[time-nuts] How to get 32.768KHz from 10MHz.

Neon John jgd at johngsbbq.com
Mon Jul 28 19:22:37 EDT 2008


On Wed, 23 Jul 2008 15:22:08 -0700, Jim Lux <James.P.Lux at jpl.nasa.gov> wrote:

>At 03:01 PM 7/23/2008, Mike S wrote:

>>You're missing the point. The application is to drive a common, readily
>>available consumer clock. Simple and cheap. It can be done with a
>>single $1 PIC. You could spend $20 or $100 and not get better results
>>for the application. If you can describe a way of doing it for $0.50,
>>please do.
>
>
>But this is time-nuts... Any approach that doesn't have the 
>performance of a hydrogen maser or cryogenic sapphire resonator just 
>isn't good enough.  Why, we haven't even started on how to build a 
>radial ruling engine to make sure the clock face is precisely divided 
>into 60 segments to ppb accuracy.

Yep.  There's turd polishing and then there is time nuts turd polishing. Going
for the angstrom finish on the turd.  The latter sometimes makes me grit my
teeth....

>
>Based on the clocks I've taken apart, dividing the 10MHz down to 1 Hz 
>is probably your best bet, rather than trying to hit 32768. However, 
>I don't know of a non-programmable single chip solution that will do 
>a divide by 1E7. If you want programmable chips, there's countless 
>ways, some more elegant than others.

Seems to me that all the solutions proposed so far are a bit complex, trying
to go for the 32khz frequency when that's not necessary.  The quartz analog
clockworks has a one or two winding stepper motor.  The SIMPLEST solution is
to drive those coils directly with the PIC output and scrap the rest of the
circuitry.

With some clever fiddling, one could use one of the 8 pin PICs and that WOULD
get the solution cost down to around 50 cents :-)

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
Save the whales, collect the whole set!





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