I'm new to electronics and servos, but I have an idea for a project: use a servo motor and PICAXE (or Arduino/similar) micro controller to automatically shift the hub gears on a bicycle depending on the current speed.
The first step is, of course, for the servo motor to be able to actually have enough torque to shift to the next gear. Any recommendations on how to do this (e.g. what motor to use, whether I need gearing etc.)? I'm thinking of having the gear cable wrapped in tension around some sort of spinner mounted to the motor, so that as the motor turns, it pulls or relaxes the gear cable, thus changing the gear.
I then need to be able to program the micro controller to automatically shift to the correct gear, depending on the speed. The speed will be measured through the use of a reed switch and magnet, located on the fork and front-wheel spoke respectively. I have no idea what the best/only approach would be to finding the speed like this (well, I do in principle of course, but not in practice).
These are my main questions for now, but more will follow as these are answered.
Thanks
Fela
The first step is, of course, for the servo motor to be able to actually have enough torque to shift to the next gear. Any recommendations on how to do this (e.g. what motor to use, whether I need gearing etc.)? I'm thinking of having the gear cable wrapped in tension around some sort of spinner mounted to the motor, so that as the motor turns, it pulls or relaxes the gear cable, thus changing the gear.
I then need to be able to program the micro controller to automatically shift to the correct gear, depending on the speed. The speed will be measured through the use of a reed switch and magnet, located on the fork and front-wheel spoke respectively. I have no idea what the best/only approach would be to finding the speed like this (well, I do in principle of course, but not in practice).
These are my main questions for now, but more will follow as these are answered.
Thanks
Fela
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