Download light meter instructions

Make Your Own Exoplanet Detector
Zach Berta-Thompson
January 14, 2016
Light emitting diodes (LED) convert energized electrons into photons. But, they can also be used in the opposite way, to convert photons into energized electrons, which you can read out as a small voltage on a multimeter. These instructions tell you how to make a small
light detector with an LED, which you could use to make the same
kind measurements we make to find and student planets orbiting
other stars.
Use an LED as a light meter
• Take a wire with alligator clips at both ends, and cut the wire in
the middle. Strip off about 1cm of insulator from each of the cut
ends, revealing the copper wire within.
• Take a LED (red and yellow work best). Tightly wrap the two
exposed copper wires around each of the LED’s legs. Be sure
wires don’t short circuit the two sides.
• To provide a sturdy base, push the LED legs into the end of a cork.
Drape the wires over the sides of the cork, and tape them in place.
• Connect the alligator clips to the two probes of a multimeter. Turn
on the multimeter and set it to measure small voltages ("200mV").
• You should see the voltage increase as you bring your light sensor
closer to a bright light.