Nema 14 Handkurbel Generator

thingiverse

The printed parts can be combined with a few M3 screws and nuts to screw onto a NEMA14 stepper motor. The stepper motor is then used as a generator. The gear ratio is 4:1. Originally, a ball bearing was supposed to come later in a later version to make the ride smoother. However, it could already be determined with the current version that the electrically generated energy in this setup is lower than expected. The coils in the stepper are equalized by a full bridge. The equalized voltage is then smoothed out by a 1000uF/40V capacitor. A step-down regulator then produces 5V to charge a power bank. At moderate speed, it was possible to generate 200mA (5V). At high pedal speed up to 500mA. This is also the typical load current for older-generation mobile phones. However, considering that theoretically you would have to pedal at high speed for two to three hours just to charge a mobile phone once, I conclude that this solution is not practical for this application, especially with the Nema 14 stepper motor in hand-crank operation.