The Ono Sendai Project

This was a very ambitious project. On April 20, 1993, Ono Sendai, a design contracting outfit in San Francisco, California, approached me about a small integrated circuit to go into the proposed Sega virtual reality helmet. A small problem -- they needed a million parts, and the helmets had to be in the stores by Christmas of 1993.

Oh, my.

The schedule was insane, the chip difficult, the physics murky, and the company disorganized. Then they said the magic words "money is no object". I had a break in the schedule with I-Cube, so I said the fateful words "sure".

The component was simple but fiendish; the driver/sensor/filter/interface for a 3 axis fluxgate magnetometer, which would be used to sense the direction of the Earth's magnetic field and provide head orientation information for the VR helmet. Fluxgate magnetometers work by saturating a ferrite toroid with a high current, then looking for the voltage blip caused by the change in the magnetic flux from the Earth through the core. A one gauss change through a tiny winding produces a millivolt blip; we had to digitize three of those blips to about 16 bits precision and 10 bits of accuracy.

Email: keithl(aT)kl-ic(doT)com


last revision Jan 11, 2013