Page 197 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

Chapter 6 Options for Creating and Controlling Motion 175

• Another option is the Adafruit Industries (www.adafruit.com) Motor/Stepper/
Servo Shield for Arduino. All you need to do is plug the shield in on top of
your existing Arduino, attach the stepper motor wires in the correct spots,
download the library, and copy a few lines of code. The shield works for
five- and six-wire unipolar steppers as well as bipolar steppers.

Bipolar Stepper Motors
Bipolar, or two-phase, stepper motors have four wires (see Figure 6-35). They have
two independent sets of wire coils in alternating positions around the housing (hence
the term two-phase). Bipolar steppers move by energizing the coils first in one
direction and then reversing the direction as the shaft is turned (hence the term
bipolar). A bipolar stepper motor
will always be stronger than a
FIGURE 6-35 Schematic of a bipolar stepper motor
unipolar motor of the same size.
The same options are available
to control the motor as with
the unipolar type: SparkFun’s
EasyDriver, the Arduino with
the stepper library and some
breadboard work, the Adafruit
motor shield, and plenty of others.

P roject 6-9: Control a Bipolar Stepper Motor

In this example, we’ll use a bipolar stepper motor and control it with SparkFun’s
EasyDriver.

Shopping List:

• Arduino with USB cable
• Breadboard (like All Electronics PB-400)
• Jumper wires (like SparkFun PRT-00124) or hook-up wire to make your own
(see Project 6-4)