[time-nuts] Sidereal timekeeping

[Brooke Clarke]

Hi:

Here are some photos of the inside of a quartz clock and some related 
patent links:
http://www.prc68.com/I/QuartzClk.shtml

Have Fun,

Brooke Clarke
http://www.PRC68.com


David Martindale wrote:
> The motor is essentially a permanent-magnet stepper motor.  The rotor
> and stator have just 2 poles each, so the rotor has two stable
> positions 180 degrees apart that provide holding torque.  Thus, the
> motor holds position with no input current for most of each cycle.  To
> move it, the drive applies a short current pulse to the motor.  The
> pulses are alternating positive and negative polarity, so you'll need
> something like an H-bridge to drive it.  Using a 3 volt supply instead
> of the 1.5 that the motor was designed for would supply more power
> than the motor needs if you keep the drive pulse the same width, but
> you should be able to reduce the pulse width until the energy is about
> the same as with 1.5 V drive and have the motor still operate.
>
> Without having actually tried it, I think you should be able to select
> a suitable tradeoff between reliable motor operation and power
> consumption just by adjusting the "on" time of the drive pulse - no
> voltage regulator or voltage dropping resistor needed.
>
> There's only one stator coil to the motor, and one drive signal, so
> you can't control motor direction.  The magnetic structures are
> apparently deliberately asymmetric to ensure that the motor always
> rotates in one direction when it receives a pulse of the appropriate
> polarity.  (Get the pulse polarity wrong, and the motor just doesn't
> rotate).
>
>       Dave
>
> On Wed, May 18, 2011 at 9:20 AM, Bob Camp<lists at rtty.us>  wrote:
>    
>> The only obvious issue is to figure out the motor drive side and see what
>> driving it straight rather than with a switcher does to the motor current.
>> That's going to involve hacking up a wall clock. Since the clock is likely a
>> single cell gizmo, the current probably will be a bit high.
>>      
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