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Has anybody here worked with crystal oscillators, like for a watch, etc?

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posted on Apr, 25 2008 @ 04:34 PM
I just got a crystal the other day, and was interested in its piezo properties for things like timing in watches or a cheap radio. It's hard to believe something so plain looking is actually useful for these things, but the material I've been reading says this can be essential. I'm curious as to why there are no noticeable effects when you physically hold the rock and try to test the piezo aspect of it. I knocked/pressed the thing against a hollow rod and the rock made a grating+buzzing+funny pitched sound. So, I guess.. this is it?
Didn't notice any static going on around it so I figured I had a dud for a crystal. It sure is squashed looking for one thing, and instead of being hexagonal in shape it's actually closer to a trapezoid when you stand it up straight and look at it over top from the tip on down. It's clear, single terminated (looks like it's been broke off - probably natural though), but I see bunch of indentations and wonder if it's damaged. *shrugs*

Is this normal? Are there any good ways to check for this piezo stuff before I get a multimeter? Also, how are the connections supposed to be applied? Is it the same like a battery?

Forgive my noobishness. Thanks.

posted on Apr, 25 2008 @ 11:08 PM
A piezoelectric crystal doesn't actually produce very much current, and I doubt you could apply enough strain to the crystal to produce anything that you could feel. Depending on what frequency the crystal is, you could have heard something like you describe.

I took a few minutes after writing the above to take a quick look at the equations on wikipedia, and depending on the size of the crystal, you could definitely have heard it oscillate, though I never thought about that aspect of it before. (here)

I've never actually played with the crystals themselves, but I have used oscillators which contain those crystals somewhere inside them. I suppose you could borrow a voltmeter and place each of the leads on the crystal ends and see if you got a voltage or not. If you got zero volts, then your crystal doesn't work. (or the leads are in the wrong place!
) I'm not sure what a typical reading would be on one of those crystals for voltage, though. The oscillators I used had external power applied to them, and then they turned a DC current into an AC one by giving it the frequency of the crystal, and if I remember right, they were something like 400 kHz, which is out of hearing range.

Again, I don't really know how much current/voltage one of those crystals would produce, but if it's enough, you could just take a wire and connect it to both ends of the crystal. Have you ever done that with a 1.5 volt battery? The wire will get hot really fast, and you probably won't be able to hold it there for long, unless it is insulated. That would cost nothing in equipment to test, but it might not work if the crystal is too weak to heat up the wire noticeably.

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