I was recently reserching on LEDs and I stumbled upon this
page as I read it I found that LEDs are not just used to emit light but the also have the ability to sense light.At first using LED as light sensor sounds complicated but it quiet quickly becomes clear. This is a fun project in which we will be experimenting with LEDs requires minimal parts.
This instructable will explain you how to use a LED as sensor,creating it on a breadboard,making a shield for arduino, how to get a reading from our LED sensor and how to change the sensitivity of our sensor.
This is my first instructable, any suggestions,corrections or comments are welcome.This instructable is a entry in the arduino contest so if you like it please vote.
A short video of the sensor in sensitive to dark mode: