Stepper motors - The Diigo Meta page

• 20 Jun 09
  

  Steve Dickie

  Stepper motors are available new, from surplus houses, or can be pulled from old electronic equipment such as floppy drives. Jameco has a nice selection, also Ax-Man typically has a variety. Parallax sells a stepper (PN # 27964), a little pricey, but comes with excellent application notes.
  
  Look for "unipolar" or "4-coil" or "4-phase" motor (they all mean the same thing) with 5 or 6 or 8 wires. Avoid "bipolar" motors because they require an entirely different control scheme. However, if you find a good 4-wire bipolar stepper motor from a printer, here is a good reference source: Interfacing a bipolar stepper to the Stamp
  
  Key specs are operating voltage (12V is convenient for robotics projects), and either coil current or coil resistance (given one spec you can get the other from V=IR). Look for motors with a coil current of 250 mA or less (coil resistance of 48 ohms or more for a 12V motor). Higher currents do give higher torque, but will also drain your battery faster. Another key spec is the holding torque which is how much torque the motor can resist when energized.
  
  If you are pulling a motor from an old floppy drive, look for a flat motor with five or six leads.

  robot electronics

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