Robust Home-Control System Design for Tamper-Resistant Door Sensor Connections

The discussion focuses on designing a robust home-control system for door sensor connections that can resist tampering such as short-circuits, open-circuits, and exposure to mains electricity surges. Key recommendations include protecting signal lines with transient voltage suppression (TVS) diodes and series resistors, and employing opto-isolators at sensitive circuit ends to prevent damage. A communication protocol involving periodic pulse exchanges between sensor and control units is advised to detect faults or tampering. Using an AC signal source, such as a square wave generated by drivers like the 422 or 485, can prevent electrolysis on switch contacts and enable a "window" detection system that distinguishes open-circuit, short-circuit, and valid signal states by monitoring voltage levels. Wired connections are preferred over wireless for reliability and security, although wireless industrial sensors with long-range capabilities were suggested but rejected by the original poster. The design aims for simplicity while ensuring resilience against environmental and malicious interference.
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