1+ 2+ 3 Penny-Powered LED By Matthew Ruschmann

Power an LED with some salty water and $1.21.

You will need:

Ice tray, salt, water, pennies ( 11), dimes ( 11), paper clips ( 11), and an LED

To turn pennies into batteries, another electrode and an electrolyte are needed. In this case, dimes (zinc) are used as the positive electrodes and salt water is used as an electrolyte. Such a battery produces a differential of about 0.5V — not enough to light an LED. You need a series of cells, which you can make using an ice cube tray and metal paper clips to hang the pennies and dimes into the electrolyte banks. Because paper clips are conductive, the cells are automatically connected in series to form a more powerful battery, providing a differential of about 2V.

1. Make the solution. Make a saltwater solution and fill the cells of the ice tray about ¾ full.

NOTE: Newer pennies don’t work as well as ones dated pre-2001. We don’t know why this is, and we aren’t going to make any politically charged guesses.

2. Set up the tray.

Illustrations by Dave McMahon

Bend each paper clip to hold one penny and one dime, as shown in the diagram. Note that the first pair of cells also has a penny-dime combo clipped to the mid-cell divider, while the last pair of cells doesn’t have this. For best results, use a multimeter to confirm a 0.5V reading on each cell first.

3. Light the LED.

To light up the LED, put the short end of the LED into the penny bath and the long end into the dime bath. The penny batteries provide about 110 micro-amps of current in series.