More volts!
Thursday, September 25th, 2008
The highest voltage most people are likely to encounter is the 117 volts AC from the wall socket. While it can knock you across the room, or even kill you, it’s not much fun to play with. It won’t even jump across an air gap. To make decent sparks, you need voltages in the thousands of volts. (The dielectric strength of air is about 30kV/cm) You can generate surprising voltages just by shuffling your feet across a carpet- the shocks that you get from your fingers in the winter are a result of your body being raised to a potential of a few thousand volts! You’re not likely to impress anyone much by doing that, however. You need to build something cool. The easiest high voltage project is probably the Jacob’s Ladder. It works on a simple principle- the high voltage strips electrons off the gasses in the air, ionizing it, which makes it more conductive. The heat of the arc pushes the ionized air up the widening gap, and so the arc is able to follow. A neon sign transformer is the best way to make a Jacob’s ladder-you want one of the old ones, which are actual transformers, not the newer solid state ones. They can be tricky to find, unless you want to spring for a new one from a sign supplier. Another possibility is a oil ignition transformer-as more houses convert to gas heating, these show up now and again. Another, more challenging project is a Tesla coil. This is essentially a tuned air-gap transformer that can produce some truly stunning voltages. Care must be taken with the design to ensure good results- the tuning can be somewhat tricky. You’ll also need high-voltage capacitors, which can be as simple as aluminum foil glued to sheets of glass! Very large Tesla coils have been made; you might want to check with your neighbours before firing up something like this. When I was in high school, we had one that was about 6 feet high, turning it on was always a special event.
A simpler, but also impressive project is a Marx Generator.This uses a series of capacitors to step up a high voltage to an insanely high voltage. Here’s a plan to build a small one. Here’s a slightly bigger one. And here’s a really big one.
As fun as all this is, remember that all of these projects are quite capable of killing you, and should not be undertaken lightly. You are responsible for your own actions.
High voltage does not always have the good manners to stay in a wire- even if you’re not grounded, the voltage may decide to take a path through you just to see where it goes. Don’t work alone. Be careful to always work with one hand behind your back (to minimize the chance of the current going through your heart), use “dead man” switches, make sure capacitors are completely discharged before touching them, and watch out for ozone, especially if you are asthmatic.
