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Topic: Wind turbine Savonious Charger based on Joule Thief - advise for a charger? (Read 6561 times) previous topic - next topic


But I cant figure out what the cap does in this case. My first thought is that it changes the frequency to fit what the transistor can commute. But I maybe wrong.
1k resistance for AC  is reduced to ohms.


Phase two: generator.

Firs fail: the toys motors cant supply the current I need to light the LED in the Jule thief  circuitry I made.

Capacitor 10uF to motor terminals may help, why you not connecting  LED directly to motor ?


I will mount a 10 uF to the motor.

Few months ago, a friend of mine mounted an white led to a PC fan. It lighted.

The wind turbine is part of the combined generator, that includes the PV charger (separate thread) and perhaps an energy harvesting module in a later stage.

Therefore, the wind, the Sun etc. will all charge the same battery. And the battery will supply current to the LED.

Modular design. :-)


I will mount a 10 uF to the motor.

Few months ago, a friend of mine mounted an white led to a PC fan. It lighted.
That is my question in post # 46.
If LED is not lighting reverse connection of it.
Basically any motor with magnet should work


I reversed the connections of the toy motor with no result. Maybe I shall check the wiring, connections again.

Ill check mounting the LED directly to the motor, to "debug" :-)).

The motor my friend used was a PC fan one, which is far lower rpm than a toys motor.


I randomly pick up a few motors and speed them quickly by hands, and the LED is always lighting, if is not I change  rotation  direction.
Jule thief  required pure DC, from motor you don't have that.


Then I have to make sure I get a pure DC from my generator.

Maybe using the same concept of Shotky + Zener as in the case of Photovoltaic charger? But the problem is now how to regulate 1 V, in absence of this value in the Zeners range.

And is also more problematic because the available power is much less than in the PV case, I dont like to throw current away.

I came across LT3022, which is manufactured by Analog, which is stated to regulate as low as few hunderd miliV. Looks interesting, although not in line with my "simple design" rule.



Another interesting idea is to use a supercapacitor. Then the motor will charge the supercap and the supercap will charge the battery via Joule thief- in order to reach the required voltage to charge the NiMH (or LiIon).

A nice point in this approach is that I can charge the capacitor during night and discharge it daytime. Or using 2 of them, each for 12 hours.


I searched the internet about supercaps as chargers but no result so far.

I suppose no matter the voltage (usually 1-3 V, very variable), the cap will charge anyway. Then the problem is how to gradually discharge the supercap into the battery.


How about not to use Joule thief, battery will be charged without it ?


OP really needs to look at the physics of what they are trying to achieve.
Small DC motors simply wont work for this kind of application as they are designed to spin
really fast, usually in the thousands of RPM, and a vertical vane wind turbine will simply not spin this fast, no matter what.
You will be lucky to get a few hundred RPM from one .
Small wind turbines use a special type of alternator, usually a 3 phase permanent magnet type with very strong Niobium magnets to get a sufficiently high magnetic field to allow the turbine to produce usable voltages at low RPM.
Do some research on small vertical vane wind turbines and the types of generators they use.




I am not a fan of Joule thief :-).

I did not find any other simple circuit (on other words - no integrated circuits) to rise the voltage from some 1V to more than 3V. 


This is a demo project. Efficiency is far less important than simplicity.

I am considering a brushless motor.


The issue isnt efficiency.
Its all about getting sufficient volts from your motor at the speed the turbine will turn it.
You need to calculate or measure how fast the turbine is going to spin via whatever method you use to spin it , and then source a motor that will provide sufficient volts to light your led at this speed .


From this motor at high speed I have 12V - post # 55


How pure is "pure"?

When I spin my motor I increase the speed in few seconds, keep the hair dryer at (relatively) constant distance to the motor's propeller for few seconds and then turn the dryer off.

I think in real life that might be some wind bursts but the reason why I choose the vertical axis turbine is exactly the fact that in the target area the wind speed is usually 1-2 m/s.

It is something confuse in all this. Why the Joule thief cant work on variable voltage? Or, at least, how much variability is OK?

If I mount a capacitor (as advised) to the motor, then some sort of equilibrum between the current sent to cap and the current sent to Joule could be achieved. That is my understanding, but I may be wrong.

A joule thief can offer higher voltage even when closing and opening the circuit by a push button. Why  it cant do the same when the voltage varies with the wind speed?


Think to the project as a sort of "close garage challenge": I have only usual components: a handful of diodes and transistors, resistors, wires.  That is fun and is also learning.

I have a toy motor in my hand. No Hall sensor or similar. How can I measure the spinning speed? We have to imagine a method. What I have in mind is to place two wires ringshape near two sides of the motor and measure the current by an multimeter. Or use some sort of optical method. Lets be innovative and imaginative.

Good engineering is simple engineering. Exceptional engineering is fun engineering. :-)


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