Stepper Motor Generator

Any stepper motor can be
used as a generator. In contrast to other generators, a stepper motor
produces a large induced voltage even at low rotational speeds. The type
used here, with a DC resistance of 2×60 Ω per winding, can generate
more than 20 V when turned by hand, without any gearing. The circuit
diagram for a ‘hand-cranked torch’ shows how you can use a stepper motor
as a generator. A supplementary circuit stores the energy. Two bridge
rectifiers, each made up of four 1N4148 diodes, charge the 4700µF
capacitor. The super-bright (white) LED is driven either via a 390-Ω resistor (Power Light), or via 22 kΩ in series with 390 Ω. In the latter case, the LED is not as bright, but it stays on longer.

Stepper Motor Generator

Stepper Motor Generator

You must restrain yourself when cranking the dynamo, since in the ‘bright’ setting it is possible to exceed the rated LED
current of 20mA, while in the ‘long’ setting it is possible to exceed
the rated capacitor voltage of 25 V. If necessary, adjust the value of
the LED series resistor. The lamp is bright
enough for reading in complete darkness. The stepper motor generator is
thus ideal for spies, thieves and children who want to read under the
bedcovers. You could also keep it handy in your hobby room, in case of a
short circuit.

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