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294 Making Things Move

P roject 10-2: Wind Lantern

In this project, we’ll build a small, vertical-axis wind turbine, or VAWT for short. These
are not as efficient as their horizontal-axis cousins, but they are better suited to urban
environments where wind can come from all different directions.

Normally, when you give electricity to a motor, it spins. The same is true in reverse: If
you give a motor a spin, it acts as a generator and creates electricity. The wind lantern
will use energy from the wind to turn a motor and the resulting energy to light up
some LEDs within the base. The wind lantern will use this electricity to create a
flickering, glowing indicator of the wind. 3,4

You already know that LEDs and diodes allow current to flow through them in only
one direction. You also know that bipolar stepper motors have two wire coils. The
challenge here is to design a circuit that directs energy generated in each coil through
an LED in the correct direction, no matter which way the lantern spins. To do this,
we’ll build a rectifier circuit for a bipolar stepper motor (see Figure 10-18 in the recipe
steps).
Shopping List:

• Electronics
• Stepper motor (SparkFun ROB-09238)
• Male header pins (SparkFun PRT-00116)
• Breadboard (like All Electronics PB-400)

• Jumper wires (like SparkFun PRT-00124) or hook-up wire to make your own
• Eight diodes (SparkFun COM-08589)
• One or more LEDs (yellow SparkFun COM-09594 used here, but choose
any color)

• One or more 1,000 μF capacitors (SparkFun COM-08982)
• Hardware
• 1/4 in acrylic plastic sheet about 15 × 30 in or equivalent (size based on
Ponoko P3 template) for gears, disks, and sail holder pieces