The Mendocino motor is a solar-powered magnetically levitated electric motor. With a very low power output, they are generally used as technical demonstrations only, but are a popular construction project with electronic enthusiasts.
The motor consists of a rotor shaft with an array of (typically four to eight) solar panels and electromagnetic coils arranged in a barrel shape around the centre of the shaft; this rotor is horizontally mounted in a frictionless radial bearings over a central magnet on the base plate of the motor. The final 6th degree of freedom, the axial or thrust direction, is not levitated, but rather supported by a needle point of contact (low friction).
There are generally two types of Mendocino motors; one type has its coils hidden underneath the solar panels, another type has larger windings placed around the solar panels. Each coil is driven by a panel on the opposite side of the shaft so that, as the bottom coils are powered by the opposite solar panel, they will be repulsed by the central magnet. This will cause the array to rotate and bring the next coil into position over the magnet and the next panel into position towards the light source — thus maintaining the rotation.
The idea of a light-commutated motor, where solar cells power the individual coils of a motor, was first described by Daryl Chapin in an experiment kit from 1962 about solar energy. The kit was distributed by Bell Labs, where Chapin together with his colleagues Calvin Fuller and Gerald Pearson had invented the modern solar cell eight years earlier, in 1954. Chapin's version of the motor uses a vertical glass cylinder on a needle point as a low-friction bearing.
A magnetic suspension of the rotor was added in 1994 by eccentric inventor Larry Spring to create "Larry Spring's Magnetic Levitation Mendocino Brushless Solar Motor" - more commonly simply "Mendocino Motor" with a horizontal rotor. The name comes from the location of his workshop on the Mendocino coast of California.
- Daryl M. Chapin (1962). "Uses and Demonstrations". Bell System Science Experiment No. 2: Energy from the Sun. Bell Telephone Laboratories, Incorporated. p. 77.
- "Bell System Memorial: Bell Labs Science Kits (Energy From The Sun)". Retrieved 2009-11-24.
- Berger, Kévin. "Solar Electric Motor on Superconducting Bearings: Design and Tests in Liquid Nitrogen". IEEE Transactions on Applied Superconductivity, Institute of Electrical and Electronics Engineers. Retrieved 29 May 2019.