Using Light Emitting Diode Arrays as Touch-Sensitive Input and Output Devices (Scott Hudson)

buildlab.org Light Emitting Diodes (LEDs) offer long life, low cost, efficiency, brightness, and a full range of colors. Because of these properties, they are widely used for simple displays in electronic devices. A previously characterized, but little known property of LEDs allows them to be used as photo sensors. We show how this capability can be used to turn unmodified, off the shelf, LED arrays into touch sensitive input devices, (while still remaining capable of producing output). The technique is simple and requires little or no extra hardware - in some cases operating with the same micro-controller based circuitry normally used to produce output, requiring only software changes. doi.acm.org