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Plastic Windmill- Science-toy windpower generator help needed. Answered


I am currently planning another kid-science project.
I am still learning about electronics myself, and therefore would apreceate any help to complete a concept to create a wind generator that could power or blink a LED (maybee just at night to save power).

I have attached a image with most info
( PNG version at http://www.nottoxic.com/wapcc/ae/aqua/windmill.htm )
but here a short review of what I am trying to achieve.

I want to build a renewable energy powered toy/project.
I thought of using windpower since we have lots here, while the weather is allways crappy, so solar cells wont be a good choice (next to price and allready used in other projects).

I recently re-read a electronic book I had as a kid myself, and saw the coil-magnet electricity experiment. This would be very easily build and save lots of money. Buying whole classroom sets where the motor/generator alone costs 1 Euro out of my own pocket would cause this project to be put aside right away.
I am aware that the magnet running over a coil wrapped around metal core will not produce much current, but I thought using a stepup converter or multiple coils, and charing the whole day, might be enough to at least charge a capacitor with 2-3v and enough milliampere that will discharge at night to blink a LED at 0.5 Hz or so.

ANY ideas aprecheated ;-)

Now prepare for another lo-fi concept image from myself...

(full PNG version at http://www.nottoxic.com/wapcc/ae/aqua/windmill.htm as well )


Have you ever looked into Picoturbine? It's an educational wind turbine, savonius type, and it includes plans for generating power by using magnets on the turbine passing over fixed coils.

Link to PDF of the plans.

Your bridge rectifyer concept is flawed. It should appear more like this:

Picture 2.png

Hello LasVegas, it is not a bridge rectifyer but a Cockroft Walton Multiplier ( http://blazelabs.com/e-exp15.asp ).
Simply converting ac to dc will not do the job, as the voltage needs to be higher to drive a 2-3v led/led blink circuit.
though the diodes will probably eat up the allready low voltage, thats another problem.

@Gyromild: Pacman rules ;-)

Due to the fact I am building it with kids I would like a design that does not involve a axis generator based concept, thats why I thought about passing magnets over coils since it would not require a axis mount device that would need more accuracy.

I know we are not building electromagnets, but at least according to my book and the experiments with the bigger copper wire I have at the moment, it will increase efficiency with the magnet-passing-coil concept, though I only have a very cheap multimeter...

I have seen the turbine quite a while ago, its pretty neat but did not remember it used a similar aproach (I was probably lazzy back then and just looked at the pictures ;-) ), thank you! I'll read it again after posting this.
Thats basicly exactly the idea i head.

Small 4-7mm diameter magnets cost about 8-12 cents, and I know some sites selling larger ones at proportional low prices. I think they would have a overall better performance then weak mangatized iron fridge magnets?

I guess blinking would be the best option. If i could charge some capacitor or battery that would be capable to produce one or two minutes glowtime of a low current led (5mah) it would probably be enough to blink a led every few seconds along with the current neccesary for a blink circuit?

I guess I need to buy some random capacitance parts to try & see, but I thought someone might have done something similar allready :-)

Oh... Sorry. I don't believe a CW multiplier would even work at low voltages. I've never seen it used except in flyback (very high voltage) circuits. I think working with children an axis generator would be most educational. All you need do in follow the same pattern as building a simple motor and spin it to generate electricity rather than run it as a motor. What I'm talking about is two coils extending from the axis, rotating within a horseshoe magnet. The hardest part is constructing the brush system on the axis.

I think so too, since diodes will have a voltate drop thats probably higher then the voltage generated ;-) But I have seen some other stepup circuits, I just have no experience on that area, so I thought Idd ask. Yes, it would be educational, but you've mentioned the problems... Building a axis and needing a horseshoestyle of magnet at best. The pringles turbine is probably the closest to what I have thought of. Kids could build a windmill just as they probably did in kindergarden allready, and then just glue a CD, coils and magnets to it. This would take the mechanical precision out of the project that would be needed if they extended the axis. I guess there are lots of different approaches to this, and I am really uncertain what to do. I bought some .15mm wire today as I read smaller works better in the pringles turbine instructable, I know its very thin, but to try out whats possible its probably good. Still, I am not even sure how to aproach this, if I should wire the coils in series but so the ac curves do not cancel each other, and such. The 3 phase system used in the pringles turbine is probably the way to go, but not an option as it would get too complex and expensive with so many magnets, wiring and coil. One simple question I simply do not know: Can I charge 1.2v rechargables with a AC current? Of course I would neet to use a rectiyier or a diode at least to charge DC, but the diode voltage drop is a problem again, any ideas? (What voltage drops do Transistors have by the way?) Then, if 0.1-1v or so "hit" the battery, will it charge? How do nicads react? Though nicads have high memory effect, so capacitors would probably the better choice, but they will need the voltage thats required later on :-/

Most commercial NiCad/NiMH chargers use little more than diodes, current limiting resistors and LEDs (I believe NiMH batteries need a little more.) The LED light when the resistance of the batteries are high enough that enough current passes through the LED instead, indicating that the batteries are fully charged. I reverse engineered a NiCad Charger a while back... Here's the schematic.

Picture 3.png

BTW: In the schematic above, the 9v battery isn't in the circuit if either or both AA batteries are present

Neat circuit, but a bit complicated for this project :-)

A simple nicad charger used for solar yard lights and such is a series of solar cells that will directly charge a nicad ( 1.2v / 0.45v = max ammount of solar panels), with a diode to avoid that the nicad will discharge over the solar cell at night.

Even with this one diode circuit a nicad would be a problem, and the nimh as well would not live too long if never charged propery, thats why I thought about capacitors which do not suffer from memory effect issues, but have low capacity...

The windmill design need to at least have a tail fin, so that it can correct itself to face the wind when the direction changes.

The windmill spins on a horizontal axis, you have two choices here, either mount the magnet/ coil/motor directly to that axis (will make the setup quite heavy, thus too rigid to move to subtle wind changes) OR come up with gear setup that converts the spin to vertical. Place the magnet/coil/motor setup at the base of the generator. Not something that the kids can whip out quickly i think.

The cup is much better, it spins on a vertical axis. Maybe you can find something with hemispherical / conical in shape (less drag when moving against the wind).
Cut a thick paper in the shape of Pac-Man (im a dork), staple into a cone, that would be easy enough for kids to do..

Btw,this just a note, its better to have 4 coils with 50 windings each, than 2 coils with 100 windings.
The diameter of the windings need not be that big (1cm), and you dont need the metal core as we are not making an electromagnet. Tape the coils so that it wont get unwind,that would suffice.
Lay the coils flat on its back, the spinning magnet should be placed facing as close as possible to the coils without touching. I dont think strong neodymium magnet is an option (quite costly in this case), thus disk-shaped fridge magnets would be a good replacement.

You may want to refer here to get more ideas on your project.
Pringles wind turbine

As my guesstimate on how long would a cheap capasitor keeps an LED glowing, my guess is, fairly quick. A couple minutes maybe.

You may need to do quite a few experiments here to come up with the cheapest simplest design.