Uploaded November 2011 | Updated September 2026, 4 hours ago
Everybody knows that LEDs can emit light. Somewhat fewer understand the LEDs can detect light. I set up a simple circuit which had a resistor in series with an LED which I reversed diode. Diodes act like capacitors when reverse biased. so we charge the led, and then measure the time it takes to return to a low state on the Arduino. But what is the mechanism? My original thought was that the ability to hold charge (its capacitance) changes, but now I believe that it is actually a photoelectric current which opposes the charge in the capacitor which returns it to the low state. Anybody know definititively? Have I got this all wrong?
Everybody knows that LEDs can emit light. Somewhat fewer understand the LEDs can detect light. I set up a simple circuit which had a resistor in series with an LED which I reversed diode. Diodes act like capacitors when reverse biased. so we charge the led, and then measure the time it takes to return to a low state on the Arduino. But what is the mechanism? My original thought was that the ability to hold charge (its capacitance) changes, but now I believe that it is actually a photoelectric current which opposes the charge in the capacitor which returns it to the low state. Anybody know definititively? Have I got this all wrong?
