What would be the best....

... LED lamp assembly to use for a science experiment that involves a potato, a penny, a zinc nail and copper wire?

Would it be better to use one that is normally powered by a single lithium battery or a CR2?

Has anyone done this experiment before and does it work with a full lamp assembly or should it be simpler?

The potato/penny/zinc will produce only a bit less than 1.5 volts IIRC. As much as I hate to admit it you'd be best off with a 1.2V incan. Or I might have an LED 5mm PR style (flanged) unit that would work. I'd have to see if I have one left. How soon do you need it?

An white LED by itself is a three potato device. If you add additional circuitry to step up the voltage, or use one with the circuitry built in like Wits' End is mentioning, you could get by with one potato.

What are you trying to do?

Cook the potato, zinc plate a penny, copper plate a nail, light a light bulb, demonstrate resistance or what?

I have seen similar where a small LCD clock is powered by the potato setup. I don't believe that there will be enough power to light any sort of light (LED or incandescent).

-Bill

Herb... the info that I've found on the net... (I've printed out three different sources)... all recommend an LED. And the experiment is due on Wednesday... yeah, that's the day after tomorrow... /ubbthreads/images/graemlins/icon6.gif ... Fortunately, this is not for MY kid. It's for one of kids of one of my co-workers.

HEY!! Wait uh minute! It says here. "Small lightbulb - flashlight or penlight bulbs work best..." What about one of the glow sticks you sent me, Herb? /ubbthreads/images/graemlins/grin.gif Just remove the three little batteries and touch the copper wires to the little strip of metal in the "battery tube"? Think that will work?

Wouldn't "three little batteries" be comparable to the "three potatos" that Empath is referring to?

I'm not thinking the glow stick led will work with one potato either? Each battery in that glow stick is 1.5 volts and a single potato is <1.5, yes?

What about a red LED? They don't take as much as a white one IIRC...

The strip that is in there is the positive lead. You'd be best off pushing the LED into the battery compartment, I use a pen cap or other plastic 'pointy thing'. That would give you the LED sort of mounted on a little pedestal, that would make it easier to handle. If you used the color changing one (did I send you one?) it would be impressive, assuming it lights /ubbthreads/images/graemlins/smile.gif . You could use a couple potatoes/pennies etc to increase the voltage. Wire them in series (LED to penny to nail to penny to nail to LED) The LED does reqire the voltage going in the right direction so hook it up with a touch to see if it lights and if it doesn't reverse it and see if it lights.
Best of luck to your friend /ubbthreads/images/graemlins/smile.gif
Pre:EDIT I see Empath already mentioned the series idea. I think that might be more impressive.

Hmmm.. maybe that 1.5V Solitaire bulb may actually be useful. /ubbthreads/images/graemlins/thinking.gif it still lights on 1.2V NiMH, because at one point of time, I actually used a NiMH to power the Solitaire because I had two sitting around doing nothing. Then I saw the light and became One with the Light.. ie. a flashaholic. /ubbthreads/images/graemlins/grin.gif

Two potatoes may give you enough juice (pardon the expression) to power a red LED. Try a red 5mm LED, their forward voltage is 2.7-3V. It might be enough.



Now, for the flashaholic way to get 3 potatoes worth of light out of 1 potato...

Take 1 potato. Make it a large one.

Core the potato. Take out the core.

Cut out the center of the core, stuff 3AA-to-D holder inside with the biggest, baddest AA NiMH, replace ends of the core, epoxy in place. Insert leads to direct-drive UX1J Lux3. /ubbthreads/images/graemlins/grin.gif

yh, that would work too!

Thanks for all of the help guys! /ubbthreads/images/graemlins/happy14.gif I've printed out this thread to give to my girlfriend. /ubbthreads/images/graemlins/grin.gif

And yes, Herb... you did send me one of the color changing ones... and that is the one I'll let them borrow. I can't wait to hear how this turns out! And people laugh at me for my "flashlight board"... they sure knew who to come to for this though, didn't they? /ubbthreads/images/graemlins/smirk.gif

If you took the circuit out of a Dorcy AAA, it would light on <1.5V. It would be less current draw than a Solitare bulb.

Huh? This sounds very interesting. A potato can power an LED with some other weird stuff? I know zinc and copper can be found in batteries, but potato? Is there a guide to this experiment?

[ QUOTE ]
KevinL said:
Now, for the flashaholic way to get 3 potatoes worth of light out of 1 potato...

Take 1 potato. Make it a large one.

Core the potato. Take out the core.

Cut out the center of the core, stuff 3AA-to-D holder inside with the biggest, baddest AA NiMH, replace ends of the core, epoxy in place. Insert leads to direct-drive UX1J Lux3. /ubbthreads/images/graemlins/grin.gif

[/ QUOTE ]
/ubbthreads/images/graemlins/crackup.gif I was thinking along the same lines!

In reply to Mags' question:

If you put two dissimilar metals in an acid bath, they will produce an electric current. That is how batteries work and that is also how you can stick metal things in food and get a current. It is a fairly common school science fair project that you can search up on the internet fairly easily. I have seen it done with an orange and two coins.

Everyone uses those darned spuds... Years ago my little sister asked me to help her with a similar little bio-power generation science project. Instead of an LED we hooked up a surplus meter movement to a grapefruit with a roofing nail and a penny. When we shoved the penny and the nail into the grapfruit the needle on that little meter movement instantly slammed to the far end of its' travel. It's newly bent tip then slowly sank back to near zero, never to move again.

Ban the Spud. Think Citrus!


Ordin

Take a Stainless Steel pan, a meal made with Tomatoe Sauce and aluminium foil. Within an hour you can have holes appear in the foil. And nasty aluminium 'web' into your Lasagna /ubbthreads/images/graemlins/icon15.gif /ubbthreads/images/graemlins/thinking.gif .
Back OT. Hope it works for your friends child /ubbthreads/images/graemlins/smile.gif .

[ QUOTE ]
Sasha said:What would be the best LED lamp assembly to use for a science experiment that involves a potato, a penny, a zinc nail and copper wire?

[/ QUOTE ]
I don't think you're going to get anything to light off of such a miniscule current producer like that, but a red micro LED ( with the classroom lights turned off ) is your best bet if you have to make something glow instead of just deflecting a meter. Quite frankly, you'd be better off hiding a 9V battery in the potato, knocking everyone's socks off with how bright it is, then selling your own special 'Miracle Gro' to the class, promising it will produce similar potatoes and end the world's energy & pollution problems if grown juuuuuuust right. /ubbthreads/images/graemlins/tongue.gif

.....Make sure you've left town by th time the first crop of potatoes starts sproutin too. Those things can hurt if people start throwing them at you.

use 2 sets of plates at opposite ends in series.
a good high brightness red should work fine.
did such a setup with lemons in school to power a small motor.