wyzzymoon

Is it possible to build a Quartz Oscilator from uncut quartz?

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Hi all, I've got a question about crystals and crystal oscillators.
I want to build one from a uncut piece of quartz crystal. Let's say 1x1x5 cm. A bit bigger or smaller is all fine but no millimeter thin plate of cut crystal.
I understand that for a reliable crystal oscillator quartz plates need to be thin and cut at specific angles,  but I don't care what frequency it has, I just want it to do something.
Either create a measurable frequency or vibrate measurably.  

Would this be possible at all?
Can you get any frequency data from an uncut raw piece of quartz?

So far I've tried connecting a crystal with 2 electrodes on it to a frequency tester but no results.
Thanks in advance!

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In principle, yes. But I'm not sure how practical it is.

You would need to find out what the resonant frequency of the crystal is between two surfaces. 

You would need to make two electrons on those surfaces (vacuum deposition or electroplating, perhaps)

Then build an oscillator circuit suitable for use with the crystal as a resonant element. From what I remember of oscillator design this would require capacitors to match the capacitance of the crystal (which might be tricky).

Getting an oscillator to operate stably at the very low frequency of the crystal might be tricky.

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7 minutes ago, Strange said:

In principle, yes. But I'm not sure how practical it is. 

Thanks for the quick replay! Since I want to do this for art purposes the practicality (or lack there of) is not really a problem.

7 minutes ago, Strange said:

You would need to find out what the resonant frequency of the crystal is between two surfaces. 

This would be different for each crystal I presume? How would I go about finding that out? Is that measurable or would I need to experiment with some kind of variable circuit?

7 minutes ago, Strange said:

You would need to make two electrons on those surfaces (vacuum deposition or electroplating, perhaps)

Wouldn't it work by just pressing two metal plates against it? quartz naturally has flat sides.

7 minutes ago, Strange said:

Getting an oscillator to operate stably at the very low frequency of the crystal might be tricky.

What do you mean with unstable in this case? if it would not be stable, would I get not the same frequency all the time or would it just not work well?

I understand if you don't have an answer to all these questions, I don't understand much about crystal oscillators yet but all the resources I can find all have a practical approach so it's very hard to find information about what could be done even if it would be unpractical (again, art is the goal, not precise timing like what crystal osc are usually meant for. )

 

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16 minutes ago, wyzzymoon said:

This would be different for each crystal I presume? How would I go about finding that out? Is that measurable or would I need to experiment with some kind of variable circuit?

Well, if you can attach electrodes to it, you could try tapping it and observing the result on an oscilloscope. You might get a few cycles of voltage as it "rings" (like a tuning fork).

18 minutes ago, wyzzymoon said:

Wouldn't it work by just pressing two metal plates against it? quartz naturally has flat sides.

I really don't know. In commercial crystals, the electrodes are bonded to the surface, but I don't know how.

18 minutes ago, wyzzymoon said:

What do you mean with unstable in this case? if it would not be stable, would I get not the same frequency all the time or would it just not work well?

Designing the electronics for a quartz oscillator from scratch is quite complex, even with manufactured crystals. Getting it to oscillate reliably can be hard. 

 

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Posted (edited)
1 hour ago, wyzzymoon said:


Would this be possible at all?

Yes you could but bonding is better because the mechanical vibration frequency of the crystal is tranducted into an electrical frequency by the bonded electrodes vibrating with the surfaces they are bonded to. Pressing/clamping the electrodes on means you are opposing the mechaical vibration of the crystal.
This introduces a varying capacitance into the circuit, but you need other circuit components to sustain oscillation and create an electrical oscillator.

Edited by studiot

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