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Jan 29, 2014, 10:44 PM
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How RC car steering works



The RC car goes to heroic lengths to achieve just bang bang steering.


It doesn't completely stall the motor, despite the motor sucking very high current when at the limit. It uses an ingenious centrifugal clutch.



The 2 hemispheres spread out when the motor speeds up, engaging the gearbox. When the steering maxes out, the clutch slips. When the motor stops, the clutch disengages, allowing a spring to force the wheels back to the center.




The plan was to use the existing geared motor as the heart of a servo. There was no practical way to install a hobby servo for steering. The 1st step was to fuse the clutch to the gearbox so the wheels would not freely move when the motor stopped. This probably can't be undone.


Next, we have a magnet hot glued on the steering horn. It was hoped that a hall effect sensor could detect the magnet's position precisely enough to control the motor.

A quick test revealed it would take more like 8 hall effect sensors to do the job. Their range, even for the 5mV/gaus version, is too short. It's not the most elegant solution, but the cheapest. Just a matter of stretching the range as much as possible. A magnetometer would probably not do the job, since it would detect the Earth's magnetic field.

A history of magnetic levitators resulted in an assortment of hall effect sensors of various ranges accumulating. Having finally analyzed their range, they probably weren't the ideal device for a levitator. An optical device would have been better.

The levitator was a huge time sink, 10 years ago, but for a 29 year old watching the time when everyone else was getting married & having kids pass by, it was the right project. 10 years later, it's a similar story of watching those same peers going into menopause, watching that age of child bearing go away, & needing to stay inspired.
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