Hall Effect Sensor and gain circuit or toroid loop

Hall effect sensor with op-amp gain circuit( 70 - 100X) to facilitate DC and DCC current detection.

Hall effect sensor better for DCC/DC

Toroid is fine for DCC, but may not work reliably for DC

Schematic

Arduino

Because we have a DCC/DC mixed environment, we need a micro-controller to monitor track voltage and when voltage drops below a set threshold, occupancy status will be latched. The controller will latch the "busy" signal for a set amount of time, or when voltage is above a threshold value to return to normal operation.