[time-nuts] Sidereal timekeeping

[Neville Michie]

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 at 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
>
>
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