HarveyH42

I was out inspecting my orange tree, to see what kind of crop to expect this year (a little pitiful), and got kind of a strange idea. I was thinking of a class demonstration from grade from grade school (35 years or so ago...), about using a lemon for battery power. I don't remember the details, but figure many of you have seen the same demo, and might know.

I realize the voltage/current isn't great, and the electrodes must be dissimilar metals. Greater the surface area, greater the output.

My idea is to build something that I can shove into the oranges as they develop on the tree, and produce enough power to light an LED, or maybe even run a low voltage microcontroller (flashy LEDs). Maybe a joule thief would work.

A few details I need to work out, are the plate/electrodes. Need some common metals, not too corrosive as this is intended to last a year. Need a surface area, but must keep damage to the fruit minimal. Thinking pins or nails, thin rods. Need to know how much power a single fruit can produce, so I can decide how many to wire series/parallel to obtain a useful power level.

It'll be several months before the fruit will be large enough to mess with, but it's a good time to get ready.

Hero999

The energy comes from the metals not the fruit so the more power you want the less time the metals will last for.

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Krumlink

The metals react to the acid in the Orange, so all you need is copper/zinc and a form of acid (citric acid)

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audioguru

Many people won't buy damaged oranges with pin pricks with copper oxide around them.

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HarveyH42

These oranges aren't that great. Mostly they are only good for juicing, small and full of seeds. A lot more work then they are worth. Past four or five years, I have gotten enough to make even one decent pitcher of juice. I just have the one tree, but there are a lot of citrus trees through out the neighborhood. Just thought it might be a neat free-energy idea. If I could come up with small, cheap, and simple, I figured I could light up the tree, or maybe do a few randomly around town while out walking the dog. Just to see how long before someone takes them.

theinfamousbob

They both hit the nail on the head, or the metals into the orange. I'm guessing that the oranges wouldn't taste very good after the process. Although a joule thief would be cool; use little hooks to dig into the orange. Plus it'd be a great exercise in building something that's REALLY tiny. You could group multiple ones on one orange.

Either way, you'd be confusing people. That alone is worth it...

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HarveyH42

Done a little searching, but not find just the zinc/copper classic combo. Seems they are good for a quick and simple demonstration, but corrode kind of quickly. I'm guessing this is the only way it works, and a few day are the best to be hoped for. I'm going to make another joule thief later today, with a red or amber LED, and see what it'll take to light with a store bought orange (been sitting in the frig a few weeks now...).

They seem to get 0.9 volts with a penny (Canadian), and a zinc plated screw, but very low current. Most of the sites I checked, use three cells just to get a red LED to light dimly. Not sure if the joule thief will make a huge difference there. Good thing about an orange tree though, can always add more cells as needed.

Hero999

The thing it you're not actually getting any power from the tree so it's a waste of time.

Try magnesium and copper, it'll give a higher current and much more voltage but won't last nearly as long. As I said before, it depends on how dissimilar the metals are and no energy is coming from the tree.

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mashersmasher

maybe if you juiced the unusable ones and used those for power?

KMoffett

When I saw the subject line "Tree Power" I immediately visualized someone mounting piezo elements all over tree limbs and generating electricity as they flex in the wind. With articles in big electronics industry magazines touting generating electricity by pieze elements in clothing...it didn't seem all that far fetched.

Ken

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audioguru

A guy in one of these forums wants to replace the floor tiles in a big Wal-Mart store with piezo tiles to generate a huge amout of electricity.

Think about all the wiring involved.
Think about the huge battery needed.
Think about the expense.
Think about the tiny amount of power that will be made.

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HarveyH42

I made a joule thief with a red LED. Really bright off rechargeable AA. I've got a bunch copper ground strap, about an inch wide. It wouldn't polish, plastic coated, so burned it off with a torch (flame, not flashlight ). Took a shiny metal strip out of an old NiCd battery pack, not sure what kind of metal, 1/4 inch wide. Couldn't solder to it at all. It would get hot enough to melt the solder, just beaded up. Alligator clip... The orange in my frig was a little dehydrated, so might have been a failure factor. Tried as a single cell, didn't light. Cut it in half, tried in parallel, still nothing. Should have put a meter on it, but figure the orange was just to far gone. Will see if there are still grapefruit on the tree down the street. About time to let the dog drag me around the block again...

Hero999

The voltage was probably too to work the Joul thief, you should've connected them in series.

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HarveyH42

I read the joule thief is good from 0.3 volts to 3.0 volts. A single lemon cell produces maybe 0.9 volts, but little current. That's why I went parallel. I'll pick up some fresh fruit, and get it going. One pitiful orange wasn't even close.

HarveyH42

Amazing coincidence, was checking out instructables.com, and this one just added...

http://www.instructables.com/id/supercharged-lemon/

If this is what it takes, then my idea isn't likely to work. The lemon is much too damaged to survive long on a tree. Even if I divide the plates into separate fruits, still pretty invasive. Winding that transformer would kind of suck, ten turns isn't bad, but 50-60...

Still going to give mine a go, even it takes 4 or 5 oranges...