As critical part of the launch safety, an area warning system (AWS) notifies personnel of operations or emergencies that occur at the launch pad, payload processing facility, and main hanger. When I joined as an intern, the AWS was clunky and ran off 120 VAC ladder relay logic. The desire was to replace the system with something that could be easily maintainable and interface it to the launch/landing command and control interface. Given a small budget and a month to get a prototype system together, I took it as an opportunity to flex some of my electrical design skills and go from the ground up and create a system based on the NEMA industrial control safety standard. This included an opto-isolated interface between the logic and the external control relays. The system interfaced to command and control via an Ethernet connection that was pushed over fiber. For reliability, two identical systems were installed in separate buildings, the payload processing facility and the main hanger and connected to each other via a CAN bus, for its low overhead and reliability.
Above is the mother board containing all the logic and optical isolation between the industrial interface board, below. The I/O were controlled with solid state relays and the could be configured for either 5V or 24V logic levels. Each input was equipped with input protection capable of preventing damage to the board due to over-voltage. Each I/O also contained a PTC fuse in case of over-current events.
The system achieved success and went into another round of development after I left my internship.