Re: [time-nuts] Sidereal timekeeping
Neville,
at present I have not enough skill with micros to solve the problem.
I think I will try modifying a crystal. This would not be that difficult using
a lapping sheet or the like. And opening the can would be quite easy using hot
air. This is the fastest way for me, and the device will continue to be powered
by a simple AA cell, which is a non negligible advantage in my application.
All the best,
Antonio I8IOV
Antonio,
it is quite easy to make an external circuit that uses a 32kHz xtal
and divides
it down to siderial seconds. It is also easy to drive most analog
quartz clock movements from
an external circuit.
Just what signal do you need? What frequency? and what does it drive?
(an alternate polarity
quartz clock motor?)
It can also be done with a micro if you have the skills.
cheers, Neville Michie
On 5/16/11 2:58 PM, iovane@inwind.it wrote:
Neville,
at present I have not enough skill with micros to solve the problem.
I think I will try modifying a crystal. This would not be that difficult using
a lapping sheet or the like. And opening the can would be quite easy using hot
air.
or a fine jeweler's saw or tubing cutter.
As you pointed out, the crystals are cheap, so you can afford to ruin a
few while figuring out how to do it.
(and then, remember us all, when you're a multi-billionaire having
cornered the market on sidereal rate crystals<grin>)
Jim Lux wrote:
On 5/16/11 2:58 PM, iovane@inwind.it wrote:
Neville,
at present I have not enough skill with micros to solve the problem.
I think I will try modifying a crystal. This would not be that
difficult using
a lapping sheet or the like. And opening the can would be quite easy
using hot
air.
or a fine jeweler's saw or tubing cutter.
As you pointed out, the crystals are cheap, so you can afford to ruin
a few while figuring out how to do it.
(and then, remember us all, when you're a multi-billionaire having
cornered the market on sidereal rate crystals<grin>)
Since the 32 kHz crystal is likely to be a tuning fork form, one merely
needs to shorten the tines to increase the frequency.
It may be feasible to do this without removing any of the electrode
metallization.
Bruce
Hi Antonio,
the 32kHz Xtals are 2mm long tuning forks (that is what I believe
although I have not opened one).
You would have very little chance of modifying it and still have
enough Q left for it to oscillate.
As an alternative you could build an external circuit (a few uA at 3V
supply) and generate a signal to inject into
the existing Xtal osc with the Xtal removed.
The type of circuit that I would build would be a cmos binary divider
connected to a quad gate.
The 4 gate inputs connect to selected binary stages of the divider.
When the gate decodes the
selected number, an extra pulse is added to the count chain. The
output is thus shifted to a higher
frequency.
If you are interested I can try to design the circuit for you, I have
intend to build a Siderial clock
dial for my TBolt.
cheers, Neville Michie
On 17/05/2011, at 7:58 AM, iovane@inwind.it wrote:
Neville,
at present I have not enough skill with micros to solve the problem.
I think I will try modifying a crystal. This would not be that
difficult using
a lapping sheet or the like. And opening the can would be quite
easy using hot
air. This is the fastest way for me, and the device will continue
to be powered
by a simple AA cell, which is a non negligible advantage in my
application.
All the best,
Antonio I8IOV
Antonio,
it is quite easy to make an external circuit that uses a 32kHz xtal
and divides
it down to siderial seconds. It is also easy to drive most analog
quartz clock movements from
an external circuit.
Just what signal do you need? What frequency? and what does it drive?
(an alternate polarity
quartz clock motor?)
It can also be done with a micro if you have the skills.
cheers, Neville Michie
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/
time-nuts
and follow the instructions there.
Hello list,
I tried that a long time ago, but the trap I went into was that the
capacitance of the 'scope probe was pulling the frequency down, so I ended
with a crystal too high in frequency...
I'm not sure that you can control the frequency without significantly
perturbing it. And waiting to check the rate between each tuning step would
take a long time...
Regards,
Jean-Louis
----- Original Message -----
From: "Bruce Griffiths" bruce.griffiths@xtra.co.nz
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Tuesday, May 17, 2011 1:22 AM
Subject: Re: [time-nuts] Sidereal timekeeping
Jim Lux wrote:
On 5/16/11 2:58 PM, iovane@inwind.it wrote:
Neville,
at present I have not enough skill with micros to solve the problem.
I think I will try modifying a crystal. This would not be that difficult
using
a lapping sheet or the like. And opening the can would be quite easy
using hot
air.
or a fine jeweler's saw or tubing cutter.
As you pointed out, the crystals are cheap, so you can afford to ruin a
few while figuring out how to do it.
(and then, remember us all, when you're a multi-billionaire having
cornered the market on sidereal rate crystals<grin>)
Since the 32 kHz crystal is likely to be a tuning fork form, one merely
needs to shorten the tines to increase the frequency.
It may be feasible to do this without removing any of the electrode
metallization.
Bruce
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi again,
I forgot to mention this nice piece of software useful to check what you're
doing:
http://www.gb.nrao.edu/~jbrandt/jLSTclock/
Jean-Louis
----- Original Message -----
From: "Jean-Louis Oneto" Jean-Louis.Oneto@obs-azur.fr
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Tuesday, May 17, 2011 12:27 PM
Subject: Re: [time-nuts] Sidereal timekeeping
Hello list,
I tried that a long time ago, but the trap I went into was that the
capacitance of the 'scope probe was pulling the frequency down, so I ended
with a crystal too high in frequency...
I'm not sure that you can control the frequency without significantly
perturbing it. And waiting to check the rate between each tuning step
would take a long time...
Regards,
Jean-Louis
----- Original Message -----
From: "Bruce Griffiths" bruce.griffiths@xtra.co.nz
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Tuesday, May 17, 2011 1:22 AM
Subject: Re: [time-nuts] Sidereal timekeeping
Jim Lux wrote:
On 5/16/11 2:58 PM, iovane@inwind.it wrote:
Neville,
at present I have not enough skill with micros to solve the problem.
I think I will try modifying a crystal. This would not be that
difficult using
a lapping sheet or the like. And opening the can would be quite easy
using hot
air.
or a fine jeweler's saw or tubing cutter.
As you pointed out, the crystals are cheap, so you can afford to ruin a
few while figuring out how to do it.
(and then, remember us all, when you're a multi-billionaire having
cornered the market on sidereal rate crystals<grin>)
Since the 32 kHz crystal is likely to be a tuning fork form, one merely
needs to shorten the tines to increase the frequency.
It may be feasible to do this without removing any of the electrode
metallization.
Bruce
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hence the advantage of your frequency counter's period averaging mode. Don't
measure the crystal, measure the divider it is connected to. That way loading
effects are not directly on the crystal.
Bob LaJeunesse
From: Jean-Louis Oneto Jean-Louis.Oneto@obs-azur.fr
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Tue, May 17, 2011 8:27:14 AM
Subject: Re: [time-nuts] Sidereal timekeeping
Hello list,
I tried that a long time ago, but the trap I went into was that the capacitance
of the 'scope probe was pulling the frequency down, so I ended with a crystal
too high in frequency...
I'm not sure that you can control the frequency without significantly perturbing
it. And waiting to check the rate between each tuning step would take a long
time...
Regards,
Jean-Louis