I have a door sensor (magnetic Hall Effect) that I want to use to build a simple indicator: red LED if closed, green LED if open.
Here's the tricky part: I want to run only two wires to those LEDs, and I'd like to do it completely in analog circuitry. Here's the approximate outline:
I've tried putting something simple together with BJTs (an inverter, a bistable multivibrator etc.), and I feel like this is the right track -- that there's just one small tweak I need to make -- but I'm stumped as to how to get the voltage to flow. I've done extensive Googling and reading up on tutorials and I've found nothing close to what I'm looking for.
How do I get voltage to flow one direction if the switch is closed and in the other direction if it's open?