One of my fave devices at Maker Faire Bay Area was (the future Mrs. Gareth Branwyn) Jeri Ellsworth’s “Brain Bulb,” a light bulb poised over her head which could read and respond to her “brain waves.” Here she describes the basic hardware and circuit design behind the device. The circuit is built around a low-power Analog Devices AD620 instrumentation amp.

Jeri (and some guy whose name I don’t recall) and her Brain Bulb at Maker Faire