[time-nuts] Bye-Bye Crystals

Adrian Godwin artgodwin at gmail.com
Tue Mar 14 06:35:05 EDT 2017


For interest, and as part of art project involving crystals. I want to show
a less third-age usage than is common in that space :).Acceleration effect
on frequency may also be featured. No way would I do it for cost or quality.

Like you, I normally use packaged oscillators for most things - though I do
still encounter plenty of the passive crystals on cheap microprocessor
boards. The oscillators may be $1, but I suspect those crystals are 10c.

My first encounters with crystals were probably with the inverter
oscillators of early micros. I gather there's a lot more black magic in
their design than analysis, and as a result they used to have problems
oscillating. The oscillators built into modern micros are a lot better.
I'll probably use a more carefully characterised amplifier if i cut my own
crystal.

On Tue, Mar 14, 2017 at 8:44 AM, Hal Murray <hmurray at megapathdsl.net> wrote:

>
> artgodwin at gmail.com said:
> > I'm not after quality - I do have an application in mind but it doesn't
> need
> > to compete with mass production. Just wondering if it's feasible to make
> > something crude that will resonate.
>
> Are you doing this for fun or ???
>
> Feasible?  Sure.  Cheaper?  That depends.
>
> The cost difference between a complete oscillator package and a simple
> crystal is tiny.  The osc is often cheaper if you include board space or
> engineering time.
>
> Is your background digital or analog?  Do you want a sine wave or a clock?
>
> My background is primarily digital.  If the chip you are using has 2 pins
> setup to drive a crystal, you can probably get it to run reliably by
> following the data sheet and/or app notes.  The usual recipe is 2 tiny caps
> and a big resistor.  (big in resistance, not physically big)
>
> An advantage of using a crystal with the on-chip amplifier that I didn't
> mention last time is that you save the osc power if you power down that
> corner of the chip.
>
> If you want a sine wave, you are out of my comfort zone.  I'd probably look
> in ham radio literature.
>
> They make logic chips like a 74HCU04, U for unbuffered.  One of their uses
> is
> for making oscillators.  I've never done it.  Try google.
>
> --
> These are my opinions.  I hate spam.
>
>
>
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