Alt-BEAM Archive
Message #00975
To: James Anderson anderson@cfht.hawaii.edu
From: Steven Bolt sbolt@xs4all.nl
Date: Thu, 25 Feb 1999 10:01:51 +0100 (CET)
Subject: [alt-beam] Re: Solar cell recommendations?
On Wed, 24 Feb 1999, James Anderson wrote:
> Anyways, after not being to impressed with the RS solar cell I
> bought, I was looking for suggestions on ones I could order.
> Price isn't a big factor, I'd prefer reliability, and presoldered
> would be really nice.
The Panasonic Suncerams are still the best small solar panels,
afaik. Each consists of 4 or more identical cells, `printed'
together on a thin piece of glass and of course connected in
series. The solder pads have never failed me. Easy to use if you
know how to handle a soldering iron. Solarbotics offers some in
that range, so does Conrad in Europe. The ones I've used most
often:
nr nominal V unloaded V nominal LxBmm price
current (Dutch fl)
-----------------------------------------------------------
BP-243318 1.8 3.45 16.4mA 24x33 4.95
BP-378234 3.2 5.52 41.7mA 37x82 12.50
===========================================================
The first in various projects like the SunEaters, the larger one in
my clock-motored photovore.
> Also, I was wondering about how many volts you usually these
> things usually put out, so I can mimic with batteries until I get
> one.
What you see in the table is the unloaded voltage in good light.
Voltage, current, power - all drop with the light intensity. For
instance, in morning daylight under fairly heavy cloud I'm
measuring... 2.9V unloaded on a BP-243318. If you want a Solar
Engine to work under those conditions, its own current consumption
must be very small, in the uA range. The common 2-transistor Solar
Engine consumes hundreds of uA or more than 1mA when approaching
trigger point, which is a Bad Thing.
Just as important are the trigger levels (on and off), which should
match your motor and task. SunEater_II consumes 10uA to 20uA and
its trigger levels are easy to adjust; very nice for photovore-type
applications. The recent `Alf' modification by Ben Hitchcock is
worth a look, as is Justin's `Bivore'.
If you can find them, very efficient SEs can be designed around the
1381 voltage triggers. They offer a choice in switch-on levels
(depending on type number, so you need a bag of them to
experiment). An off-level determining latch has to be added - or
you could time the switch-off, which works fine if the motor load
is always the same. Andrew Miller turned these into an art and had
them working "in moonlight."
Best,
Steve
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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