For my latest workshop in my daughter’s school I wanted to let the children each make a wind turbine. It wanted it to be functional, powering a small light and it needed to be cheaper than 6 Euro a piece, which ruled out any commercial kits.
The workshop was for 20 kids, which ruled out scavenging hard discs motors or stepper motors and such. Low cost “toy” motors on the other hand need really high rpm to light up a small bulb or a led. Fortunately the type of motors used in solar cell driven toys and kits work better. And these are still available for under 2 Euro.
A small flashlight bulb was actually easier to get to glow than lighting a LED, when driving a 6 to 1 gear on a “solar grade” motor by hand. But it required too much torque for a small and simple wind turbine.
A LED worked with a turbine and a single step 6 to 1 gearing, but only at really high wind speeds, needed to get a high enough voltage. But I wanted the kids see it functioning, without having to wait for a strong wind. To apply a higher gear ratio in one step needed a larger gear wheel which I could not find at a low price. A two step gearing gives to much friction with the cheap and simple construction techniques suitable for a kids workshop (remember we are talking about gearing up, which is more critical to build quality).
But our good friend the Joule Thief came to the rescue. With this little circuit added, the LED lights up at a breeze. Moving the wind turbine by hand easily lights up the LED. I estimate it starts at wind speeds below 10km/h. And everything still holds up at strong winds.
Apart from attaching leads to the motor/generator in advance (“solar” motors are often sold with leads anyway) the circuit is built up without soldering, as I prefer to avoid that when working with 20 kids aged 6 to 12.
All that was left was making some “templates” for the steps that need accuracy and gathering the materials and I was ready for the workshop. Check the result in the video below and read how we built the wind turbines in this Instructable.
My special thanks goes to Emma, for her assistance when taking extra pictures showing the detailed construction steps.
Thanks for the votes for this entrie in the MakerBot Challenge!
Step 1: Materials and tools
1 piece of 2mm thick balsa 10 cm by 40 cm or 4 pieces 10 cm by 10 cm
4 bamboo (meat) skewers 30 cm long, about 3mm diameter
some cellotape, at least 19mm wide
large gear (about 60 mm diameter, Opitec part 840088)
a piece of scrap wood, 3 cm thick and about 6 cm by 6cm in size.
some non-stick paper,
1 small stick of hotmelt glue (low temp type when working with kids)
a cabinet screw with an unthreaded part, fitting loosely the gear hole (4mm for the gear mentioned above), about 35 mm long. A brass screw will last longer in humid conditions, I found out screws with a nominal diameter equal to the gear hole, actually fit loosely.
4 washers fitting the screw
paint and varnish (optional)
For the generator:
a “solar grade” toy motor with 7cm leads (FF 130 “solar motor”, Opitec part 224176 works great, but needs leads to be soldered to the motor. The RF 300, Opitec 224154, comes with leads, but is less resistant to rain)
a small pinion gear of the same module as the large gear (Opitec 841187 with adapter 842022)
a (steel spring) clamp fitting the motor/generator (Opitec 225074)
a 25 mm long bolt and nut. I choose M3, allowing for all drilling to be done with a 3 mm bit.
For the Joule Thief:
a ferrite toroid (e.g. Conrad 507997 or 508039)
a 2N3904, BC 337 or equivalent transistor
a 1kOhm resistor
1 to 3 LEDs (the clear ones are easiest to see lighting up in sunlight)
2 times 20 cm of insulated thin gauge electrical wire (twisted strands from telephone or network cable are perfect)
5 small cabinet screws, preferably brass (more durable contact). I choose shortest 3 mm diameter ones I found, allowing for all drilling to be done with a 3 mm bit.
For the mast
a 27 cm piece of 20mm diameter PVC electrical tube
a 75 cm to 1 m long piece of 16 mm PVC electrical tube
2 tie-wraps (pretty small ones are OK)
a junior hacksaw
a flat working surface (theoretically 31 by 31 cm, but take double to work with some comfort)
a hotmelt gun (low temp type when working with kids)
a drill (preferably column-type) and a 3mm drill bit
screwdrivers fitting the screws and bolts used
some templates can be made out of scrap wood as explained in the following steps