[Robotgroup] Wind info

[Paul Atkinson]

I looked at the kidwind.org site and found that the basic turbine is capable
of generating
 *Power Output - Good Blades, High Winds
0.5-1 Volt / .08 - .10 Amps
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Although this is enough current to light LEDs, it is not enough voltage.

Even with a fan generating wind to drive the turbine, they expect
1.0-1.5Vat 80-100ma.
That probably won't light a red LED. (If you spin the shaft by hand, you get
more than this,
but in very short bursts.)

They claim a geared motor in the turbine will get about 3-4V and 100-500ma.
That's enough
voltage and current to light a number of LEDs.

The questions we were asked last night about adding a capacitor to store
energy
so that an LED could run for a while did not mention this low voltage range.

It will be necessary to boost the voltage somehow to get to 1.5 Volts for a
red LED, 1.8V for green,
or approximately 3.2V for blue or white. If the motor puts out AC, then we
can use a transformer to
raise the voltage. If the motor puts out DC, we need a circuit. The circuit
to do this is called a boost
converter or inverter.

(There are at least 2 uses for the term 'inverter'. One changes voltage to a
different magnitude -
that's the type I mean here. The other 'inverter' just give the inverse or
opposite voltage, for example
high in = low out and low in = high out. This is not the type needed for
this application.)

I'm going to check some of the BEAM resources and see if they have a handy
circuit. I've seen at least
one application where a small microprocessor was used as a DC-DC convertor
(to raise small voltages to
a "useful" range.) So there is hope! Also, the microprocessor could be
useful for the doing the animation
that was mentioned with the LEDs.

Paul

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