audioguru

A Joule Thief circuit boosts the voltage by using more current Thjen the power output equals the power input minus some losses). A fruit doesn't produce the current. An entire tree full of fruit might light one LED dimly.

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HarveyH42

I've visited quite a few websites, it seems to take three lemon cells to get a red LED to light, without a joule thief. I do have some doubts about whether small plate size will work, and for how long.

Was wondering where I might find a site, that compares different metals to use as plates. I've only found copper and zinc, and one mention of magnesium and copper. I think they use copper/zinc because its most common and cheapest (who doesn't have a few Canadian pennies laying around). I'd rather stay away from the magnesium, as I remember it burn kind of violently and can't be extinguished easily.

Hero999

That huge 2W resistor looks a bit overkill.

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HarveyH42

Yeah, I hate doing that... I've got a bunch of 1/2 watts I seldom need, but occasionally can't find the right value in anything else.

ka1mwp

http://www.magcap.com/pdf/press_release.pdf

Maybe a repeat in here, but interesting.

Chuck

Nigel Goodwin

Sorry, but it's a complete load of utter rubbish!.

It's just the dissimilar metals in a lemon all over again!.

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ka1mwp

it didn't have anything to do with lemons...just trees in general..
I never ended up following this, I use the company for thier HV tx's.
They got a grant and farmed it out to I think MIT or someplace last I heard..

Nigel Goodwin

It's usually done with lemons, you place two dissimilar metals in a lemon and the chemical reaction generates a small amount of electricity and destroys the electrodes - the tree sap works in the same way, it's the metal being consumed that generates the small amount of electricity.

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WVProfessor

Ken has the right idea.
With some of these big trees you could put a pole to the top and use the wind to pump water or compress air. There would be energy in that, maybe even a few watts.

Hero999

Exactly Nigel, I've been trying to explain this all along. The energy comes from the metals, not the tree. You always get less energy out than what was required to extract the metals from their ores.

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HarveyH42

Not many oranges this year, maybe 30 on the whole tree. These are about as big around as my thumb. Couple of months, and I should be able to try a joule thief. Figure four electrodes, thick copper wire and zinc plated screws.

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erosennin

... Tree Power?
1. Cut down the trees
2. Burn the trees
3. Use the heat to boil water to drive turbines.

Hahaa... how un-environmentally friendly, greenpeace is after me now...

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Hero999

That would be better, at least it's carbon neutral.

I remember seeing some supposidly water powered digital clocks in a camping shop claiming they are environmentally friendly. I wonder how long they would have lasted until the electrodes totally corroded away. It's of course rubbish, the energy to power the clock was still comming from fossil fuels used to separate the electrode metals from their ores.

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atferrari

Try one potato instead of lemon, properly cut in small cubes, (each one in an appropriate recipient) allows for easier series/parallel combination testing.

It works.

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In theory, there is no difference between theory and practice. In practice, however, there is.

Oznog

I don't think the message got to you.

The electrode metals provide the energy, and are fundamentally consumed in the reaction, because you can't get energy for free. The lemon or potato acts as an electrolyte and is just a carrier medium. Salt water works some too. Acids/bases work better than salt water, whether you need an acid or base depends on the plate material.

When the battery is run down, washing out the electrolyte (lemon juice) and replacing it with a fresh lemon will not restore power. To restore the batt would mean replacing the consumable plates.

So unless you can come up with a tree which refines copper/zinc/lead/etc into a higher energy state, it won't be the basis for a battery.

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