LOCK signal propagates through the entire system architecture. AR1 includes LOCK state in every command frame it sends (CMD:...LOCK:0/1...) and in every status frame (STAT:...LOCK:0/1...). AR3 extracts LOCK state from these frames and stores it in a local variable. Before executing any pump command, AR3 checks LOCK status and forces the pump request to off if LOCK is active. Before setting peripheral outputs P1, P3, or P4, AR3 checks LOCK and forces them off if LOCK is active.
A particular safety scenario arises when LOCK engages while the pump happens to be running. This might occur if an operator activates LOCK during autonomous fire defence, or if communication recovers and Home Assistant reports LOCK was engaged during the outage. To handle this case, AR3 implements active LOCK enforcement: if LOCK is active AND the pump is currently on, AR3 sends a pump-off command every 500 milliseconds until the pump state changes to off. This "kicking" behavior ensures that LOCK enforcement cannot be circumvented by timing issues where the LOCK signal arrives between command evaluations, and ensures that the pump turns off within half a second of LOCK activation.
The LOCK system is a defence-in-depth safety approach—both AR1 and AR3 enforce LOCK, so even if RS-485 communication partially fails such that AR3 doesn't receive updated LOCK status, AR1 will refuse to send pump-on commands, and even if AR1's enforcement fails, AR3 will refuse to execute them.
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