[Power] ReadySet Go: How A Simple Solar Power Pack Is Driving Wealth In The Developing World | Gadget Lab | Wired.com

[Nicholas]

Sameer, The MPP device I have uses the LM2596 buck converter on a tiny
board complete with inductor and capacitors and a diode or two.

These boards just by themselves are robust high efficiency voltage
regulators that are sold on ebay for $US3 shipped anywhere in the
world. They generally all come with the adjustable version of this
chip (it is also made in fixed voltage versions). They handle a wide
voltage range and need only 2v headroom. They will provide for up to
30w of regulation. However, they really need a lot of heatsinking to
provide for even 15w. These boards have very stable regulation and
have various protection measures built in (I think thermal and
overcurrent). They would work well in your XS-0.7 running on the
XO-1.5 project for anywhere where you need stable voltage regulation
from a higher voltage.
These are bare boards only and need heatsinks (the tricky part) and
boxes. If buying on ebay, look carefully for the input capacitors as
some are only 35v and the better ones seem to have 50v input caps all
for $3US. I have used these boards successfully to help build a
friend's art project called "Free of Charge" which used large
scrolling LED boards and arduinos running off deep cycle batteries on
an Auckland beach earlier this year over a weekend, so very suitable
for the XS on XO projects.

The solar MPP converter I built is a straight copy of Chris Graecen's
Linear Current Booster circuit from Homepower magazine in 93' I think.
His circuit uses a LM2576 (older version of LM2596) and a LM723 on the
front end to monitor voltage coming IN to the regulator. There is a
very big cap on the front end and a big cap on the output. It will
keep the solar panel at the maximum power point by high speed
switching the LM2596 on and off. There is a potentiometer in the
circuit to adjust this point. There are other variations of these
circuits documented at the LOW COST MPPT LM2596 on fieldlines.com The
biggest cost for these circuits are the big caps 50v 2200uf and 35v
1000uf on the output. They can be scrounged although I think at least
the output cap should be low ESR.

On 7/22/12, Sameer Verma <sverma at sfsu.edu> wrote:
> http://www.wired.com/gadgetlab/2012/07/ready-set-go-how-a-simple-solar-power-pack-is-driving-wealth-in-the-developing-world/
>
> From what I remember, these are the same guys who were doing the yoyo
> charger...
>
> Also reminds me of George Hunt's efforts of preventing the batteries
> from completely draining
> out...https://schoolserver.wordpress.com/2012/05/16/does-school-server-need-a-lead-acid-battery-interface/
>
> cheers,
> Sameer
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