I've been playing around a bit with light sensors and found some threads on using LEDs as light sensors.<br><br>Yes, not only can LEDs be used to **make** light, they can also be used to **detect** light by reverse biasing the LED<br>
<br>ie. by the wonders of ASCII art...<br><br> Ground ---|>|------- ADC pin<br><br>Testing with an arbitrary LED from my junk box this gave a voltage of very close to zero when dark and almost 1V when pointed towards a bright light.<br>
<br>That's quite a useful property given how easy it is to get LEDs relative to phototransistors etc.<br><br>Regards<br><br>Charles<br>