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Piezoelectricity Experiments. Help Needed! Answered

I'm currently experimenting with piezoelectricity.

And at the moment my experiment is limited to just a few piezo sparkers extracted from cigarette lighters.

The sparker works with observable voltage spike on my multimeter. No voltage spike however when I use the tiny crystal (the size of a zippo flint) taken out from the sparker.
I was trying to replicate this experiment (without the oscilloscope):
Piezoelectric Rochelle Salt

Another thing, Would continuous vibration produce continuous voltage?

It is known that piezo crystals produce high voltage, yet very low current. What are the options to increase the current? Would winding un-insulated copper wire around it (or any kind of contact with conductive metal) increase the current?

Apart from lighter, what other surplus sources of piezoelectric crystals (i.e. quartz, PZT, Rochelle)? Can the crystal in RC toys, radios be used to generate electricity?

Although there is the option to grow my own Rochelle salt, I'm not looking into it at the moment since it's going to take quite a while to grow.

Thanks in advance!

13 Replies

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westfw (author)2008-04-15

The piezoelectric sounder disks from smoke alarms, cheap noisy toys, and so on can work in reverse (as chooseausername points out.) These are also available on the surplus market, sometimes at attractive prices.
Some modern CCFL inverters are supposed to be based on piezoelectric transformers, that seem like a pretty neat idea...

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scrappunk (author)2008-04-14

Hey I have inherited about a hundred and fifty pounds of quartz crystals and I want to start experimenting with piezo electrics to either charge a battery then power an led or just light an led in bursts. Any suggestions on how to use the quartz to this end?

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RimstarOrg (author)2008-03-01

I'm the one who's experiment you're trying to replicate (http://rimstar.org is my website.) I'm not familiar with the crystal you're using but often you strike the crystal on one side and the voltage appears across sides at 90 degrees to it. That's why with my experiment you see the crystal wedged between the two aluminium foil cushions for measuring and then I strike the top. I had to keep rotating and twisting the crystal around until I found which side to strike and which sides to measure across. Are you reproducing the geometry of how it was done wherever you got it from? Other than that, all I can think of is, as tanntraad suggested, you may not be hitting it hard enough, or you broke it (don't know how.) In case it helps, here're tests done with an ignitor crystal:
http://rimstar.org/materials/piezo/ignitor1.htm

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tanntraad (author)2007-11-23

The strain on the crystal (when struck) in piezoelectric lighters is like hitting a hammer on a nail. In fact, this is exactly what's going on inside the sparker. I've done some experimenting on this; http://folk.ntnu.no/bardlund/lighteraccelerometer.jsp
Gonna catch up on that one day..

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Kiteman (author)2007-11-23

I would guess that the crystal inside the sparker is put under much greater strain that when you take it out and bash it.

The crystals in many mint sweets are piezoelectric, but don't spark until they are strained to the limit (i.e. crack) - maybe (still guessing here) the sparkers are designed to use leverage to put a near-fatal strain on the crystal?

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chooseausername (author)2007-11-23

What are the options to increase the current?

Use more crystals in parallel ?

An other two phase method (but difficult to implement) :
1) Charge a line of capacitors (in series) with the high voltage.
2) Put every charged capacitors of the line in parallel and discharge them all together (divide the voltage, and multiply the current)

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Goodhart (author)2007-11-23

I can answer this part:

Another thing, Would continuous vibration produce continuous voltage?

There is no such thing as continuous vibration. A vibration, by very nature, moves in one direction, makes a FULL stop, then reverts back in the other direction. A continuous vibration would mean movement in one direction until it breaks.
What you are speaking of however, the continuous oscillation, will produce voltage up to the full stop, and then start again when the vibration or oscillation reverts in the other direction. A piezo electric buzzer illustrates this (in reverse) quite well.

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chooseausername (author)Goodhart2007-11-23

A piezo electric buzzer illustrates this (in reverse) quite well

BTW, I found it's possible to use this kind of piezoelectric speakers (see the picture) as microphones.

So, yes, a tiny vibration will generate an tiny alternating voltage.

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chooseausername (author)2007-11-23

Can the crystal in RC toys, radios be used to generate electricity?

If it's possible, I don't think it would easy ...

I, once, opened an old oscillator and found a thin disc of crystal in sandwich between the two terminals.
I don't think modern and recent crystal oscillators contain a bigger crystal :o/

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Juklop (author)2007-11-23

If i knew what you were talking about I would post something useful, but alas.

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gyromild (author)Juklop2007-11-23

I've clarified a few thing in the post. Hope they help. :)

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guyfrom7up (author)2007-11-23

BUMP can you show your setup when you're measuring the voltage?

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gyromild (author)guyfrom7up2007-11-23

Sorry, no picture of the setup, however, I've provided the link (in the post) to the experiment I'm trying to replicate. I used multimeter instead of oscilloscope, and sparker's PZT crystal instead of Rochelle salt.

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