crystal oscillator question...thx

[Sommes]

How to adjust the oscillation frequency from the output frequency of 1MHz
crystal oscillator?
Thanks

 

[BobGardner]

How to adjust the oscillation frequency from the output frequency of 1MHz
crystal oscillator?
=======================

You can pull the freq off a little lo by adding caps... few tenths of a
percent....

 

[Sommes]

but what if I want the range from 1KHz to 1MHz?
Thank you very much

 

[Sommes]

I am doing a analog project.
The topic: High stability variable oscillator
Select and test an appropriate digital oscillator circuit for producing an
accurate variable oscillation from 1kHz to 1MHz

What I think is I have to use crystal oscillator to make stable oscillation.
I will chose 1MHz crystal oscillation...after I may need to adjust 1MHz to
1KHz range.

Please let me know the right track...Thanks...

 

[Sommes]

Thank you mike. I've a stupid question to ask.
What if I use 1MHz crystal oscillator produce frequency and make another
circuit(parts) to adjust the frequency from 1KHz to 1MHz?

Thanks for reply

 

[BobGardner]

I am doing a analog project.
The topic: High stability variable oscillator
Select and test an appropriate digital oscillator circuit for producing an
accurate variable oscillation from 1kHz to 1MHz
=========================

So are you supposed to use analog or digital circuits to do this? Also, you
don't mention the freq accuracy you need.... .1hz steps, 1hz steps, 10 hz
steps???
If you do this digitally, you are designing a frequency synthesizer... divide
down a master clock that is the least common multiple of all the frequencies
you want with a big counter chain.

 

[Bob Masta]

On Wed, 27 Oct 2004 01:17:24 +1000, "Sommes" <j@jl.com> wrote:

Thank you mike. I've a stupid question to ask.
What if I use 1MHz crystal oscillator produce frequency and make another
circuit(parts) to adjust the frequency from 1KHz to 1MHz?

Thanks for reply


To echo the prior response, please tell what you really need to do.

If you need high stability and only need certain frequencies in
the 1kHz-1Mhz range, you can use frequency dividers.
If you need the stablity of a crystal, then obviously the output
frequency can't be under control of something like an
adjustable potentiometer... only a digital control would
make sense.




Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com

 

[Michael Black]

"Sommes" (j@jl.com) writes:

but what if I want the range from 1KHz to 1MHz?
Thank you very much


Then you don't use a crystal.

You use a crystal when you want stable frequency source, and/or one
where you can be sure of the frequency.

It's stable because it's not variable. Any attempt at moving a crystal
more than a very small percentage will result in a loss of that stability,
and the crystal will not be controlling the frequency.

If you need a wider range, then you use an oscillator where a coil
and capacitor determine the frequency. This is inherently variable, though
of course it won't be as stable, and you'll need some means of measuring
the frequency.

Once ICs became commonly available, PLL synthesizers became common. This
use an LC oscillator, but lock it to a crystal oscillator; a combination of
stability and yet changeable frequency. But this does add to the complication
of the circuit.

More recently, a common choice would be a DDS IC, "direct digital synthesis".

It might be better to say what you want to do, and then the solution may
be more obvious.

Michael