My Favorite Halloween
One year while I was in high school in
In the front yard, off to one side and on top of a ladder so that kids and adults couldn’t touch it, was a Jacob’s Ladder (http://en.wikipedia.org/wiki/Spark_gap) constructed from a heavy large neon sign transformer and two brass brazing rods. The transformer was about a foot wide and had large insulators on each side with terminals. The rods were attached to the terminals, and then bent to come over the top of the transformer towards each other until they were a few inches apart. From there, the rods diverged as they extended upward about two feet. When the transformer was plugged in, a large electrical arc would form where the rods were close together, then it would move up the rods to their tops and disappear, to be immediately followed by another arc forming at the bottom, and so on. This particular transformer produced about 50,000 volts with enough amperage to produce a heavy arc. We knew the setup was dangerous and on a separate occasion dared a not-too-bright friend of ours to blow it out with his breath. He didn’t touch the arc but still was knocked across the room.
For the front door, I constructed a “robot” similar to Gort in The Day the Earth Stood Still (http://www.imdb.com/title/tt0043456/), except squared off, out of cardboard and painted it silver. It had two “eyes” and a “mouth” and filled the door frame. The eyes were flashing lights, with perhaps more flashing lights elsewhere on the robot. The flashing lights were timed with an electro-mechanical timer which I “borrowed” from a Navy jet on display in a local park. The mouth was an audio speaker “accidently” removed from a local drive-in movie place. (We were poor and got parts wherever we could find them.) The speaker was connected to an AM radio and I used an AM transmitter to talk through the speaker, as I didn’t have an amplifier but did have a small neighborhood AM radio station at that time. One of the arms had a “hand” through which I could dispense candy from behind the robot.
I suspected that the kids coming to trick-or-treat might get too rambunctious and harm my creation, so that I also rigged a defense mechanism. The front door had an outside screen door with a wooden frame. (The screen material was metallic.) I attached the output of an automobile spark coil (about 10,000 volts, low current) to the screen, and had a way to power it on if needed. Sure enough, at one point during the night, a large group of kids descended on the front door all at once, grabbing for the candy which I was dispensing piece by piece, and threatening to tear off the robot’s hand. I activated the spark coil and instantly the front porch was cleared and the kids were scattered around the yard.
A good time was had by all.
Snips and snails, and puppy-dogs' tails
As mentioned above, we were poor and if we wanted to build electrical devices, then we had to be creative with what was available. One time I used an inverted ice-cube tray as a chassis for a power supply.
I once built a small but serviceable Tesla Coil (http://en.wikipedia.org/wiki/Tesla_coil) using plans from Electronic Experimenter's Handbook 1961 edition and using parts from around the house and garage. The high-voltage secondary coil was wound around the cardboard tube from a roll of paper towels and was topped with a sharpened nail. The primary coil was wound around part of a plastic shampoo bottle. The primary coil was powered by a car spark coil driven by a doorbell transformer through a car electrical vibrator (a device used in old cars to produce the high voltage needed by the radio) ( http://en.wikipedia.org/wiki/Vibrator_(electronic)). The output of the spark coil went through a spark gap composed of two sharpened nails. The capacitor (made of glass plates in the plans) was a plastic waste basket, lined inside and out with aluminum foil. Except for the capacitor, the whole assembly was mounted on a wooden board.
This jury-rigged assemblage worked amazingly well. The tip of the output coil threw out easily visible electrical discharges and it could be used to demonstrate other phenomena like producing a glow in light bulbs held nearby. It also produced radio static which covered the neighborhood.
