This is a collection of the work I’ve done with using the bi-directional properties of LEDs. I have also included links to information I’ve found on the subject and the project by an NYU researcher that inspired me.

My writings in chronological order (more or less):
Forum Discussion: How is it done?
Forum Discussion: LED Sensor Array * Updated
Blog Entry: Bi-Directional LEDs
Blog Entry: Bi-Directional LEDs II
Blog Entry: LED Sensors
Blog Entry: LED Sensors II
Blog Entry: Stuck in the mud
Blog Entry: LED Sensors III
Blog Entry: Pictures of Sensors III
Blog Entry: More than a few days…
Blog Entry: Matrices as Sensors * New
Blog Entry: LEDs As Sensors: Revisted * New
Blog Entry: Touch Sensing Building Blocks I * New

Inspiration and reference:
Multi-Touch Sensing through LED Matrix Displays
LED array turned into touch button
Very Low-Cost Sensing and Communication Using Bidirectional LEDs
LED doubles as emitter and detector