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How-To:  Use a Stepper Motor as a DC Generator

MAKE pal Dino Segovis brings us this handy tutorial on running a stepper motor in “reverse,” i.e. turning the shaft mechanically in order to generate electrical power, instead of the normal usage. He writes:

Any electric motor will also output a voltage when it’s freely spinning. Stepper motors are much better at this because they have many times more poles to pass next to each other thus generating electrical pulses.

The AC current can be used as-is, he reports, to run LEDs, or easily rectified to give DC. [Thanks, Dino!]

6 thoughts on “How-To: Use a Stepper Motor as a DC Generator

  1. instead of a stepper motor, will this work?

    would this work?
    I found a DC magnetic motor. Will this work? It looks like a motor used in electric cars or vehicles. The power rating caught my eye. Could it be that simple? I’m not worried about the RPM, I have that problem solved so I can get any RPM needed without wind power. Could this motor put out as it states 11.5 KW continuous? If so, Why would I buy a 10kw windmill or solar system for $30,000.00 USD when I can use a permanent magnet DC motor like this for 600.00 capable of 11.5 KW continuous. The equations V(V) × I(A) = P(W). Is this motor really going to put out 11KW of electricity or am I missing something here? Geez, I’d be ecstatic if it would even do 5KW. Sorry for the stupid question. I’m sure you are probably laughing at my craziness.

    Power: 11.5 kW cont– 23 kW pk <—– ?
    Voltage: 12-72 Volt rated
    Max Speed: 3700 rpm @ 72V unloaded
    EMC-RT200 w/
    Alltrax AXE7245 Controller
    38HP pk. Electric Drive Kit


    EMC-RT200 Motor
    Alltrax AXE7245 Controller
    Choice of Throttle
    Wire Kit
    Fuse Holder w/ Fuse

    EMC-RT200 Motor

    The EMC-RT200 is a brush-type, permanent magnet DC motor with very high efficiency. Capable of 11.5 KW continuous and 23 KW for 1 minute. For voltages from 12 to 72 VDC input and 200 amps continuous (400 amps for 1 minute). Designed for battery operated equipment. For more information, see the Performance Information section. Motor weight of 39 pounds. This motor has similar performance to the Lynch, Lemco, and AGNI motors

    Power: 11.5 kW cont– 23 kW pk
    Voltage: 12-72 Volt rated
    Max Speed: 3700 rpm @ 72V unloaded
    Size: 8" OD, 7.4 " long (w/o shaft)
    Shaft: 7/8"x 1-3/4", 3/16" key
    Weight: 39 lbs.

    Click on an image above to enlarge in a new window ^

    Alltrax AXE7245 72V 450A Programmable Controller

    Alltrax controllers are fully programmable speed controllers for permanent magnet and series motors. The free Windows compatible programming software allows for complete control of max current, max speed, hi and lo voltage cut off, acceleration and deceleration rates and custom throttle settings.

    Programmable via RS232 comm port using PC or Laptop
    Integrated anodized heat-sink with multi bolt pattern for flexibility
    Fully encapsulated epoxy fill – environmentally rugged design
    Advanced MOSFET power transistor design for excellent efficiency and power transfer
    1/2 Speed reverse option and "Plug Brake" options available

    450 Amps
    24-72 Volts
    Works with 0-1k, 0-5k, k5-0 ohms, 6-10.5V & ITS Throttles


    Choose from…
    – Magura Twist-Grip Potentiometer Throttle
    – EZ-GO Pot Box Throttle (PB-6 Drop-in Replacement)


    Please specify your contactor coil voltage at checkout. 24V, 36/48V, or 72V

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I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I am a long-time contributor to MAKE magazine and My work has also appeared in ReadyMade, c't – Magazin für Computertechnik, and The Wall Street Journal.

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