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 light emitting diodes (LEDs) within the base. The wind lantern will use this electricity to create a flickering, glowing indicator of the wind.
LEDs, like any other diodes, allow current to flow through them in only one direction. 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 wind lantern spins. Because even the best intentioned design is no match for NYC wind -it has a mind of its own. To do this, we’ll build a rectifier circuit for a bipolar stepper motor.
This project was recently featured in an episode of Make: Live - thanks Matt and Becky!
Step 1: Shopping List
• 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)
• 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. You can download the FREE template here on Thingiverse, or go ahead and buy them from my Ponoko showroom.
• 10 in wide aluminum flashing (usually sold in rolls; you need about 2 ft length for this project)
• 5mm bore shaft collar with set screw (McMaster 57485K65)
• 7 1/2 in bore shaft collars with set screws (McMaster 6166K25)
• 18 in length of 1/2 in outer diameter aluminum tube (McMaster 1658T45 is 8 ft long but a good value if you have the means to cut it down to 18 in—any hacksaw will work (like McMaster 4077A1))
• Two flanged sleeve bearings for 1/2 in shaft diameter (McMaster 2938T12)
• Thrust bearing cage assembly for 1/2 in shaft diameter (McMaster 5909K31) with two matching washers (McMaster 5909K44)
• Three female threaded standoffs, 4 in length, 1/4 in -20 screw size (McMaster 92230A350)
• Six socket head cap screws, 1/4 in -20 thread, 3/4 in length (McMaster 92196A540)
• Six lock washers for 1/4 in screw size (McMaster 92146A029)
• Six flat washers for 1/4 in screw size (McMaster 92141A029)
• Four M3 screws 40mm long (McMaster 91292A024)
• Four M3 lock washers (McMaster 92148A150)
• Four M3 washers (McMaster 91116A120)
• Set of inch and metric hex keys (like McMaster 7324A18)
• Deburring tool (like McMaster 4289A35) and/or rounded file