I'm trying to come up with a small, cheap, simple circuit that will detect a human. I plan to use a grid of luxeon rebel OLEDs and whatever detector I come up with embedded in my ceiling to light up only when you are under them. I've looked into passive infrared, but it's fairly expensive for the components I could find.
Any leads for circuits, ideas, or parts? I'd use parts from cheap security lights, but they tend to be around $10 each and I would probably need around12-18 ... kinda painful on the pocketbook.
Thanks in advance for any help!