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How to Build a Photocell

A photocell is a sensor that reacts to light exposure. Photoresistor cells have varying electrical resistance depending on the amount of light they are exposed to. Photovoltaic cells produce voltage when exposed to light, and large arrays, such as solar panels, can produce significant amounts of renewable electricity. A simple, low-output photovoltaic cell can be easily constructed using common materials.

Things You'll Need

0.006-inch sheet of copper
Propane torch
Salt
Water
Copper wire
Wood block
Tape
Voltmeter

Instructions

- 1
  Use a propane torch to heat one end of a thin sheet of copper until it is red hot; do not heat the entire sheet. Keep the copper at that temperature for one minute, then allow it to air cool.
- 2
  Mix a concentrated salt solution by adding 30 to 35 grams of salt for every 100 milliliters of water. Heat or shake the mixture to speed up the dissolving process. Put a few drops of the concentrated salt solution of the scorched part of the copper sheet.
- 3
  Place one end of a copper wire into the salt solution on the copper sheet and allow it to rest there freely. Secure the other end of the wire to a block of wood with some tape for stability, making sure to leave the end of the wire exposed.
- 4
  Shine a flashlight or other source of light on the scorched copper and salt solution to generate small amounts of electricity, in the range of millivolts.
- 5
  Connect the end of the copper wire to the negative terminal of a voltmeter. Attach another copper wire to the unburned end of the copper sheet, and connect the opposite end of that wire to the positive terminal of the voltmeter to measure the electricity produced by light exposure.

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