Internet-of-Things (“IoT”) controllers built using hardened industrial technologies which improve functionality and reliability, such as a fixed-loop model in which a loop is repeated with configured time periodicity where sensors are queried, sensor responses are read, configured calculations are performed, and logic rules are evaluated resulting in decisions made and outputs activated. A variety of redundancy techniques are utilized to provide continuous non-stop operation of IoT controllers to compensate for possible hardware and software failures. Robust IoT controller redundancy also allows periodic maintenance, software updates and security patch installation without shutting down the IoT controllers.