I ran across a design for a mechanical chopper that looks like an excellent choice for a starting or backup controller.
It's so simple a caveman can do it!
Fundamentally you mount an insulator and conductor rod together in a V shaped wedge configuration. Then you mount motor brushes on a sliding assembly opposite one another touching the combined rod. Finally you spin the rod with a motor. As the brush assembly slides from the insulated side towards the conductor side, the brushes spend more time touching the conductor thereby providing more power to the motor.
No mosfets, no electronics, no drivers. Completely mechanical.
I think I have my first project to work on.
I'm also already thinking that if the sliding brush assembly is controlled by a microcontroller, then the possibility of having current control becomes possible to do because the pedal and the brushes are no longer directly coupled.
Take a look. Give a comment. If this actually works then a truly inexpensive, easy to build, high powered, high voltage alternative may be available.
Battery Vehicle Society :: View topic - Mechanical Speed Controller
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