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Lightning pendulums are a dramatic display of the force of high voltage electricity. It is also a reminder of how powerful a NST (neon sign transformer) is. This apparatus is a moving high voltage device, and so should only be constructed and demonstrated by those with adequate knowledge of high voltage.

This lightning pendulum is powered by a 15kV/120mA NST. This is a potentially lethal transformer! The ball of the pendulum is a hollow doorknob. It is suspended by a length of 22 gauge magnet wire. The stand employed is an old halogen light stand, with a wooden arm attached on top. The soda cans are ¾ full of sand to prevent them from tipping over. DO NOT USE WATER! This would be an extreme safety hazard if the can got knocked over.

One side of the NST goes to BOTH of the soda cans. The other side goes to the wire suspending the ball. 30kV wire is used for these connections, and even so I don't count on it. Therefore I consider the stand to be "hot" during operation, even though it isn't. As you can see in the picture I am using a glass surface. Wood should not be considered unless it has been well dried and coated. Plastic is fine. Set the cans up so that they are inline with ball, about 16-18" apart. Distance here will of course vary with factors such as power supply and weight of ball.

In order to start the pendulum, one needs a "chicken stick". This is an insulated pole or stick of some variety. Again, wood should not be considered adequate, and in this case I wouldn't even use dried and coated wood. PVC pipe is fine, or acrylic plastic. I have a really nice chicken stick, rated to 25kV, given to me by a kind friend.

Using the chicken stick, set the pendulum in motion. It will take you a while at first to adjust the cans and so on, but once you get it going, it will keep going forever. As you can see, the arc created performs like a JACOB'S LADDER does. It is initiated quite close to the can, as in the first picture. As the pendulum is pushed away, the arc grows, and climbs up both the can and the ball. Finally it reaches the lid of the can and the neck of the doorknob.

Not only does it look really cool, but it makes a very soothing mad science noise. If it wasn't so dangerous, I'd run one as I was falling asleep! Some day I do plan to build a model safe to leave running at a science fair, enclosed in plexi-glass probably.