[Olpc-open] Foot power revisited...

[Steve Holton]

On Wed, Jan 7, 2009 at 7:36 AM, Mike Dawson <mikeofmanchester at gmail.com>wrote:

> Dear All,
>
> We tried to create a sewing machine based trial to power an XO - we
> geared it at about 90:1 so that the two dynamos should spin at about
> the same speeed as they would on a bike.
>
> When connecting the bike light it does light - a little dimmer than
> normal - but the digital voltmeter for some reason when just starting
> slowly to spin the wheel by hand registers 0.1V or so when it's going
> smoothly at full speed it registers absolutely nothing.  I tested
> measuring a few batteries and it seemed fine.


Most "bicycle dynamos' will produce alternating current. The XO requires
direct current for charging. A light bulb can operate off either.

I suggest you re-test the bike dynamo with the AC setting of your volt
meter.

If this is the case, you can use a bridge rectifier to change the
alternating current into direct current, at the cost of about 1.4 volts.


-- 
Steve Holton
sph0lt0n at gmail.com
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