[time-nuts] Sidereal timekeeping
iovane at inwind.it
iovane at inwind.it
Mon May 16 10:02:06 UTC 2011
The background of my request is an OT story. Just to mention briefly, I already
have an ordinary (non-radio-controlled) clock machine which turns a miniature
torsion balance in a sealed glass vessel. It runs on a single AA battery. No
extreme accuracy needed. I wont to modify the rate to sidereal, and might have
to replicate the setup too. I figure that the solution I should pursue is
getting the "odd" crystals.
Now it is clear to me that I have to explore two options, a) contacting a
crystal manufacturer, b) modifying 32768 crystals.
Thanks,
Antonio
hmurray at megapathdsl.net wrote:
>
>> does anybody out there have any ideas as where to find a 32859Hz crystal
(1/
>> 2 that value would be better) to be used to replace 32768 crystals in
>> ordinary clocks? I think that 32768 crystals cannot be dragged that much.
>> I've already read the JimLux article somewhere on the web, but I would be
>> pleased finding a simpler solution. Also, I already have computer programs
>> that show sidereal time.
>
>I think it depends upon what you mean by "ordinary clocks".
>
>Most of the recent wall clocks I've seen are battery powered (single AA) and
>resynchronize nightly via WWVB.
>
>If you want sidereal time, you won't have anything to synchronize to. What
>sort of accuracy are you interested in? If you want reasonable accuracy,
you
>will need an external signal. (You can provide power over the same cable.)
>
>My straw man would be to send 32859Hz down coax or twisted pair and feed it
>into the xtal-in pin on the clock chip. I'm not sure how to set the time.
>You can cut the lead to the antenna to make sure it doesn't sync to WWVB.
>
>You can make 32859Hz from a PIC (or any micro you like) running off any
handy
>frequency. Given that this is time-nuts, I'd suggest 10 MHz from a GPSDO.
>
>It might be simpler to dump the 32KHz and WWVB chip and drive the motor
>directly from a 1 PPS signal. Just use a sidereal second rather than a
>normal second.
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