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solar powered throwies Answered

in case you didn't know, a throwie is an LED with a small battery and magnet attached, that can be stuck to any metal surface. would it be practical to make a throwie with a long lasting lithium battery? or a small solar cell? just a thought

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heartxcore803 (author)2008-12-17

I got this idea as well. Except I was thinking a battery and something to keep the light off if it is light (like a night light) That would mean we could get the full time at night and not waste the precious battery life

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user

What your thinking of is a photoresistor. It;s a special kind of switch that closes (connects) when in low-light enviroments.

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11010010110 (author)2008-12-18

i think of antenna powered one there is lots of rf noise in the air. enough to power a small radio with antenna only (without any apparent power source). so why not a small led ?

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Antimatter500 (author)2008-03-19

all really good ideas! thanks!

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schorhr (author)2008-03-16

At least for super-bright LEDs you would need quite some large solarpanels.
For a 2mA low current LED it would work though.
I double the argument about batteries and the enviroment, but if you pick them up again or hang them on your property no trouble there.
NiCDs are rather cheap (25 cents a AA-Cell) and easy to charge. All you need is a diode, really, in order to avoid discharging through the solar cells, but as Kiteman suggested a day/night circuit would be best.
https://www.instructables.com/id/Give-the-gift-of-Robot-Invasion/ has a rather simple circuit (Solar cell, battery, diode, LED, transistor and a resistor.), or you could dissasemble one of these solar yard lights, I've seen them for arround 3 bucks a piece here in germany.

NiMh and Lithium-rechargables need a more complex charging circuit but also have less of a memory effect issue. Capacitors lack of high capacity, but it may be enough to use a goldcap and a 2mA low current LED.

Another Idea for an alternative power source would be wind power.
It will take up more space though, but you could also just abuse a small pagermotor and a joule thief circuit or such to power a LED.
It would only work when there is fair wind, but no battery to leak!

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Kiteman (author)2008-03-16

If you're actually going to throw them, then a solar cell is no good - it could break, or end up in the shade.

If you want to make a solar-powered LED to hang in the garden, google for pummer circuit - the solar cell charges a supercap or battery in the daylight, then switches on the LED when it goes dark.

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Kiteman (author)Kiteman2008-03-16

whoops - messed up formatting.

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littlechef37 (author)2008-03-15

First of all batteries are toxic for the environment and leaving them on a metal surface ( outside ) isn't good for plants or the water table. And how would you guarantee that sunlight would reach the cells ? What happens At night ?

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