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Ben Fleskes wrote in message ...
> It's not easy. Generally you need to wire several of them in series to get a
> voltage well above what you need and wire them through a voltage regulator or a
> battery charger circuit (with rechargable batteries) to give reliable output.
Realistically, the load when you try to drive a couple of motors off your RCX
is such that solar cells are not a Lego option. 9V at 300mA per motor means
you need about 6W coming in. To get that reliably you're looking at about 10W
minimum, preferably 15W worth of solar cells. A Siemans ad I have handy claims
100W from about 0.9 square metres, so we'd need about 0.14m^2, or about a square
foot. With that much cell area you probably will want a controller and battery,
as otherwise you could fry the RCX. And once you have a battery and controller,
you can cut down the area a bit if you don't need continuous operation. But
you still need to meet the minimum charging current of your cells, which for
AA nicads is only about 10mA so that's not too hard.
> On a side note. An interesting design challenge is to build a motor control
> circuit that rotates a solar panel to track the path of the sun accross the
> sky such that the panel is always directly exposed to the sun.
It's better if you just make it to track the most powerful light source
and have a no-light rest position that you can align east. Otherwise your
panel spends a lot of time gathering only "ground light". For a "dumb"
tracker that just does a 24 hour rotation you'll need a rotation sensor
because unregulated Lego motors change speed to much under varying load.
Either would make an interesting project.
Moz
("home power" magazine is also on the web at http://www.homepower.com and the
whole mag is there in pdf format).
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Message is in Reply To:
 | | Re: Solar Power & LEGO
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| Not a direct question. In general. Each photo cell will give a certain amount of voltage and current capability. If a cell is rated at .5 volts, that is generally under very well lit/bright conditions, which are unusual. It also assumes the panel is (...) (25 years ago, 9-Jul-99, to lugnet.build)
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