[Olpc-open] Foot power revisited...

[Mike Dawson]

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.

I notice that on instructibles for the bicycle generator it mentions
using a car alternator - I thought is a bit too much...

http://www.instructables.com/id/Bicyle-Power-for-Your-Television,-Laptop,-or-Cell-/?download=pdf

So we found two dynamos that can be purchased for less than $1 in the
local market each one claiming 5.5W.

I am not sure if it is that the rpms aren't suitable for the dynamo,
or perhaps the speed varies too much...

We want to go with foot power as it's not distracting, not obtrusive,
can work indoors and out and during the night so that the learning for
the child and family can continue all hours...

I was also thinking about using one of the OLPC hand cranks and
connecting it to a foot powered pedal or something like that...

Would very much welcome anyone who might be able to explain what we
saw and hope that we can find the way to harness the energy that is
definitely there.  I also saw
http://news.bbc.co.uk/2/hi/technology/7796215.stm re. a gym and they
get 100W from an exercise bike machine... 10W would be enough for us I
reckon...

Thanks/Regards,

-Mike
(Working in Kabul to support OLPC Afghanistan)