How Do I Build a Lightning Strike Detector?

Written by shellie braeuner Google
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How Do I Build a Lightning Strike Detector?
A lightning strike detector can be made at home with a few typical materials. (Lightning image by Justin Pirtle from

Lightning is formed from a static charge that is created in the atmosphere. Benjamin Franklin not only made the use of a lightning rod popular, but he also invented the Franklin bells. Using the static charge that is attracted to a lightning rod, Franklin was able to make the bells ring and detect the approach of lightning. If there is no lightning rod available, try attaching the appropriate lead to a piece of foil and place the foil against the screen of a TV or computer monitor. Both devices also create a strong static charge.

Skill level:

Things you need

  • 2 small brass bells, with or without clappers
  • 2 blocks of wood at least 2 inches taller than the bell's
  • drill
  • 3/8-inch drill bit
  • 3/8-inch diameter wooden dowel 12 inches long
  • wood glue
  • 10 inches of string
  • 1 small washer
  • 6 inches of thread
  • 2 wires with alligator clips on both ends

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  1. 1

    Measure the bells against the wooden blocks. Drill a 3/8-inch hole through both blocks of wood near the top.

  2. 2

    Apply wood glue to both ends of the dowel and push the ends into the holes in the blocks of wood. Let the glue dry.

  3. 3

    Cut the string in half and tie both bells to the dowel. Make sure that neither bell touches anything but hangs freely.

  4. 4

    Tie the small washer to the thread. Measure the thread against the bells and make sure that the washer, when swinging, will hit the bell. Tie off the other end of the thread to the centre of the dowel.

  5. 5

    Clip one end of a wire to a ground source, such as a pipe or heavy metal object. The other end of the wire is clipped to one of the bells.

  6. 6

    Clip the second wire to the other bell on one side and a lightning rod on the other. If the building has a lightning rod, a wire can be run to make access easier. If there is no lightning rod around, and you still want to test the device, clip the wire to a piece of foil and attach the foil to a TV or computer screen.

Tips and warnings

  • The lighter the washer, the better the lightning detector will work. Or, a soda pop top can be substituted for the washer. The device works as the static charge on one bell attracts the washer or pop top and pulls it toward the bell. When the two metal pieces touch, the charge is dissipated, and the washer falls, striking the other bell.
  • Do not stand out in a field and wait for lightning to hit the detector. Be safe and don't touch any of the components while they are attached to a lightning rod.

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