[aprssig] Re: now, 1.5 Lptops Per Child : power options?

Richard Amirault ramirault at verizon.net
Mon Dec 31 18:09:50 EST 2007

----- Original Message ----- 
From: "Scott Miller"

>I was thinking about this the other day... when I was in Hong Kong, I saw 
>tons of little gadgets hitting the market that have little hand-crank 
>dynamos.  Smaller ones than I've seen before in flashlights and radios, 
>too - little LED lights and cell phone chargers and such.
> My first thought was to try building a regular windmill with one, but 
> perhaps a simpler mechanism like a cup vane anemometer would work.  If you 
> could get a couple hundred mW out of it, that'd be enough to power remote 
> sensors and such where solar power might not be suitable.


One thing you forgot .. when you are generating electricity with a crank 
generator .. you are doing *work*.

I bought one of those emergency radios with a hand crank as one of the power 
options. When I got it the first thing I did is turn the crank ... EASY .. 
in fact it was *too* easy.  The next thing I did was read the  instructions 
.. then I plugged the rechargeable battery pack into the charging circuit 
(it came unplugged from the factory) and tried cranking again ... it was 
considerably HARDER to crank now!!   Hard to tell but I'd say at least 4 or 
5 times harder to crank.

My point is that a windmill or anemometer needs to overcome this resistance 
to generate electricity .. and it is a considerable amount of resistance 
believe me. Unless your windmill or anemometer has 15 or 20 foot arms .. or 
you plan on waiting for a hurricane .. I don't think it will work.

Richard Amirault
Boston, MA, USA

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