# foot power

Nathaniel Theis natetheis at gmail.com
Thu Jan 27 22:18:24 EST 2011

```On Thu, Jan 27, 2011 at 07:54:16PM -0700, Alan Eliasen wrote:

>    Again, I will note that the only way to make the XO reasonably
> powerable by a child (or an adult) is to reduce its power consumption.

Well, this isn't entirely true. For example, something like a potter's
wheel pedal could potentially generate sufficient (25+ W) amounts of power,
given a reasonably efficient dynamo (and a reasonably efficient
child!) However, the endurance problem is still *huge*.

The XO-1 takes about 2-3 hours to charge from 10% battery level. If
you have a foot-pedal system that generates 25 watts, you still need
the child to do this for _several hours_.

Alright, you may say, maybe you make it ultra-efficient and very easy
to push the pedal down (repetitively, for hours on end!) But that's
just the tip of the iceberg.

Noise is another big problem. The crank charger is quite loud (for
only putting out 15~ W or so). Imagine a classroom with even 5
foot-chargers going at a time... it's an issue.

The only reasonable solution I can think of is playground equipment
turned to power generation (a la PlayPump).

Swings, seesaws, and carousels all can generate _significant_ amounts
of power (100watts as a conservative estimate for a converted
carousel!), and _store_ that energy in a battery or flywheel for later
laptop charging.

Thus, we don't just need a 15w charger for one XO... the endurance
problem makes this near impossible. We need a 150watt charger for one
XO (full charge), so the child(ren) can put out significant amounts of
power for a short time, and charge the XO's batteries over extended
timescales.

Higher-wattage chargers also work well with solar panels (they can
both charge the same set of batteries.)

Just some thoughts,
Nate

```