Van De Graaff Generator

A few years ago a fellow colleague introduced me to a leyden jar. A leyden jar is simply a jar that acts a capacitor. You use some object to generate static electricity and store it in the jar. After a few minutes of generation you can get the jar to produce a spark across a one inch gap. The process of ‘charging’ the jar took way too long. This made me begin to look at quicker ways of building up static electricity…

A Van De Graaff generator is a machine that produces static electricity. You have probably seen them at COSI. It normally has a large steel ball on top. On extremely large ones the static can be enough to cause ones hair to lift. The process for static generation is simple enough. A Van De Draaff generator contains a flat belt running on a pair of rollers similar to a conveyor belt. The belt must be made of a non-conductive material. A metal “comb” is placed adjacent to each roller, with “teeth” pointing toward the belt surface. One of the rollers is spun causing the belt to spin. To create a static charge, the machine pulls one type of charge ( either pos. or neg. ) out of one comb and places it onto the belt’s surface. As the belt spins, it transports the charge to the other roller. The charge is then pushed off the belt’s surface and onto the top comb. The comb is connected to the metal sphere on top. This causes a charge to slowly build up in the metal sphere. The type of charge depends on the material used for the rollers.

My generator was constructed from a 4″ diameter PVC tube. At the top and bottom of the tube metal rollers were used to hold the belt in place. The belt was constructed from an ace bandaged. I cut it to the proper length and sewed the ends together to form a belt. The metal dome was made from two old metal camping bowls glued together. I made the combs by simply striping a wire and spreading out the individual strands of copper. The motor to drive the unit was taken out of an old fan.