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# Need info on this wind generator circuit! Answered

I'm trying to build a very compact wind generator, and found some circuit schematics over the internet for the voltage regulator. I have some experience with eletronics, but get lost sometimes... any help on this schematic would be very welcome!

Also, for a small (say, 15" diameter propeller) turbine, what kind of eletrical motor would be best suited?

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## Discussions

The circuit diagram you have posted looks to me like a buck-boost converter, described here in this Wiki article:
http://en.wikipedia.org/wiki/Buck-boost_converter

This circuit is one of a family of three DC-to-DC converter circuits, named "buck", "boost", and "buck-boost" Sometimes the "buck-boost" is called "inverting".
http://en.wikipedia.org/wiki/Buck_converter
http://en.wikipedia.org/wiki/Boost_converter
http://en.wikipedia.org/wiki/Buck-boost_converter

The trick to modeling/understanding these circuits is to assume the voltage across the inductor is one constant or another (depending on how the transistor is switched), and hence the current through the inductor always has a derivative with a constant slope, since dIL/dt=VL/L. The current is either constantly increasing or constantly decreasing. This is complicated to say in words, and I think it looks better if you draw a graph of it, of VL and IL as functions of time.

Anyway you start out with these assumptions, then when you do the math, it turns out the ratio  |Vout|/|Vin| depends on the duty cycle at which the transistor is being switched.

Looks like that's the thing! Now I have some direction to begin my research, thanks!

It looks like there's some simple DC/DC conversion going on here, to even out the varying voltage produced by the turbine. I'd say a motor that outputs 12V at a known rpm would do the trick.

That said, I'd search the net a bit longer for a different schematic. This one is more of a "proof of concept" than an actual circuit you can build.

Caveat: There is a LOT of energy needed to power a cell phone. I have a hand-crank generator for the purpose (part of an emergency radio/light system), and it takes ten solid minutes of cranking against nontrivial resistance to power ONE minute of phone call.

A small fan might be able to keep a phone topped up... but doing a complete charge is going to involve a very long wait, even if you have reliable winds.

Worth trying the experiment, but I wouldn't expect too much from it.