Building a Voltaic pile

Sorry for the wide distribution, but I'm casting a wide net in the hopes of a speedy solution.
My daughter is trying to build a simple Volta's pile for a school
project. We took twelve shiny new US pennies, twelve circles of aluminum foil cut slightly smaller than the pennies, and twelve 1-inch squares of paper towel soaked in salt water. I can't seem to get any current off of the thing. First we tried touching two wires together in a darkroom, but couldn't see any sparks. Then I got out my trusty Radio Shack battery tester, but its needle wouldn't budge. Then I soaked the paper towels in heavily salted vinegar, but got the same results. I also tried using several individual pennies and pieces of foil, but still can't get the battery tester to measure anything.
I'm pretty sure that the battery tester's uncalibrated meter is measuring voltage, not current, so I'd expect it to show *something*. All US pennies since 1982 are copper-coated zinc wafers, so I'd expect there to be enough Cu to react with the vinegar. The foil is plain heavy-duty Reynolds wrap for baking, so I don't expect that there's any coating. The salt is Morton's iodized table salt. My stranded wire will light a flashlight bulb from a AA cell, so it doesn't have any internal breaks.
This whole thing has me stumped. If anyone can offer any suggestions, I'd love to hear them; otherwise I'll probably try using an old piece of copper pipe wrapped in wet paper towels and foil, and if that doesn't work I'll buy a steel bowl and try a ball of foil floating in vinegar.
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That pile is not going to be capable of generating enough current to make a visible spark nor drive a battery tester. Try measuring the voltage using a digital multimeter. They require far less current; I'm sure you read some kind of voltage.
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the battery tester is probably meant to read current to tell you how good the battery is.
also, get rid of the salt, you want acid like vinegar or lemon juice or dissolved vitamin c tablets. and remember, the towels need to be very wet so the metals have a good path to drive ions through liquid... but they shouldn't be so wet that the acid bridges between cells or it essentially just shorts them out. a better material for the dividers is blotting paper, but the towels will work if you get them wet enough.
just as a quick sanity check, with apple cider vinegar, one penny, and one square of foil I get .7v at about 2ma. that won't be enough to budge a battery meter but it registers well on a volt meter. and remember, the current is limited by the diameter of the penny and foil, stacking more in series won't increase the current it can generate only the voltage. you need more surface area to get more current. or hook them in parallel.

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Many thanks to everyone who replied!
Dave wrote:

Here's the incredibly cheap tester I used: http://tinyurl.com/8djef -or- http://www.radioshack.com/product/index.jsp?productId !03165&cp 32058.2032235.2032306&parentPagemily

That may be my problem, then. I worried about the foil shorting things out, but not the paper. Those 1" squares flopped everywhere.

As an ex-EE, I'm ashamed to say that I haven't seen my voltmeter in ages. I guess I need to go buy a new one.

We're working off of a project in a book which claimed that twelve cells in series would create a visible spark. Oh, well.
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snipped-for-privacy@gmail.com wrote:

Connect it to a big electrolytic capacitor if that's permissible and let it charge for a little while. You should be able to get a decent spark when it's shorted.
Roy Lewallen
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As an ex-EE, you might also appreciate that a little added inductance in the circuit could enhance the sparking effect nicely, if that's your aim.
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On Sun, 11 Dec 2005 16:36:12 GMT, "John R. Copeland"

DMMs can be purchased very cheaply nowadays, some of them even have transistor and diode testing.

Did you use alkalines or NiCd cells? Carbon-Zinc or Ni-Mh don't work so well.

Or even a large capacitor, to compensate for the internal impedance of the batteries.
Sig: "Whether you believe you can do a thing or not, you are right." -Henry Ford
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Rotes Sapiens wrote:

nuh uh, there are accidents
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p.s. make sure the foil isn't some of that new anti-stick coated stuff, that may act as an insulator.

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Come to think of it, the oxide layer on aluminium almost certainly won't make it good choice for this sort of experiment. Good electrode potential, poor reaction kinetics.
Cheers, J/.
--
John Beardmore

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On 12/10/05 6:35 AM, in article snipped-for-privacy@z14g2000cwz.googlegroups.com, " snipped-for-privacy@gmail.com"

My guess is that the oxide coating on the Al foil is preventing conduction. Even if you scrape the foil, the oxide will reform. Use your meter in the ohmmeter mode to see if the foil contacts the penny electrically.
Even so, this is not a good way to go. You would be better off removing the Cu from the pennies so as to get Zn disks. You should be able to find Zn sheet or at least galvanized steel. These will form the anodes of the cell. Get sheet Cu for the cathodes. If nowhere else, sheet Cu is available at many garden centers for repelling snails.
It would be best to use a diluted real acid. Start with 5:1 (water:acid) for the HCl or 10:1 for the H2SO4. Hydrochloric acid is available at pool supply stores as muriatic acid. Sulfuric acid is also good and available as drain cleaner. Be careful with either one, especially the concentrated H2SO4. Always add the acid to the standing water. Ammonium sulfate might also do the job, because it will be acidic in water solution.
Bill
-- Ferme le Bush
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try some pennies and get some galvanized sheet metal...any heating and cooling outfit can cut you some little squares of sheetmetal. might even have some copper sheet laying around...or you could get some copper pipe and cut it down the middle...spread and beat out flat with hammer and cut some squares.....or you could get some galvanized washers at the hardware store.... hardware store alsom might have small piece of galvanized metal strapping they could let you have.
try lemon juice as an acid.....and maybe do some research on sal ammoniac....I think thats what people used years ago to make homemade cells......
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----------------------------

Put the lemon juice on blotting paper between the pennies and galvanised washers. This keeps the electrolyte where it belongs. Alternatively stick a copper wire and a galvanised nail into a lemon.
--

Don Kelly @shawcross.ca
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snipped-for-privacy@hotmail.com wrote:

I wasn't going to go quite that far yet, although I was thinking about a length of copper pipe wrapped in vinegar-soaked paper towels, with aluminum foil wrapped around that. Theoretically, that should produce 1.6 volts, and the surface area of the pipe should generate a fair current.

I recall seeing a cell made from a penny and a dime stuck into a lemon. I'll look into the sal ammoniac as well. Thanks!
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