 BS2SX Controlled Van De Graff Generator
Information and Data was submitted to Parallax by Cris Wagner
of the Boston Museum of Science
The Boston Museum of Science is home to the world's largest open air Van De Graff generator, standing over 25' tall and able to generate a potential of over 2.5 million volts. A year and a half ago, it was decided that the control system needed to be replaced with a more reliable and accurate system. The old system was built on relay logic and motor-variac controllers. To complicate matters, since the machine is so large, a secondary power supply in the high voltage terminal is required to pull the charge off the belts and change the polarity of the system. The original secondary system was controlled with many strands of fishing line linking solenoids and switches, and a long glass rod linking a motor and a variac. This isolation is required since at times there may be more than 2.5 million volts on the terminal.
This entire system has been replaced with a master/slave control system based on the BS2SX OEM module. The master and slave modules are linked via a fiber optic link running through the 25' columns. The current revision of the software interfaces with the old pushbutton interface in the Faraday cage where the operator stands during performances. A new revision of the software is currently being implemented that accepts MIDI control codes from the new touch screen based user interface. Additionally, hardware that measures the high voltage on the belts, belt current, as well as terminal voltage from a generating voltmeter is being built at this time, also based on the BS2SX module. This system will send data to a workstation that will create a visual display that is projected behind the machine for the audience.
I am very pleased with how well the BS2SX has performed in the system, especially since it is exposed to very strong EMF and EMP when the machine is on. I attempted to minimize this interference with heavy shielding and robust filtering on all of the controller interface connectors.
Link for the Master Source code.
Link to the Official Museum of Science web page for the Van De Graff Generator:
http://www.mos.org/sln/toe/toe.html
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