Light-dependent LED reverse-bias voltage discharge times (my 453 design project)
Originally uploaded by CCmcGeek.

Measuring the light-sensitive fall time of the voltage across a reverse-biased LED. The LED essentially acts like a variable capacitor, so the RC constant of the exponential decay depends on the intensity of light hitting it. We observed significant variations in fall time with one LED being exposed to ambient light vs being covered with a hand. Unfortunately, we aren’t getting any kind of useful results when we include more than one LED in the circuit… stay tuned for more details.