"Standard" Crystals?

So, I was browsing the electronic goldmine today, and I came across these. What do they do and how are they used? Do you apply voltage to the leads and it emits rf in all directions or what?

rickharris6 years ago
Link not working for me..

A crystal is normally a tuned Pizeo crystal which is normally used to provide a set precise frequency reference for some other electronic circuit or micro controller.

Your link is broken, but I am guessing it was pointing here:

A "standard" quartz crystal is a real physical chunk of quartz with two electrodes plated, or otherwise attached, to two sides of it, for the purpose of coupling it electrically to an external circuit. As an electrical device, it has two terminals.

This circuit element exhibits resonance,
much like a bell or a tuning fork. If you were to "hit" it, with a small voltage pulse via its electrodes, it would "ring", which is to say if you examined the voltage across its electrodes, a short time after hitting it with the voltage pulse, you would see a decaying sinusoidal voltage at its resonant frequency (or frequencies?)

The following Wiki article has a bunch of info on crystals, and also pictures of what they look inside, if you strip away the little protective metal cases:

Of course there are better ways to make a true, contstant amplitude, oscillator.  I means something more subtle  than just hitting something to make it ring.  I think the usual circuit for a crystal-based oscillator is a Pierce oscillator.

In practice, building your own crystal oscillator can be kind of tricky, so that's why complete crystal-oscillator ICs are sold too, as you've already discovered here:
As an electrical device, this complete oscillator has three terminals: V+, ground, and signal-output.  Often it comes in a rectangular package, with 4 pins, where one of the four pins is redundant or unconnected.
AndyGadget6 years ago
Your link isn't working, but if these are standard crystals they are meant to be used with other components in an oscillator circuit and they will lock the frequency of the oscillator to the crystal frequency.