I recently stumbled upon this site which mentions, "In 1977, Forrest M. Mims reminds us in one of his "Engineer's Notebooks" that LEDs can also be used as photodiodes... " The page features a LED matrix being used as a multi-touch input but offers very little information. I still have no idea how to make his project, but I did learn how to use LEDs as light sensors.
This instructable goes over my experimenting with different kinds of LEDs as light sensors and making a dark activated night light using LEDs as sensors.
Step 1: What You Will Need
- random assortment of LEDs
- current limiting resistors for LEDs
- bright flashlight
- microcontroller (I used Arduino)
Step 2: How Does it Work?
LED as light sensor:
"A LED is simply a diode that has been doped specifically for efficient light emission and has been packaged in a transparent case. Therefore, if inserted into a circuit in the same way as a photodiode, which is essentially the same thing, the LED will perform the same function."
"A photodiode is a type of photodetector capable of converting light into either current or voltage, depending upon the mode of operation."